LSD research

Dendrite-vasal relationships

2012-01-26T11:25:00.000-08:00

Golgi had observed that dendrites often terminate close to blood vessels, and he suggested that dendrites might be involved in nutritive functions, as an extension of his theory that dendrites form a continuous reticulum in the brain. The reticulum theory was rejected in favor of the neuron doctrine, relegating the dendrites to receiving centers for information coming from the axon, yet the importance of dendrites in microcirculation and gap junction communication between neurons has received new attention by Sotnikov and others. Figure 8 below illustrates the relationship between blood microvessels and dendrites of Sotnikov's primary sensory neurons, which are a class of neurons with dendrites that respond to photic or mechanical stimuli. Cortical interneurons (IN) are pictured on the left, with dendrites branching on capillaries (C). Its axon synapses on a pyramidal neuron (PN). A Lugaro cell is shown on the right, with dendrites that branch near microvessels (V) and Purkinje cell bodies (PC). According to Sotnikov, the dendrite-vasal situation was noted in the cerebellar cortex in cells first described by Lugaro in 1894.

Another group of neurons whose dendrites have a close relationship to blood vessels are found in the raphe nuclei. In Figure 5 below, a raphe neuron with bipolar shape and thick dendrites branches onto a capillary.

Raphe neurons form dendrite bundles near the basilar arteries, as depicted in Figure 3 (below). A vertical arrow marks the midline. Two large basilar arteries carry fresh oxygenated blood to the brain, so the amine-laden dendrites are positioned to release 5-HT into the bloodstream to the brain in order to regulate blood partial pressure O2 (pO2) levels. It has been established that raphe dendrites respond to changes in pO2 levels, and 5-HT has famous vasoconstrictor actions, representing a reflex arc.

In the figure below, the dendrites and soma of raphe neurons appear to contact the basilar artery on each side of the midline. Individual dendrites were observed contacting one or more underlying blood vessels. Electron microscopy techniques were used to show the close apposition of blood vessels with neuronal perikarya and dendrites of medullary raphe neurons, and no intervening glia were reported.

Raphe dendrites could be stretched as the blood vessels constrict and dilate. Electrophysiologists who have inserted glass pipettes into the raphe neurons have noted that the raphe nuclei can be verified by the presence of characteristic blood pressure responses upon stimulation.

Dendrite-vasal relationships occur in various regions of the brain. Blood vessels adjacent to dendrites have been described in cortex, locus coruleus, substantia nigra, reticular thalamic nucleus, and hypothalamus. The dendrites adjacent to blood vessels often store amine-rich vesicles and are very active in protein synthesis. Hypothalamic magnocellular neurons have dendrites that secrete vasopressin and oxytocin into the blood stream, which are chemicals that are known to affect water balance and mood, thus many important functions are under control of the secretion products of dendrites.

Dendrite-vasal relationships in substantia nigra are notably absent from Parkinson's patients. Overall length and thickness of dendrites of cortical pyramidal neurons are reduced in older animals, when cognitive decline sets in, highlighting the possible importance of dendrite connectivity (thickness and length) in consciousness.

"The melanin-containing neurons of pars compacta in normal substantia nigra have a close spatial relationship with the intrinsic blood vessels. The walls of the substantia nigra capillaries fused to the plasmalemma of the nigral perikarya and dendrites. However, this neuronal-vascular relationship was not present in the brain stem of patients with Parkinson's disease." (J.P. Cummings, 1979)

Reference

Scheibel M. E., U. Tomiyasu and A. B. Scheibel. (1975). Do raphe nuclei of the reticular formation have a neurosecretory or vascular sensor function? Exp.Neurol. 47, 316-329. 10.1016/0014-4886(75)90260-5

Cummings J. P. and D. L. Felten. (1979). A raphe dendrite bundle in the rabbit medulla. J.Comp.Neurol. 183, 1-23. 10.1002/cne.901830102

Brain lesion

2011-12-20T04:34:00.000-08:00

About brain lesions in general.

"One of the oldest and still most important techniques for studying neurons in aggregate is to destroy all of the cells in one small region of the brain and then to observe how brain operation is altered as a result of the lesion. Lesion is used as a noun to indicate the area of destroyed cells and also as a verb to denote the act of destroying cells; From the nature of the change in brain function, together with other types of evidence, it is often possible to assign a role in nervous system operation to neurons in the area destroyed. Quite frequently, some function of the brain will be lost completely: for example the animal may be blind, or deaf, or unable to move a limb after the brain area has been destroyed. In such cases of a deficit following the loss of cells in a specific area, it is usually inferred that those cells were intimately involved in performing the lost function. Some lesions do not cause deficits, but rather result in exaggerated performance of some operation. For example, destruction of cells in a particular area of the hypothalamus leads to almost continuous eating and to enormous increases in body weight. Such an increase in a type of behavior is known as a release phenomenon, and is taken to indicate that the cells which were destroyed normally serve to inhibit other neurons responsible for the behavior which has become exaggerated. " (C.F. Stevens, 1966)

Reference

Stevens, C. F. 1966. Neurophysiology: a primer. John Wiley and Sons, New York.

you or your memory

2011-11-01T01:56:00.000-07:00

YOU OR YOUR MEMORY

Putting aside for a moment the short-comings of Aristotelian two-value logic, "A thing is either A or not-A", we can think of the brain as sustaining the activity of cells whose firing represents information derived from 1) readout from long-term memory or 2) brief sensory input.

Our perceptions of reality are limited by what we can perceive with the brain. We can think of reality as a blend of:
1) MEMORY: readout from long-term memory
2) INPUT: brief sensory input

MEMORY
"Memory” is the brain program that is capable of responding to specific, predictable stimulus inputs, and has sometimes been referred to as being unconscious. The example of driving along a familiar route has been used by many authors to describe this type of memory.

"Whilst driving home from work our conscious minds may be busy reviewing the events of the day whilst at the same time, we are watching traffic, changing gear, following the road but are unaware of any of these operations. Yet if we encounter a hazardous situation - such as a child in the road - we instantly become aware of the child, the road, the motor operations of driving, and thereafter slow down to drive more carefully under conscious control. Our conscious mind seems to take over the control of our body in these situations." (J. McFadden, 2002)

In other words, there may be some unexpected events that happen on the way to work, but things generally proceed as expected, based on what the memory program computes to be most probably out there.

The information in the adult brain largely depends on this dense and unconscious memory. Timothy Leary said that the individual world each person occupies is his reality tunnel. In the reality tunnel mode of operation, the adult brain can screen out unfavorable stimuli which are present in the environment. For example, the memory of a crack addict may construct a reality in which a crack pipe is more significant than the baby in the same room. In this reality tunnel mode of thinking, it is possible to confuse our expectations with reality.

However, activation of "memory" programs during sustained wakefulness never achieves total autonomy from the stimulus environment, because we always encounter children in the middle of the road, unforeseen traffic delays, and accidents.

BRIEF SENSORY INPUT
"Input" is the brain program that is activated by the arrival of certain unpredictable stimuli. Activation of the "input" program during wakefulness never achieves total autonomy from "memory".

There is far more information out there than the mind can behold. The brain only samples a fraction of the information out there and then it fills in the rest. The sampling of information "out there" is accomplished by the input program, while its left up to memory to fill in the rest. To the extent that memory is successful, brief sensory input will be put on hold.

During adulthood in mid-life, when we have a strong sense of memory, we are merely the brain that looks at the universe. The beauty is there, but it is the expected kind. When we forego as many expectations as possible at the beginning and end of life, we are more likely to turn on to the input, and the weirdness of the big existence. . . . Terrence McKenna referred to the Input program as an alien intelligence, "Whatever you think it is, its not what you think it is."

A hypothesis about LSD and the 2 modes: memory and brief sensory input

It seem likely that LSD has a powerful dismantling effect on memory, defined above as the reality tunnel existence in which most adult human beings operate. Anyone who has taken LSD may have experienced firsthand the uncomfortable feeling of abulia in place of a normal sense of confidence of "who I am".

LSD may cause a failure of the cortex to predict what is out there, when you begin to see things of undescribable beauty which you have never possibly seen before in your entire life. So, without prediction to guide us, nearly all experience becomes reactive and primitive. It could be hypothesized that LSD turns on the "input" brain program, or else that it turns off the "memory" brain program. Either way it leaves the impression of an influx of sensory information, followed by a reorganization of the "reality tunnel" brain program. Studies in pigeon and rabbit have shown that low doses of LSD facilitate certain types of sensory awareness that get translated into new memory. Memory of the LSD experience does not differ much from memory of any memorable event. Afterall what is an LSD flash-back besides a powerful memory recollection?

Primitive learning may happen so effectively under LSD that we caution people about making good choices about the "set" and "setting", the people and stimuli who are present when tripping.

LSD and other hallucinogens seem to be able to enhance certain types of learning without necessarily promoting the intent to learn (over achievers take note). Loss of ego functioning does not necessarily prevent memory formation, because much learning takes place without being conscious of the details (e.g. language acquisition in children).

The facilitation of a new learning experience can help people to break out of addiction, or other memory programs that have become toxic.

"[Under the influence of LSD] other types of learning may be unimpaired and may be much improved. If this were not so, the psychedelic experience would help no one. A large number of alcoholic subjects learn concepts and ideas in a few moments that they had not grasped for years. These are termed flashes of Inspiration or Insight but they seem to me to be the acquisition of new concepts. One subject, a brilliant physician alcoholic, prided himself on the fact he took no drugs. Under LSD he vividly learned alcohol Is a chemical and, by his old definition, a drug. Other subjects learned understanding, tolerance, compassion, the meaning of psychotic fear, etc." (A. Hoffer, 1956)

Summary

For convenience I have described reality as a blend of memory and brief sensory input, but Phillip K. Dick reminds us that Aristotelian two-value logic is fucked. Afterall, how would a physical reality that is separate from the mind exist when the brain emerged from this order? To quote Sherrington's famous pupil,

"It is not the code or the message coming from the outside world that is being transmitted, but rather it is the neuronal element that responds to the message from the outside that is itself the message! " (R. Llinas, 2001)

This complicates the definition of the "input" program as having sampled something from the "outside", and is the point in the conversation when people like to mention "intrinsic properties" related to certain Ca2+ conductances.

At one extreme, the brain is capable of emulating reality in the absence of input from such reality, and at the other extreme, sensory contents gain internal context. Like the immune system, the brain may keep a border between the self and the environment, the function of which enables sensitization to the environment with time.

One electron, two electrons

2011-10-27T20:42:00.000-07:00

“In molecular orbital theory, the fact that most molecules contain electron pair bonds is explained as a consequence of the Pauli principle, according to which in the stable state of any system, any given orbital can be occupied by 2 (and only 2) electrons with opposite spins. This fact greatly favors the stability of even-electron as compared with odd-electron molecules." (R.S. Mulliken, 1978)

Most of the stuff in the material world that we encounter has even-electron configurations, which is accounted for by the familiar Pauli principle. Molecules with odd electrons are more rare. Just how frequently do we encounter odd electron molecules? In frozen sugar solutions, it was approximated that there is one unpaired spin for every 10E4 molecules of irradiated sugar in solution.

Why is the odd-electron configuration so rare? To begin with, theories that account for unpaired electrons are much less developed than theories that describe the types of matter that contain ordinary electron pairs. Most molecules have even numbers of electrons that fill the available molecular energy levels in pairs, and therefore a lot of theories just assume the Pauli exclusion principle. In the case of unpaired electrons, we may need to be prepared to find a new type of physical law.

Second, the existence of odd-electron configurations is often associated with a pronounced color in the system. For example, aniline is colorless when pure but turns brown when oxygen is bubbled through it, and becomes colorless again on sweeping out the oxygen. There are many colorimetric methods for estimating the concentration of unpaired electrons. It is interesting in itself that the human visual system detects the presence of free radicals as color.

Another reason that unpaired electrons differ from electrons in pairs is that unpaired electrons are more delocalized in space. Whereas paired electrons stay in the neighborhood of one nucleus, unpaired electrons are contained in orbitals that may extend over several adjacent atoms. In the cell where biopolymers are intimate contact with each other, it is quite conceivable that unpaired electron migration may take place over large distances involving a number of aggregated biopolymers.

Diphenylpicrylhydrazyl (DPPH) is a stable free radical that is often employed as an EPR standard, and its EPR spectra is shown below. The HOMO electron in molecules such as DPPH (Figure 26 below) is spread out over multiple bonding orbitals. The unpaired electron in this embraces at least 30 other nuclei possessing magnetic moments, causing the splitting pattern.

From ESR free radical signals

The wave function of the unpaired electron in DPPH extends throughout a region which encompasses most of its structure, which means that no definite atomic orbital such as an s- or p-orbital may be assigned to it. The electron may be considered to be highly mobile within the structure, and capable of mediating conduction within it. It is critical to understand that the unpaired electron in DPPH whose ESR signal is shown above is a very different species from the paired electrons in DPPH, which are found in the inner shells.

"In the case of DPPH, the unpaired electron is in an anti-bonding orbital and one would expect electron conductivity with a low value of delta e (1.5 eV); the direction of the orbitals of the unpaired electron coincides with the direction of the c axis, where there is the greatest overlapping of orbitals - this also corresponds to the increased electrical conductivity in this direction." (A. Buchachenko, 1965)

The existence of an unpaired electron in a system like DPPH strongly perturbs the molecular orbitals of nearby electrons, which brings us to the fourth reason why unpaired electrons are so interesting.

Unpaired electrons are associated with an abnormally high chemical reactivity, that can permit the initiation of otherwise forbidden chemical reactions. Not only are free radicals highly reactive, but many types of chemical reactivity including oxidation, irradiation, UV photolysis, and charge-transfer reactions are directly related to the spin density of a molecule's unpaired electron or electrons. For example, the stability of charge-transfer complexes are undoubtedly connected with the unpaired electron delocalized through the pi-system.

Compare the reactivity of molecules with unpaired electrons in the outer shells with the noble gases like Argon and Xenon that are chemically inert. Electron pairs fill the outer shells of Argon, which has almost no chemical properties at all, and explains why it was named Argon, "the lazy one."

II.

Sugar is an example of a "united molecule", with electron pairs that are held strongly in place, and will remain strongly held in place until some light energy comes along. The light energy can promote an electron to the outer and anti-bonding orbitals. Normally, the anti-bonding orbitals of sugar are devoid of electrons in the ground state, and may be occupied only in excited states.

The molecular organization of organisms is actually very different from the organization of simple sugar. Unlike sugar, the anti-bonding orbitals of the ground state of biological proteins are occupied by an electron transport chain, a life-contributing force in the organism that is involved in respiration. In the molecular description of sugar, the incoming light energy is said to "disrupt" the electronic configuration of sugar; as long as sugar is kept away from light or chemical energy then sugar will have a completed set of electrons which makes it sugar. In contrast to the simple sugar molecule, the configuration of the animal body relies upon electronic "disruption" for its existence. In the organism, it is less easy to distinguish which electrons belong to organism, and which electrons belong to the excited state.

Wait a minute, are you saying that there are unpaired electrons in the human body?

There is very good reason to believe, if we accept the Pauli exclusion principle (and we should), that most types of matter around us contain electron pairs. Yet the behavioural activities of lifeforms (beetles, whales) depend on the existence of unpaired electrons for many processes including the all-important process of respiration. It is interesting to compare the bonding of atoms in the worlds of the living and the inanimate. There seems to be an important difference between matter with electron pairs and the matter of our dear selves: organic lifeforms, that twitch, grow, and reproduce. That difference is the high concentration of unpaired electrons in biological systems. EPR experiments on mammalian tissues have shown that liver and brain tissue are the richest source of unpaired electrons in nature. Living things such as seeds and green leaves have relatively higher concentrations of free radicals compared to dead wood or stone. Reconstituted enzyme systems, like polymerase chain reactions, have a higher concentration of unpaired electrons than distilled water in a test tube. Thus the essential nature of odd-electron transfer reactions is central to the electronic and molecular organization of life. There are many oxidation-reduction reactions in biology that wouldn't be possible without single-electron transfer reactions. Szent-Gyorgyi was interested in charge-transfer reactions.

“In photosynthetic chromatophores, or chloroplasts, as well as in phosphorylating mitochondria, single electrons are transferred in a series of reactions from substance to substance. It seems possible that a similar transfer of electrons plays a wider role in the various activities of the cells or the maintenance of their living state. It is still an open question how such a transfer of electrons takes place. Our attention has been occupied, in this context, in an increasing degree by “charge transfer.” (Szent-Gyorgyi, 1961)

Now that you have told me about the unusually high concentrations of unpaired electron in brain and liver, I'm curious to know, at what stage of life can I expect to be filled with a high concentration of unpaired electrons?

The concentration of free radicals depends on age. Take a look at this figure. Baby rats are born with a relatively low concentration of free radicals which increases rapidly during their development, and reaches a maximum in early adolescence. Early stages of animal development take place in the midst of a very high concentration of free radical generation, propagation, and termination processes.

From ESR free radical signals

Then the adult lifeforms (rats, lightning bugs, human beings) live within the burnt-out shells of this initial polymerization process. In the mature form of the human animal, the establishment of an equilibrium between the free radicals in a human being and its environment may be related to its alpha EEG rhythms.

The potential differences that are recorded from muscle or cortex verify the existence of unpaired electrons, or electricity, in the mammalian form. Brain oscillations are derived from these unpaired electrons, until brain death when a flat line EEG is recorded. An example of this is shown in the figure below. Crude cobra venom or rattlesnake venom in doses of 0.5 mg/kg led to a complete EEG silence within 1 minute.

From 94Nunez EEG

If the EEG is related to free radical content of the brain, then the death state may be associated with a time when the free radical concentration of the nervous system reaches equilibrium with the spins in the world exterior. At that point, does the Pauli exclusion principle fully apply in its description of the molecular configuration of a dead body? If each 1/2 spin finds -1/2 spin, then in death, the electrons can fully belong to the organism as a giant "united molecule."

What about free radical content and cancer?

The stability of the animal body differs from the stability of simple sugar, because organisms move, shed cells and grow new ones in its place. Yet for the form of the organism to be somewhat stable, most of the tissues of the body do have even numbers of electrons that fill the available molecular energy levels in pairs according to the Pauli exclusion principle. The balance between odd electrons and paired electrons is critical for the health of tissues. As studied by Mallard and Kent in 1964, healthy liver has a much higher concentration of free radicals than cancerous liver tissue, suggesting that tissues can become cancerous by acquiring an excess of bonding electrons in the outer shells. Since many cancers are deadly, we may conclude for the time being that a certain concentration of unpaired electrons in outer shells is essential for life.

Summary

The entire richness and diversity of the material world is formed by union of only a hundred kinds of atomic particles. For the most part, assemblies of atoms must adopt a configuration with paired electrons. Electrons in pairs remain in the confines of the molecule and cannot drift throughout its structure, thus many solids in the external world are electrical insulators. In contrast, the animal body is a highly ordered crystalline array of proteins, starches, and lipids that are associated with unpaired electrons that range over long distances, the function of which is not completely understood.

Biological entities, with their composition of even and odd electrons, are expected to have semi-conducting properties, that is, properties of electrical conductivity between that of a conductor and an insulator. Szent-Gyorgyi was one of first people to point out the connection between the theory of semi-conductors and biological lifeforms. Lightning bugs can be thought of as diodes that conduct electricity when a small current is applied across it. It is likely that all living entities have semi-conducting properties, among them the ability to emit light. Besides the light within the creatures of this planet, hardly any light but sunlight occurs in nature: occasional fires, lightning, and starlight.

References

Hart, E. J., Anbar, M. The hydrated electron. Wiley-Interscience: New York, 1970.

Buchachenko, A. L. Stable radicals. Consultants Bureau
Enterprises: New York, 1965.

Gamma (40 Hz) power is the Instantaneous Envelope of the EEG First Derivative

2011-09-03T14:00:00.000-07:00

From Gamma (40 Hz) power, Barlow method

Abramson's "Cold Spring Harbor Questionnaire" for human LSD research

2010-06-12T23:51:00.000-07:00

“One of the serious objections to questionnaires is that the validity of individual items is doubtful. Nevertheless, there are many items whose validity cannot be pushed further than a subjective response. Unfortunately, the only way to tell whether a person has hallucinations, or a headache, for that matter, is to ask him. As our science progresses, more objective tests for these phenomena may be evolved. In the meantime, it would seem that the proper course for the scientific psychologist to follow lies somewhere between complete dependence upon verbal reports of individuals and complete rejection of such material." (M.E. Jarvik, 1955)

Many of the workers who have studied mescaline or LSD intoxication have been puzzled at the subjects. Their attitude seems to be one of an interested spectator whose planned action is waived for the duration of the show. Efforts of the investigator to involve the subject in organized activities, such as answering questions, may be answered with reluctance or frank refusal whereas a verbal account of the experiences may be given more freely.

Even though the questionnaire technique is not always reliable, it has been valuable in connection with psychoactive drug research to assess the relative potency of LSD and LSD congeners in humans. The most common questionnaire used is the Cold Spring Harbor Questionnaire, shown below.

From lsd dose

The 59-item questionnaire has short questions like, "Do you feel unsteady?" and "Are you anxious?". In 1955, Jarvik and Abramson found that LSD led to a large number of positive responses on the Cold Spring Harbor Questionnaire, and far more positive responses than the drugs LAE-32, BOL-148, ergonovine, scopolamine, alcohol, methamphetamine (methedrine), and two placebos. The subjects were 5 nonpsychotic volunteers, who received all drugs on different occasions. Questionnaires and physiological tests were given during the drug effects. As shown in the results below, LSD produced the most positive responses on the questionnaire of all the drugs tested, thus validating the usefulness of the Cold Spring Harbor questionnaire for LSD research.

From lsd dose

Not only did LSD produce the most positive responses on the questionnaire, it was the study drug with the smallest dose by weight. The concentration of alcohol was about a million times as great, expressed in terms of weight, as the concentration of LSD, as shown in the figure below.

From lsd dose

“In comparing the effects of seven different chemical and two tap water placebos upon the responses to a questionnaire, it is apparent that the chemical structure of the compound ingested is of paramount importance in determining responses to these questionnaires.” (M.E. Jarvik, 1955)

An abbreviated version of the questionnaire with 47 items was used with much of Abramson's human LSD research. The Table below gives the questions and responses by 26 volunteers, at 0.5 h, 1.5 h, 2.5 h, and 3.5 h after LSD ingestion. The questions that frequently gave a "yes" answer were, "Is salivation increased?", "Do you have a funny taste in your mouth?", "Is it a bitter taste?", "Does your head ache?", "Do your hands and feet feel peculiar?", "Is there pressure in your ears?", "Is your hearing abnormal?", "Do you tremble inside?", and "Are you anxious?"

From lsd dose

The test situation asking a subject to respond to these questions has turned out to be relevant to certain basic questions.

References

JARVIK M. E., H. A. ABRAMSON and M. W. HIRSCH. (1955). Comparative subjective effects of seven drugs including lysergic acid diethylamide (LSD-25). J.Abnorm.Psychol. 51, 657-662. 10.1037/h0041073

Abramson, H. A., M.E. Jarvik, M.R. Kaufman, C. Kornetsky, A. Levine and M. Wagner 1955. Lysergic acid diethylamide (LSD-25): I. physiological and perceptual responses. J Psychol. 39, 3-60.

Habituation

2010-03-07T16:50:00.000-08:00

In a paper to the Psychological Bulletin, J. Donald Harris used the word "habituation" to refer to behaviors of accommodation, inhibition, extinction, stimulatory inactivation, acclimatization, negative adaptation, etc. He called habituation a "law of forgetting," a respite from sensory stimulation.

From Protista to man,

"Perhaps the most ubiquitous phenomenon in animal behavior is that of response decrement as the result of repeated stimulation." (J.D. Harris, 1943)

A great number of stimuli will cause Ameba (Rhizopoda) to cease protoplasmic streaming, and if the stimulus is continuous and not too intense, the streaming will shortly begin anew.

"Ameba react negatively to tap water or to water from any foreign culture, but after transference to such water they behave normally."

Paramaceium soon becomes acclimatized to an energy pattern which ceases to change, whether it be chemical, thermal, photic, or electrical. However, habituation occurs when stimuli are weak, but not if the stimuli is too intense. Habituation does not occur under the condition where the environmental change is becoming lethal. If Paramecia is dropped into an injurious chemical solution it will dash about till necrosed.

Hydrozoa spread their highly-colored discs near the surface of the water. A drop a water falling from a height of 30 cm causes the animal to react, but rarely to the second and third drop and infrequently the fourth drop. Certain Hydra are much more active than others in habituating, although somewhat similar results are obtained from all species.

Mosquita larvae come to the surface of water in sunlight, and if a shadow passes over they swim towards the bottom. Yet after a number of shadows, few larvae are seen to dive.

A case report of habituation in a spider,

"Not until she had fallen out of the web 22 times, at the approach of the [tuning] fork, could she restrain the impulse to drop. It was apparent, however, after the seventh or eight time, that she was less startled by the sound than at first, since the distance that she fell and the period of time that elapsed before she returned to the web grew shorter and shorter in the later experiment. At first she fell 15 or 18 inches, and remained at the end of her line for several minutes, while toward the last she fell only an inch or two, and immediately ran back to her web. After the twenty-second trial she only held up her legs as the fork approached. Finally, completely worn out and disgusted, she retreated to a neighboring branch, drew in her legs, and remained sullenly unresponsive to all further attempts."

Harris's accounts of response decrement in these organisms cannot be explained by a decrement in reflexes containing intermediary neurons. Explanations given in terms of homeostasis are unsatisfactory, wrote Harris, and,

"Habituation due to changes in the strength of synapses cannot apply in Protozoa. Current theories of long-term potentiation at a synapse do nothing more than roughly to suggest the locus of the phenomenon."

Sixty-five years after Harris, enormous effort has been spent trying to understand how, when, why, and by what mechanisms chemical synapses can be modified, yet a complete explanation of memory in terms of dendritic spine stability and changes in synaptic transmission is still forthcoming. Rodolfo Llinas spent more than the past 40 years studying synaptic transmission of the giant squid synapse, and he wrote,

"There are many elements of nature, completely lacking a brain in a traditional sense, which still have a peculiar amount of intelligence." (R. Llinas, 2002)

References

Harris, J. D. 1943. Habituatory response decrement in the intact organism. Psychol Bull. 40, 385-422.

Llinás, R. R. 2002. I of the vortex. MIT Press, Cambridge.

The Wada test

2010-02-18T09:42:00.000-08:00

"A perfectly bilateral machine or organism could not perform left-right discriminations, which much include scanning in a preferred (e.g. left-to-right) direction and distinguishing between such letters as d and b, p and q and such words as saw and was, such organisms could only make mirror-image responses to mirror-image stimuli..." (J.L. Bradshaw, 1983)

The right hemisphere is biased toward global processing and the left for local processing. Robert Sperry listed the following specializations for the right hemisphere: rhythm, spatial awareness, Gestalt (the whole picture), imagination, daydreaming, color, dimension. This supposedly describes the creative right brain of many left-handed artists. The left hemisphere, which controls the right hand - typically the dominant hand for writing the name - and which has a higher ratio of grey to white matter than the right hemisphere, specializes in verbal-linguistic and analytic functions.

Many techniques have been developed in the field of left-right brain research, but the Wada test must be one of the most dramatic and conclusive experiments. During a surgical procedure where the large arteries leading to the brain are exposed, injection of drugs into the bloodstream will selectively anesthetize one hemisphere. The Wada test is not performed very often, but it might be used before major brain surgery to determine which hemisphere is dominant for language.

From Human cerebral asymmetry, J.L. Bradshaw writes,

"Wada (1949) first developed the procedure known as the Wada test: an injection of the barbiturate sodium amytal (amobarbital) into one (left or right) of the common carotid arteries that supplies its ipsilateral hemisphere. A temporary loss of function is produced on the affected side of the brain: a flattening of the EEG, along with hemiparesis, hemianesthesia, and hemianopsia. It is in effect a reversible hemispherectomy, permitting tests of higher mental functions in the other hemisphere. If the drug is injected into the dominant hemisphere, there is usually total and abrupt cessation of speech. In view of the slight but definite risk accompanying the insertion of the needle or catheter into the carotid artery, the Wada test is employed only when absolutely necessary, and consequently such patients usually have more or less severe existing abnormalities of cerebral function. Moreover, since the unilateral suppression lasts only five to ten minutes and the experience itself is probably disturbing to the patient, usually all that can be determined is which hemisphere is specialized for speech production. Typically, the upraised contralateral arm and leg fall to the bed with a flaccid paralysis a few seconds after the injection. If the injected hemisphere is nondominant for speech, there is an abrupt and more or less total cessation of speech shortly after the injection; it lasts until recovery from the hemiparesis is well advanced. The patient makes characteristic dysphasic responses (perseveration, misnaming, mixing up the sequence of numbers and of days of the week, etc.) for several minutes before speech returns to normal. The Wada test has shown that dextrals have clear left hemisphere language dominance in over 90 percent of the cases, and sinistrals in 70 percent of cases. The effects of unilateral ECT are similar to those of unilaterally injected sodium amytal." (J.L. Bradshaw, 1983)

Depression of the left hemisphere with the Wada technique is associated with a depressive catastrophic reaction and for most people the traumatic loss of speech. Depression of the right hemisphere with sodium amytal leads to a euphoric or manic response.

Reference

Bradshaw, J. L. and N. C. Nettleton (1983). Human cerebral asymmetry. Prentice-Hall, New Jersey.

BOL-148

2010-02-01T04:03:00.000-08:00

BOL-148 is the 2-brom derivative of LSD. There is a Bromine (Br) in place of Hydrogen at position 2.

From molecules

In spite of its close structural relationship to LSD, BOL-148 has no psychedelic effects. Among the LSD analogs, BOL-148 is especially important because it indicates that substitution at the 2-position changes the activity of the whole molecule, as outlined by the studies below.

In 15 healthy males, doses of 75-110 ug/kg BOL-148, which 100X exceed an effective dose of LSD, caused no change in pupillary dilation, patellar reflex, or blood pressure (H. Isbell, 1959). BOL-148 did not alter the behavior of 6 individuals with schizophrenia, when given at 10X the dosage of active LSD, although for BOL-148 these doses may have been too low to observe any effect. One mg BOL-148 twice a day for 2 weeks, or 5 mg for 3 days had no evident effect on their psychoses (W.J. Turner, 1958).

With newly developed drugs and low doses of known drugs, there is frequently a problem in deciding whether the drug has an effect on the EEG. Generally where there is no EEG effect, no drug effect is expected. There is evidence of the contrasting pharmacological effects of LSD and BOL-148 on the EEG. While LSD affects the EEG in doses of 100 ug/kg, BOL-148 in doses of 100+ ug/kg are reported to be without effect on the EEG. BOL-148 did not cause any sign of the fast electrical activity or alerting behaviour seen with injections of LSD in cats, even when doses of up to 100 ug/kg of BOL-148 were used intraventricular, to avoid the blood-brain barrier (P.B. Bradley, 1956). BOL-148 is reported to produce no EEG changes in Macaca mulatta, in high dose ranges 110-175 ug/kg (R.R. Monroe, 1961). Saline gave the same response as 1000 ug/kg BOL-148 in cats with permanently implanted EEG electrodes (E. Eidelberg, 1965). In rabbits, 500 ug/kg BOL-148 failed to produce EEG alerting for longer than 15 minutes (A.K. Schweigerdt, 1966). These studies indicate a lack of effect of BOL-148 across a range of species.

BOL-148 has a very slight change in molecular structure compared to LSD, but it has none of the behavioral effects of LSD. LSD caused behavioral arousal in cats whereas BOL-148 produced mild sedation, when the two drugs were administered intraventricularly (P.B. Bradley, 1956). In rabbits, LSD enhances eyeblink conditionining, whereas BOL-148 had a neutral effect (J.A. Harvey, 2003). No affective changes in Papio papio were observed after BOL-148 in doses of 2-4 mg/kg (M.D. Fairchild, 1980).

Table 3 below shows the questionnaire responses for LSD and several LSD derivatives. LSD is the most potent drug, and caused the most positive responses on the questionnaire. BOL-148 is on this table, and there were few positive responses on the questionnaire at doses of 80 ug/kg, or 50 times the active dose LSD. This shows a lack of effect of BOL-148 as reported by human volunteers.

From other human hallucinogens, LSD derivatives

There is some evidence that BOL-148 pre-treatment protects against LSD psychosis. Studies in rabbit have shown that BOL-148 1 mg/kg had no direct temperature effect - as LSD does - but prevented the pyretogenic actions of LSD (A. Horita, 1958). In humans, BOL-148 did not function as a direct LSD antagonist since intravenous injections of BOL-148 at the height of a LSD trip did not cancel the LSD effects, but pre-treatment with BOL-148 in nonpsychotic humans did produce tolerance to the LSD reaction, though the tolerance-producing effect of BOL-148 for equal weights of LSD is much less, approximately 1/30 that of LSD and the attenuation of the LSD reaction observed after pre-treatment with BOL-148 is still less than that which occurs after pre-treatment with LSD. (H. Isbell, 1959)

In an experiment with 10 men, pretreatment with BOL-148 for 5 days (1 mg BOL-148 three times daily) significantly attenuated LSD 0.5-1.5 ug/kg psychosis. As shown in Table 3 (below), blood pressure, pupil size and number of positive responses to questionnaire were reduced during LSD challenge 5 days after BOL-148 pretreatment (Isbell, H. 1959).

From other human hallucinogens, LSD derivatives

Some assays have indicated similarities between LSD and BOL-148. For example, LSD and BOL-148 were found to have the same affinity for beta-adrenergic receptors (A. Dolphin, 1978), and were equally effective as MAO and acetylcholinesterase inhibitors in histochemical analysis of rat brain (T.R. Shanthaveerappa, 1963). However it is important to keep in mind that these samples did not involve the whole organism. More research in needed into the general significance of the 2-position for the pharmacological and EEG effects of LSD.

There is one report from 1957 indicating that BOL-148 may function as a hallucinogen in high doses. Two normal volunteers experienced psychic effects when BOL-148 was administered intravenously to total doses of 18 and 22 mg, or equivalent to ~200 LSD doses.

"In man small doses of bromo-LSD are said to produce none of the bizarre psychic effects noted with LSD but this is not the case when bromo-LSD is administered intravenously in large doses. Thus, when constant intravenous infusions of bromo-LSD were given to normal subjects, both experienced psychic changes, which became more severe as the infusion continued and persisted for 3 to 4 hours after the infusion was stopped. No hallucinations were noted but there were feelings initially of drowsiness, depression, anxiety, and apprehension followed by feelings of irritation, restlessness, and tenseness, and later, intensely disagreeable sensations of unreality and depersonalization, inexplicable feelings of strangeness and mild confusion." (R. Schneckloth, 1957)

A relatively large body of work exists on human studies with BOL-148, making it one of the most well characterized LSD analogs. BOL-148 shows that structure-activity relationships can be quite revealing about the mechanism of action of LSD, since substitution at the 2-position can change the activity of the whole molecule. Another important research finding related to BOL-148 research is that LSD does not induce a psychosis by creating a relative deficiency of 5-HT within the brain. BOL-148 has been shown to have more anti-5-HT activity than LSD in vitro and in vivo, thus if LSD worked by blocking 5-HT neurotransmission, BOL-148 would be expected to be a more potent hallucinogenic drug, but BOL-148 is inactive on many accounts.

References

BRADLEY P. B. and A. J. HANCE. (1956). The effects of intraventricular injection of d-lysergic acid diethylamide (LSD 25) and 5-hydroxytryptamine (serotonin) on the electrical activity of the brain of the conscious cat. J.Physiol. 132, 50-1P.

Dolphin, A., A. Enjalbert, J.P. Tassin, M. Lucas and J. Bockaert (1978). Direct interaction of LSD with central "beta"-adrenergic receptors. Life Sci. 22, 345-352.

Eidelberg E., M. Long and M. K. Miller. (1965). Spectrum analysis of EEG changes induced by psychotomimetic agents. Int.J.Neuropharmacol. 4, 255-264.Fairchild M. D.,

D. J. Jenden, M. R. Mickey and C. Yale. (1980). EEG effects of hallucinogens and cannabinoids using sleep-waking behavior as baseline. Pharmacol.Biochem.Behav. 12, 99-105.

Harvey J. A. (2003). Role of the serotonin 5-HT(2A) receptor in learning. Learn.Mem. 10, 355-362.

HORITA A. and J. H. GOGERTY. (1958). The pyretogenic effect of 5-hydroxytryptophan and its comparison with that of ISD. J.Pharmacol.Exp.Ther. 122, 195-200.

ISBELL H., E. J. MINER and C. R. LOGAN. (1959). Relationships of psychotomimetic to anti-serotonin potencies of congeners of lysergic acid diethylamide (LSD-25). Psychopharmacologia. 1, 20-28.

ISBELL H., E. J. MINER and C. R. LOGAN. (1959). Cross tolerance between D-2-brom-lysergic acid diethylamide (BOL-148) and the D-diethylamide of lysergic acid (LSD-25). Psychopharmacologia. 1, 109-116.

MONROE R. R. and R. G. HEATH. (1961). Effects of lysergic acid and various derivatives on depth and cortical electrograms. J.Neuropsychiatr. 3, 75-82.

SCHNECKLOTH R., I. H. PAGE, F. DEL GRECO and A. C. CORCORAN. (1957). Effects of serotonin antagonists in normal subjects and patients with carcinoid tumors. Circulation. 16, 523-532.

Schweigerdt A. K., A. H. Stewart and H. E. Himwich. (1966). An electrographic study of d-lysergic acid diethylamide and nine congeners. J.Pharmacol.Exp.Ther. 151, 353-359.

SHANTHAVEERAPPA, T. R., K. NANDY and G.H. BOURNE (1963). Histochemical studies on the mechanism of action of the hallucinogens D-lysergic acid diethylamide tartrate (lsd-25) and D-2-bromo-lysergic acid tartrate (bol-148) in rat brain. Acta Neuropathol. 3, 29-39.

TURNER W. J. and S. MERLIS. (1958). Chemotherapeutic trials in psychosis. III. 2-Brom-d-lysergic acid diethylamide (BOL 148). Am.J.Psychiatry. 114, 751-752.

Apical and basilar dendrites of pyramidal neurons

2009-11-15T16:34:00.000-08:00

Scheibel and Scheibel used Golgi staining to study arrangements of dendrites in the spinal cord, and later, the neocortex. Dendrodendritic synapses were found in bundles of basal and apical dendrites of pyramidal neurons. It is unknown whether apical dendrites and basal dendrites are two separate systems with different tasks, or just apparently different for reasons of the construction of the network.

APICAL DENDRITES

The cortex is filled with pyramidal cells, a type of neuron with a large cell body and very long dendrites extending in the basal and apical directions. The apical dendrites of pyramidal cells are oriented towards the pia of the brain, as shown in the figure below. Cell bodies in Layer 6 have dendrites that form a bundle extending to Layer 1.

From dendrites

A cross-section of apical dendrites is shown in the box (figure above), with an arrow pointing to the region where dendritic membranes are closely opposed. Microtubule, mitochondria, and other proteins are stained at the site of communication between two dendrites.

The next figure shows apical dendrite bundles in cat visual cortex, cut in cross-section (the lower half of the figure).

From dendrites

Each white spot represents a dendrite; where two white spots touch is the place of dendritic membrane contact. These constellations of dots are sometimes called puncta or puncta adherentia by histologists to refer to an ambiguous structure, but in many cases puncta resemble dendrites in cross-section.

BASILAR DENDRITES

The basilar dendrites of pyramidal neurons are very long. Scheibel and Scheibel were impressed with the length of the Betz cell basilar dendrites, and suggested that the great length of the dendrites was a unique feature for which these cells evolved. In mice, rats, and cats, giant pyramidal cells of Betz and large solitary cells of Meynert in visual cortex have long basilar dendrites organized into bundles. As shown in the figure below, cat cortex had thick patches of basilar dendrites in layer 5 and layer 2/3. In human cortex, basilar dendrite bundles can reach a length of 2000-3000 um, with diameters of 12-40 um.

From dendrites

Part C of Figure 2 (below) shows a close-up view of a dendrite bundle, which contains 6-10 basilar dendrite shafts and varies in total diameter from 7-8 um to 1-3 um. It appears to change as individual dendrites are added or subtracted along its length.

From dendrites

The length of basilar dendrites permits Mountcastle's columns to link to each other, as shown in the figure below. Gap junction coupling at dendrite bundles could serve as an averaging mechanism, uniting the neurons involved into an assembly.

From dendrites

Studies on ventral horn motoneurons had led to a presumptive relationship between onset of reciprocal flexor-extensor activity in the muscle masses of the leg and the appearance of bundling in motoneuron dendrites. The onset of dendritic bundles with the development of discrete items of output performance could have implications for non-motor memory as well. Scheibel and Scheibel surmised that age-related problems with cognitive association skills could be due, as shown in the figure below, to a loss of the large dendrite bundles within basilar shafts of giant pyramidal neurons.

From dendrites

Senility may be associated with dendrite retraction and less thickness of basilar dendrite bundles. The figures (above, below) are from Golgi-impregnated sections of human cortex at different stages of aging. In particular, there is a loss of horizontal lengths (basilar dendrites) during aging rather than vertical (apical) dendrites. The decline of effective dendrite connectivity may be an important contribution for the fading of human consciousness.

From dendrites

Like the dendrite bundles in spinal cord, thalamic reticular nucleus, and raphe, dendrite bundles formed by the apical and basilar dendrites of pyramidal neurons appear to make direct dendrodendritic connections. It has been estimated that the dendritic bundles of the rabbit neocortex are characterized by such a close packing that about 20% of the surface of every dendrite is common to adjacent dendrite surfaces, separated by the extracellular space only. There are no intervening glia between the dendrites, and no post-synaptic specializations that resemble axon-synapses machinery, thus gap junctions appear to be the primary means of communication between two or more dendrites in a bundle, although it is controversial whether adult pyramidal neurons have significant numbers of gap junctions.

Chemical material not exceeding a molecular weight of ~1 kDa can fit through an open gap junction. There is a slight time lag as the chemical moves from one cell to another, but this is how low molecular weight messengers such as cyclic AMP move through gap junction-connected cells, allowing two or more cells to synchronize their metabolic state. If many gap junctions are open, millions of cells in the network can be coupled at once. This may contribute to an ancient way of communicating between cells that does not depend on synaptic activity. While axons are busy firing, dendrites are synchronizing subthreshold activities and debris with neighboring neurons.

Dendrite bundles in particular seem to serve as one collecting system for many afferent influences. Dendrites contain a large surface area for the interplay of fractional changes in membrane potentials. It is generally believed that the current paths of individual neurons that summate in the extracellular space in and around the dendrites gives rise to summed extracellular potentials, the EEG, and rhythmic EEG potentials.

From dendrites

Reference

Roney K. J., A. B. Scheibel and G. L. Shaw. 1979. Dendritic bundles: survey of anatomical experiments and physiological theories. Brain Res. 180, 225-271.

Dendrite bundles in spinal cord

2009-11-15T11:52:00.000-08:00

Virtually all neurons within the central nervous system and certainly the pyramidal neurons in cortex have extensive dendritic trees, which in fact contain most of the membrane of the cells.

Dendrites participate in very old forms of cell-to-cell communication, which pre-date axon potentials. Suppose two cells want to communicate for the first time. Whereas hundreds of proteins are needed to form a chemical synapse between two cells, just one protein, connexin, must be expressed in the dendrite region of each cell in order to form a gap junction synapse, then information can be transferred from dendrite to dendrite (G.D. Pappas, 1972).

The tendency of neuroscientists to explain what is happening in the brain in terms of action potentials fired and received is due partly to work on the axon by Hodgkin and Huxley. Dendrites are often regarded as receiving stations for axons, or structural components of the cell that support axons. However, dendrites have primary sensory functions, for example, the dendrites of internal retinal ganglion cells are sites of phototransduction. Dendrites typically represent regions of excitable cell membrane, which initially served an important function in gathering sensory information.

“We thus find a type of response of excitable tissue occurring over a range from the protozoan slime mold to the mammalian cortex which in essential respects is distinct from the all-or-none response of nerve, and probably is the more primitive process.” (M.H. Clare, 1955)

Dendrites in spinal cord

Enormously long dendrites of motoneurons were first identified in the ventral spinal cord of reptiles and amphibians. Ramon y Cajal illustrated these dendrodendritic bundles in the ventral commissure of spinal cord (below).

From dendrites

The next figure shows a motoneuron dendrite bundle in the cat spinal cord. There are electrotonic synapses, or gap junctions, between motoneuron dendrites.

From dendrites

Electrophysiological demonstration of gap junctions between motoneuron dendrites occurred first in the spinal cord of toadfish (Pappas et al, 1966) and then the supramedullary neurons of Atlantic puffer fish (Bennett et al, 1967), although as early as 1948 Eccles and colleagues were onto subthreshold responses.

What do you mean by subthreshold responses?

Its actually quite easy to understand. When large currents are injected in motorneurons, the motoneurons show action potentials, as expected. However, when the current injection is small enough that it does not cause a full action potential, the cell still responds with small graded potentials (bottom traces of A and B, figure below). The graded potentials are referred to as subthreshold responses.

From gap junction development

A coupling coefficient of 0.13 was determined for gap junction transmission in toadfish motoneurons. These experiments showed that electronic coupling can take place between motoneurons; even if there is no spike, the areas of close apposition of dendrites give a graded response to current injection, and nearby neurons are somewhat "connected" in a way that doesn't rely on neurotransmitter release.

What is the function of dendrite bundles?

In early 1970s, Scheibel and Scheibel began to study dendrite bundles with the Golgi staining technique. Investigations in the ventral spinal cord of cat revealed dendrites of motoneuron pools innervating muscles of antagonistic function. In kittens, bundles are not present at birth but develop near the end of the second week, when kittens start using hind limbs for weight bearing and walking.

From dendrites

A gain in dendrite bundle thickness coincided with the kittens' use of coordinated limb movements, so the authors suggested that dendrite bundles may serve as reservoirs harboring central programs necessary to the inception of movement in the antigravity (weight-bearing) muscles of the lower extremities and back. At birth in kittens, motoneuron dendrites are poorly developed, and motor behavior is minimal, but at 12 days, lengthening of dendrites is apparent, and at 4-5 months, dendrite bundles are dense and well-developed, at which time the animals can make coordinated limb movements for jumping and running. It was also found that a loss in motor strength with aging was associated with a loss of dendritic bundles, and re-exertion of effort.

In addition to the spinal cord, bundled dendrites exist in the thalamus, cortex, hypothalamus, and reticular formation.

References

Pappas, G. D. and M.V. Bennett (1966). Specialized junctions involved in electrical transmission between neurons. Ann. N. Y. Acad. Sci. 137, 495-508.

Bennett, M. V., Y. Nakajima and G.D. Pappas (1967). Physiology and ultrastructure of electrotonic junctions. I. supramedullary neurons. J. Neurophysiol. 30, 161-179.

Scheibel M. E. and A. B. Scheibel. (1970). Developmental relationship between spinal motoneuron dendrite bundles and patterned activity in the hind limb of cats. Exp.Neurol. 29, 328-335. 10.1016/0014-4886(70)90062-2

Scheibel M. E. and A. B. Scheibel. (1971). Developmental relationship between spinal motoneuron dendrite bundles and patterned activity in the forelimb of cats. Exp.Neurol. 30, 367-373. 10.1016/S0014-4886(71)80015-8

Scheibel M. E. and A. B. Scheibel. (1973). Dendrite bundles in the ventral commissure of cat spinal cord. Exp.Neurol. 39, 482-488. 10.1016/0014-4886(73)90032-0

LD50, lethal dose 50

2009-11-11T08:35:00.000-08:00

Terrence McKenna explains the concept of LD50.

"We want to take an excursion here and learn a little pharmacology. If you're going to talk about pharmacology, there is one concept that you should get straight, and that's called LD50. It means "lethal dose 50". What does this mean? Well, you have 20 rats and you give them a certain amount of, let's say, mescaline. When half the rats die, that dose, expressed as milligrams per kilogram of body weight, is called the LD50. And when pharmacologists assess the danger in a drug, they ask the following question, "what is the relation of the LD50 to the effective dose?", and if the LD50 of a drug is only 20 times the effective dose, that's considered an incredibly toxic, dangerous, and dubious drug. A good drug is a drug where the LD50 is 200 times more than the effective dose. In the case of LSD, the LD50 for man has never been determined. That's how safe LSD is. We're talking about lethality here, not you know. So people say, "Well are there unsafe psychedelics?" Well, yes, you just look up the LD50s, line them up, and see which ones have the better ratios. By that measurement, by that standard, LSD is the most desirable. But the LD50 of psilocybin is very impressive. You can take 100 times the effective dose of psilocybin and expect to live. Mescaline, not. Mescaline has a bad profile. As an amphetamine, if you took 20 times the effective dose of mescaline, you would probably die. Of course, an effective dose of mescaline is nearly a gram of pure material, 700 milligrams. If you took 20 times 700 milligrams you would be taking nearly 2/3 of an ounce of mescaline..." (Terrence McKenna)

The LD50 of LSD varies from species to species. Rabbit is the most sensitive species known, with LD50 of 0.3 mg/kg i.v. The LD50 for rats is ten times higher at 16.5 mg/kg i.v. Mice tolerate 46-60 mg/kg i.v. LSD (Passie et al, 2008). An intraperitoneal dose of LSD 5.0 mg/kg reportedly caused death in a rat within 30-45 minutes and was associated with cardiac irregularities and general rigidity of musculature (Sylar et al, 1971). A too high dose of LSD typically causes animals to expire by paralysis, bradycardia, or respiratory failure; these effects probably involve centers in the caudal brain stem.

In an experiment with Macacus rhesus, one animal received 240 ug/kg and the other 140 ug/kg, which are enormous doses of LSD. In terms of a 70 kg person, the animals received 168 and 98 hits of LSD. These doses did not produce an excited behavior in monkeys as small doses do, but instead produced sedation. The monkeys became quiet and more sluggish around the cage, and did not jump about the cage as they did before. The monkeys lived.

Reference

Passie, T., J.H. Halpern, D.O. Stichtenoth, H.M. Emrich and A. Hintzen 2008. The pharmacology of lysergic acid diethylamide: A review. CNS Neurosci. Ther. 14, 295-314.

Sklar, S., K.A. Nieforth and M. Malone 1971. Synthesis and preliminary screening of N-ethyltryptamine derivatives related to reserpine and lysergic acid. J. Pharm. Sci. 60, 304-306.

Hydrophobic interactions 1. Meyer and Overton: Loss of consciousness by volatile gases depends upon molecular orbital parameters

2009-11-02T18:46:00.000-08:00

What distinguishes an anesthetic drug from an inert molecule?

Many inert drugs are soluble in water, whereas anesthetic drugs such as halothane, nitric oxide, and LSD are soluble in fats like olive oil. That's the main difference. Most inert molecules like sugars and amino acids cannot absorb to a van der Waals surface because they are too engaged in strong interactions with water. Most inert molecules are covered by a hydration shell.

One of the most remarkable discoveries of the century was made by Meyer and Overton, who related the effective dose of anesthetic gases to their lipid-water coefficient. They were the first to show a quantitative relationship between physicochemical and biological data in aliphatic systems. This research occurred before protein crystallography, and one idea that emerged from their discovery is that the hydrophobic properties of a drug (e.g. its lipid-water coefficient) are more fundamental for biological activity than a drug's steric properties.

In 1965, Agin and colleagues extended the work of Overton and Meyer, by showing that the biological activity of an anesthetic drug (to block electrical activity) depends on its molecular orbital parameters. A large group of structurally diverse anesthetic drugs were studied. For each drug, the researchers assayed the minimum blocking concentration (MBC) of electrical activity with experiments involving isolated muscle fibers of the frog, Rana pipiens. Ionization potential and polarizability were calculated with standard methods. Then they did correlations and found that over an 8-fold concentration range of activity, there was a close relationship between a drug's log(MBC) and the product of its polarizability and ionization potential.

From lipophilicity, log P

Agin and colleagues only studied local anesthetics that were considered neutral or possessed only small dipole moments, thus the major contribution to the energy of drug-tissue interaction is assumed to be from the drug's dispersion energy. The inescapable conclusion from their work is that the biological activity of local anaesthetic gases is related to dispersion energy.

References

Agin, D., L. Hersh and D. Holtzman 1965. The action of anesthetics on excitable membranes: A quantum-chemical analysis. Proc. Natl. Acad. Sci. U. S. A. 53, 952-958.

Microtubule inhibitors block sense of touch in cockroaches

2009-10-13T14:12:00.000-07:00

Microtubules are involved in the sense of touch, vision, and other senses. The cockroach's sense of touch is probably related to the organization of microtubules in its legs.

Mechanical stimulation is sensed by a cockroach through the spines (Campaniform sensilla) on its leg. There is a burst of spikes in the bipolar nerve cell (sensory neuron) associated with the spine, by pressing gently on the mechanoreceptor apparatus in the cockroach leg.

From Microtubules

Colchicine or vinblastine, drugs known to disassemble microtubules, are inferred to disrupt the sense of touch in a cockroach. From 1 to 2 hr after exposure of the leg spine to colchicine or vinblastine, electron microscopy showed no microtubules in the bipolar cell connected to the sensilla, and the typical burst of spikes produced by the tactile probe was replaced by neuronal silence after colchicine drug treatment.

Besides the physical evidence showing microtubule detachment from the basal body in the cockroach spine, there was a change in the electrophysiological response of the bipolar nerve cell after microtubule disruption. These experiments support the hypothesis that sense perception is related to the organization of microtubules in the dendrites of neurons. It is suggested that the proliferation of microtubules in sensory processes may serve to increase the gain of the cell membrane.

Reference

Moran D. T. and F. G. Varela. (1971). Microtubules and sensory transduction. Proc.Natl.Acad.Sci.U.S.A. 68, 757-760. 10.1073/pnas.68.4.757

Serotonin-binding protein and LSD

2009-07-24T10:25:00.000-07:00

Serotonin-binding protein

A ~50 kDa protein that binds serotonin was first identified in 1974. It was discovered by passing all of the soluble extracts of a cell over a 5-HT affinity column, and then eluting the column with 5-HT. The protein was stored with 5-HT to prevent degradation.

Serotonin-binding protein is expressed in enteric and central serotonergic neurons, including enterochromaffin cells, the nuclei raphe dorsalis, centralis superior, raphe medianus, raphe magnus, raphe obscurus, and raphe pallidus. Also, dense staining with antibodies to serotonin-binding protein was found in the supraependymal plexus lining the ventricular surfaces.

Serotonin-binding protein and LSD

In 1977, Shih and colleagues performed spectroscopic analysis of free LSD and LSD bound to serotonin-binding protein. Free LSD exhibited max fluorescence at 435 nm with excitation at 330 nm, while serotonin-binding-protein-bound-LSD shifted its fluorescence and excitation maximum to 465 nm and 375 nm. These results suggest that the interaction between LSD and serotonin-binding-protein caused a delocalization of the molecular orbital electrons and thereby lengthened the electronic conjugation of the drug molecule.

Figure 2 below shows the excitation (330 nm) and emission (435 nm) wavelengths of free LSD.

From lsd spectroscopy

Figure 3 shows the excitation (375 nm) and emission (465 nm) wavelengths for protein-bound-LSD.

From lsd spectroscopy

An increase in the absorption and emission wavelengths was also observed when bovine serum albumin (BSA) was mixed with LSD, as shown in Figure 4 below. Peak 1 is the fluorescence of BSA. Peak 2 is shifted towards longer wavelengths, and represents the BSA-LSD complex.

From lsd spectroscopy

Generally, a shift of the absorbance towards longer wavelengths can be accomplished by adding Sulfur, Nitrogen, or Oxygen to a molecule, which increases the number of loosely bound electrons. Serotonin-binding-protein and other proteins contains lone pairs of electrons from S, N, and O that can add to the pi-electron system of the LSD molecule, thus modifying its spectra absorbance.

References

Shih J. C. and J. Rho. (1977). The specific interaction between LSD and serotonin-binding protein. Res.Commun.Chem.Pathol.Pharmacol. 16, 637-647.

Qualia of blue

2009-06-13T04:56:00.000-07:00

What makes up the qualia of blue? Where does the meaning of blue actually lie? In the rays of blue light itself, or in your interpretation of blue? The fact that we perceive such "things" as blue light or macroscopic objects lying at distinct places is due, partly at least, to the structure of our sensory and intellectual equipment. Even if blue light were abundant in the universe, it would still require a human brain to decode the message of blue light. Whatever we see as "blue" is a construct of the brain, and blue may be merely an interpretation of otherwise white light. In Moby Dick, Melville wrote,

"Consider that the mystical cosmetic which produces every one of her hues, the great principle of light, for ever remains white or colorless in itself, and if operating without medium upon matter, would touch all objects, even tulips and roses, with its own blank tinge-" (H. Melville, 1851)

I love Melville's description of mind as "medium upon matter". Our access to the mystical cosmetic is largely mediated through our senses and other factors.

when kids accidentally ingested LSD

2009-06-04T16:31:00.000-07:00

There are reports of autistic or schizophrenic children who have taken LSD in a therapeutic setting, with variable effects. What happens when psychologically normal kids accidentally ingest LSD? Here are 3 anecdotal cases.

CASE 1

In 1966 on a Wednesday morning in April, a 5-year-old girl accidentally ingested 100 ug LSD on a sugar tablet in the refrigerator belonging to her 18-year-old uncle. Her name was Donna, but after the trip she substitutes Deborah for herself Donna, and thought that her body had been torn in half. The story told by the interviewing psychiatrist is very descriptive:

"Within an estimated 15 or 20 minutes the patient began to scream and cry, creating a commotion that awakened the household and alerted the uncle to the mishap. She was alternately screaming and silent. During her quiet periods she was motionless and unresponsive and apparently unaware of her surroundings. Physical examination about three hours after ingestion showed a screaming child with a temperature of 99 F (37 C), a pulse rate of 130 beats per minutes, 30 respirations per minutes, dilated pupils, and hyperreflexia. Treatment consisted of bed-rest and intravenous infusion of saline. Blood cell count and findings from examination of the urine were normal. The serum glutamic oxoloacetic transaminase value was elevated to 82 units and the alkaline phosphatase was elevated to 20.1 units."

"After four or five hours of hospitalization and intermittent napping, the patient became relatively calm, unfrightened, and responsive. At the same time she expressed many bizarre and apparently delusional ideas, such as that her body was cut off at the waist, that she was not herself but was a girl named Dorothy (a name similar to her own, Donna), that it was not she but Dorothy who had eaten supper, that she had gone home and her bed was occupied by a girl named Dorothy. The following morning, after an uneventful night's sleep, she seemed superficially responsive and rational. However, she still maintained that Donna had gone home during the night and that she was Dorothy and she wrote her name as Dorothy. In the course of the morning she became better oriented and began to recognize that she was Donna again."

"Psychiatric examination on the afternoon of April 7, about 30 hours after ingestion, showed a quiet, unreactive, apathetic girl. She responded promptly when questioned, and displayed an alertness that was in marked contrast to her prevailing apathetic mood. Her emotional range was very narrow and lacked normal modulation. Her verbalizations, although brief, were responsive and appropriate and she had a fairly good recollection of the events preceding hospitalization. In contrast to her condition of a few hours earlier, she was oriented and lucid. Her thinking was somewhat concrete. She was not able to express subjective feelings or experiences. It was inferred from her refusal to stand her complaint that her legs "hurt" that she was experiencing either paresthesias or a residuum of the preceding day's profound distortion of body image. She described a dream in which "they stole my mommy and tried to cut her in half" which seemed to be expressing the same distortion of body image or body perception." (D.H. Milman, 1967)

A psychiatric evaluation 5 days later showed that Donna was still abnormal and her IQ had dropped. At evaluation five months later, IQ levels had returned to normal, and the girl had returned completely to her typical behavior with flexible thinking processes. At the final examination nine months after the incident, the patient was in first grade and progressing well. She had a normal IQ, good concentration and cheerful mood with logical and appropriate thinking.

The substitution of her name for Dorothy provides an example of "depersonalization" after LSD, which generally refers to one not being oneself. The description of her body being torn in half suggests that she experienced a major alteration in body image.

CASE #2

A 25-month male infant ingested an estimated 200 ug LSD in the form of 2 purple microdots.

"At 10:30 AM on the day of admission the mother noted the onset of unusual behavior in her child: He appeared unsteady and stumbled, he was frightened and screamed while looking at a colored rug, at the ceiling, or upon seeing a housefly, and he frequently opened his eyes widely and covered his ears with his hands as if to block out unpleasant sounds. The mother recalled she had had two tablets of LSD, purple microdots, in her purse; she found the purse opened and both tablets missing. The child was taken to a local hospital where the family's physician noted that the child was in a state of "stark terror." He clung tightly to his mother, screaming at apparent visual hallucinations perceived on the walls of the examining room; he did not fix his gaze on persons or other objects." (B.M. Ianzito, 1972)

The child received an intramuscular injection of 10 mg chlorpromazine at 12:20 PM, one hour after which he had normal vital signs, was quiet, and fixed his gaze on objects for brief periods. Chlorpromazine seemed to be effective in the case of this 2-year old, although in other subjects chlorpromazine has reportedly intensify the LSD experience.

CASE #3

In 1973, a 23-month male infant admitted to hospital had ingested one LSD tablet 2 hr before admission. The child was very hysterical and hyperreactive. He was given 15 mL ipecac syrup to induce vomiting and he was given water, and a urine sample was collected for spectroscopy analysis. At 3 hours, the patient had calmed down and at 4 hours could recognize his mother. He was sent home from the hospital 2 days later in general good condition.

The dosages of LSD given to these 3 children were well above the adult threshold levels, and there was no indication of brain damage. Screaming and crying seemed to be a common reaction to LSD within the first 2 hours. There was a temperature increase to 99 F in the 5-year-old girl, consistent with an emotionally hyperactive state.

Reference

Ianzito B. M., B. Liskow and M. A. Stewart. (1972). Reaction to LSD in a two-year-old child. J.Pediatr. 80, 643-647. 10.1016/S0022-3476(72)80064-7

Milman D. H. (1967). An untoward reaction to accidental ingestion of LSD in a 5-year-old girl. JAMA. 201, 821-825. 10.1001/jama.201.11.821

Mueller R. G. and G. E. Lang. (1973). Fluorescent spectra of lysergic acid diethylamide: observations on a gastric extract. Am.J.Clin.Pathol. 60, 487-492.

LSD affects spinal cord activity in salamander

2009-05-24T09:58:00.000-07:00

The behavior of fish is altered in a characteristic way when LSD is dissolved in the tank water. Instead of swimming around the tank, the fish hold still at the surface of the water. Likewise, salamanders exhibit statue-like postures and slow movements when injected abdominally with 0.7-0.8 mg/g LSD.

From LSD salamander

A few minutes after the injection of LSD the electrical activity of both brain and spinal cord showed a brief drop in potential, followed by the appearance of a strong and sustained increase in potential, especially in the spinal cord, even though the salamander appeared quiet and motionless. During the peak of drug action the salamander assumes statue-like postures and the electrical activity of the spinal cord shows a sustained discharge of waves of high frequency and amplitude.

“Within 5 to 15 minutes after the injection of LSD-25 the salamander, when placed in water, shows disturbances of equilibrium during which the animal slowly writhes, comes to rest on its side, back, or belly, and assumes statue-like postures representing some stage in standing or walking. These floating postures are interrupted by slow movements of trunk or limbs as if the salamander were attempting to maintain its balance. The trunk and limbs are not limp, but have the firmness of soft wax, so that the animal allows itself to be moved passively, especially in water. During this phase of drug action, tactile stimuli applied to the tip of the tail are followed by ambiguous results, i.e. they may evoke a prompt escaping reaction as vigorous as that of an untreated animal, or a slow response delayed 5 to 10 seconds, or no response at all.” (J.J. Peters, 1956)

The EEG recorded from the brain electrode was somewhat unchanged by LSD, but the electrode over spinal cord showed much more high voltage activity compared to untreated salamander. This result seems to indicates a more powerful effect of the drug on electrical activity in the spinal cord rather than the brain.

From LSD salamander

The powerful mental effects of LSD have led many researchers to suspect that the mechanism of LSD is to affect firing of neurons of the brain, but in the case of salamander the electrical activity of spinal cord was specifically affected. It may be an important hypothesis to consider - that LSD does not necessarily affect neurons. For example, in the brain, LSD binds epithelial cells of choroid plexus cells the most, as compared to neuronal cells.

Reference

PETERS J. J. and A. R. VONDERAHE. (1956). Behavior of the salamander under the influence of LSD-25 and Frenquel, and accompanying electrical activity of brain and spinal cord. J.Nerv.Ment.Dis. 124, 69-73.

LSD dose

2009-05-23T07:47:00.000-07:00

The effective dose of LSD varies enormously among species. In salamander, the effective LSD dosage is 700,000 ug/kg. Intracranial injections of 300 ug/kg in goldfish produce the characteristic LSD fish surfacing reaction. In mouse the effective dose is 180 ug/kg of body weight. With LSD behavioral changes are discernible in rat at 80-160 ug/kg but in the cat at 25 ug/kg. A 20 ug/kg LSD affects pigeons' performance in learned discrimination tasks. In rabbit the effective dose is 15 ug/kg. In man, where we have the advantage of verbal reporting, the effective dose is less than 1 ug/kg. According to Albert Hofmann, the effective human dose of LSD is 0.5 ug/kg.

A flat dosage of 100 ug per person is used commonly in human LSD research. This dosage quantity is convenient to remember because it doesn't take body weight in kilograms into consideration. A dosage of 100 ug per person typically results in dramatic symptoms, but the threshold for activity generally is placed at 20 ug LSD per person.

Very low doses of LSD (4-40 ug per person) were tested in human volunteers by Greiner and colleagues in 1958. Psychic changes were established by way of interviews and measurement of pupil size, heart rate, and galvanic skin response. The data below showed that mood and psychomotor effects were detectable in human volunteers at dosages as low as 4 ug LSD per person, which is approximately 0.05 ug/kg of body weight, or 10 times less than the effective dose according to E. Rothlin and Hofmann. The objective measures showed that the galvanic skin response was activated after only 7 ug LSD per person. There was a dose-dependent increase in pupil size, heart rate, and other parameters.

From lsd dose

The researchers observed sudden shifts in affect in the volunteers after 4 ug, 7 ug, or 12 ug of LSD per person, but no significant changes in thought process or content. This data puts the threshold dose for LSD intoxication at about 20 ug per person.

LSD is one of the most potent drugs known to man. Whereas most drugs are administered at doses of tens or hundreds of milligrams, LSD is active at tens or hundreds of micrograms. The potency of LSD is best compared to other drugs on a log scale, as shown in Figure 1 below. It can be seen that the concentration of an active dose of alcohol is about a million times as great, expressed in terms of weight, as the concentration of LSD.

From lsd dose

Of course, the effective dose of LSD depends highly on the person, set, and setting. The dose threshold may be lower for people who are generally inexperienced with drugs, and higher for alcoholics and drug addicts.

“Familiarity with other drugs which produce psychological changes is also relevant. Alcoholics and drug addicts seem better able to cope with the LSD experience than normal subjects. I have had more difficulty with anxiety and panic in normal subjects than in patients who have had long experience with drugs.” (A. Hoffer, 1965)

Fasting or not can change the effective LSD dose too. Plasma concentrations of orally ingested LSD were twice as much on an empty stomach. The amount of the meal as well as the pH of the stomach will influence LSD absorption.

References

GREINER T., N. R. BURCH and R. EDELBERG. (1958). Psychopathology and psychophysiology of minimal LSD-25 dosage; a preliminary dosage-response spectrum. AMA Arch.Neurol.Psychiatry. 79, 208-210.

Passie T., J. H. Halpern, D. O. Stichtenoth, H. M. Emrich and A. Hintzen. (2008). The pharmacology of lysergic Acid diethylamide: a review. CNS Neurosci.Ther. 14, 295-314.

LSD charge-transfer complexes 3. LSD-riboflavin

2009-04-14T10:29:00.000-07:00

Hallucinogenic agents are probably electron donors in some key step involving a charge-transfer complex with a biological acceptor molecule entity. Previously I covered the topic of electrostatic and charge-transfer forces in LSD-TCNE and LSD-NAD+ small molecule complexes. This article will present studies on a LSD-riboflavin complex.

In 1958, Isenberg and Szent-Gyorgyi mixed LSD-25 with riboflavin-5'-phosphate and observed a red color at –78 C. They discovered that the riboflavin molecule had taken up one electron from LSD. LSD was functioning as an electron donor in the formation of riboflavin charge-transfer complexes; the transferred electron (e.g. to reduce riboflavin) comes from the pi-electron pool of the LSD indole system. In the same publication, the authors reported on tryptopan-riboflavin, 5-HT-riboflavin, and 1-methyl-medmain-riboflavin complexes, all of which led to the appearance of a red color at -78 C. The results are shown in Table 1 below.

From hallucinogens HOMO, charge-transfer

Histidine-riboflavin or tyrosine-riboflavin did not give a red color, indicating that no charge-transfer complex had been formed, and that histidine and tyrosine are inferior in electron-donating ability compared to drugs such as tryptophan and LSD. There were variations among the drugs which formed a charge-transfer complex with riboflavin. For example, the 5-HT-riboflavin complex was 7X stronger than the tryptophan-riboflavin complex indicating that serotonin was a better electron donor than tryptophan.

Some tissues such as liver have a great quantity of strongly bound riboflavin. The brown color of the liver can be attributed to the flavin radical formed in a charge-transfer interaction with liver protein. If liver tissue becomes cancerous, it takes on a different balance of reductive and oxidative processes and changes color.

References

Isenberg I. and A. Szent-Gyorgyi. (1958). FREE RADICAL FORMATION IN RIBOFLAVIN COMPLEXES. Proc.Natl.Acad.Sci.U.S.A. 44, 857-862. doi:10.1073/pnas.44.9.857

LSD charge-transfer complexes 2. LSD-NAD+

2009-04-13T09:17:00.000-07:00

The electron acceptor NAD+ forms a charge-transfer complex with LSD, in which an electron is transferred from the highest occupied molecular orbital (HOMO) of the LSD pi system to the lowest empty molecular orbital of NAD+.

The charge-transfer process is accompanied by the appearance of a new absorption band. In 1967, Fulton and colleagues studied the wavelength of the absorption maximum of NAD+ charge-transfer complexes.

“We have shown that NAD+ of concentration 1.03E-2M, when mixed with fairly strong electron donors, such as substituted pteridines, uric acid, serotonin creatine sulphate, lysergic acid, and phenothiazines, gave solutions which were coloured yellow to orange because of the formation of charge-transfer complexes." (A. Fulton, 1967)

Some of the electron donor molecules studied were LSD, indole, uric acid, promazine, and promethazine, and different absorption maximums were obtained for each donor-NAD+ complex as shown in Table 1 below. Also the researchers measured the ionization potential energies of the electron donors, and found that LSD had an ionization potential of 7.8 electron Volts, indole (7.9), uric acid (7.5), promazine (7.2), promethazine (7.2), and chlorpromazine (7.3).

From hallucinogens HOMO, charge-transfer

The authors found that the absorption maximum of the charge-transfer complex correlated reasonably with the ionization potential of the electron donor drug, but not so well with the energies of the HOMO, perhaps because there are many approximations involved in the theoretical studies of the HOMO energy. However other groups have found a correlation between the absorption maximum and kHOMO energies.

As listed in Table 1 above, the LSD-NAD+ charge-transfer complex had an absorption maximum at 340 nm, which is the absorption maximum of the native LSD molecule. This compares to the 520 nm absorption maximum that is characteristic of LSD-TCNE or LSD-Ehrlich complexes.

References

Fulton A. and L. E. Lyons. (1967). Electron-accepting strength of NAD+. Aust.J.Chem. 20, 2267-2268.

LSD charge-transfer complexes 1. LSD-tetracyanoethylene

2009-04-12T18:49:00.000-07:00

The electron donor molecule LSD forms a charge-transfer complex with the electron acceptor tetracyanoethylene (TCNE). The charge-transfer complex has a characteristic absorption band, allowing the detection of the presence of LSD. When LSD or other hallucinogen drugs are applied to a silica gel plate and then sprayed with either TCNE or electron acceptor drugs, a color band is detected.

In 1968, Millie and colleagues studied the electronic properties of methoxylated indoles and tryptamines by their ability to form charge-transfer complexes with TCNE or 1,3,5-trinitrobenzene (TNB), another electron acceptor. Many indoles and phenothiazines form a charge-transfer complex with TCNE or TNB; the wavelength of the absorption maximum of the complex is often between 300-720 nm. As shown in the figure below, the authors found a correlation between the absorption maximum of the acceptor-TCNE or acceptor-TNB complexes and kHOMO values of the electron donors (i.e. indoles or tryptamines). The y-axis is 1000/lambda, where lambda is the maximum absorption wavelength of the charge-transfer reaction product.

From hallucinogens HOMO, charge-transfer

1-methyl-LSD was among the indoles and phenothiazines that were tested. The charge-transfer complex of TCNE and 1-methyl-LSD (letter p, Figure 1 above) had an absorption maximum at 520 nm. As determined by Huckel calculations, 1-methyl-LSD had kHOMO=0.487. This kHOMO value is slightly larger than Karreman's 1959 report of Ehomo=0.218 for LSD, suggesting slightly less electron donating ability. According to the figure above, the electron-donating ability of 1-methyl-LSD (p) lies between 4-methoxy-indole (i) and 5-methoxy-indole (k). I don't know why Millie and colleagues choose to study 1-methyl-LSD, which has one tenth the potency of LSD, instead of LSD.

TCNE-bezene complexes are used to study the electron-donating properties of different benzene derivatives

The ionization potential of an electron donor molecule can predict the rate of formation of its drug-TCNE complex. This was shown by Domelsmith in 1977. Several different benzene derivatives were mixed with the electron acceptor TCNE, and the rate of formation of benzene-TCNE complexes was measured. When the apparent enthalpy of formation of the benzene-TCNE complexes was plotted versus the average of the first and second ionization potential energies of the benzene molecules, as shown in Figure 12 below, an excellent linear correlation was obtained.

There is no mystery about the physical and chemical forces that bind a hallucinogen drug to biological receptors. The forces may be compared with the physical and chemical forces that bind TCNE to benzene or indoles. Charge-transfer forces predict the extent of drug binding to biological receptors, and the extent of behavior disarrangement produced by mescaline or LSD is correlated with the kHOMO, showing a direct role of charge-transfer forces on the extent of consciousness alteration.

Quantum mechanics is the method used to calculate the kHOMO energy. The dose of structurally diverse hallucinogens to produce consciousness alteration is correlated with the drug's kHOMO value, so it is very likely that quantum electronic properties of matter play a role in the mechanism of consciousness alteration.

References

Domelsmith, L. N., L.L. Munchausen and K.N. Houk (1977). Photoelectron spectra of psychotropic drugs. 1. phenethylamines, tryptamines, and LSD. J. Am. Chem. Soc. 99, 4311-4321.

Fulton A. and L. E. Lyons. (1967). Electron-accepting strength of NAD+. Aust. J. Chem. 20, 2267-2268.

Millie P., J. P. Malrieu, J. Benaim, J. Y. Lallemand and M. Julia. (1968). Researches in the indole series. XX. Quantum mechanical calculations and charge-transfer complexes of substituted indoles. J. Med. Chem. 11, 207-211. 10.1021/jm00308a003

LSD absorption and fluorescence

2009-03-05T10:07:00.000-08:00

The LSD molecule contains a number of pi-electrons. These pi-electrons absorb electromagnetic radiation very strongly, like many aromatic or conjugated systems. LSD absorption is maximal at 320 nm, and LSD fluorescence is maximal at 435 nm. These values are somewhat flexible depending on the spectrophotometer, with some authors reporting LSD absorption at 325 nm, and LSD fluorescence at 445 nm. The spectroscopic properties of radioactive [3H]-LSD are the same as LSD, with a maximum fluorescence at 445 nm, and an excitation wavelength of 325 nm. For LSD spotted onto chromatography plates, maximum excitation occurs at 330 nm, and emission at 410 nm. Spots of LSD on thin-layer chromatography plates give a violet-blue fluorescence under a UV lamp.

From lsd spectroscopy

Muller and Lang carefully studied the absorption and fluorescence of LSD as a function of pH. As shown in Figure 1 above, there is a minor excitation peak at 240-250 nm in addition to the major excitation peak of LSD at 330 nm. The major excitation peak of LSD could be shifted by placing the LSD sample in either acid or alkali conditions. The major LSD excitation peak was 327 nm in 0.01 N HCl and 319 nm in 0.05 M Na2HPO4. In basic solution, the 319 nm peak was approximately 25% greater in amplitude than the height of 327 nm in HCl. Major emission peaks of LSD were at 420-430 nm, with a shoulder at 536 nm.

In 1971, in situ fluorometry was performed on LSD using quinine as an internal reference. As seen in the figure below, quinine (A2, B2) and LSD (A1, B1) have the same excitation and fluorescence wavelengths.

From lsd spectroscopy

LSD fluorescence can be used to check its potency. Niwaguchi and colleagues found a linear relationship between fluorescence emission intensity and the amount of LSD on thin-layer chromatograms. If the 9,10 double bond of the D-ring is intact, blue fluorescence is observed under UV lamp.

Since the fluorescence emission intensity is proportional to the amount of LSD, the concentration of an unknown LSD solution can be measured in a Farrand or Bowman spectrophotometer. After blanking with water at 300 nm, solutions of LSD are scanned with 350 to 250 nm light, and the maximum absorbance, which occurs at approximately 330 nm, is compared to a standard solution of LSD. As little as 0.001 microgram of LSD, or 1/100,000 of a dose, can be analyzed this way, thus LSD detected by spectroscopic methods has better sensitivity than LSD detection by coloration with Van Urk reagent.

LSD is among the most fluorescent substances known. LSD is more strongly fluorescent than NN-DMT, diethyltryptamine, psilocybin, or mescaline. For comparison, DMT absorbs at 280 nm, and fluoresces at 350 nm. Psilocybin absorbs at 270 nm and fluoresces at 340 nm.

LSD decomposition

It has been reported that LSD loses its fluorescence very rapidly upon strong ultraviolet irradiation, as shown in the decomposition curves below. After just 5 seconds of irradiation at 320 nm, the LSD fluorescence reading was significantly diminished.

From lsd spectroscopy

If UV irradiation was continued for 15 to 60 minutes, a significant amount of decomposition of LSD was shown by paper chromatography. Only 10% of LSD remained after 60 min UV irradiation while in the control experiment 90% of LSD remained after 17 h standing in the dark.

From lsd spectroscopy

A decrease in LSD fluorescence with irradiation occurs when UV light catalyzes the hydration of LSD to a non-fluorescent derivative. A molecule of water is added across the C9-C10 double bond of LSD to produce the non-fluorescent lumi-derivative. In 1972, Upshall and colleagues described an easy-to-follow procedure for analyzing LSD in human plasma, by measuring the difference in fluorescence (318 nm excitation, 413 nm fluorescence) of plasma extracts before and after intense UV irradiation (at 254 nm). This analytical method (detection of change) is greatly preferable to a direct reading of UV fluorescence in plasma, since the plasma blank reading has sufficient enough magnitude to seriously interfere with the determination of LSD. Upshall determined an average of 1-10 ng LSD per 1 mL human plasma.

From lsd spectroscopy

Upshall's analytical method is superior to spectroscopic techniques that are based on one measurement of LSD fluorescence, because contents of plasma can obscure the native fluorescence of the LSD molecule. When Aghajanian and colleagues measured LSD concentrations in human plasma in 1964, they found a concentration which corresponded to a level of LSD in the plasma that was higher than expected based on a known injection amount. In this case, the contents of plasma may have added to the native fluorescence of the LSD molecule because the researchers obtained a value of 6-7 ng/mL plasma, about 10X higher than expected. The difference in fluorescence of plasma extracts before and after intense UV irradiation is the best way to a measure LSD concentrations in human plasma.

References

AGHAJANIAN G. K. and O. H. BING. (1964). Persistence of Lysergic Acid Diethylamide in the Plasma of Human Subjects. Clin.Pharmacol.Ther. 5, 611-614.

AXELROD J., R. O. BRADY, B. WITKOP and E. V. EVARTS. (1956). Metabolism of lysergic acid diethylamide. Nature. 178, 143-144. 10.1038/178143a0

BOYD E. S. (1958). The fluorometric determination of lysergic acid diethylamide and ergonovine. Arch.Int.Pharmacodyn.Ther. 115, 43-51.

Niwaguchi T. and T. Inoue. (1971). Studies on quantitative in situ fluorometry of lysergic acid diethylamide (LSD) on thin-layer chromatograms. J.Chromatogr. 59, 127-133. 10.1016/S0021-9673(01)80012-1

Sperling A. (1972). Analysis of hallucinogenic drugs. J.Chromatogr.Sci. 10, 268-275.

Upshall D. G. and D. G. Wailling. (1972). The determination of LSD in human plasma following oral administration. Clin.Chim.Acta. 36, 67-73.

Theoretical studies of the LSD HOMO energy

2009-02-07T11:16:00.000-08:00

The highest occupied molecular orbital (HOMO) energies of hallucinogens have been thoroughly investigated, experimentally as well as theoretically. There is a direct relationship between molecular orbital parameters and hallucinogenicity. It is well-known that hallucinogen dose is correlated with the affinity to 5-HT receptors, but within this index are other relationships more directly related, in this case, the HOMO energy of the hallucinogen molecule. Receptor affinities reflect the likelihood of formation of a charge-transfer complex between drug and receptor, and these charge-transfer energies are directly related to the HOMO energy of electron donor molecules, or in this case, hallucinogen molecules. Other factors such as hydrophobicity and steric factors are incorporated within the index of receptor binding as well, but some minimum level of HOMO energy is necessary for hallucinogenic activity. Here is a chronological review of the research on HOMO energies of hallucinogen molecules.

In 1965, Snyder and colleagues calculated the HOMO energies of several hallucinogens using the Huckel method. Table 4 below lists the HOMO energy for LSD, psilocin, and TMA-2. The authors used the value (HOMO=0.218) obtained by Karreman and Szent-Gyorgyi for the LSD HOMO energy.

From hallucinogens HOMO LEMO

Psilocin, LSD, TMA-2, and TMA had a more energetic HOMO compared to the non-hallucinogenic drugs tyramine, dopamine, and phenyethylamine. Snyder and colleagues concluded that there is a relationship between hallucinogenic activity and the ability to donate electrons, as indicated by the energy of the HOMOs.

In 1968, Millie and colleagues investigated the HOMO energy of 1-methyl-LSD. They report Ehomo=0.487 for 1-methyl-LSD, thus placing 1-methyl-LSD somewhere in between 4-methoxy-indole and 5-methoxy-indole in terms of its electron donor ability. To my knowledge, Millie, Kang and Green, and Karreman and Szent-Gyorgyi are the only authors that have calculated the Ehomo for LSD-type molecules.

In 1970, Kang and Green calculated the HOMO energy of 13 psychotomimetic amphetamines, using the INDO (intermediate neglect of differential overlap) method, which is superior to the Huckel method. Table I lists the HOMO energy, Eh, of the hallucinogenic amphetamines. The most potent drugs had a smaller Eh value. There was a linear correlation between Eh and hallucinogenic activity in man.

From hallucinogens HOMO LEMO

Kang and Green also reported the Ehomo value for N,N-DMT and LSD, in Table 1 (below).

From hallucinogens HOMO, charge-transfer

In Kang and Green's research, the compound 4-hydroxy-N,N-DMT (psilocin, Eh=-0.4493) was predicted to be more potent than LSD (Eh=-0.4745) going by Eh value alone, but overall, these authors were successful at correlating the actions of hallucinogens agents with Huckel molecular orbital calculations.

In 1971, Nieforth wrote a review about HOMO energy and hallucinogens, which copied Snyder's 1965 data.

From hallucinogens HOMO LEMO

Nieforth concluded that electronic energy parameters were not the only factor involved in the biological activity of hallucinogens, since other compounds such as chlorpromazine are powerful electron donors and do not possess hallucinogenic activity. (5)

By 1979, another review on hallucinogen HOMO energies appeared, which reproduced Snyder's 1965 data yet again.

From hallucinogens HOMO LEMO

Gupta verified the conclusion that there is a highly significant correlation between Ehomo and hallucinogenic activity, but he suggested that a charge-transfer phenomenon may not be the only factor responsible for the biological activity of the drugs. According to Gupta, the theory of charge-transfer formation does not fully explain drug potency in the case of anesthetic drugs.

By 1987, another review summarized the charge-transfer complexes of receptors with hallucinogens.

“In hallucinogens the electron transfer is considered to be an outer-sphere, charge-transfer process. An overall electrostatic interaction with the receptor is envisioned as a result of the charge transfer from the aromatic portion of hallucinogens to their putative receptors. .. The hallucinogenic activity of phenyl alkyl amines, indole alkl amines, and LSD was first linked to the electron transfer ability of these drugs almost three decades ago. Huckel molecular orbital calculations of a series of hallucinogenic drugs and their nonhallucinogenic structural analogues indicated the close relationship between the HOMO energy, an index of electron-donating ability, and the hallucinogenic potency. Based on these results, an electron donation model of interaction between hallucinogenic drugs and their putative receptors was proposed. Later, a series of more sophisticated molecular orbital calculations confirmed the trends initially observed with the simple Huckel method. The HOMO energies of hallucinogens were also assessed experimentally, via measurements of ionization potentials and charge-transfer capabilities of these drugs. A good agreement was obtained between the calculated and the experimentally-deduced HOMO energies.” (Kolb,V.M., 1987)

The HOMO energy, which is an index of electron-donating ability of a molecule, has been studied because of its relation to the threshold dose of hallucinogen drugs. The HOMO energy reflects the compounds’ ability to donate electrons in a charge-transfer type of interaction, thus molecular orbital calculations of hallucinogen molecules support a charge-transfer mechanism of action of hallucinogenic drugs.

References

1. Snyder S. H. and C. R. Merril. (1965). A relationship between the hallucinogenic activity of drugs and their electronic configuration. Proc.Natl.Acad.Sci.U.S.A. 54, 258-266. doi:10.1073/pnas.54.1.258

2. Millie P., J. P. Malrieu, J. Benaim, J. Y. Lallemand and M. Julia. (1968). Researches in the indole series. XX. Quantum mechanical calculations and charge-transfer complexes of substituted indoles. J.Med.Chem. 11, 207-211. doi:10.1021/jm00308a003

3. Kang S. and J. P. Green. (1970). Steric and electronic relationships among some hallucinogenic compounds. Proc.Natl.Acad.Sci.U.S.A. 67, 62-67. doi:10.1073/pnas.67.1.62

4. Kang S. and J. P. Green. (1970). Correlation between activity and electronic state of hallucinogenic amphetamines. Nature. 226, 645.

5. Nieforth K. A. (1971). Psychotomimetic phenethylamines. J.Pharm.Sci. 60, 655-665. doi:10.1002/jps.2600600502

6. Kolb V. M. (1987). Electron-transfer and charge-transfer clastic binding hypotheses for drug-receptor interactions. Pharm.Res. 4, 450-456. doi:10.1023/A:1016415202819

Indole charge-transfer complexes

2009-02-04T09:31:00.000-08:00

What is a charge-transfer complex? It is an assembly consisting of an electron donor and electron acceptor molecule. The electron donor possesses a weakly bound electron or pair of electrons, and the electron acceptor has vacant orbitals. Electrons may come to be shared between the acceptor and donor, where they were not shared before. When a single electron participates in the transfer, the transferred electron goes from the highest filled orbital of the donor to the lowest empty orbital of the acceptor. The resulting charge-transfer complex can be a strikingly different color than the reagents.

5-HT is an exceptional electron donor. It tends to have the effect of shifting the outer shell electrons from one molecule to another, thus 5-HT has the propensity to form donor-acceptor complexes with electron acceptors such as picric acid. In the formation of serotonin-picrate crystals, serotonin is the donor molecule and picrate is the electron acceptor. A red-colored charge-transfer complex is formed when serotonin is added to picric acid.

The geometry of charge-transfer electronic transitions has been studied with crystal structures of serotonin-picrate. In serotonin-picrate crystals, the nitro groups of picric acid interact with C2 and C3 of the indole ring, suggesting that the nitro group of the electron acceptor associates with the pi electron cloud of 5-HT.

"It is significant that the observed geometry is such that charge-transfer electronic transitions apparently can occur and impart color to the [red serotonin picrate] crystals." (C.E. Bugg, 1970)

Indoles in general form charge-transfer complexes. The exceptional electron-donating ability of the indole nucleus is related to a high-lying pi electron on the carbon atom at position-3 of the indole donor. Serotonin, tryptophan, aminotryptophan, and methoxytryptophan all function as electron donor molecules in the formation of charge-transfer complexes. These indole donors can pair with electron acceptor molecules of biological importance, such as riboflavin, nicotinamide, or DPN.

Tryptophan is an indole derivative, and it is a better electron donor than most aromatic amino acids, thus proteins are known to participate in charge-transfer reactions via their tryptophan residues. When tryptophan is mixed with riboflavin, and cooled to -78 C, a strong red color is observed. Tryptophan also forms a visible charge-transfer complex with electron acceptors DPN+ or TPN+. At the temperature of dry ice, tryptophan-DPN+ and tryptophan-TPN+ complexes had a yellow color, with strong absorption in the region of 400 nm.

Overall, serotonin is a better electron donor than tryptophan. This has been shown theoretically by calculating the kHOMO energy of 5-HT and tryptophan, and experimentally by mixing 5-HT or tryptophan with the same electron acceptor, riboflavin. 5-HT and tryptophan both form charge-transfer complexes with riboflavin but serotonin complexes much more strongly, thus it has been verified that serotonin is a better electron donor than tryptophan. The physiological properties of 5-HT might be related to the exceptional electron donor capabilities of the hydroxyindole moiety.

Coming to the present topic, LSD is an extremely good electron donor with kHOMO=0.218-0.487, which has been shown to form charge-transfer complexes with small molecules such as riboflavin, TCNE, and dimethylaminobenzaldehyde. Also, LSD forms charge-transfer complexes with electron acceptor macromolecules, such as wool protein, dopamine receptors, and 5-HT2A receptors. It has long been suspected that psychoactive drugs, including chlorpromazine and phenothiazine derivatives, function as electron donors in a key step involving charge-transfer interactions. Drugs may donate or accept electrons, disrupting the normal pathway for electron transport and thus interfering with oxidation-reduction processes such as the respiration chain.

References

Bugg C. E. and U. Thewalt. (1970). Crystal structure of serotonin picrate, a donor-acceptor complex. Science. 170, 852-854. 10.1126/science.170.3960.852

Isenberg I. and A. Szent-Gyorgyi. (1959). On Charge Transfer Complexes between Substances of Biochemical Interest. Proc.Natl.Acad.Sci.U.S.A. 45, 1229-1231. 10.1073/pnas.45.8.1229

SZENT-GYORGYI A., I. ISENBERG and J. McLAUGHLIN. (1961). Local and pi-pi interactions in charge transfer. Proc.Natl.Acad.Sci.U.S.A. 47, 1089-1094. 10.1073/pnas.47.8.1089

LSD in psychotherapy

2009-01-16T07:40:00.000-08:00

excepts from The use of LSD in psychotherapy. Transactions of a conference on d-lysergic acid diethylamide (LSD-25).

"We have not been as interested in studying the drug itself as in studying people, and LSD is an interesting approach to this. It produces some dramatic changes in homeostatic mechanisms, psychologically, physiologically, and biochemically." (Klee)

"The striking feature of the Conference so far is that we have not communicated. The verbal image that was good for one of us was not good for eight-tenths of the others. This has happened again and again in this Conference, and is perhaps one of the most worth-while things which has happened to us, if we see that we really aren't yet able to communicate really adequately with each other about the problems under discussion. We really aren't successful in communicating; we mesh only occasionally. Every once in a while, two people agree, and there is a flash of communication between them." (Fremont-Smith)

"I am a research psychiatry in the Department of Psychiatry at UCLA and direct an alcoholism research clinic, so I am naturally interested in finding a therapy, chemical or otherwise, which will advance the understanding and treatment of alcoholism." (Ditman)

"LSD had just become familiar to most of us, and we used it at first to produce a model of schizophrenia. Within 1 or 2 years, we found that LSD was more than just a psychotomimetic, and so we began to experiment with what we called the "psychodelic" properties of LSD, that is, its utility in changing personality for the better, and for therapeutic purposes. .. In particular, we began to study a group of very difficult psychopathic alcoholics. We have now treated sixty of them, and half are no longer alcoholic after one treatment; so we do see that this drug has great potential for changing people."

"This meeting is most valuable because it allows us to see all at once results ranging from the nihilistic conclusions of some to the evangelical ones of others. Because the results are so much influenced by the personality, aims, and expectations of the therapist, and by the setting, only such a meeting as this could provide us with such a variety of personalities and settings. We thus have access to a rich amount of as yet unpublished data. We still lack adequate controlled studies, but I think that these studies may not be long in coming. It seems clear, first of all, that where there is no therapeutic intent, there is no therapeutic result. At the National Institutes of Health, we studied many volunteers. A large number of them had personal problems, but it did not appear that any of them benefited from the LSD experience. Two factors opposed such benefit. Their religion was essentially a rigid, controlling one. Secondly, there was no therapeutic intent. We told them we were studying a drug to help us understand mental illness. The setting, then, did not permit them to integrate, utilize, or incorporate their experience. What, for example, could the young man do who had hallucinations of naked women, which offended his sense of religious propriety? He could only pray not to see them again. What could the girl do who discovered new and tremendous reservoirs of hostility to her mother, which for her violated the Fifth Commandment? They could only fight off, dissociate, or deny their experiences. On the contrary, the volunteers at the Palo Alto Mental Research Institute, who are more sophisticated psychologically, are instructed that they can have a rewarding and esthetic experience, and many of them do report that it has been helpful to them... I think we can also say that where the atmosphere is fear-ridden and skeptical, the results are generally not good. Finally, with some patients such as chronic schizophrenics, the LSD experience seems of no use, no matter how therapeutic the setting. This is all of tremendous significance, for few drugs are so dependent on the milieu and require such careful attention to it as LSD does. This is not to discount the influence of the drug, but to show how greatly the reaction is shaped by the setting." (C. Savage)

"There are a variety of ways of viewing the therapeutic action of the drug: First of all is the euphoria. In the words of a patient of an earlier day, who suffered from feelings of depersonalization and was treated with mescaline: "I have seen what it is like to be well again." With some of the clouds of depression, apathy, and depersonalization lifted by the LSD, the patient then has new hope of regaining his former state of well-being. I think it is easier to produce the euphoria in a group setting with a maximum of two patients. However, the patients can use the euphoria, the laughter, and the ironic wisecracks as a means of avoiding coming to grips with some of the deeper layers of experience. Second, there is the increased rapport. The patient, relieved of his inhibitions, is freer to enter into communication with the therapist. With this, there is the increased transference, not only in the sense of rapport and dependence, but of actually seeing the therapist as a figure from the past. This, of course, may result in transference cures. It may also make more difficult the resolution of the transference, where this is necessary, as in psychoanalytic therapy. The third effect is the increased perceptivity and sensitivity. Not only can the patient discover new things about himself and his surroundings, but this can also lead to a new and improved relationship between him and the rest of the world, including the therapist. With this, comes a willingness to surrender defences and the barriers between oneself and the outer world, between oneself and one's unconscious. This may lead to the development of considerable insight." (C. Savage)

"But it would seem that the facilitation of psychotherapy is in itself no great boon to mankind. Mood improvement, increased rapport, transference, insight, recall, and the breaking down of defences can all be achieved by doing better or more skillful psychotherapy. Furthermore, such facilitation of therapy under LSD may be quite temporary. I have seen two cases of compulsive characters who, having obtained insight under LSD into their compulsive hoarding, have thrown out great masses of accumulated trash and papers, only to retrieve them from the waste basket a few days later, as they reverted to their former selves. What I consider more important is the therapeutic effect of LSD itself. By that, I mean the use of LSD in a therapeutic setting, such as described by Dr. van Rhijn, with no active psychotherapeutic intervention. It seems to me that here LSD may be of the greatest value. I would feel that there are three bases for the beneficial results such as Dr. van Rhijn has described. First, there is the more accurate perception and reconstruction of the past. Often, the patient's experiences have embittered him and filled him with such hate that he cannot remember the good in anything that happened to him. LSD softens the hatred and allows the more pleasant aspects of memories to unfold. I recall one alcoholic patient watching a painting of the ocean. She reported she could hear the waves and see the surf, and that she and her husband were strolling hand in hand on the beach together. She had forgotten that once they had been happy. As she watched this scene, I could almost see the bitterness and hardness in her face melting away. Another person, looking at a picture of his mother, came to understand her and see her as someone with problems, who did her best. He was then able to be at peace with his mother." (C. savage)

"There is also the more accurate perception of the self, such as occurred in Dr. van Rhijn's patient, who saw himself as an vomited-up herring lying in the gutter. But such new self-perceptions are of little value, leading only to depression, unless they are accompanied by a constructive experience, whether we call it transcendental or spiritual rebirth. One of our patients felt herself brought before God, tried, condemned, and dragged away in chains to be executed. Awakening and finding herself alive, she felt that she had had a reprieve, a chance for a new beginning. It was not enough that she see herself as an unregenerate sinner (alcohol has frequently brought such insight). She also had to have hope of redemption. This experience occurred without any props or therapeutic intervention, except for my presence, the presence of another patient, and the music of a Dixieland jazz band. Nor was it necessary that she relate it to us, except to validate it afterwards." (C. savage)

Reference

Abramson, H. A., Ed. The use of LSD in psychotherapy. Transactions of a conference on d-lysergic acid diethylamide (LSD-25). Madison Printing Company: Madison, N.J., 1959.

Ergotamine mysteries

2009-01-14T06:19:00.000-08:00

LSD is related to ergotamine. There are many unsolved mysteries related to ergotamine chemistry.

Two and a half millennia ago, Grecians celebrated Demeter by drinking kykeon, a drink made from fermented barley water. This special drink contained ergotamine and caused in participants intensive psychic changes, which cleared their souls, and made them accept death not so much as harm as a blessing, as one of the ancient diarists reported. Kykeon was consumed on a 14 mile walk from Athens to Eleusis, which culminated in a mysterious all-night ceremony. The site of Eleusis was burned by a Christian barbarian, according to Terrence McKenna.

Ergot is the name given to the dark-colored fungus growing on pods of rye (below). It is a horn-shaped growth that is typically in the neighborhood of 10 to 15 mm long, and can reach diameters of about 5 mm. The ergot consists of tightly interwoven hyphae of fungus. The ergotamine-containing fungus is named Claviceps purpurea.

From LSD research

Breads made from contaminated grains may have led to bizarre events in history such as the Salem Witch Trials in 1692. Around 1830, in rural areas of Germany, the scientist Karl von Reichenbach built a special conservatory for studying "sensitive" individuals, and he refracted moonbeams into the room for their amusement. Presumably, von Reichenbach's "sensitives" were patients who had consumed ergotamine from contaminated bread crops.

LSD exhibits a low transport number in glass pipettes

2009-01-05T13:13:00.000-08:00

The ionotophoretic method for the application of drugs from micropipettes is important for the good spatial and temporal resolution which it offers. With ionotophoretic methods, drugs can be applied to single neurons in a specific area of the brain. Ionotophoretic experiments significantly change the natural chemical environment of a neuron, yet the effects of drugs on neuron spiking are frequently assessed with ionotophoresis.

A iontophoretic pipette is a thin metal wire in a glass cylinder, that is filled with a solution of drug. A "retaining" current is passed through the micropipette via the wire to suppress the spontaneous release of drug. A large retaining current will greatly depress the release of drug from the pipette tip, although no value of retaining current will prevent completely the diffusional efflux of drug from the ionotophoretic pipette. When the pipette is in place and the experimenter is ready to release the drug, an "ejection" current is applied. This stimulus is applied as a brief current pulse, not a steady current. There is a theoretical relationship between the ejection current and release of drug ions. The drug solution will be expelled from the tip of the pipette, depending on the amount of current passed and the drug's "transport number," which is the ratio of drug released to charge passed.

LSD has an exceptionally low transport number (t=0.02) for a chemical substance, thus very long periods of iontophoresis must be used for LSD. Most of the LSD molecules tend to stay in the pipette, even with large ejection currents. In comparison, acetylcholine and 5-HT have high transport numbers (t=0.2-0.4), and require short bursts of current to be released from the pipette.

When dealing with iontophoretic release of drugs from pipettes, we usually want to know the amount of drug released, but the value known with confidence is the ejection current. To calculate the transport number of each drug, the electrophysiologist must use pipettes that are filled with a radioactive isotope of the drug, and different ejection currents. Then, the electrical charge (ucoulomb) in the pipette is plotted versus iontophoretic release (pmol) of [3H]-LSD, as shown in the figure below. LSD-25 release from pipettes was directly proportional to the charge passed through the pipette. The transport number of LSD was obtained from this data by multiplying the slope (expressed in mol/coulomb) by Faraday's number.

From lsd transport number

In 1974, Haigler and colleagues reported that the transport number of LSD (0.0023) was much smaller than 5-HT (0.219). According to these researchers, 100 nA of ejection current of LSD would be equivalent to 1 nA ejection current of 5-HT in terms of the number of drug molecules ejected.

“since equal currents of both agents inhibit the raphe, LSD emerges as being more potent than 5-HT, molecule for molecule, on the raphe neurons." (H.J. Haigler, 1974)

Some researchers found it difficult to pass current through LSD-containing glass electrodes.

“It was often impossible to pass current through barrels containing 2% LSD 25 solution for long periods. Longer applications of LSD 25 from a 0.5% solution had a depressant action on 22 out of 35 neurons tested.” (Boakes,R.J., 1970)

Chlorpromazine and Levallorphan, a drug similar to naloxone, have low transport numbers too. The transport numbers of chlorpromazine and Levallorphan are 0.0858 and 0.0737.

A molecule's transport number is easy to measure, and it gives information about the electronic properties of a drug. There was more similarity between chlorpromazine and LSD than LSD and 5-HT. The similarity of physical properties of chlorpromazine and LSD may be due to more conjugation of the rings compared to 5-HT molecules.

Reference

Boakes R. J., P. B. Bradley, I. Briggs and A. Dray. (1970). Antagonism of 5-hydroxytryptamine by LSD 25 in the central nervous system: a possible neuronal basis for the actions of LSD 25. Br.J.Pharmacol. 40, 202-218.

Bradley P. B. and J. M. Candy. (1970). Iontophoretic release of acetylcholine, noradrenaline, 5-hydroxytryptamine and D-lysergic acid diethylamide from micropipettes. Br.J.Pharmacol. 40, 194-201.

Haigler H. J. and G. K. Aghajanian. (1974). Lysergic acid diethylamide and serotonin: a comparison of effects on serotonergic neurons and neurons receiving a serotonergic input. J.Pharmacol.Exp.Ther. 188, 688-699.

Zieglgansberger W., G. Sothmann and A. Herz. (1974). Iontophoretic release of substances from micropipettes in vitro. Neuropharmacology. 13, 417-422. 10.1016/0028-3908(74)90129-4

LSD chromatography

2008-12-21T11:54:00.000-08:00

The formation of a charge-transfer complex is accompanied by the appearance of a new color band. Histologists have long been interested in charge-transfer reactions for developing staining procedures based on the appearance of a visible color. For example, Romanowsky-Giemsa staining is due to azure B and eosin Y molecules, which act as electron acceptor and donor in the formation of a purple-colored charge-transfer complex.

Color tests for the detection of hallucinogenic drugs hafe beenn developed. This was shown in 1973, when twenty different hallucinogens were applied to chromatography plates and then sprayed with one of various chromogenic reagents. The formation of a color band was dependent on the electron-donating properties of the drug molecule.

“As would have been expected, the polycyclic and consequently more “electron-rich” hallucinogens, such as the harmine derivatives gave stronger colors than the simple monocyclic beta-phenylethylamines derivatives such as mescaline, TMA, DOM, or 2,3-dimethoxy-amphetamine,” (R.A. Heacock, 1973)

The tryptamine derivatives DMT, methyltryptamine, and alpha-methyltryptamine reacted strongly with tetracyanoethylene (TCNE), an electron acceptor used as the color test reagent. Beta-carboline derivatives 6-methoxyharmalan and harmaline gave intense colors with TCNE and all electron acceptors studied. Ibogaine and LSD were easily detected with TCNE. The chromatographic evidence suggests that the broadly defined class of hallucinogens function as electron donors, because one of the most characteristic evidence for a charge-transfer process is the appearance of a new absorption band.

Erspamer was the first scientist to study enteramine (serotonin) in depth. His technique involved staining with the Ehrlich reaction to test for the presence of serotonin. Also referred to as Van Urk's reagent, Ehrlich's reagent is 2% dimethylaminobenzaldehyde in hydrochloric acid. It forms a purple charge-transfer complex with serotonin as well as most indoles and chlorpromazine. A purple charge-transfer complex is formed when Ehrlich's reagent is mixed with LSD. Psilocybin gives a violet color characteristic of indoles in the Van Urk reaction (A. Hofmann, 1961).

From lsd spectroscopy

The LSD-Van Urk complex has an absorption band at 520 nm. Chlorpromazine-Van Urk complex also has an absorption peak at 520 nm. As predicted by its HOMO energy, chlorpromazine is an excellent electron donor, so it is not surprising that chlorpromazine would form a charge-transfer reactions with the Van Urk reagent which functions as an electron acceptor.

"The procedure allows for a simple, rapid, and accurate determination of small quantities of chlorpromazine." (B.S. Murty, 1970)

Chlorpromazine is considered to be an antipsychotic drug and LSD is considered to be one of the most powerful hallucinogen drugs known to man. There aren't too many similarities of the effects of these drugs, but they cause a distinguishable effect on the brain, and may be able to provide some information about consciousness alteration by their mechanism. There are many electronic similarities between LSD and chlorpromazine. LSD and chlorpromazine both have a low transport number, and they both react with Van Urk reagent to produce a macromolecular complex with an absorption peak at 520 nm. The similarites between LSD and chlorpromazine could be related to their common anthracene-like structure, known to have exceptional electron-donating and electron-receiving properties.

Reference

Heacock R. A. and J. E. Forrest. (1973). The use of electron-acceptor reagents for the detection of some hallucinogens. J.Chromatogr. 78, 240-250. 10.1016/S0021-9673(01)99063-6

HOFMANN A. (1961). Chemical pharmacological and medical aspects of psychotomimetics. J.Exp.Med.Sci. 5, 31-51.

Murty B. S. and R. M. Baxter. (1970). Spectrophotometric determination of chlorpromazine in pharmaceutical dosage forms. J.Pharm.Sci. 59, 1010-1011. 10.1002/jps.2600590721

LSD antagonizes serotonin pain

2008-12-20T16:26:00.000-08:00

5-HT and histamine are involved in allergic shock and pain responses. A painful swelling of the rat paw was triggered by an injection of 1 ug 5-HT.

The 5-HT edema reaction in rat paw was completely blocked by LSD and some LSD derivatives, lending support to the hypothesis that LSD functions as an anti-serotonin agent. Certain LSD derivatives actually antagonized the 5-HT swelling reaction more effectively than LSD. Preparations of UML-491, 1-methyl-lysergic acid butanolamide, had a similar effect as LSD in 4-6X smaller doses. Figure 2 below shows that pre-treatment with 1-methyl-lysergic acid butanolamide caused a dose-dependent decrease of 5-HT pain in the rat paw. Pain was assessed by taking measurements of the thickness of the paw every 15 minutes during two hours after the 5-HT injection. As shown below, the maximal swelling occurred within the first half hour and then diminished. At a dose of 70 ug/kg, UML-491 almost completely prevented the swelling reaction.

Methylation of LSD occurs in the drugs MLD-41 and UML-491. These two drugs together with LSD were the most effective compounds at blocking 5-HT pain in the rat paw. Other LSD derivatives had no effect on the pain reaction, for example, hydrogenation of LSD led to a loss of blocking activity of nearly 90%.

Figure 4 below shows that UML-491 was more effective at inhibiting rat paw edema than LSD. The 2-position methyl group seems to be important for the physiological activity in this case, since UML-491 was more potent at inhibiting rat paw edema than lysergic acid butanolamide (unmethylated UML-491).

Phenothiazine derivatives are nearly as effective as LSD at preventing 5-HT pain. Benditt found that 5-HT- or histamine-edema of rat's paw could be prevented by the prior administration of chlorpromazine. Antihistamine drugs including phenothiazine, chlorpromazine, promethazine, and diethazine partly prevented 5-HT-edema, although these drugs were not as effective as LSD or UML-491. Relative to LSD (if LSD inhibits 5-HT edema by 100%), chlorpromazine inhibited 5-HT edema by 64%. UML-491 was the most potent derivative tested, inhibiting 5-HT edema by 440%, and MLD-41 inhibited 5-HT edema by 91%.

Drugs that block 5-HT or histamine are used to control allergic reactions. In guinea pig who inhaled an aerosol spray of 5-HT or histamine, LSD prevented death by anaphylactic shock. The research showing that LSD and UML-491 can prevent 5-HT-induced swelling is where Abramson found support for his ideas about LSD and UML-491 as therapeutic drugs for allergies.

Reference

BENDITT E. P. and D. A. ROWLEY. (1956). Antagonism of 5-hydroxytryptamine by chlorpromazine. Science. 123, 24.

CERLETTI A. and W. DOEPFNER. (1958). Comparative study on the serotonin antagonism of amide derivatives of lysergic acid and of ergot alkaloids. J.Pharmacol.Exp.Ther. 122, 124-136.

DOEPFNER W. and A. CERLETTI. (1958). Comparison of lysergic acid derivatives and antihistamines as inhibitors of the edema provoked in the rat's paw by serotonin. Int.Arch.Allergy Appl.Immunol. 12, 89-97.

Dorsal root neurons in spinal cord

2008-12-13T08:04:00.000-08:00

The neuronal pathways of touch are well-known. Primary sensory neurons for touch and proprioception are located nearby the spinal cord, in clusters (e.g. ganglia) of neurons referred to as dorsal root ganglia. Sensory endings of dorsal root ganglion cells like Pacinian corpuscles are superficially located in the skin. The Pacinian corpuscle is a large subcutaneous mechanoreceptor that senses vibration. Stimuli that indent or deform the surface of the Pacinian corpuscle are conveyed to the dorsal root neuron, but first this information (sense of vibration) must cover a distance of meters between the mechanoreceptor and the cell body. Since axons are known to cross such distances, the appendage of the dorsal root ganglion neuron that carries the sensory current from the Pacinian corpuscle has been referred to as an axon.

The puzzling aspect about dorsal root ganglion neurons is that the long appendage might be classified as a dendrite because dendrites tend to be oriented towards the external world, and carry sensory current toward the cell body. This will be discussed later. An important lesson could be learned here. Although the cell body is often the internal junction or transition point between receptive and conducting tissue, it does not have to be. The afferent pathway from skin is so well-worn that the cell body seems to spare itself this activity and grow off to the side in an odd place, which is nonetheless highly conserved across organisms. Dorsal roots carry sensory information into the spinal cord from skin and muscles, and from internal organs.

Each dorsal root ganglion cell has a thick and a thin process. The thick, outer branch grows towards the periphery and ends in the skin. The thin conducting process has ascending and descending fibers, which carry the current as far as the medulla. Ramon-Cajal's diagram below places the dorsal root ganglion neuron (D) in context with its skin receptors (D') and axon projections to the medulla. From the medulla, another neuron carries the sensory current to the thalamus and cortex.

From Ramon y Cajal

All dorsal root ganglion cells belong to a primordial group of neurons called bipolar neurons. There are many similarities between dorsal spinal ganglion cells, bipolar cells of the olfactory bulb, bipolar cells in the retina, and spiral ganglion in the organ of hearing. All of these sensory neurons were bipolar in the embryo. Cajal wrote:

"The bipolar cell is a very common phase in the evolution of nerve cells of the spinal cord, cerebrum, and retina." (Cajal,R. 1933)

The neurons in the dorsal root ganglia are bipolar at first. By adulthood in nearly all mammals, the bipolar cells convert into unipolar spinal ganglion cells. The figure below shows the transition of bipolar to unipolar spinal ganglion neuron.

In the process of transitioning to a unipolar spinal ganglion cell, the nucleus and cell body migrate away from the conducting process, so that the signal traveling from the periphery skips by the cell body. Certain fish are an exception, and maintain the more primordial bipolar spinal ganglion cells in adulthood.

Each bipolar cell exhibits two primordial extensions, a thin and thick branch. The thick process gathers external stimuli and is associated with dendrite function, while the thin process conducts information away from the cell body. As a general rule, the thick processes of bipolar cells contact ciliated cells or mechanoreceptors at the periphery (e.g. Pacinian corpuscle), which are directly involved in gathering sound or pressure waves. Dendrites of retinal bipolar neurons contact rods and cones, which are special ciliated cells, thus dendrites of bipolar cells are involved with the external stimuli in vision pathways. In the ear, dendrites of auditory bipolar nerve cells end among ciliated hair cells. Ciliated hair cells convey the auditory stimulus gathered to the "thick process" of auditory bipolar nerve cells. Then the axon ("thin process") of the auditory bipolar cell travels in a nerve fiber called the vestibulocochlear nerve towards the auditory cortex.

Bipolar sensory neurons are derived from epithelial layers. In worms, the bipolar or fusiform sensory neurons originate from the ectodermal layer, and then occupy a submuscular position. Nemertinea provides an example of the gradual displacement of the nervous apparatus into the ganglia of the body. Individual bipolar sensory neurons begin to function as sensory transducers before they aggregate into ganglia, thus it is likely that there are sketchy patches of primary sensory neurons, such as the ventral 5-HT neurons, which represent sensory neurons originated recently by the epidermis, that are in the initial stages of migrating toward the center of the brain. The amount of top-down information that these neurons receive is considered to be minimal. Whereas centers for touch and proprioception (e.g. dorsal root ganglion neurons) form recognizable ganglia near the center of the body cavity, there are bipolar sensory neurons that are still clustering. It is unclear what sensory inputs these neurons can detect.

Cajal noticed that in both retina and olfactory bulb, dendrites usually follow a path towards the locations from which they receive their external influences, whereas axons are oriented toward central neural centers. Based on this observation, Ramon-Cajal proposed that dendrites conduct centripetally while axons conduct away from the cell body. To his dismay he realized that centripetal current conduction in dendrites could not constitute a general rule of operation in the case of the dorsal root sensory ganglia, where axonal-looking processes were oriented toward the periphery, however Cajal reexamined this issue 2 years later, and he then concluded (1923) that the processes in sensory ganglion neurons that appeared to be axons were, in fact, dendrites. The "thick" appendage between a Porcinian corpuscle cell body of a dorsal root neuron is formed in a manner analogous to dendrite formation, by protoplasmic stretching. The whole cell body migrates, leaving a dendrite in its path like snail slime. In the dorsal root ganglion neuron, the structure left behind the migrating cell body ultimately becomes myelinated axon, although it is certainly atypical since most axons are generated by a growth cone. The part of the neuron that is most proximal to external stimuli, was once part of the cell body.

According to Ramon-Cajal the bipolar neuron process constitutes part of the cell body rather than an axonal fiber, however the "thick process" of dorsal root ganglion neuron appears to be classified as an axon by most neuroscientists.

Reference

Ramon-Cajal, S. (1990). New ideas on the structure of the nervous system in man and vertebrates; Swanson, N., Swanson, L. W., Eds.; MIT Press: Cambridge.

LSD and human pain

2008-11-24T20:22:00.000-08:00

LSD has been used to treat physical pain. E. Kast compared the analgesic action of LSD with meperidine (Demerol) and dihydromorphinone (Dilaudid) in 50 gravely ill humans. As shown in the figure below, the onset of therapeutic action of LSD was somewhat slower than meperidine or dihydromorphinone, but LSD was more effective than meperidine or dihydromorphinone, with pain diminishment lasting up to 2 weeks after LSD treatment.

From 5-HT pain

Kast reported no medical complications with LSD. Even though LSD relieved pain, patients were indifferent about receiving a second dose of 100 ug LSD.

Reference

KAST E. C. and V. J. COLLINS. (1964). Study of Lysergic Acid Diethylamide as an Analgesic Agent. Anesth.Analg. 43, 285-291. doi:10.1213/00000539-196405000-00013

Serotonin pain

2008-11-23T19:57:00.000-08:00

Pain researchers devised a method for assessing human pain. A blister was induced to the same part of the hand of each subject, and the blister base used as the testing ground for certain drugs. When serotonin was applied to a blister base, there were 19 sec between the time of 5-HT administration and the perception of pain as reported by human volunteers. The figure below is a graphic representation of pain (y-axis). Higher concentrations of 5-HT caused more intense pain. This experiment verified the hypothesis that the pain of a wasp sting is related to the high 5-HT and histamine content of wasp venom.

In human volunteers, 5-HT was more potent at causing pain than DMT, bufotenin, or tryptophan (Table 1).

From 5-HT pain

An animal model of pain was developed with rats. Each test chemical was injected into the paw of a rat, and the amount of swelling (edema) in the paw was measured, in terms of the thickness of the paw in millimeters. A photo of this procedure is shown below. Chemicals such as 5-HT and histamine injected subcutaneously caused local inflammation of the paw.

From 5-HT pain

Injected 5-HT to the rat paw was 200X more potent than histamine at causing edema. The graph below shows that 5-HT is more painful than histamine, causing more edema at lower doses. A mere dose of 1 ug 5-HT per paw caused a swelling reaction.

The swelling caused by 5-HT injection was prevented by pre-treatment of rats with LSD and certain phenothiazine drugs.

References

Lewis, G. P., Ed. 5-Hydroxytryptamine. Pergamon Press: New York, 1958.

Drug lipophilicity

2008-11-19T19:27:00.000-08:00

Meyer and Overton were the first to show a quantitative relationship between physicochemical and biological data in aliphatic systems. Their work related the activity of anesthetics to their olive oil-water partition coefficient, thus showing the importance of oil solubility for drug action.

Lipophilicity is a well-established factor in drug potency. Promazine and chlorpromazine, which differ substantially in activity, have essentially identical ionization potentials, but the chlorpromazine dodecane/water partition coefficient is 366, while promazine has a partition coefficient of only 42. That means that dodecane can "solubilize" about 9 molecules of chlorpromazine for every molecule of promazine. Since chlorpromazine has more affinity for lipid membranes than promazine, chlorpromazine is a more potent drug than promazine, effective at smaller doses. The most potent drugs exhibit an optimum combination of lipophilicity and electron donating ability.

The importance of drug lipophilicity is illustrated by the example of bufotenin, which has a high-affinity for the 5-HT receptor but usually does not produce central effects, because bufotenin is deflected by a shield of fatty acids at the blood-brain barrier. Change bufotenin to its more lipid soluble isomere, 5-acetyl-N,N-dimethyltryptamine, and this drug elicits DMT-like intoxication. Once it has entered the CNS, 5-acetyl-N,N-dimethytryptamine can cross the blood-brain barrier, where it is hydrolyzed to bufotenin.

Lop P is obtained by measuring octanol-water paritition coefficients. Nichols measured the log P values for 11 different substituted amphetamines, shown below. The ideal value predicted by this series of psychotomimetic amines is log P = 2.89-3.72.

Many CNS-acting drugs have log P > 2, but the potency begins to decrease if the value of log P is too high. In the series above, activity drops off for highly lipophilic methoxy-substituted amphetamines with log P>3.0. For LSD, log P = 2.96 (not shown).

It is not desirable to increase the lipid solubility of drugs over a certain value since most of the drug will become stuck to membranes and unable to achieve maximum concentration at the site of action. Conversely, drugs with a low value of log P are washed out since they are not lipophilic enough to stick to biological membranes. From principles of additivity, the number of carbon atoms is directly related to log P, thus the log P value of a drug can be increased by simply adding carbon atoms. Drugs with a large number of carbon atoms have a high degree of protein binding, but too large lop P will decrease the rate of absorption of the drug.

The relationship between activity and partition coefficients (log P) is due to the movement of hydrocarbons to the site of action. This movement is considered to be a random walk process with depends on the lipophilic character of the molecules. There is an ideal log P and any deviation from this value results in a slow rate of movement to the site of action and consequently, in a decrease in biological activity. Mathematically this results in a parabolic relationship between log A and log P (Barfknecht figure above).

Hallucinogenicity is a combination of lipophilicity plus electron donating ability. Shulgin has reported that the hallucinogenic potency of phenalkylamines is critically affected by the hydrophobic nature of the 4-substitutent. For molecules without a hydrophobic 4-substitutent, the first ionization potential energy was the determining factor. Shulgin and colleagues have obtained an empirical relationship that relates the log P value and HOMO energy to a molecule's hallucinogenic activity, in mescaline units. The simultaneous consideration of both ionization potential energy and lipophilicity provides better insight into the problem of hallucinogenic activity than the consideration of electron donation potential alone.

References

Barfknecht C. F. and D. E. Nichols. (1975). Correlation of psychotomimetic activity of phenethylamines and amphetamines with 1-octanol-water partition coefficients. J.Med.Chem. 18, 208-210. 10.1021/jm00236a023

Kumbar M., V. Cusimano and D. V. Sankar. (1976). Quantum chemical studies on drug action V: Involvement of structure-activity, quantum chemical, and hydrophobicity factors in thrombocyte uptake of 5-hydroxytryptamine. J.Pharm.Sci. 65, 1014-1019. 10.1002/jps.2600650715

Nichols D. E., A. T. Shulgin and D. C. Dyer. (1977). Directional lipophilic character in a series of psychotomimetic phenethylamine derivatives. Life Sci. 21, 569-575. 10.1016/0024-3205(77)90099-6

LSD and raphe neurons

2008-09-23T12:20:00.000-07:00

LSD has actions at the level of the reticular formation in the brainstem. Years and years of research have led to the consensus that LSD inhibits the firing of dorsal raphe neurons, yet there remains the question of the function of the raphe nuclei and the physiological significance of their inhibition.

In 1968, Aghajanian and colleagues studied freely moving rats with electrode implants in the raphe. LSD inhibited the spontaneous firing of neurons in the caudal midbrain raphe. Raphe units ceased firing within 1 to 2 minutes after the intravenous injections of 200 ug/kg LSD or within 5 minutes after the intraperitoneal injection (LSD 200 ug/kg). Once inhibited, raphe units did not return to original firing rates for at least 20 to 30 minutes. (G.K. Aghajanian, 1968)

In 1969, it was reported that LSD caused a cessation of dorsal or median raphe unit activity in anesthetized rat. A typical procedure consisted of locating a unit, observing its spontaneous activity for a period of 5-10 min and then giving an initial intravenous dose of either amphetamine or LSD. Figure 1 below shows a decrease in the spikes/min fired by a raphe neuron, when LSD was given as intravenous injection. In this case, the subsequent injection of amphetamine (A) caused the neuron to fire again. Most raphe cells showed a decrease and cessation of firing after LSD, and some units showed an increase in spontaneous firing rate to amphetamine, although in some cases, LSD and amphetamine had depressant effects on units in the reticular formation. (W.E. Foote, 1969)

From lsd raphe, lsd LGN

In preparations of decerebrate, unanaesthetized cat brain, LSD blocked the firing of brainstem neurons. With currents of 50 nA for periods of 5 min or longer, LSD reduced or completely blocked the excitatory effects of glutamate-excitation of brain stem neurons, more effectively than 2-bromo-LSD. (R.J. Boakes, 1969)

By 1970, in decerebrate cat preparations, it was found that iontophoretic release of LSD had a depressant action on 22 out of 35 neurons tested. LSD was found to antagonize the excitatory actions of glutamate, and no potentiation of glutamate excitation by LSD was ever observed. Figure 3 below shows the firing rate (y-axis) and glutamate current (x-axis) of a control neuron (open circles). In neurons exposed to LSD (closed circles), the curve is shifted to the right, indicating that larger pulses of glutamate were required to excite the neuron and increase its firing rate. In the LSD condition, firing rates were generally lower compared to the control neuron. (R.J.Boakes, 1970)

From lsd raphe, lsd LGN

An experiment in 1974 showed that dorsal raphe neurons are very sensitive to LSD, when compared with other neurons in the brain. Dorsal raphe neurons were compared with neurons that receive a serotonergic input, including the ventral lateral geniculate, amygdala, optic tectum and subiculum. Even though LSD inhibited neurons in these structures, the dorsal raphe nuclei neurons were inhibited at much lower ejection currents of LSD. (H.J. Haigler, 1974)

From lsd raphe, lsd LGN

LSD generally has a depressant effect on neurons, that is rarely excitatory. When a mesencephalon-diencephalon lesion was made, to ensure that no possible feedback pathways from the forebrain to the dorsal raphe nucleus existed, the responses recorded from the cell bodies of raphe neurons were basically the same – they were inhibited by LSD. This suggested that LSD affects electrical activity in the raphe dendrite bundle in the medulla, with subsequent effects on the firing of action potentials from the axons of raphe neurons.

In 1981, Trulson and others reported that LSD and mescaline are associated with a depression of raphe nuclei activity in freely moving, awake cats with implanted electrodes. (M.E. Trulson, 1981)

Aghajanian and colleagues in 1984 found that 5-HT and LSD had a similar inhibitory effect on 5-HT neurons in the dorsal raphe nucleus, and that this inhibitory effect on 5-HT neurons was caused by an increase in K+ conductance in the raphe neurons. The concentrations of 5-HT and LSD used were 80 uM and 80 nM. Serotonin or LSD caused a hyperpolarization of raphe neurons, which was not reversed by chloride-containing electrodes, suggesting that the inhibition of raphe neuron firing was caused by an increase in K+ conductance, and not mediated by chloride, which is typically a GABAA-receptor-related current. In slices of rat dorsal raphe nuclei, both 5-HT and LSD induce a hyperpolarization via K+ currents, but the LSD effect was longer-lasting and more pronounced than 5-HT, for example several hours were required for full recovery during washout. The main results suggested that 5-HT and LSD hyperpolarize serotonergic neurons predominantly through increasing potassium conductance. (G.K. Aghajanian, 1984)

In 1985, cats underwent surgery and were implanted with electrodes and a cyclic voltammetry device. An electrode array recorded from dorsal raphe neurons, while the cyclic voltammetry device measured 5-HT release in the striatum. Thus it was possible to simultaneously analyze the axonal 5-HT output in striatum in relationship to raphe spiking activity (field potentials) in the raphe medulla. In this research, a 50 ug/kg dose of LSD decreased raphe units activity by 50%, and LSD treatment produced a 88% decrease in the release of 5-hydroxyindole, a metabolite of 5-HT, measured by the voltammetric response. The authors concluded that LSD blocks the release of 5-HT from raphe neuron terminals. They speculated that LSD inhibits the metabolism of raphe neurons that so that less neurotransmitter is released at the synapse. (M.E. Trulson, 1985)

In 1987, LSD dose-dependently decreased the firing rate of 5-HT raphe neurons in anesthetized rats, and this effect was antagonized by pertussis toxin. Pertussis toxin is known to inactive the alpha subunits of G-proteins, thus it was inferred that the inhibition of raphe firing by LSD was dependent upon a mechanism involving G-proteins, particularly GABAB receptors which couple with K+ channels. It is possible that LSD activates local inhibitory neurons, which contribute to the inhibition of raphe neurons by releasing GABA. (R.B. Innis, 1987 )

References

1. Aghajanian G. K., W. E. Foote and M. H. Sheard. (1968). Lysergic acid diethylamide: sensitive neuronal units in the midbrain raphe. Science. 161, 706-708. 10.1126/science.161.3842.706

2. Foote W. E., M. H. Sheard and G. K. Aghajanian. (1969). Comparison of effects of LSD and amphetamine on midbrain raphe units. Nature. 222, 567-569. 10.1038/222567a0

3. Boakes R. J., P. B. Bradley, I. Briggs and A. Dray. (1969). Antagonism by LSD to effects of 5-HT on single neurones. Brain Res. 15, 529-531. 10.1016/0006-8993(69)90176-0

4. Boakes R. J., P. B. Bradley, I. Briggs and A. Dray. (1970). Antagonism of 5-hydroxytryptamine by LSD 25 in the central nervous system: a possible neuronal basis for the actions of LSD 25. Br.J.Pharmacol. 40, 202-218.

5. Haigler H. J. and G. K. Aghajanian. (1974). Lysergic acid diethylamide and serotonin: a comparison of effects on serotonergic neurons and neurons receiving a serotonergic input. J.Pharmacol.Exp.Ther. 188, 688-699.

6. Trulson M. E., J. Heym and B. L. Jacobs. (1981). Dissociations between the effects of hallucinogenic drugs on behavior and raphe unit activity in freely moving cats. Brain Res. 215, 275-293. 10.1016/0006-8993(81)90507-2

7. Aghajanian G. K. and J. M. Lakoski. (1984). Hyperpolarization of serotonergic neurons by serotonin and LSD: studies in brain slices showing increased K+ conductance. Brain Res. 305, 181-185. 10.1016/0006-8993(84)91137-5

8. Trulson M. E. (1985). Simultaneous recording of dorsal raphe unit activity and serotonin release in the striatum using voltammetry in awake, behaving cats. Life Sci. 37, 2199-2204. 10.1016/0024-3205(85)90572-7

9. Innis R. B. and G. K. Aghajanian. (1987). Pertussis toxin blocks 5-HT1A and GABAB receptor-mediated inhibition of serotonergic neurons. Eur.J.Pharmacol. 143, 195-204. 10.1016/0014-2999(87)90533-4

2-position of LSD

2008-09-06T12:36:00.000-07:00

The 2-position of LSD has the highest free valence, suggesting that this site may be involved in electron donation in charge-transfer complexes (Kier, L.B. 1971).

The LSD molecule has an indole as part of its fused ring system. Indoles in general form localized charge-transfer complexes, and the indole nucleus is described as an exceptional electron donor. Electron acceptor molecules interact with specific sites of the indole ring, rather than with the pi electron system as a whole, for example in the formation of serotonin-picrate crystals, the nitro groups of picric acid were found to interact with C-2 and C-3 of 5-HT (Bugg, C.E. 1970). These sites are most likely to be involved in the formation of donor-acceptor complexes, because of the high free valence, also called superdelocalizability, at C-2 and C-3.

The 2-position of LSD is analogous to C-2 and C-3 in indoles. In both cases, it refers to the Carbon atom that is bonded to the Nitrogen on the indole. (In the LSD molecule the functionality of the C-3 position cannot be examined because it is bonded to a ring). The 2-position of LSD has been claimed as the region of the highest frontier electron density (Snyder, S.H. 1965) and the highest free valence of the molecule (Kier, L.B. 1971). The 2-position of LSD may be critical for electron donation reactions with biological substrates like proteins (Ariens, E.J. 1971). In this regard, it is notable that 2-Brom-LSD and 2-oxy-LSD, which contain sterically obstructing substituents at the 2-position carbon, are devoid of psychedelic activity. In humans, the 2-Brom derivative of LSD (BOL-148) has greatly diminished or no psychedelic effects. It has also been reported, by Kumbar and Sankar who analyzed 42 lysergates with Huckel methods, that there is a significant frontier electron density present on carbon 8 of LSD (Kumbar, M. 1973).

In phenothiazine-type drug, the 2-position is critical for high neuroleptic activity; it is necessary to have an electronegative substituent. Substituents at the 2-position noticeably tune the differences in potency between promazine - no substituent, chlorpromazine - 2-position, Chlorine, and trifluoperazine - 2-position, trifluoromethyl. In studies of the ionization potential, chlorpromazine (7.16 eV) slightly surpasses promazine (7.20 eV) and trifluoperazine (7.31 eV) as an electron donor, showing the effect of 2-position valence on the electronic donating properties of the molecule. The shape of the first ionization band of chlorpromazine has substantial N lone-pair character, and the second ionization potential band is most heavily S-lone-pair in character, thus the most electron density is thought to be located on the ring Sulfur and Nitrogen atoms.

References

Ariens, E. J. 1971. Drug design. Medicinal chemistry. De Stevens, G., editors. Academic press, New York.

Bugg, C. E. and U. Thewalt (1970). Crystal structure of serotonin picrate, a donor-acceptor complex. Science. 170, 852-854.

Kier, L. B. 1971. Molecular orbital theory in drug research. Academic press, New York.

Kumbar, M. and D.V. Sankar (1973). Quantum chemical studies on drug actions. 3. correlation of hallucinogenic and anti-serotonin activity of lysergic acid derivatives with quantum chemical data. Res. Commun. Chem. Pathol. Pharmacol. 6, 65-100.

Snyder S. H. and C. R. Merril (1965). A relationship between the hallucinogenic activity of drugs and their electronic configuration. Proc. Natl. Acad. Sci. U.S.A. 54, 258-266.

Domelsmith 8, harmaline ionization potentials

2008-09-04T05:01:00.000-07:00

LN Domelsmith investigated the ionization potential energies of LSD and harmala alkaloids. Table II summarizes the first four pi ionization potential energies, ranging from 7.38-10.5 electron volts (eV), for norharmane, harmane, harmol, harmine, and harmaline. Harmaline was the best electron donor in this series, with a first ionization potential energy of 7.38 eV.

From Domelsmith ionization potential

Dihydro-harmine (harmaline) and harmine differ by 2 electrons, the saturation of one bond, which in this case changed the energy of the ionization potential by 0.5 eV, a very significant quantity.

From molecules

The trend continues that harmine and harmaline are the most psychoactive in this series of harmala alkaloids, and have the lowest energy ionization potential.

Reference

Domelsmith L. N. and K. N. Houk. (1978). Photoelectron spectroscopic studies of hallucinogens: the use of ionization potentials in QSAR. NIDA Res.Monogr. (22), 423-440.

Chlorpromazine competes for [3H]-LSD binding site

2008-07-23T09:06:00.000-07:00

Radioactive LSD binds to cerebral cortex and subcortex of rat brain. The largest amounts of [3H]-LSD are bound to the choroid plexus, claustrum, striatum and diencephalons, with very little binding in the cerebellum.

LSD binding at receptors can be directly measured in studies with drugs that emit radioactive particles. First [3H]-LSD is mixed with rat brain homogenate, and then exposed to a special plate for counting radioactivity. The amount of radioactivity is quantified and converted into membrane affinity. In this way, it is possible to obtain an approximate value of the binding affinity of [3H]-LSD to receptors, and of the ability of certain inhibitor drugs to act as antagonists on receptors that bind [3H]-LSD.

Co-incubation of [3H]-LSD with certain inhibitor drugs suppressed the amount of radioactive LSD bound (Table I).

Chlorpromazine at a rather low concentration displaced [3H]-LSD in rat brain membranes, suggesting that chlorpromazine might bind the same brain receptor as LSD. Chlorpromazine is an antipsychotic drug used in the treatment of schizophrenia, that may exert its influence on behavior by changing the levels of signaling of serotonin and dopamine.

The most effective inhibitor of [3H]-LSD binding was D-LSD itself, followed by methysergide, 5-HT, DMT, promethazine, and chlorpromazine. The psychologically inert stereoisomer L-LSD was approximately 10,000 times less effective than D-LSD at competing for the [3H]-LSD binding site, showing the stereoselectivity of biological receptors.

The EC50 values (table above) obtained by Bennett and Aghajanian are correlated with Domelsmith's ionization potentials. The average of the first and second ionization potentials of dopamine, mescaline, DOM, dimethyltryptamine, promethazine, chlorpromazine and LSD are 8.54, 8.16, 8.15, 7.80, 7.73, 7.71, and 7.65 eV while the membrane affinity (-log ED50) of these compounds are 3.52, 4.40, 5.30, 6.52, 7.00, 7.00, and 8.22 respectively. Thus, there is a linear correlation between the ionization potential and drug potency at displacing [3H]-LSD binding to rat brain homogenates. Increasing ability of drugs to displace LSD from rat brain homogenates was paralleled by decreasing ionization potential.

Reference

Bennett J. L. and G. K. Aghajanian. (1974). d-LSD binding to brain homogenates: possible relationship to serotonin receptors. Life Sci. 15, 1935-1944. doi:10.1016/0024-3205(74)90044-7

Domelsmith 7, relationship of hallucinogenic activity to ionization potential

2008-07-23T08:33:00.000-07:00

There is an empirical relationship between hallucinogenic activity and the ionization potential energy of hallucinogen molecules. Predictions and identification of hallucinogen molecules must therefore consider 2 parameters: the ionization potential energy and lipophilicity. Despite huge simplifications, those two electronic parameters correlate with drug effects.

“The model here arises from a reduction of variables until the molecule in the isolated state remains as the governing structure dictating the magnitude of observable phenomena. The extraction of structure-activity relationships from this model leads to information which is necessarily limited by certain exclusions of reality, but which is frequently the most attainable kind of relationship.” (Kier, L.B., 1978)

Domelsmith studied the ionization potential of LSD, tryptamines, and amphetamines. The ionization potential was significantly correlated with the quantities of drug needed to displace LSD binding from rat brain membranes (-log ED50). Out of 5 drugs plotted here, LSD is the most potent binder to rat brain membranes, and the best electron donor with eV=7.65 eV. This plot includes mescaline and LSD, regarded as two very different types of hallucinogens.

There are many dissimilarities in chemical structure between LSD (1), chlorpromazine (2), promethazine (3), DMT (4), and mescaline (5), yet there is a correlation between these compounds in terms of electron-donating ability.

In another series of correlations, the average of the first and second ionization potential energies was plotted versus Vogel's minimum effective brain level (MEBL), a measure of hallucinogenic activity in rats. Out of 10 drugs, LSD had the lowest ionization potential and the highest biological potency (MEBL).

Here is the same exact plot, with labels beside each data point. The unsubstituted compounds phenethylamine (PA) and amphetamine (A) are the least potent psychotomimetics and have the largest ionization potential energies (~9 eV). LSD and 5-methoxy-tryptamine are the most potent in terms of MEBL and have the smallest ionization potential energies (~7.5 eV).

The electron-donating ability of the LSD molecule itself deserves special attention.
It is thought that the productive binding of a drug to its receptor is responsible for the primary biological response, but embodied within this index of receptor binding are other relationships more directly related, like hydrophobic factors, and as Domelsmith's research shows, the electronic parameters of hallucinogen molecules. A correlation between hallucinogenic potency in humans and 5-HT2 receptor affinity may in fact be correlating activity with HOMO energy.

References

Kier, L. B. (1971). In Molecular orbital theory in drug research, De Stevens, G., Ed., Medicinal chemistry, Academic press: New York, Vol. 10.

Domelsmith L. N., L. L. Munchausen and K. N. Houk. (1977). Lysergic acid diethylamide. Photoelectron ionization potentials as indices of behavioral activity. J.Med.Chem. 20, 1346-1348.

Dendrite bundles in medulla and raphe

2008-07-22T08:13:00.000-07:00

The medulla is a central brain structure that contains the raphe neurons, which are some of the oldest neurons in the nervous system. Global state functions like arousal and sleep are attributed to neurons in the medulla. As shown in the figure below, dendrite bundles are the major feature of the rabbit medulla, thus dendrodendritic activities are presumably important for global arousal functions.

From raphe neurons

The dendrites of raphe neurons form a midline bundle, a defining feature of the serotonergic system.

From raphe neurons

The dendrites of each neuron in the bundle extend for several hundred micrometers. Dendrites from a single neuron were noted ascending and descending in the bundle. Some dendrites leave the bundle at right angles and extend towards the reticular formation, making contact with perikarya and dendrites of other raphe neurons and reticular formation cells.

Dendritic communication networks serve to connect raphe dendrites of the bundle to other serotonergic dendrites, and to the dendrites of reticular formation cells. Large multipolar reticular formation neurons send numerous dendrites towards and away from the midline 5-HT bundle. The close relationship between raphe neurons and reticular formation neurons has led some authors to conclude that the raphe nuclei should be considered as part of the reticular formation on the basis of cytoarchitecture. These neurons are characterized by a few long, straight dendrites with long spines, and possess a small soma in comparison to the length and thickness of the dendrites.

One difference between the raphe and reticular formation neurons is that most of the raphe dendrites stay in the plane of the midline, and the raphe neurons seem to have a special relationship to the blood and cerebrospinal fluid (CSF).

The figure below is a drawing of a medium-sized neuron in raphe obscuris, one of several nuclei that compose the raphe. One ascending dendrite ends in the third ventricle, which is a brain cavity filled with CSF. The raphe neuron dendrites are laden with amine-rich vesicles than can be released into the blood stream and CSF, thus reaching wide territories of the body. Alternatively CSF-borne substances may be uptaken by dendrite bundles and transported into raphe soma.

Dye-coupling experiments with raphe neurons (figure below, rat) suggest that raphe neuron dendrites contain gap junctions. Dendrodendritic connections in raphe obscurus and raphe pallidus have been identified with electron micrograph experiments too.

From raphe neurons

Electrical communication in the raphe and medulla may be important for the coordination of wakefulness and sleep. The receptive fields for many arousal processes overlap extensively in the midline dendrite bundle.

References

Cummings J. P. and D. L. Felten. (1979). A raphe dendrite bundle in the rabbit medulla. J.Comp.Neurol. 183, 1-23.

Felten D. L. and J. P. Cummings. (1979). The raphe nuclei of the rabbit brain stem. J.Comp.Neurol. 187, 199-243.

Serotonin in wasp venom

2008-07-22T06:53:00.000-07:00

5-HT is present in the venom of wasp, scorpion, stinging plants, sea anemone and portugese man-of-war. Poisonous salivary glands of octopus are known to contain large amounts of 5-HT. Table 8 below shows that scorpion and Bufo marinus contain the highest concentration of 5-HT.

Histamine is the other major component in the venom of some wasps. In Table I below, the amount of histamine was quantified relative to the weight in grams (g) of the venom sac. The mean 5-HT concentration in venom was 0.32 mg/g, and the mean histamine concentration was 4.3 mg/g.

Histamine and 5-HT probably contribute to the pain following a wasp sting, since these chemicals cause pain when applied to a blister in human skin.

Reference

Lewis, G. P. (1958). 5-Hydroxytryptamine, Lewis, G. P., Ed., Pergamon Press: New York.

Lyttle T., D. Goldstein and J. Gartz. (1996). Bufo toads and bufotenine: fact and fiction surrounding an alleged psychedelic. J.Psychoactive Drugs. 28, 267-290.

Lugaro cells

2008-07-14T16:16:00.000-07:00

The cerebellum mostly contains interneurons. Purkinje cells are the well-known ganglion cells of the cerebellum which contain mostly GABA. Purkinje neurons form powerful inhibitory synapses on neurons in the deep cerebellar nuclei, which directly relay to spinal cord motoneurons. Therefore the inhibitory output of the cerebellum is important for sculpting motor behavior.

Lugaro cells are one class of interneuron in the cerebellum, which were first described by Lugaro in the early nineteenth century. The Lugaro cell is shown in red and Purkinje cells are yellow.

From Lugaro cells

The neuron of Lugaro has been described in the granular layer of various species of mammals including humans. Lugaro neurons are found just inferior to the Purkinje (p) cell bodies. They are positioned between the molecular (m) and granular (g) layers of the cerebellum.

From Lugaro cells

Lugaro cells have thick principal dendrites that emerge from opposite poles of the cell body and extend for remarkably long distances, up to 230-300 um, along the boundary between the Purkinje neuron layer and granular layer. The dendrites appear to contact 5-15 Purkinje cell bodies in a horizontal direction.

Like the dendrites of olfactory and taste sensory neurons, Lugaro cells exhibit specialized dendrites with the ability to sense nearby chemical or mechanical stimuli, therefore Sotnikov included Lugaro cells in a list of possible bipolar sensory neurons, based on morphological criteria. The dendrites of Lugaro cells form an extensive receptive surface that monitors the chemical and physical environment in the vicinity of Purkinje cells. Since its dendrites contact 5-15 Purkinje cells bodies in a horizontal direction, and receive inputs from recurrent branches of Purkinje neuron axons, the Lugaro cells appears to have a role in the sampling and integration of the outputs converging from neighbouring Purkinje cells.

In some instances, Lugaro cells form clusters of 2-5 tightly packed cells. Golgi staining revealed 2 or 3 Lugaro cells impregnated near each other. This dye-coupling could be explained if the dendrites of Lugaro cells contain electrical synapses through which the dye may pass in a bidirectional manner. Lugaro cell dendrites, like other primary sensory neurons of the brain, may form bundles that are connected via electrical synapses and gap junctions at dendrosomatic and dendrodendritic junctions.

The horizontally disposed basket cell axons in the supraganglionic plexus occupy the layer superior to the Purkinje cells. The layer inferior to the Purkinje cell layer is known as the infraganglionic plexus. Lugaro cell dendrite bundles course through the infraganglionic plexus, forming a sheet adjacent to the ganglion neurons of the cerebellum, much like the dendrites of TRN neurons form a layer dorsal to the thalamus. Immunocytochemical investigations have demonstrated GAD or GABA immunoreactivity in the Lugaro cell of the rat and human, indicating its putative GABAergic, inhibitory nautre, and also the presence of the inhibitory amino acid glycine and of a co-localization of glycine and GABA.

Lugaro cell axon

Though little is known about Lugaro cells in general, it is thought that Lugaro cell axons target basket and stellate cells in the molecular layer. The major target of the Lugaro cell axon is the inferior 1/3 of the molecular layer, where the Lugaro cell axon runs with the parallel fibers, giving off branches in the molecular layer. Lugaro cell axon collaterals extend for quite a long distance in the latero-lateral direction, exactly parallel to the parallel fibers, as shown in the figure below.

Sometimes the Lugaro cell axon takes a curving route through the granule layer, before running its parallel course in the molecular layer. The axon dips through the granular layer, then the white matter, before ascending to terminate on basket or stellate cells in the molecular layer. In the figure below, the Lugaro cell axon passes through the white matter before ascending to terminate on target cells about 400 micrometers from the original cell soma. Notice the dendrites of the Lugaro cell are adjacent to Purkinje cell bodies.

The Lugaro cell axon also terminates on Golgi cells in the granular layer. In some cases, the Lugaro cell axon never reascends to the molecular layer in which case the Golgi neurons are its postsynaptic target. According to Dieudonne, the Lugaro cell forms a major input to Golgi cells, and one Lugaro cell may contact up to 100 Golgi cells.

From Lugaro cells

The figure above is a Lugaro cell from rat cerebellum that has been stained with the Golgi technique. The thick dendrites are confined to the region of Purkinje cell bodies. The axon, marked by a carrot, travels into the granular layer and cannot be followed any farther in this sample.

The next figure shows another Golgi-impregnanted Lugaro cell. The dendrites are restricted to the region of Purkine cells bodies, and the axon spreads to the molecular and granular zones.

From Lugaro cells

The Lugaro cells axon contacts exclusively inhibitory interneurons, including stellate, basket, and Golgi cells. The parallel axon preferentially contacts stellate and basket cells and the transverse axon contacts Golgi cells. The Lugaro cell is a key interneuron in the cerebellum, because it interconnects many neurons located in all cortex layers. It samples information at the level of the Purkinje cell axon collaterals and distributes information to the molecular and granular layers of cerebellum.

Lugaro cell electrophysiology

Very little is known about the electrophysiology of Lugaro neurons, because Lugaro cells are normally silent in cerebellar slice preparations. It has been reported that Lugaro cells are sensitive to 5-HT, although the significance of this finding is unclear since the cerebellum has comparatively little 5-HT compared to other brain regions. Lugaro cell excitation and subsequent Golgi cell inhibition can be evoked by submicromolar concentrations of 5-HT. Application of 5-HT to Lugaro cells triggered IPSPs on Golgi cells. The excitation of Lugaro cells by 5-HT could be inhibited by 10 uM ketanserin, showing the involvement of 5-HT2A receptors.

From Lugaro
cells

Because of the well-known organization of the cerebellar system, Lugaro cells may represent valuable cellular models to analyze the function of Sotnikov's primary sensory neurons within the brain.

References

Laine J. and H. Axelrad. (1996). Morphology of the Golgi-impregnated Lugaro cell in the rat cerebellar cortex: a reappraisal with a description of its axon. J.Comp.Neurol. 375, 618-640.

Domelsmith 6, photoelectron spectra of 4,5-methylenedioxy-DMT

2008-06-23T10:11:00.000-07:00

In 1982, Domelsmith and colleagues studied 5 DMT analogs with photoelectron spectroscopy. Figure 1 is the photoelectron spectra of methylenedioxy- and methylthio-substituted dimethyl-tryptamine (DMT). The compounds studied were 4,5-methylenedioxy-DMT (first ionization potential, 7.25 eV), 5,6-methylenedioxy-DMT (7.46 eV), 4-methylthio-DMT (7.43 eV), 5-methylthio-DMT (7.68 eV), and 6-methylthio-DMT (7.52 eV).

Methylthio substitution of DMT at the 4-, or 6-position enhanced the electron donating properties of the drug. These experiments with photoelectron spectroscopy confirm for us the importance of attachment at the 4-position of DMT, which is evident in psilocin (4-hydroxy substituted DMT). Compared to 5- or 6-methylthio-DMT, the drug 4-methylthio-DMT had the most favorable configuration, with a first ionization potential energy of 7.43 eV, compared with the parent molecule DMT (first ionization potential energy, 7.57 eV).

The readers of this blog know that 5-methoxy-DMT is a very powerful hallucinogen, and methoxy groups often have the effect of lowering the ionization potential energy, but it turns out that the first ionization potential energies of 5-methoxy-DMT (7.61 eV) and 5-methylthio-DMT (7.68 eV) are slightly higher in energy than the parent molecule DMT (first ionization potential energy=7.57 eV). The evidence presented suggests that the potency of 5-methoxy-DMT may have more to do with lipid solubility, than electron-donating ability.

The methylenedioxy-substituted DMT analogs were even better electron donors than methylthio-substituted DMT. The electronic configuration of 4,5-methylenedioxy-DMT is very interesting because it is the only tryptamine studied by Domelsmith that has an ionization potential energy equal to 7.25 eV, which is equivalent to the first ionization potential energy of LSD. These two drugs are very different structurally, see below, but they have the same electron-donating ability.

From molecules

It is noteworthy that 4,5-methylenedioxy-DMT had the lowest ionization potential of the 5 DMT analogs, and it was the most rigid tryptamine studied. This is a clue to the importance of a rigid planar structure for electron donation. Another way to see the effects of planarity on the ionization potential is to compare between 4,5-dimethoxy-amphetamine and 4,5-methythlenedioxy-amphetamine.

From molecules

4,5-dimethoxy-amphetamine has one planar and one perpendicular methoxy group, whereas oxygens from the the methylenedioxy group are both in the plane of the ring. Conformational constraint in 4,5-methylenedioxy-amphetamine would force the p orbitals of oxygen into maximal overlap with the planar pi system; this configuration has a pi system that will eject a single electron or pair of electrons with slightly less external perturbation than the pi system of 4,5-dimethoxy-amphetamine. The first ionization potentials energies of 4,5-dimethoxy-amphetamine and 4,5-methylenedioxy-amphetamine are almost identical, but the methylenedioxy compound is a slightly better electron donor by 0.02 eV.

Reference

Kline T. B., F. Benington, R. D. Morin, J. M. Beaton, R. A. Glennon, L. N. Domelsmith, K. N. Houk and M. D. Rozeboom. (1982). Structure-activity relationships for hallucinogenic N,N-dialkyltryptamines: photoelectron spectra and serotonin receptor affinities of methylthio and methylenedioxy derivatives. J.Med.Chem. 25, 1381-1383. 10.1021/jm00353a021

Domelsmith 5, photoelectron spectra of DOB, DOM

2008-06-20T14:12:00.000-07:00

Photoelectron spectroscopy is a technique that measures the ionization potential energy of a molecule. Domelsmith and colleagues used photoelectron spectroscopy to analyze the electron-donating ability of LSD and other amphetamines. As compared with amphetamine, the 2,5-dimethoxy pattern is very effective at lowering the energy of the first ionization potential energy. This section will examine the parent molecule 2,5-dimethoxy-amphetamine, and the effects of further methyl (DOM) or bromo (DOB) substitution.

The photoelectron spectra of dimethoxy-amphetamine is very similar to dimethoxy-methyl-amphetamine. The photoelectron spectra of dimethoxy-methyl-amphetamines (including DOM) are given in the figure below. Shulgin and others have stated the importance of 4-substitution for psychotomimetic amphetamines, yet the similarity between the photoelectron spectra of DOM and dimethoxy-amphetamine indicates that 4-methyl added to 2,5-dimethoxyamphetamine causes little change in the electronic arrangement of the parent molecule.

Halogens can serve as electron-donating or electron-withdrawing substituents depending on the site of attachment. The photoelectron spectra of DOB is shown in Figure 6 below.

In the case of DOB, bromination at the 4-position caused little change in the electronic structure, and in fact, DOB was a poorer electron-doner as compared with the parent molecule 2,5-dimethoxy-amphetamine. The photoelectron spectra of DOB was quite similar to DOM, except for additional strong bands in the 10.2-10.4 eV region due to bromine lone-pair ionizations. According to the ionization potential energies measured by Domelsmith, 3-brom-2,4-dimethoxy-amphetamine should be a better electron donor than 4-brom-2,5-dimethoxy-amphetamine (DOB), and no bromine substitution should be even better. Overall, the electronic structure of the parent molecule dimethoxy-amphetamine was not significantly altered by 4-position bromine or methyl.

Domelsmith commented on DOB as an outlier, when discussing the correlations between the ionization potential energy and hallucinogen potency in mescaline units. The authors wrote,

"the most significant deviation from either of these equations is observed for DOB, and this molecule was not included in the correlation."

This discrepancy could be explained if Shulgin overestimated the human potency of DOB.

Reference

Domelsmith L. N. and K. N. Houk. (1978). Photoelectron spectra of psychotropic drugs. 3. Ionization potentials and partition coefficients as predictors of substituted amphetamine psychoactivities. Int.J.Quant.Chem.,Quant.Biol.Symp. 5, 257-268.

Domelsmith L. N., T. A. Eaton, K. N. Houk, G. M. Anderson 3rd, R. A. Glennon, A. T. Shulgin, N. Castagnoli Jr and P. A. Kollman. (1981). Photoelectron spectra of psychotropic drugs. 6. Relationships between the physical properties and pharmacological actions of amphetamine analogues. J.Med.Chem. 24, 1414-1421.

Domelsmith 4, photoelectron spectra of phenothiazines

2008-06-20T14:01:00.000-07:00

Many phenothiazine antipsychotic drugs are excellent electron donors. In 1977, Domelsmith studied phenothiazine, N-methyl-phenothiazine, promazine, chlorpromazine, thioridazine, and trifluoperazine with photoelectron spectroscopy. The first ionization potential was insufficient to predict antipsychotic activity in this series, so it was inconclusvie whether neuroleptic properties are related to low ionization potentials and good electron donating ability.

Phenothiazine, N-methyl-phenothiazine and promazine have 4-5 ionization bands from pi orbitals, corresponding to 4 very clear peaks in the photoelectron spectra (Figure 3), and ranging in energy from 7.26-10.43 eV. The first two ionization potentials at 7.26 eV and 8.35 eV were assigned to central Nitrogen and Sulfur pi orbitals, which are significantly delocalized over the whole ring.

The photoelectron spectra of chlorpromazine, thioridazine, and trifluoperazine are shown below. Thioridazine, with 2-position methylthio, has the lowest ionization energy (7.00 eV) studied in Domelsmith's research, meaning that its electrons are very much on the fringe. Like promazine, the first and second ionization potential bands are assigned to the ring Sulfur and Nitrogen. In chlorpromazine, the 2-position Chlorine atom gives rise to a band at 11.24 eV. The trifluoromethyl groups in position-2 of trifluoperazine were not as electron withdrawing as predited by calculations. Trifluoperazine's first ionization potential energy of 7.31 eV was slightly higher than that of phenothiazine, 7.26 eV.

Nitrogen methylation tended to enhance the overall electron-donating ability of the molecule, as revealed by comparison between phenothiazine (first ionization potential energy, 7.26 eV) and N-methyl-phenothiazine (7.15 eV). A similar trend was observed in the tryptamine series; a Nitrogen side chain ionization potential was lowered from 9.25 eV in tryptamine, to 8.9 eV in N-methyl-tryptamine, to 8 eV in N,N-dimethyl-tryptamine.

From Domelsmith ionization potential

Thioridazine (first ionization potential, 7.00 eV) surpassed chlorpromazine (7.16 eV), and LSD (7.25 eV) as an electron donating molecule.

Reference

Domelsmith L. N., L. L. Munchausen and K. N. Houk. (1977). Photoelectron spectra of psychotropic drugs. 2. Phenothiazine and related tranquilizers. J. Am. Chem. Soc. 99, 6506-6514. doi:10.1021/ja00462a007

Ventral 5-HT neurons

2008-06-11T11:20:00.000-07:00

A cluster of serotonin-containing neurons has been identified on the subpial surface of ventral medulla, marked by the white asterisk in the figure below.

From raphe neurons

The ventral 5-HT neurons are also referred to as supramedullary 5-HT neurons. The ventral 5-HT neurons are unique because they are situated more superficially than the brain parenchyma, above the layer of white matter and glia cells. Located merely 200-400 um beneath the pia layer, the supramedullary neurons are nearby to blood vessels, cerebrospinal fluid (CSF), and subarachnoid spaces.

Supramedullary neurons are classified by Sotnikov as primary sensory neurons of the brain, which are notable for the sensing capabilities of their dendrites. The dendritic processes of supramedullary neurons directly abut the surface of the brain, suggesting a sensory role for them in monitoring nutrient and gas levels in the CSF. With the nearby raphe neurons, the supramedullary neurons function as a response system to glucose, pH, and CO2 overload. The ventral 5-HT neurons an excellent example of Sotnikov's sensory interoceptor neurons because they have a bipolar cell body shape, and a superficial location, so these neurons were presumably born recently from epithelial layers and have not migrated into the body cavity. These neurons may be involved in early sensory processes that are not yet affected by top-down influences.

Using an antibody to 5-HT-binding protein, Gorcs and colleagues stained the ventral 5-HT neurons, in Figure 3 below. Ventral raphe cell bodies are spread along the midline from the caudal tip of the inferior olive (IO) to the level of the oculomotor nucleus. The cell bodies cluster by cranial nerve roots of CN 9, CN 10 (vagus), and CN 12 (hypoglossal).

In summary,

"The presence of serotonergic neurons in contact with CSF in the supraependymal plexus, in the area postrema, and in the subpial location on the ventral surface of the brain apparently projecting to the leptomeninges is consistent with the possibility that 5-HT plays a humoral role in the CSF." (A.L. Kirchgessner, 1988)

Supermedullary neurons of pufferfish have exceptionally high DNA contents and ribosomal gene expression, indicating that these 5-HT-containing neurons are very active in protein synthesis, like raphe neurons in the medulla.

References

Gorcs T. J., Z. Liposits, S. L. Palay and V. Chan-Palay. (1985). Serotonin neurons on the ventral brain surface. Proc. Natl. Acad. Sci. U.S.A. 82, 7449-7452.

Bennett M. V., Y. Nakajima and G. D. Pappas. (1967). Physiology and ultrastructure of electrotonic junctions. I. Supramedullary neurons. J. Neurophysiol. 30, 161-179.

Cuoghi B. and M. Marini. (2001). Ultrastructural and cytochemical features of the supramedullary neurons of the pufferfish Diodon holacanthus (L.) (Osteichthyes). Tissue Cell. 33, 491-499.

Kirchgessner A. L., M. D. Gershon, K. P. Liu and H. Tamir. (1988). Costorage of serotonin binding protein with serotonin in the rat CNS. J.Neurosci. 8, 3879-3890.

Raphe neurons

2008-06-11T11:10:00.000-07:00

The raphe neurons project axons to widespread areas of cortex. Numerous studies have shown that the raphe inhibits distant structures.

The raphe nuclei are part of the reticular formation of the mesencephalon. There are 2 major clusters of 5-HT-synthesizing neurons, shown in the Figure below. There is also a group of 5-HT-containing neurons located on the ventral medulla (white asterisk).

The two main groups of raphe neurons are referred to as the rostral and caudal groups. The rostral group of 5-HT neurons, localized in the pons and mesencephalon, contains the nucleus centralis superior and dorsal raphe nucleus (DRN), which supply most of the 5-HT to the forebrain. The rostral group ascends in the medial forebrain bundle to widespread areas of the diencephalon and telencephalon. Some of the targets of DRN axons include the medial prefrontal cortex, sensorimotor and associative parietal cortex, non-specific intrathalamic nuclei and midline nuclei of thalamus, striatum, and the mesencephalic reticular formation. The rostral-projecting DRN contains the largest aggregate of 5-HT-containing cells in the nervous system, and it has been the subject of a disproportionately large amount of research relative to the other raphe nuclei.

The caudal or inferior group of 5-HT-synthesizing neurons, localized in the medulla, contains nuclei which supply most of the 5-HT to the spinal cord. The axons of caudal 5-HT nuclei form a bulbospinal tract that descends in the lateral and ventral funiculi of spinal cord, and terminates in the substantia gelatinosa of spinal cord, a region involved in pain perception. Medullary 5-HT-containing neurons in the brain stem also project to the sympathetic outflow in the spinal cord, targeting the sympathetic intermediolateral cell column. Serotonin is involved in mediating inhibition of sympathetic activity, because lesions of 5-HT containing axons in the cervical spinal cord can abolish the inhibition of sympathetic discharge produced by raphe stimulation. The caudal raphe nuclei contain the serotonergic neurons which are thought to regulate sympathetic activity and blood pressure.

Neuronal afferents to raphe neurons are from spinal cord, cerebellum, cortex, caudate nucleus, hypothalamus, and habenular nuclei. Raphe cells also receive afferent input from fluid-borne substances in the blood and cerebrospinal fluid. Raphe cell bodies tend to cluster near blood vessels, branching off the vertebral and basilar arteries. Dendrites are the most commonly found profiles in the raphe nucleus.

The DRN is composed of dopaminergic and GABAergic neurons, not only serotonergic neurons. In some areas of the rat DRN, GABA and 5-HT co-exist in the same neuron. The DRN displays immunoreactivity for GABA, tyrosine hydroxylase, substance P, calbindin, parvalbumin, and calretinin.

Why are the raphe neurons so great?

With far-reaching axons that can have a million or more synaptic contacts, and dendrites that sense body temperature, glucose, pH, and CO2 and O2 levels in nearby blood and CSF, the raphe neurons exert a powerful effect on widespread regions of the body. How do the raphe neurons accomplish this wide array of tasks? Serotonin-containing neurons have a historical role as some of the largest, central neurons in the organism. These neurons are very active in DNA and protein synthesis, and build larger cell bodies and innervate larger postsynaptic target areas compared to most neurons.

Some of the largest neurons in the snail and leech are 5-HT-containing giant neurons. The nuclei of the largest neurons of mature Aplysia contain >0.2 ug DNA, more than 200,000 times the haploid amount. What distinguishes neuronal giants from other cells is that their dendrites provide a large receptive area for synaptic input and their axons allow communication with target organs over great distances, consequently these neuronal giants are required to synthesize more DNA and RNA than other cells to maintain the structural integrity of their extensive processes. Neuronal giants require a large turnover of protein for enzymatic and structural function. Most, if not all, of this intense DNA and protein synthesis occurs in the cell body where large quantities of ribosomes surround the nucleus. Some neuronal giants synthesize more DNA and RNA through polyploidy and polyteny.

The raphe neurons in human do not have exceptionally large cell bodies, but 5-HT neurons in the raphe nucleus do sustain high levels of DNA synthesis, and some of them exhibit polyploidy. In a study of adult rabbit 5-HT neurons, approximately 10% of raphe magnus neurons had two nucleoli, as shown below. Cresyl violet staining in the figure below reveals minimal cytoplasm in raphe magnus cell bodies. The function of this high DNA content is unknown, but it might be related to endoreplication, e.g. replication of specific parts of the genome.

The diagram below shows two large 5-HT-containing neurons in snail. This bilateral pair of serotonergic giant cells in Helix pomatia sends large axons to the esophagus and buccal ganglia and feeding musculature of the oral region. Giant neurons of the snail are involved in secretory processes and are more metabolically active.

The largest cells in the leech Hirudoo medicinalis nervous system are the colossal cells of Retzius, shown below. These cells survive well in culture and have been studied extensively. Retzius cells synthesize and contain 5-HT, and have an exceptionally large size and DNA content. Much of the secretion of 5-HT from Retzius cells is from the somatic release of neurotransmitter from the huge cell body, a process that involves dense core vesicles.

From raphe neurons

It is known that Retizus cells contain a high amount of 5-HT because the cell bodies of dehydrated Retzius cells fluoresce strongly when exposed to formaldehyde vapor. Like raphe neurons, Retizus cells have gap junctions that electrically couple to other Retzius cells.

Reference

Jacobs B. L. and C. A. Fornal. (1999). Activity of serotonergic neurons in behaving animals. Neuropsychopharmacology. 21, 9S-15S.

Gillette R. (1991). On the Significance of Neuronal Giantism in Gastropods. Biol.Bull. 180, 234-240. doi:10.2307/1542393

Domelsmith 3, photoelectron spectra of substituted amphetamines

2008-06-11T09:24:00.000-07:00

The photoelectron spectra of phenethylamine and amphetamine are given in Figure 7 below. The ionizations between 8-10 eV are due to 2 high-lying pi orbitals in the ring system. The broad featureless band is due to the amino lone pair orbital of the side chain. Phenethylamine and amphetamine are mostly equivalent in terms of the energy levels of the outermost molecular orbitals.

In the next figures, we will see the effects of methoxy and methylthio substitution on the photoelectron spectra of amphetamine. Photoelectron spectroscopy permits the assessment of substituent effects on individual molecular orbitals.

Methoxy-substitution of amphetamine lowers the aromatic ionization potential energies. TMA-2 (2,4,5-trimethoxy-amphetamine) has a much lower first ionization potential (7.66 eV) than that of amphetamine (~8 eV). The figure below is the photoelectron spectra of TMA-2. It requires less energy to ionize the high-lying orbitals of TMA-2 than amphetamine.

It is known that 2,5-dimethoxy substitution is generally associated with high psychotomimetic activity, so it is quite remarkable that, out of a series of ortho-, para-, and meta-substituted amphetamines, para-dimethoxy-amphetamine had the lowest first ionization potential energy (7.70 eV). The evidence of this trend is provided in Figure 2, the photoelectron spectra of 2,3-dimethoxy-amphetamine (first ionization potential energy, 8.03 eV), 2,5-dimethoxy-amphetamine (7.7o eV), and 2,4-dimethoxy-amphetamine (7.91 eV). The 2,5-dimethoxy pattern is particularly effective at lowering the ionization potential energy. The increased electron donating ability may have some significance in understanding the enhanced hallucinogenic activity of 2,5-dimethoxy-substituted drugs.

From Domelsmith ionization potential

Table IV, column 1, indicates that the best electron donors (e.g. drugs that donate an electron or pair of electrons with the least amount of energy input) are those with 2,5-dimethoxy- and 2,4,5-trimethoxy-substitution. This pattern is also present in the most potent amphetamine hallucinogens.

The effectiveness of methoxy-substitution in lowering the ionization potential is clearly seen in benzene, which is a much simpler molecule than 2,5-dimethoxy-amphetamine. Benzene is electronically similar to amphetamine and phenethylamine, except that its aromatic ionization potentials have slightly less electron-donating ability. In the bottom row of the next figure, starting from the left, benzene shows a first ionization potential energy = 9.25 eV. Methoxy-benzene is a slightly better electron donor than benzene, with first ionization potential energy = 8.39 eV. Para- and meta-dimethoxy-benzene have two methoxy groups, and both have a lower ionization potential and higher electron-donating ability than methoxy-benzene. There is a general trend for methoxy groups to lower the ionization potential energy.

From Domelsmith ionization potential

The last figure shows the effect of methylthio-substitution of amphetamine. Two methoxy groups and one methylthio group were attached to amphetamine in a 2,4,5-pattern. The optimum configuration is 2,5-dimethoxy-4-methythio-amphetamine, which is nearly equivalent to 2,4-dimethoxy-5-methylthio-amphetamine. Methoxy and methylthio groups have similar electron-donating properties, thus all 3 drugs (2,4,5-substituted) are very similar electronically. As compared with methoxy-substituted amphetamine, the methylthio sulfur atoms have high-lying lone-pair orbitals which give rise to ionization potential energies in the same region as aromatic ionization potentials, near 8-9 eV, giving rise to extra peaks in the photoelectron spectra of methylthio-amphetamines.

References

Domelsmith L. N. and K. N. Houk. (1978). Photoelectron spectra of psychotropic drugs. 3. Ionization potentials and partition coefficients as predictors of substituted amphetamine psychoactivities. Int.J.Quant.Chem.,Quant.Biol.Symp. 5, 257-268.

Domelsmith L. N., T. A. Eaton, K. N. Houk, G. M. Anderson 3rd, R. A. Glennon, A. T. Shulgin, N. Castagnoli Jr and P. A. Kollman. (1981). Photoelectron spectra of psychotropic drugs. 6. Relationships between the physical properties and pharmacological actions of amphetamine analogues. J.Med.Chem. 24, 1414-1421. 10.1021/jm00144a009

Domelsmith 2, photoelectron spectra of LSD, DMT, indoles

2008-06-11T09:06:00.000-07:00

Figure 1 is the photoelectron spectra of LSD and DMT. The lowest pi ionization potential of LSD (7.25 eV) is significantly lower than that of N,N-DMT (7.57 eV).

The photoelectron spectrum of LSD revealed 7 ionization potentials between 7.25 and 9.75 eV. Four ionization potentials are assigned to the pi ring system; they are 7.25, 8.05, 8.5, and 9.75 eV. The other 3 ionization potentials of LSD are assigned to the diethylamide group. The amine lone pair ionization energy is 8.4 eV. The carbonyl-nitrogen gives rise to the peak in the 8.8 eV region of the spectra, while the carbonyl pi orbital gives rise to an ionization potential at 9.08 eV.

In the photoelectron spectrum of DMT, 3 ionization potentials are assigned to the pi ring system, and 1 ionization potential energy to the nitrogen lone pair on the side-chain. The pi ionization potentials of DMT occur at 7.6, 8.2, and 9.5 eV, and the tertiary amine lone pair gives rise to an an ionization near 8 eV.

Figure 7 below is the photoelectron spectra of indole, tryptamine, N-methyl-tryptamine, N,N-dimethyl-tryptamine, 5-methyl-tryptamine, and 5-methoxy-tryptamine.

Tryptamines have a side chain bearing a nitrogen with lone pair orbitals. The ionization potential energy of the nitrogen lone pair falls consistently near 9.0 eV. In the tryptamine spectra, the broad band centered at 9.25 eV is attributed to ionization from the nitrogen lone pair. This ionization potential is lowered from 9.25 eV in tryptamine, to 8.9 eV in N-methyl-tryptamine, and finally to around 8 eV in N,N-dimethyl-tryptamine. Thus we see that the degree of carbon bulk on the side-chain nitrogen, not just the aromatic moiety, can significantly affect the electron-donating ability of the nitrogen lone pair.

Table I summarizes the first (IP1) and second (IP2) ionization potential energies of several tryptamines. LSD is the best electron donor in this series.

From Domelsmith ionization potential

References

Domelsmith L. N., L. L. Munchausen and K. N. Houk. (1977). Photoelectron spectra of psychotropic drugs. 1. Phenethylamines, tryptamines, and LSD. J.Am.Chem.Soc. 99, 4311-4321. doi:10.1021/ja00455a018

Sotnikov's primary sensory neurons

2008-06-10T12:12:00.000-07:00

The inside of the body is no more secret than perception of the outside of the body. It is commonly assumed that five senses provide us with information we must have about our bodies and the world, but Sotnikov challenges this position and asks,

"Why are only the sensory cells of the organs of hearing, balance, vision, olfaction, taste, and touch regarded as exteroceptive, while primary extero- and interoceptive neurons within the brain are left out of the discussion?" (O.S. Sotnikov, 2006)

Based on morphological criteria, there is no distinction between the nerves which take messages from ear, eye, nose, skin and taste buds to the brain, and certain groups of nerves which take messages from inside the body as sensory input. Sotnikov argues that the brain, like skin and retina, is innervated by bipolar cells with sensory receptors. Bipolar neurons in the brain have dendrites and other structural features that strongly resemble identified sensory terminals at the periphery. These sensory neurons may be communicating information to us, which our primitive awareness of sight, touch, and smell hasn't described.

Sotnikov identified many interoceptor sensory cells located throughout the brain, based on similar electron microscopic profiles of the terminals of the dendrites of sensory neurons and the sensory terminals of taste and hearing senses. Figure 6 below shows many possible locations for interoceptor sensory cells.

From 06Sotnikov

The list includes Lugaro cells, Cajal-Retzius cells, supraependymal neurons, and supramedullary neurons on the ventrolateral surface of the medulla. Many of these neurons have a bipolar cell shape, and possess specialized dendrites that form bundles. The large external cell membrane surface on the dendrites leads to a high surface/volume coefficient, and thus a high sensitivity for sensing chemical or physical stimuli in the periphery.

Based on the criteria offered by Sotnikov, the raphe and neurons of the thalamic reticular nuclei may be primary sensory cells.

References

Sotnikov O. S. (2006). Primary sensory neurons in the central nervous system. Neurosci.Behav.Physiol. 36, 541-548. 10.1007/s11055-006-0053-5

Sotnikov O. S. (2006). Sensory innervation of the brain (primary interoceptor neurons of the brain and their asynaptic dendrites). Neurosci.Behav.Physiol. 36, 453-462. 10.1007/s11055-006-0039-3

Minimum effective brain level (MEBL) demonstrates high potency of tryptamine

2008-05-18T11:31:00.000-07:00

Vogel and colleagues assigned a value called the minimum effective brain level (MEBL) to several hallucinogenic drugs. These researchers wanted to know the true potency of drugs, without the effects of drug uptake, elimination, distribution, and biotransformation.

MEBL is the brain level of a drug expressed as moles/g of brain. After receiving the drug, when a rat begins to show a significant deviation from its normal behavior, the rat is sacrificed and the drug in its brain is quantified at that point. In this case, the rat learned a conditioned avoidance response, and at a certain time after receiving LSD, it was unable to execute the learned response, e.g. to escape from a box. After receiving LSD, the rats apparently forgot how to perform the learned behavior or didn't care.

The Table below lists several drugs by the effective dose (left) or MEBL (right). The MEBL data provides a behavioral index of drug potency, and was correlated with Domelsmith's ionization potentials.

Based on MEBL criteria, LSD and 5-methoxytryptamine were the most potent compounds tested. Tryptamine plus MAO inhibition was close to 5-methoxytryptamine in potency, thus revealing the true potency of tryptamine when its inactivating enzyme is blocked. Diethyltryptamine, DMT, and 5-methoxy-DMT were relatively weak, and phenethanolamines were very weak.

Vogel wrote:

"It is of interest to note that the two compounds with the highest potency, tryptamine and 5-methoxytryptamine, are naturally occurring in the mammalian brain."

Reference

Vogel W. H. and B. D. Evans. (1977). Structure-activity-relationships of certain hallucinogenic substances based on brain levels. Life Sci. 20, 1629-1635. doi:10.1016/0024-3205(77)90335-6

Who was Dr. Harold A. Abramson ?

2008-05-17T12:52:00.000-07:00

HA Abramson was one of the most prevalent LSD researchers of the 20th century.

Abramson spent his life as a clinical allergist, and he had an intense interest in the actions of LSD. He treated humans with methysergide, LSD, and psilocybin, and he pioneered the LSD fish surfacing reaction. He was involved in research with LSD analogs including methysergide and BOL-148, and cross-tolerance between LSD and these drugs in human subjects. He wrote a series of 40 papers about "Lysergic acid diethylamide."

At a conference on LSD in 1959, Abramson indicated that

"If I were to say what LSD does, I would refer to experimental work I have done on the Siamese fighting fish, where 1 mg/kg of potassium cyanide (a cytochrome oxidase inhibitor) and sodium azide and LSD will act in very much the same fashion: The fish will be in a nose-up, tail-down stupor, lasting for days in the case of sodium azide, and for a shorter period in the case of potassium cyanide, because it is more rapidly oxidized. We can produce the same effect with hypoxia." (H.A. Abramson, 1959)

Early in his career, Abramson acquired skills in basic immunology, human physiology and pharmacology. At a conference in 1959 on the use of LSD in psychotherapy, Abramson said,

"About 30 years ago, Dr. Fremont-Smith and I were tutors together at Harvard in the Division of Biochemical Sciences. My main interests originally were physical chemistry and immunology. About 1935, I began the private practice of medicine in New York. Though I had been teaching immunology, I found that conventional treatment yielded very poor results in the many cases of eczema and asthma which I met in practice. It was Dr. Fremont-Smith, by this time in New York, who made me realize that I knew a lot about allergy, but very little about patients. In going over my cases with him, I learned how to appraise an illness, not only in terms of the organic factors, but from the standpoint of the individual as a whole. Soon, I was practicing some psychiatry under his guidance. Realizing that my interests lay in psychiatry and psychotherapy, I proceeded to get training in these areas. But one of my difficulties was being unable to bring the laboratory into the area of psychiatry in the way in which I had been accustomed. I had been working with mathematics and surface chemistry and was really very concerned about the lack of contact between psychiatry, as I knew it then, and the laboratory. Then I saw some papers on LSD. These studies seemed to me to bring the laboratory and psychiatry together. I began to work with LSD in 1951, work which has given me great satisfaction, because it involves my interests in psychoanalysis, psychotherapy, enzyme reactions, and surface chemistry, as well as biochemistry and pharmacology." (H.A. Abramson, 1959)

Abramson frequently wrote about the usefulness of LSD to treat "allergic" phenomena.

"... the use of methysergide and LSD in the treatment of migraine and similar phenomenon especially allergic phenomenon, is of the greatest importance. The discoveries of Hoffman have opened new routes to medical progress." (H.A. Abramson, 1965)

LSD saved guinea pigs lives

The role between allergic phenomenon and LSD was shown by Herxheimer's experiments in 1955, in which LSD administration prevented death by prophylactic shock in guinea pigs. An aerosol spray of 5-HT normally leads to respiratory failure in guinea pigs by causing the contraction of bronchial muscles and shortness of breath. LSD given 15-60 minutes before inhalation of an aerosol spray of 5-HT prevented respiratory failure in the guinea pigs. In 1955, Cerletti and colleagues demonstrated the ability of LSD to block 5-HT-contraction of smooth muscle preparations, and the ability of LSD to prevent 5-HT-swelling in rat paw, further suggesting that LSD interferes with histamine and catecholamine release, and could be of use when these pathways become abnormally activated. Abramson may have been familiar with work by Cerletti and Herxheimer, and as a clinician he was interested in the possibility of using LSD and methysergide to block excess amounts of 5-HT in migraines.

UML-491 is methysergide. Abramson wrote,

“UML-491 (Sansert) is the best drug known for the prevention of certain headaches, many of which may be of allergic origin. The antiserotonin activity of UML is among the highest of certain LSD congeners and derivatives of LSD… the relationship of these drugs to their anti-serotonin activity is of particular interest to the allergist because of the way in which the congeners and derivatives of LSD block the action of serotonin on smooth muscle.” (H.A. Abramson, 1979)

Abramson knew certain drugs that block 5-HT and histamine release, like LSD or methysergide, can exert therapeutic effects by antagonizing the metabolites that are involved in migraine and allergic reactions. The prophylactic action of methysergide has strongly indicated the involvement of serotonin and vascular pressure in the etiology of migraines.

Methysergide is still prescribed for migraine with the name Sansert, in 2 mg quantities, however it is usually not the preferred treatment. Sumitriptan is more commonly prescribed for migraine because methysergide can lead to retroperitoneal psorisis in a small percentage of people taking it.

Methysergide is not considered to be a hallucinogenic drug unless the dose is 4.3 milligrams or greater. Because Sansert comes in 2 mg quantitites, one would have to take 2.5 Sansert to experience LSD-like symptoms. Abramson notes in one article that it is unfortunate that more researchers do not acknowledge the similarities between the LSD and Sansert (methysergide) experience, however its effects are usually not reported because like LSD, methysergide induces tolerance within a few days in patients who take it for headaches.

Abramson cited the huge disservice done to the medical community by associating LSD with brain damage, when there were successful uses of LSD to treat migraine and alcoholism.

“It seems important to stress at this time that many derivatives of LSD play a most important role in medical treatment. To label any one of these derivatives as the cause of “chronic brain damage” without direct evidence, validated statistically, constitutes a disservice to science and to the practice of medicine… Let us hope that the anxieties of a small group will be replaced by a more hardy spirit of inquiry and scientific investigation.” (H.A. Abramson, 1964)

Towards the end of his research career, Abramson began to have some interesting ideas about the electronic desaturation of certain molecules, and its relation to drug psychoses. In certain hypnotic drugs, he pointed out that if a double bond is present in an unsaturated hydrocarbon, the unsaturated compound is more active than the saturated analog.

"The study of derivatives of arachidonic acid might be another part of the still undisclosed chemical mechanisms which produce mental illness in man.” (H.A. Abramson, 1979)

Reference

Abramson H. A. and A. Rolo. (1965). Lysergic acid diethylamide (LSD-25). 38. Comparison with action of methysergide and psilocybin on test subjects. J.Asthma Res. 3, 81-96.

Effect of Cyanide and Sodium azide on fish surfacing reaction

2008-05-17T12:44:00.000-07:00

Weiss and colleagues tested the hypothesis that LSD acts by anoxia and asphyxia. They added Siamese fighting fish to water containing the oxidase inhibitors, potassium cyanide (KCN) and sodium azide. KCN and sodium azide affected Siamese fighting fish in a way which was very similar to LSD, suggesting that LSD might normally work by preventing oxygen uptake. Figure 2 shows the fish surfacing reaction for 1 ug LSD and 1 ug KCN. There is no surfacing reaction in the H2O control.

It was interesting that KCN was nearly as potent as LSD, since I am unaware of any other drugs, with the exception of other hallucinogens, that cause LSD-like behavior in the same concentration range as LSD in a biological assay. There were some differences between KCN and LSD, for example fish recovered more quickly from 1 ug/mL KCN than 1 ug/mL LSD. Each chemical had a slightly different effect on the fish, for example, sodium azide was more toxic than potassium cyanide. The figure on the right is the KCN surfacing curve plotted on the LSD surfacing curve.

The authors observed that CO2 poisoning causes nose up-tail down reactions in fish. When carbon dioxide was permitted to accumulate in the absence of renewed oxygen, all the fish assumed the nose up-tail down position in several hours. Thus inhibition of O2 oxidation was a general feature of the fish intoxication produced by LSD, KCN, and sodium azide.

"A decreased oxygen supply with simultaneous prevention of accumulation of carbon dioxide resulted in the nose up-tail down position similar to that for LSD in several hours, the fish remaining alive." (B. Weiss, 1958)

A concentration of methylene blue of 100 ug/mL also caused a nose up-tail down reaction. There were similar results with gentian violet and Bindschedler's green.

Reference

WEISS B., H. A. ABRAMSON and M. O. BARON. (1958). Lysergic acid diethylamide (LSD-25). XXV. Effect of potassium cyanide and other oxidase and respiratory inhibitors on the Siamese fighting fish. AMA Arch.Neurol.Psychiatry. 80, 345-350.

pH 5.0 prevents fish surfacing reaction

2008-05-17T12:18:00.000-07:00

Betta fish show a "surfacing reaction" when LSD is added to the tank water. About 10 minutes after 1 ug/mL LSD is added to water, almost 100 per cent of fish ascend to the surface of the tank and swim very slowly or not at all. Abramson and Gettner attempted to block the LSD surfacing reaction in goldfish by lowering the water pH. In a bowl at pH 5.0, only 30 percent of the fish demonstrated the fish surfacing reaction. When shifted to pH 5.8, nearly all of the fish began the surfacing reaction.

The authors suspected that pH affects the absorption of LSD across the gills. They wrote:

“Alkaloids are not absorbed to any extent from the stomach when the reaction of the gastric juice is strongly acid. If the gastric juice is rendered alkaline, however, alkaloids are rapidly absorbed from the ligated stomach. It is of interest that absorption slows at about pH 5.0 and is fairly rapid at pH 6.0.” (H.H. Gettner, 1973)

Using a different methodological approach, the researchers dipped goldfish for 30 seconds in LSD-containing liquid, and then placed them in normal tank water. Drug concentrations in the dipping tank ranged from 5 to 50 ug/mL. About 70% of the fish that were briefly dunked in LSD-containing water still demonstrated the fish surfacing reaction, but recovered more quickly than fish who were immersed in LSD-containing water for hours. The dotted lines in the figure below represent the die-away curves when fish were dipped for 30 s only, which demonstrated that LSD can be rapidly absorbed by the animal body. The surfacing reaction was more persistent when the fish are immersed in LSD solutions (solid black lines).

Similar curves were obtained with goldfish by dipping for 30 seconds into solutions of methysergide.

Reference

Gettner H. H., P. A. Carone and H. A. Abramson. (1973). Lysergic acid diethylamide (LSD 25). XXXX. Effect of pH on transport of methysergide and LSD 25 across gill membrane. J.Psychol. 84, 111-118.

HOMO calculations of phenothiazines

2008-05-17T11:49:00.000-07:00

Molecular orbital calculations of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies reflect the electron-donating and electron-accepting properties of a molecule. The HOMO energies of tricyclic antidepressants and phenothiazines neuroleptics were calculated with 3 different methods, referred to as the RHF, LSD, and SE-AM1 methods. The drugs studied were promazine, chlorprothixene, chlorpromazine, dibenzepine, amitriptyline, imipramine, clomipramine and opipramol. These eight drugs have a phenothiazine-like nucleus in common.

When the HOMO energies of these 8 drugs were calculated using the RHF method, all values were between 7.4-8.87 electron volts (eV). HOMO values for these drugs ranged from 7.36-8.34 eV using the SE-AM1 method. The HOMO energies obtained by the theoretical methods reported here are similar to the ionization energies of phenothiazine drugs obtained experimentally with photoelectron spectroscopy.

Promazine consistently had the smallest absolute value for HOMO energy.

“The contribution to the HOMO and LUMO from the atomic orbitals of the Nitrogen in the central ring is remarkable.” (J.A. Cogordan, 1999)

Reference

Cogordan J. A., M. Mayoral, E. Angeles, R. A. Toscano and R. Martinez. (1999). Neuroleptic and antidepressant tricyclic compounds: Theoretical study for predicting their biological activity by semiempirical, density functional, and hartree-fock methods. Int J Quant Chem. 71, 415-432.

Mescaline interferes with axoplasmic transport

2008-05-04T05:26:00.000-07:00

Microtubules are involved in axonal transport, the movement of lipid-protein cargo from the cell body to the axon. Paulson and McClure showed that colchicine and mescaline inhibit axoplasmic transport in the cat optic nerve preparation, probably by interfering with microtubules. It had been shown previously that mescaline and colchicine directly bind to microtubules, and inhibit the formation of mitotic spindles.

In Figure 1 below, the authors compared mescaline, TMA, and TMA-2. TMA (middle panel) was more effective than mescaline (top panel), while the most potent inhibitor of axonal transport was TMA-2 (lower panel), which has a 2,4,5-trimethoxy configuration. This is interesting because TMA-2 is a more potent psychotomimetic drug than TMA or mescaline. The authors proposed a correlation between the relative effectiveness of several trimethoxyphenylalkylamines as hallucinogens and as inhibitors of fast axoplasmic transport.

The authors wrote,

“Inhibition of axoplasmic transport is also observed with two classes of anti-mitotic drugs, typified by colchicine and vinblastine. These drugs are thought to inhibit cell division through disruption of the microtubules of the mitotic spindle. Isolated microtubule subunits, designated as tubulin or microtubule protein, bind colchicine and vinblastine at different sites. Inhibition of axoplasmic transport by colchicine and vinblastine has been cited as support for the hypothesis that the microtubules which are always present in axons are involved in the transport process.” (J.C. Paulson, 1973)

Reference

Paulson J. C. and W. O. McClure. (1973). Inhibition of axoplasmic transport by mescaline and other trimethoxyphenylalkylamines. Mol.Pharmacol. 9, 41-50.

2008-04-27T16:15:00.001-07:00

"In the cell where biopolymers are intimate contact with each other, it is quite conceivable that electron migration may take place over large distances involving a number of aggregated biopolymers. Irrespective of the mechanism of this electron transfer, whether by the persistence of an electron in a conduction band, by free migration throughout the polymeric molecules, or by electron tunneling between the individual nonconjugated trapping sites, the electron is likely to be eventually trapped in the site of highest electron affinity." (Hart,E.J. 1970)

The site of highest electron affinity is typically a HOMO or an electron conduction band.

Reference
Hart, E. J. and M. Anbar 1970. The hydrated electron. Wiley-Interscience, New York.

Dense core vesicles

2008-04-27T11:56:00.000-07:00

Serotonin is stored in eccentric, electron-opaque granules that are referred to as "dense core granules" or "dense core vesicles." The diameter of a dense core vesicle is 750-1000 Angstroms, with a variably dense center that does not completely fill the vesicle. Dense core organelles are known to contain various neurotransmitters, including 5-HT, adrenaline, noradrenaline, dopamine, histamine, ATP, or peptides.

Dense core vesicles can be highly purified and obtained in large quantity from rabbit platelets, which are a rich source of dense core vesicles and contain 10X more 5-HT than human platelets. Figure 2 is an electron micrograph of 5-HT dense core vesicles that have been purified from rabbit platelets.

Dense osmiophilic organelles were first identified in the adrenal medulla of the gut. The cytoplasm of enterochromaffin cells stain readily with potassium bichromate, showing fine brown granules as chromium salts. The investigation of these "chromaffin vesicles" in the gut led to the discovery of amine-containing vesicles in the brain. The electron micrograph below shows monoaminergic dense core vesicles forming a synapse in the cortex of 6-day-old rat.

Dense core vesicles are found in the axon terminals of noradrenaline-, dopamine-, and 5-HT-containing neurons, but the majority of dense core vesicles are located in dendrites.
The dendrites of raphe neurons are characterized by many 5-HT-containing dense core vesicles. Dopamine in the dendrites of rat substantia nigra and norepinephrine in dendrites of rhesus monkey locus coeruleus suggest that the storage, release, and uptake of catecholamines may not be exclusive properties of the terminal axons.

Sources of 5-HT in nature

2008-04-10T23:13:00.000-07:00

5-HT has a widespread occurrence in nature. It occurs in plants, insect stingers, sea creatures, and mammals.

“The occurrence of 5-HT in groups so far removed from a common ancestor as vertebrates and flowering plants indicates either that the ability to produce 5-HT is primitive in evolution, or that this capacity is readily evolved as occasion demands.” (Lewis, G.P., 1958)

Table 4 lists the sources of 5-HT in different species. The 5-HT content in varies conspicuously from one animal species to another. Remarkable also are individual variations in the same species.

Serotonin was first studied as the specific secretion product (enteramine) of the enterochromaffin cells. Located in the gastrointestinal tract, the enterochromaffin cells synthesize about 90% of the total 5-HT in the body, thus enterochromaffin cells are the primary source of 5-HT in the body. Enterochromaffin cells fluoresce after fixation with formaldehyde, showing the characteristic fluorescence reaction of 5-HT with formaldehyde. It is further indicated that the enterochromaffin cells are the major source of 5-HT in the body, since certain groups of fishes do not contain 5-HT, such as the fish Teleostei and Cyclostomata, and these fish lack enterochromaffin cells altogether.

Tunicates and echinoderms are unable to uptake radioactive 5-HT (3H-5-HT), and lack 5-HT in the gut or elsewhere. In comparison, abundant amounts of 5-HT can be found in the digestive tracts of hagfish, goldfish and bullfrog. In goldfish and bullfrog, 3H-5-HT labeling was most intense over the intestinal cells, Auerbach's plexus and the circular muscle layer.

There is much more 5-HT in stomach, small intestine, and tongue than brain. The early 5-HT researchers believed that 5-HT was concerned with intestinal mobility. According to these researchers, enterochromaffin cells are a “diffuse endocrine organ” designed for the production and storage of 5-HT. They believed that 5-HT was released in the digestive tract and carried away by the blood stream. They believed that the high concentration of amine oxidase in the liver was to help prevent a flooding of the general circulation with free 5-HT. Once 5-HT enters the blood stream, it is absorbed by platelets, thus platelets are a rich source of 5-HT in nature. It is well-known that rabbit platelets contain 10X more 5-HT than human platelets (Table 9). Poison salivary glands of octopus are rich in 5-HT (Table 9).

Spleen is a rich source of 5-HT (Table 9). In mammals and birds, 1 gram of spleen tissue usually contains from 2 to 7 times more than 1 mL of the blood serum. 5-HT is produced in the enterochromaffin cells and thence released into the plasma, where it is taken up by platelets and thrombocytes. The origin of the 5-HT in the spleen is due to disintegrating thrombocytes, since the spleen is the organ which destroys thrombocytes.

The brain has relatively little 5-HT compared to other areas of the body. Brain areas richest in 5-HT are the hypothalamus, the midbrain, colliculi, grey matter of spinal cord, the medial part of thalamus and layer 4 of the cortex. It is interesting that the medial thalamus, which is connected with autonomic activity and the hypothalamus, contains a much higher concentration of 5-HT and of noradrenaline than the lateral thalamus which relays sensory impulses to the cortex. 5-HT is also found in high quantities in area postrema, pineal organ, and cranial nerves 10 (vagus) and 12 (hypoglossal).

Finally we see in Table 9 that the highest amounts of 5-HT in nature are found in human carcinoid tumors, which are derived from enterochromaffin cells. Malignant gastrointestinal carcinoid tumors can produce excessive amounts of 5-HT in the carcinoid patient. The side effects of carcinoid tumors in humans are flushing, diarrhea, abdominal cramps, and attacks of breathing difficulties. In carcinoid patients, the 5-HT content of blood platelets and urinary excretion of 5-HIAA is consistently elevated. Carcinoid patients are flushed due to high 5-HT levels, and episodes of flushing are accompanied by an increased release of 5-HT from the tumor.

"Intravenous injections of serotonin in both control and carcinoid subjects were followed by flushes of the skin similar to spontaneous attacks occurring in the carcinoid patient and by pressor responses of 29 to 58 mm Hg systolic and 9 to 57 mm Hg diastolic. The flush, involving the face, neck, and extremities, was intense in 4 patients and mild in 1. Subjective discomfort was profound in all subjects and characterized by nausea, paresthesias, breathlessness, and an urge to empty the bowel and bladder. These effects were transient and lasted for about the same length of time, 2 to 3 minutes, as the rise in arterial pressure." (R. Schneckloth, 1957)

In patients with carcinoid tumor in whom the peripheral production of 5-HT is excessive, no particular behavioral effects can be described. The fact that patients with carcinoid tumors have large amounts of circulating 5-HT without showing marked symptoms of mental derangement could represent an adaptation to very high levels of 5-HT that has developed and accumulated gradually. The sources of serotonin in nature indicate that it has an important role in the digestive and circulation system.

References

ERSPAMER V. (1954). Pharmacology of indole-alkylamines. Pharmacol.Rev. 6, 425-487.

Lewis, G. P., Ed. 5-Hydroxytryptamine. Pergamon Press: New York, 1958.

SJOERDSMA A., H. WEISSBACH, L. L. TERRY and S. UDENFRIEND. (1957). Further observations on patients with malignant carcinoid. Am.J.Med. 23, 5-15.
10.1016/0002-9343(57)90353-4

2008-04-10T14:55:00.001-07:00

From Terrence Mckenna,

"There are thousands of altered states. We know them - orgasm, indigestion, two cappuccinos, where tequila takes you, so endless altered states. And I'm not really interested in them more or less than any of you are, I mean they're part of life. But what I'm interested in, as an experimentalist, as a connoisoir of nature, as someone who loves fossils, butterflies, rainforests, that kind of thing, is this family of compounds called the indole hallucinogens. Indoles. And they cause hallucination.

"Some people say that I am a fetishist, or that "who cares," or that there are other things besides hallucinations. Yes, I know, maybe, and of course, there are other things besides hallucination. But the reason I'm so fascinated by hallucinations is, to my mind, when you're hallucinating, you have an absolutely clear proof that _you_ are not generating this material. Its not funny ideas, its not racing thoughts, its not insight into what your boyfriend really meant yesterday. That kind of thing we can all generate by just inspecting our own minds. But a hallucination is to be in the presence of that which could previously not be imagined. And if it could previously not be imagined, then there is no grounds for believing that you generated it out of yourself.

"I mean, we should each know our own inventory. You know what's in your cupboard, you know what's in your chest of drawers, for God's sake, you ought to know what's in your mind. Then if something comes forward, and you say, "That's not mine, That's not in my inventory," then you have a kind of perfect proof that this is coming from somewhere else. Then the question becomes, where? And we can set off into that, opinions differ."

Indole nucleus inhibits tubulin polymerization

2008-03-31T17:53:00.000-07:00

An extensive review of microtubule inhibitors and anti-cancer drugs revealed a common indole nucleus, which is correlated with enhanced cytotoxic activity.

The 3,4,5-trimethoxyphenyl moiety, common to colchicine and mescaline, was crucial for inhibiting the growth of tumor cells.

Reference

Brancale A. and R. Silvestri. (2007). Indole, a core nucleus for potent inhibitors of tubulin polymerization. Med.Res.Rev. 27, 209-238. 10.1002/med.20080

Hallucinogens disrupt the cytoskeleton?

2008-03-31T17:02:00.000-07:00

In 1990, A.E. Van Woerkom suggested that hallucinogens disrupt the cytoskeleton. He noted the similarities between mescaline, LSD, and the microtubule inhibitors colchicine and vincristine. Colchicine and vincristine are used in cancer chemotherapy because they disrupt microtubules, thus weakening the cytoskeleton of cancer cells.

Like LSD, the microtubule toxin vincristine allegedly causes not-unpleasant visual hallucinations in humans. Other side-effects of vincristine include depression, agitation, and insomnia. Very small doses are needed for the effects of LSD or vincristine, for example, these drugs are active at concentrations of 4.3E-7 M-1 vincristine and 1.0E-8 M-1 LSD.

Many researchers have favoured the drug-receptor theory to explain drug-induced hallucinations, usually at the 5-HT2A receptor. In the drug-receptor theory, signal amplification takes place when one molecule of drug binds to a receptor, which activates G-proteins, which affects more proteins, thus signaling cascades explain how a small amount of LSD can lead to widespread changes in the cell.

Van Woerkom does not go along with the drug-receptor theory, suggesting instead that LSD binds an element of the cytoskeleton, in a fashion similar to colchicine or vinblastine, which directly bind microtubules. The amount of LSD needed to produce hallucinations is so vanishly small, that it seems hard to believe that a submicromolar dosage of LSD could act on a substrate as vast as the cytoskeleton. However, some microtubule inhibitors such as vincristine are effective at very low dosages. The potency of vincristine may partly explain the success of this drug as a chemotherapeutic drug.

Vincristine and vinblastine are indole alkaloids that block mitosis and cell division.

Reference

van Woerkom A. E. (1990). The major hallucinogens and the central cytoskeleton: an association beyond coincidence? Towards sub-cellular mechanisms in schizophrenia. Med.Hypotheses. 31, 7-15. 10.1016/0306-9877(90)90044-F

Mescaline as mitotic spindle inhibitor

2008-03-31T16:56:00.000-07:00

Several drugs are known to inhibit microtubule assembly. Colchicine is a well-known microtubule poison. Vincristine disrupts microtubules and is used therapeutically as a chemotherapeutic drug. Some hallucinogens including mescaline are reported microtubule inhibitors.

Harrisson and others asked whether mescaline could inhibit microtubule formation and mitotic spindles in human skin fibroblasts. The authors compared the actions of mescaline to colchicine.

In fibroblast cultures, colchicine (C) and mescaline (M) dose-dependently arrested cells in mid-metaphase. Fibroblast cells that were treated with Hank's saline solution (H) did not have a significant change in mitotic spindles.

The authors reported that radioactive mescaline binds directly to purified microtubule protein, suggesting that the hallucinogen psychosis begins with a binding event to the cytoskeleton, not necessarily involving receptors.

There was a significant price difference between the two microtubule inhibitor drugs.

“Mescaline has the advantage that it is 1,000 times less expensive to purchase than colcemid.” (C.M. Harrisson, 1976)

Reference

Harrisson C. M., B. M. Page and H. M. Keir. (1976). Mescaline as a mitotic spindle inhibitor. Nature. 260, 138-139. 10.1038/260138a0

Imipramine blue color and EPR signal

2008-03-22T14:38:00.000-07:00

The first phenothiazine ever used in psychiatry was Ehrlich's methylene blue. Imipramine is a related phenothiazine drug that is an antidepressant. A blue product is observed when imipramine is dissolved in water. The blue product is referred to as a free radical or a hydrated electron. The greater the number of hydrated electrons, the more intense the color.

Odd electrons give the molecules that host them their color and high reactivity, and in the case of imipramine and other mind-affecting drugs, its biological activity is thought to result from a disruption of electron transport processes in the organism.

Borg and colleagues studied the EPR spectra and UV spectra of imipramine, a tricyclic antidepressant. A solution of imipramine contains free radicals, as evidenced by its EPR signal below. The subsequent decay of EPR intensity seemed to parallel the observed loss of blue color, and the loss of electroconductivity in the solution. Thus imipramine is a example of a molecule that exhibits the relationship between color, EPR signal, and electrical conductivity.

Authors wrote,

"Production of a free radical from imipramine can be confirmed further by generating it electrolytically. Electrolysis of 0.1 M imipramine hydrochloride at 1 to 3 V in a flat EPR sample cell allows EPR to be observed while anodic electrode products are generated in situ. An EPR signal can be recorded, and within a few minutes its intensity stabilizes, presumably as an equilibrium is established between free radical decay and the diffusion of unreacted imipramine to the electrode. The EPR spectrum is identical with that recorded after reaction with ceric ion. Upon cessation of electrolysis, the EPR signal disappears in less than 15 sec." (D.C. Borg, 1965)

The study of imipramine molecules, in an EPR spectrometer and under the influence of electric currents, provides a clear example of the relationship between color, EPR signal, and electrical conductivity, which is also exhibited by proteins such as lysozyme. When the electroconductivity of the sample was changed, there was a decay of EPR intensity that paralleled the observed loss of blue color. The blue color and EPR signal of imipramine lasted about 20 sec, and then faded to pale green when electrolysis was discontinued. The authors could stabilize the blue product for many hours by placing the sample in strong sulfur acid, or quench any residual blue or green color by the addition of ascorbic acid.

Imipramine has a phenothiazine-like nucleus in common with chlorpromazine, another psychoactive drug that is know to generate free radicals. It has long been suspected that the pharmacological actions of phenothiazine drugs may be due to their effects on oxidation-reduction processes, such as respiration, that depend on free radical intermediates.

Reference

BORG D. C. (1965). Free Radicals from Imipramine. Biochem.Pharmacol. 14, 115-120. doi:10.1016/0006-2952(65)90066-3

Color and ESR signal

2008-03-22T14:25:00.001-07:00

Color and ESR signal are closely related. They are in fact an expression of the same electronic disbalance. Szent-Gyorgyi's research focused on the close relationship between visible color, electronic desaturation, and biological activity. He observed that preparations of normal liver gave an ESR signal, whereas cancerous liver tissue had an undetectable ESR signal, and he further observed that cancer liver had a dull grey color while healthy liver had a brown-pink color, thus he began to investigate the putative relationship between ESR and color.

Szent-Gyorgyi had a simple hypothesis, that cancer could be reversed by restoring its ESR signal and healthy pink color, by means of decreasing the electron acceptor/donor quotient. Szent-Gyorgyi wrote:

"The malignant nature of cancer, due to its senseless proliferation, is intimately connected with the physical state that makes the cancer uncolored and makes it give a poor ESR signal. This makes it likely that the restoration of color and ESR signal to such cancer could also abolish malignancy."

White casein is a poor electron acceptor until it reacts with methylglyoxal. When pure white casein powder was added to methylglyoxal, it changed to a vivid brown color, and its ESR signal changed too. White casein powder had no ESR signal while brown casein had a large ESR signal, about 100X larger than untreated white protein. The action of methylglyoxal was to desaturate the otherwise electron-filled ground states of the casein macromolecules, so the change in color and ESR signal was related to a rearrangement of electrons in the outer orbital shells of the reagents.

Collagen and white lysozyme were used besides white casein. On reacting with methylglyoxal these proteins assumed a stable brown color. In summary, McLaughlin wrote:

"When proteins such as casein, collagen, bovine serum albumin, and lysozyme react with methylglyoxal they assume a stable brown color and exhibit a greatly enhanced electronic conductivity and ESR activity compared with the normal unreacted proteins." (J.A. McLaughlin, 1980)

In the figure below, curve 1 is an absorption peak with lambda max of 328 nm (yellow color) of methylgloxal-treated bovine serum albumin (BSA-MG).

The peak at 328 nm (e.g. curve 1) could be a resonance stabilized n-pi* transition for a Schiff base linked to an aldehydic carbonyl group of methylglyoxal. The conversion of white to colored BSA indicates the formation of a Schiff base (-HC=N-) linkage between the amino group of lysine side chains and methylglyoxal. The involvement of a Schiff base in the color transition was demonstrated by chemically blocking the lysine side chains of BSA (curve 2, Figure 1 above), leading to a complex with no yellow color. This showed that the presence of lysine side-chains, probably nitrogen p orbitals, are essential for brown coloration in the proteins.

The appearance of the yellow color reaction was sensitive to pH. When the reaction was held at pH 4 (curve 3, Figue 1 above), there was no appearance of yellow color or an absorption peak at 328 nm, because at pH below 7, protonation of the lysine amine side groups is expected to prevent the color reaction and the formation of a protein-methylglyoxal complex.

In Figure 4 below, the absorption peak at 330 nm was monitored in time, for a BSA-methylgloxal complex in a variable pH environment. Figure 4 illustrates a diminishment of the absorbance upon a shift to pH 2, and an increase in the absorbance of the complex upon a shift to pH 7, further showing the relationship between visible color, electronic desaturation, and the transition states of charge-transfer complexes.

Brown and white casein also differed in electroconductive properties. Brown methylgloxal-treated BSA (BSA-MG) exhibited a larger D.C. conductivity than untreated BSA, as shown in the plot below.

References

Bone, S. and R. Pethig (1978). Electronic and dielectric properties of protein--methylglyoxal complexes. Ciba found. Symp. 67, 83-105.

McLaughlin, J. A., R. Pethig and A. Szent-Gyorgyi (1980). Spectroscopic studies of the protein-methylglyoxal adduct. Proc. Natl. Acad. Sci. U. S. A. 77, 949-951. doi:10.1073/pnas.77.2.949

Electrons and tubulin

2008-03-22T13:00:00.001-07:00

Pohl and Szent-Gyorgyi observed a very different ESR signal from extracts of soluble v insoluble proteins of mice liver. Liver was chosen as the sample since it is one the tissues in the body with the highest ESR signal. It was observed that the ESR signal of insoluble liver proteins was strong, while the signal from soluble proteins was weak. This indicated that membrane proteins, which are thought to be a part of the insoluble fraction, may be semiconductors whereas proteins in the soluble fraction cannot be expected to be semiconductors.

Figure 1 shows the prominent ESR spectra observed from insoluble proteins of healthy liver.

Pohl and Szent-Gyorgyi explained the difference between "vegetative" and "work" proteins based on the ESR spectra. The vegetative or soluble proteins of liver lack an ESR signal because they are likely to have closed shell orbitals, whereas the work or insoluble proteins have unpaired electrons which confer electroconductive properties, that essentially allow the proteins to do work. Pohl and Szent-Gyorgyi wrote:

"According to the concepts developed in this laboratory, the simple "vegetative" functions are still performed by soluble molecules with closed shells of electrons, while the more complex "animal" functions which produce work, W, and involve energy transformations are performed by the insoluble structures, characterized by their electronic disbalance." (H.A. Pohl, 1977)

Microtubules, which are composed of tubulin protein, are associated with "work" functions of the cell, since they form a large component of the insoluble liver proteins that gives rise to an ESR signal. Microtubules have a long history of work at separating the chromosomes of dividing cells.

Whereas DNA and proteins are held together by covalent linkages, microtubules are held together by weak non-covalent interactions, which means that their assembly and disassembly is controlled without covalent bonds being formed or broken. A change to rapid shrinkage is called catastrophe and the change to growth is called rescue. Typically the microtubule switches between catastrophe and rescue a few times per minute, as microtubules maintain a dynamic equilibrium. Nearby dipoles and electromagnetic fields have an essential role in initiating the assembly and disassembly of tubulin monomers and affecting microtubule dynamics.

Microtubules undergo rounds of depolymerization and polymerization. Tubulin protein is very unique and different when compared with the soluble proteins of the cell, because it is capable of undergoing transformation because of its access to "free" electrons. Most proteins in the soluble fraction of liver are incapable of such transformations. Szent-Gyorgyi and colleagues showed that the soluble portion of the cell has almost no ESR signal compared to the insoluble portion, because most biological and other organic molecules have even numbers of electrons that fill the available energy levels in pairs.

In the cell where biopolymers are intimate contact with each other, it is quite conceivable that unpaired electron migration may take place over large distances involving a number of aggregated biopolymers. In a lattice of multiple tubulin proteins, numerous molecular orbitals overlap, forming what is known as a conduction band, along which unpaired electrons travel. Microtubules can be aligned by electric currents, as shown below.

In the absence of electric fields, microtubules translocate in random directions, however, as soon as the electric field is applied, microtubules start to turn toward the anode and align with the direction of electric fields. After 30 seconds, nearly all the microtubules are translocating roughly parallel to the electric field toward the anode.

Clearly, there is an interplay between the assembly of the cytoskeleton and the electrical fields of the body. Bioelectric fields of the body (e.g. EEG) certainly interact with cytoskeletal proteins in the radical state (e.g. tubulin proteins that give rise to a large ESR signal), whereas the insoluble "vegetative" proteins with closed shell orbitals may be more resistant to these field currents.

References

Pohl, H. A., P.R. Gascoyne and A. Szent-Gyorgyi 1977. Electron spin resonance absorption of tissue constituents. Proc. Natl. Acad. Sci. U. S. A. 74, 1558-1560. DOI:10.1073/pnas.74.4.1558

Kim, T., M.T. Kao, E.F. Hasselbrink and E. Meyhofer 2007. Active alignment of microtubules with electric fields. Nano Lett. 7, 211-217. DOI:10.1021/nl061474k

Cancer structural proteins lack ESR properties

2008-03-22T11:19:00.001-07:00

Human liver cancer does not have the same ESR signal as normal liver. [1]

Samples of liver normally have a very prominent ESR, which is undetected in cancerous liver samples. Mallard and Kent compared normal rats with rats treated with the carcinogen butter yellow. Figure 1 below shows that normal liver tissue has an ESR peak, which is absent from chemically-induced liver cancer. The signal intensity is proportional to the number of unpaired electrons sensed by the instrument, thus the authors concluded that free radicals were absent from rat cancer. [2]

The insoluble protein fraction of rat liver carcinoma, which contributes a significant portion of the signal, lacked a detectable ESR signal, shown in Figure 5 below. The absence of ESR signal in cancerous tissue could be related to faulty cytoskeletal proteins, such as tubulin.

Szent-Gyorgyi gave the explanation that cancerous proteins lack the normal ESR signal because malignant proteins have paired electrons that fill the available molecular energy levels, and not enough unpaired electrons. He put forth an elaborate history for the living state and cancer. [3,4]

In the period before aerobic life, Szent-Gyorgyi presumed that the atmosphere would be strongly reducing, dominated by electron donors, that is, molecules would tend rather to give off than take up electrons. During pre-aerobic times, proteins contained full orbitals, occupied mostly by electron pairs. This situation still persists in the plant kingdom, where plants are mostly involved with chemical processes of reduction, not oxidation. In plants and during pre-aerobic times, there would be little electronic mobility between one molecule and the next, because filled orbitals tend to have a low reactivity with other electron pairs that are held strongly in place. Szent-Gyorgyi speculated that primitive cells would be unable to develop charge-transfer reactions between neighboring proteins, because few proteins could enter the radical state. Then he imagined the appearance of oxidative chemical processes. Oxygen, an electron acceptor, began the second aerobic phase of life's existence. Free radicals such as oxygen contain an uncoupled electron (radicals), and radicals are known for their great reactivity. Szent-Gyorgyi wrote:

"The appearance of oxygen meant the appearance of an electron acceptor capable of taking up single electrons and in so doing separating electrons of electron pairs, leading to the production of unpaired electrons, electron holes, and partially occupied orbitals. This lent a high and subtle reactivity to proteins, generating the unbalanced forces capable of linking molecules together to form integrated functional structures." [4]

When Szent-Gyorgyi and colleagues failed to detect free radicals in cancer tissue, they predicted that cancer therapies one day might aim to restore free radical content.

References

1. COMMONER, B. and J.L. TERNBERG 1961. Free radicals in surviving tissues. Proc. Natl. Acad. Sci. U. S. A. 47, 1374-1384. DOI:10.1073/pnas.47.9.1374

2. MALLARD, J. R. and J. KENT 1964. Differences observed between electron spin resonance signals from surviving tumour tissues and from their corresponding normal tissues. Nature. 204, 1192. DOI:10.1038/2041192a0

3. Szent-Gyorgyi, A. 1977. The living state and cancer. Proc. Natl. Acad. Sci. U. S. A. 74, 2844-2847. DOI:10.1073/pnas.74.7.2844

4. Pohl, H. A., P.R. Gascoyne and A. Szent-Gyorgyi 1977. Electron spin resonance absorption of tissue constituents. Proc. Natl. Acad. Sci. U. S. A. 74, 1558-1560. DOI:10.1073/pnas.74.4.1558

Mitosis and field potentials

2008-02-24T15:08:00.000-08:00

"For more than a century various investigators have noted similarities between the pattern of the mitotic spindle apparatus and the field geometry of electric and magnetic dipole moments (see Fig. 1).

From Microtubules

Cooper (1981) further proposed that the onset of mitosis is associated with a ferroelectric phase transition that establishes an axis of oscillation for the cellular polarization wave. The mitotic spindle apparatus would delineate the polarization field with microtubules lined up along the electric field lines. The poles would represent regions of the highest field intensity and the equatorial plane would provide a nodal manifold. The chromosome condensation during this transformation would, in this picture, be induced by the static dielectric polarization of the chromatin complex resulting from the cellular ferroelectric phase transition." (J.A. Tuszynski, 1997)

Reference

Tuszynski J. A., B. Trpisova, D. Sept and J. A. Brown. (1997). Selected physical issues in the structure and function of microtubules. J.Struct.Biol. 118, 94-106. doi:10.1006/jsbi.1997.3843

Beta2-Adrenergic receptor crystal structure

2007-12-18T21:40:00.001-08:00

Good news from The Scripps Research Institute. The human beta2-adrenergic receptor (beta2-AR) has been crystallized ! !

Hallucinogenic molecules bind to G-protein coupled receptors (GPCRs), a large family that includes the beta2-AR and serotonin 2A receptor (5-HT2AR). A popular theory is that hallucinogens such as psilocybin and DMT affect constitutive signaling at the 5-HT2AR. Hallucinogenic drugs probably bind to dopamine GPCRs too. The results with the carazolol-bound beta2-AR structure can be extended to psychedelic research since the 5-HT2AR is highly conserved with the beta2-AR, and the beta2-AR was crystallized with the inverse agonist carazolol, which closely resembles psilocin.

From beta2-AR

Figure 5 shows carazolol (yellow) bound to the beta2-AR.

The beta2-AR has seven transmembrane helices (Figure 1 below). Intracellular loop 3 (ICL3) is found on the intracellular side of the cell membrane, where G-proteins bind to the receptor. The 5-HT2AR couples to Gq/11, via interactions involving ICL3. The ICL3 domains of various GPCRs have been shown to provide docking sites for beta/gamma G-proteins subunits, as well as arrestins.

GPCRs have amazing structural plasticity to accommodate many different binding ligands. In particular, ICL3 has been identified as a highly unstructured region using protease susceptibility and intramolecular fluorescence resonance energy transfer experiments. Obtaining high-resolution structures of GPCRs other than rhodopsin has been challenging because of their inherent structural flexibility and instability. The flexibility of the ICL3 region probably leads to the receptor's conformational heterogeneity and crystallization problems.

The authors developed a clever strategy to obtain the beta2-AR crystals. They replaced ICL3 with T4 lysozyme (T4L), a well-folded protein that restricts the movement of helices. The final construct used for crystallization trials had residues 231 to 262 of the beta2-AR replaced by amino acids 2 to 161 of T4L. The authors called the fusion protein "beta2-adrenergic receptor-T4L," or beta2-AR-T4L.

The beta2-AR-T4L did not couple to G-proteins, so it was not a functional G-protein, and the presence of T4L at the ICL3 region could potentially affect the arrangement of the normal protein, but there didn't seem to be another option. The researchers set up over 2,000 conditions at 4 C and 20 C to attempt to grow wild-type crystals of beta2-AR.

"Despite substantial efforts, we were unable to grow diffraction-quality crystals from purified, homogeneous wild-type (WT) beta2-adrenergic receptor." (D.M. Rosenbaum, 2007)

This effort is a testimony to the flexibility of the beta2-AR and perhaps GPCRs in general. A tightly packed protein such as T4 lysozyme can be crystallized easily, but a native GPCR cannot be crystallized because it vibrates too much to "freeze out". By attaching T4L as a seed for the crystallization process, the researchers sufficiently minimized the molecular motions of the beta2-AR protein. Another strategy for obtaining beta2-AR crystals involved making monoclonal antibodies to the ICL3, and then fragments of an antibody (Fab). The researchers were able to crystallize a beta2-AR-Fab5 construct, and remarkably, binding of Fab5 to beta2-AR did not alter agonist or antagonist binding affinities, so presumably the native structure of the beta2-AR was unaffected.

The figure below shows beta2-AR-T4L (blue/grey) and the beta2-AR-Fab (yellow/grey).

In the previous 7 years, rhodopsin was the only GPCR structure that was available. The beta2-AR crystal structure will be utilized in the next months to generate better theoretical models of the 5-HT2AR, and make predictions about the orientation of hallucinogens in the binding pocket.

References

Cherezov V., D. M. Rosenbaum, M. A. Hanson, S. G. Rasmussen, F. S. Thian, T. S. Kobilka, H. J. Choi, P. Kuhn, W. I. Weis, B. K. Kobilka and R. C. Stevens. (2007). High-resolution crystal structure of an engineered human beta2-adrenergic G protein-coupled receptor. Science. 318, 1258-1265. 10.1126/science.1150577

Rosenbaum D. M., V. Cherezov, M. A. Hanson, S. G. Rasmussen, F. S. Thian, T. S. Kobilka, H. J. Choi, X. J. Yao, W. I. Weis, R. C. Stevens and B. K. Kobilka. (2007). GPCR engineering yields high-resolution structural insights into beta2-adrenergic receptor function. Science. 318, 1266-1273. 10.1126/science.1150609

Rasmussen S. G., H. J. Choi, D. M. Rosenbaum, T. S. Kobilka, F. S. Thian, P. C. Edwards, M. Burghammer, V. R. Ratnala, R. Sanishvili, R. F. Fischetti, G. F. Schertler, W. I. Weis and B. K. Kobilka. (2007). Crystal structure of the human beta2 adrenergic G-protein-coupled receptor. Nature. 450, 383-387. 10.1038/nature06325