Methysergide fish surfacing reaction

Methysergide, also referred to as UML-491, causes the fish surfacing reaction in the same way that LSD does, but a higher dose is needed. Methysergide is about 250X less potent than LSD in goldfish. The figure below shows the fish surfacing curve for methysergide. A concentration of 50 ug/mL of UML-491 in the outside liquid gives approximately the same per cent of goldfish reacting as does 0.2 ug/mL LSD.

Methysergide is considered to be a hallucinogenic drug in humans. As a larger dose of methysergide is needed to elicit the fish surfacing reaction, a larger dose of methysergide is needed for human effects.


Reference

Gettner, H. H., A. Rolo and H.A. Abramson 1965. Lysergic acid diethylamide (LSD 25). 36. comparison of effect of methysergide (UML 491) on goldfish and siamese fighting fish. J. Psychol. 61, 87-92.