Methysergide fish surfacing reaction

Methysergide 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 UML-491 (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.

The figure below is the goldfish surfacing curve for 0.5 ug/mL LSD in water. About 95% of the fish show a nose-up, tail-down reaction within 20 minutes.



Methysergide is hallucinogenic in humans; like 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.