Chromatic Responses of Fundulus to Lysergic Acid

¹ From the Physiology Division, Directorate of Medical Research, U.S. Army Chemical Warfare Laboratories, Army Chemical Center, Maryland

Lysergic acid diethylamide (LSD) was administered to Fundulus heteroclitus by injection and by immersion. In all experiments light-adapted fish became darker: the concentrated melanophores were dispersed. The degree of dispersal was directly related to the dose by a nearly straight line. A few behavioral changes in the fish were observed. If immersed in suitable concentrations of the drug in sea water, Fundulus absorbed a sufficient amount, probably through the respiratory surfaces of the gills, to disperse the melanophores. To darken immersed fish, a 1-hour Ct (concentration x time) of 120,000 mg min/m³ is required. Apparently the drug exerts a depressant action on specific loci in the brain from which the melanophore-concentrating fibers originate; this action allows the melanophore-dispersing fibers to darken the fish.