Action of Biogenic Amines, Amine Oxidase Inhibitors, and Other Agents on Chromatophores of Squid, Loligo pealii.

(1) The multicellular system that controls chromatophores of Loligo pealii has been a useful tool for study of smooth muscle function in non-narcotized living animals. (2) Acetylcholine opened chromatophores. The following compounds closed them: Monamine-serotonin. tryptamine HCl, tyramine HCl; indoles-LSD 25; monamine oxidase inhibitors-iproniazid, PIH, Ro-5-0700; autonomic blockers-chlorpromazine; competitors for choline esterase-eserine sulfate. (3) Diamine, histamine dihydrochloride, had no effect. Other monamines, L-lysine and L-alanine, had no effect in comparable dosage. Catechol amines epinephrine and norepinephrine were ineffective. A precursor of serotonin, 5-hydroxytryptophan, had no effect. (4) Closure of chromatophores by an active substance was not reversible by electrical stimulation. (5) Attention is called to the fact that constricting agents all share a common property, that of resonance, and that a number of them are capable of electron donation. (6) Results obtained are consonant with theory that chromatophore control is achieved by an amine-amine oxidase system (closure), opposed by an acetylcholine-choline esterase system (expansion).