Comparison of Lysergic Acid Derivatives and Antihistamines as Inhibitors of the Edema Provoked in the Rat’s Paw by Serotonin

Abstract

The edema-provoking effects of locally injected serotonin and histamine in the rat''s paw are compared. With 1 [mu]g serotonin per paw a more marked edema is obtained than with 200 times larger amounts of histamine. This serotonin edema can easily be blocked by various amide derivatives of lysergic acid. Two of these derivatives proved to be definitely stronger antiserotonin compounds than the well known hallucinogenic compound LSD, namely the methyl-derivatives of ergonovine and of methylergonovine. Among the series of 8 antihistamines included in this study, only representatives of the phenothiazine and piperidine group exert a marked inhibition of the serotonin edema, when used in a dose range which is between 100 and 1000 times higher than the effective doses of the most potent lysergic acid derivatives.