Abstract

Several indole compounds related to HT were found to have marked action on the inferior mesenteric ganglia of the cat.

Methylation of the terminal N atom of HT maintained or increased ganglionic stimulant action dependent upon the number of methyl substituents. N-Dimethylation of tryptamine definitely increased ganglionic stimulant potency as compared to the weak activity of tryptamine. The stimulant action of some of the N methylated compounds (bufotenidine, N,N,N-trimethyl-tryptamine) was, however, not HT-like but rather of cholinergic type. N,N-Diethyl and di-n-propyl derivatives of tryptamine and N,N-di-propyl HT were considerably weaker than the corresponding N,N-dimethyl compounds.

Methylation of the 5-OH group of HT or altering its ethylamine chain by methyl substitution, or both, brought about marked loss of ganglionic stimulant and blocking potencies. 4- and 6-hydroxy indole alkylamines were inactive on the inferior mesenteric ganglion as compared to HT and bufotenine.

Introduction of an amidine group in the molecules of tryptamine and HT resulted in compounds which primarily blocked the action of HT.

Marked divergence between the ganglionic and smooth muscle stimulant actions of these agents has been demonstrated.