Actions of some analogues of tryptamine on the isolated rat uterus and on the isolated rat fundus strip preparations.

Some 3-(2-dialkylaminoethyl)-, 3-(2-alkylaminoethyl)-, and 3-(2-dialkylaminoethyl)-2-methylindoles have been synthesized and tested, along with 5-benzyloxygramine, 5-benzyloxy-3-(2-dimethylaminoethyl)-, 3-(2-aminopropyl)- and 3-(2-aminobutyl)-indoles, on the rat uterus and rat fundus strip. 5-Benzyloxy-3-(2-dimethylaminoethyl)indole, even though it contains an ethylene side-chain, was a less potent antagonist of 5-hydroxytryptamine than was 5-benzyloxygramine. The remaining compounds were still less active. There are differences between the ability of some of them to antagonize 5-hydroxytryptamine and to antagonize tryptamine. 3-(2-Dimethylaminoethyl)-2-methylindole, in particular, shows a considerable degree of specific antagonism of 5-hydroxytryptamine on both tissues.Nearly all the compounds stimulate the preparations, some combining antagonism of 5-hydroxytryptamine at low concentrations with stimulant activity at higher concentrations. The most active compound is 3-(2-dipropylaminoethyl)indole. On the rat fundus strip this has, on a molar basis, 1/40th of the stimulant activity of 5-hydroxytryptamine, and is 20 times as active as tryptamine: on the rat uterus it is only 1/200th as active as 5-hydroxytryptamine, and equal in activity to tryptamine.