THE RELATIVE ACTIVITIES OF SOME TRYPTAMINE ANALOGUES ON THE ISOLATED RAT STOMACH STRIP PREPARATION

Abstract

The relative potencies of analogues of tryptamine and 5‐hydroxytryptamine have been determined on the rat fundus preparation. This tissue had an amine oxidase activity, which, in the homogenate, was able to inactivate both tryptamine and 5‐hydroxytryptamine to about the same degree. Amine oxidase inhibitors potentiated the action of tryptamine and many analogues on the isolated rat fundus preparation, but not the action of 5‐hydroxytryptamine or of other hydroxytryptamines. This suggested that, in the isolated organ, the amine oxidase was unable to inactivate 5‐hydroxytryptamine, but could inactivate tryptamine, 5‐methoxytryptamine and many others. These results may be explained if it is supposed that tryptamine entered the cell, but because of the polar hydroxy 1 group 5‐hydroxytryptamine did not. This hypothesis is supported by the oil/water partition coefficients. The structure/activity of the various tryptamine derivatives is discussed in the light of this assumption. 1959 British Pharmacological Society