Action of bretylium on the isolated guinea-pig ileum

Bretylium inhibits the contractions of the longitudinal muscle caused by histamine and, to a lesser extent, those by acetylcholine, carbachol and nicotine. It is a very weak antagonist of 5-hydroxytryptamine and in concentrations of up to 190 μg/ml. does not inhibit the actions of bradykinin and substance P on the longitudinal muscle. The inhibitory effect of bretylium on the emptying phase of the peristaltic reflex is similar to that of ganglion blocking agents, while the much less pronounced effect on the contraction of the longitudinal muscle during the preparatory phase is assumed to be due to a weak atropine-like action.