The electrically stimulated ileum of the guinea-pig for measuring acetylcholine antagonism at different sites

Abstract

Abstract The transmurally stimulated guinea-pig ileum preparation was used to determine quantitatively the antagonism developed by hexamethonium and atropine against the emptying reaction and the longitudinal muscle response. Hexamethonium in concentrations of 1·5–6·0 μg/ml blocked the emptying reaction but larger doses, 8–10 μg/ml, failed to depress the longitudinal response to less than 50% of its original height. Atropine, on the other hand, in concentrations of 0·001–0·02 μg/ml, reduced the longitudinal response without affecting the emptying reaction. Thus, the preparation discriminates between acetylcholine antagonists acting at either the nicotinic or muscarinic site.