[Possibility of substance selective action on the m-cholinoreceptors of a specific site].

Effects of a number of agents on the muscarine-sensitive acetylcholine receptors (muscarinic receptors) of different localization were investigated. Experiments on anesthetized cats revealed the following effects of acetylcholine: hypotension, bradycardia, bronchospasm, contractions of the ileum and urinary bladder, hypersalivation. It was shown that the highest sensitivity to bisquaternary ammonium derivatives of diphenyl cyclobutanedicarboxylic (truxillic) acid is exhibited by the muscarinic receptors of the heart. The sensitivity of bronchial muscarinic receptors is slightly lower. The prevailing action on the muscarinic receptors of the heart was also shown by some N-adamantyl bisquaternary ammonium compounds. Procaine and the antihistaminics mebhydroline and diphenhydramine eliminated bradycardia induced by acetylcholine without affecting the latter's hypotensive effect. The evidence obtained indicates the heterogeneity of the muscarinic receptors of different localization.