Antimuscarinic cholinergic effects of scopolamine and other cholinergic antagonists

The effects of 36 M-antagonists, including QNB (3-quinuclidinyl benzilate), scopolamine, atropine. benzhexol, anisodine, anisodamine, B-7601,8025 and 8018 were compared for their receptor binding activities, antitremor and anticatalepsy potencies. The interaction with muscarinic (M-) choliner8;icreceptors was measured by the inhibition of [3H]QNB specificajly bound to the membrane preparations from rat cerebral cortex. Dose-response plots of the binding data showed that the slopes of compounds studied were approximatelyl. so the binding of these antagonists seemed to follow simply a mass action law and bind to the same receptor pool. The affinity constants (Ki) for most of them were correlated with theif antitremor potencies (r = 0.71, P