Muscarinic inhibitory receptors in pulmonary parasympathetic nerves in the guinea‐pig

Open Access
Publisher Website
Google Scholar
Abstract
1 In anaesthetized guinea-pigs, gallamine produced a dose-related potentiation of the bronchoconstriction induced by electrical stimulation of the cervical vagus nerves; (+)-tubocurarine and suxamethonium lacked this effect. 2 The bronchoconstriction produced by intravenous injection of acetylcholine or histamine, however, was not potentiated by gallamine. 3 Vagally-induced bradycardia was abolished by gallamine, confirming antagonism of the effect of acetylcholine on muscarinic receptors in the heart. 4 The muscarinic receptor agonist pilocarpine, had the opposite effect to gallamine in the lung as it inhibited vagally-mediated bronchoconstriction. 5 Pretreatment of guinea-pigs with either guanethidine or propranolol did not affect the gallamine-induced potentiation of vagally-mediated bronchoconstriction. 6 The potentiating effect of gallamine in the lung can be explained by blockade of inhibitory, muscarinic receptors located in the parasympathetic nerves supplying the lungs.