Non-atropinic anticholinergic action of quinidine on the ferret stomach

1 The effect of quinidine on the cholinergic response of the ferret gastric corpus was investigated in vivo and in vitro. 2 In vivo, the atropine sensitive contractions of the gastric corpus evoked by stimulation of the cervical vagus in the anaesthetized ferret were antagonized by quinidine (10-30 mg/kg). 3 In vitro, quinidine (10 micrograms/ml) antagonized the contractile response elicited by transmural stimulation (T.M.) of strips of corpus. At this dose of quinidine, the response to acetylcholine at doses adjusted to match the response to T.M. stimulation were unaffected. At higher doses of quinidine (50 micrograms/ml) the response to stimulation of the non-cholinergic, non-adrenergic inhibitory neurones was also antagonized. 4 These results indicate that, at low doses, quinidine has an inhibitory effect on the cholinergic neurones.