Afferent nerve fibre activity from left ventricular mechanoreceptors was recorded in 10 anaesthetized cats before and after two intravenous injections of 15 micrograms/kg digoxin at 1 hour interval. These receptors are activated by coronary artery occlusion and induce a depressor cardiovascular reflex resulting in bradycardia and hypotension. Neither the spontaneous activity of the receptor's afferent nerve fibres nor their maximum activity during temporary coronary artery occlusion was affected by digoxin. The results show that digoxin in therapeutic doses has no sensitizing effect on left ventricular mechanoreceptors with vagal afferent fibres. The sensitization of cardiopulmonary baroreflexes by digitalis glycosides shown in previous investigations is thus more likely to be mediated by a central nervous effect of the drug.

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Actions of diazepam on the discharge pattern of phrenic motoneurones in rats.

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