Vagus-induced changes in ventricular electrophysiology of the dog heart with and without beta-blockade.
We tested the electrophysiologic effects of vagus stimulation in six dogs in the presence or absence of beta-adrenoreceptor blockade. Monophasic action potentials were obtained by the suction electrode technique and programmed electrical stimulation was used to determine heart rate-independent changes in 50 and 90% repolarization times and in the effective (V-ERP) and functional (V-FRP) refractory periods of the right ventricle. Vagus stimulation decreased heart rate both in the presence and in the absence of beta-adrenoceptor blockade. It also increased action potential duration and refractoriness during high sympathetic tone induced by pentobarbital anesthesia. The effect is probably due mainly to inhibition of beta 1-adrenoreceptors, since it was decreased by beta 1-adrenoceptor blockade with atenolol. We conclude that stimulation of the vagus has antiarrhythmic effects in ventricles under high sympathetic stimulation.
D000109:Acetylcholine / Q000494:pharmacology; D000200:Action Potentials; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D005260:Female; D006321:Heart / Q000502:physiology*; D006801:Humans; D008297:Male; D011941:Receptors, Adrenergic / Q000502:physiology*; D011943:Receptors, Adrenergic, beta / Q000502:physiology*; D012032:Refractory Period, Electrophysiological; D014630:Vagus Nerve / Q000502:physiology*
D000319:Adrenergic beta-Antagonists; D011941:Receptors, Adrenergic; D011943:Receptors, Adrenergic, beta; D000109:Acetylcholine