Interaction between Alpha-1 Adrenergic and Vagal Effects on Cardiac Rate and Repolarization

摘要: Alpha-1 adrenergic stimulation modulates ventricular automaticity via an alpha-1 adrenoceptor (AR) subtype blocked by the alpha-1B antagonist chloroethylclonidine (CEC) and alters repolarization receptor subtype(s) (alpha-1A alpha-1D) WB4101. Our objective was to determine AR specific effects vagal interactions on heart rate repolarization. We studied right vagally innervated Langendorff-perfused guinea pig hearts, beta-blocked with propranolol, 5 x 10(-7) M. Heart QT interval were measured from bipolar epicardial electrodes. In some experiments corrected (QTc) (Bazett formula) calculated, as well. Phenylephrine (PE) alone, 10(-8) M, reduced sinus significantly (P .05). studies of repolarization, QTc shortening elicited PE alone induced attributable change rather than a direct effect conclusion, in setting beta blockade, appears responsible for decrease facilitation responsiveness. A WB4101 or is shortening. Whereas shortens interval, this action reflects ventricle.