Electrophysiological effects of nicardipine hydrochloride on the isolated sinoatrial and atrioventricular nodes of the rabbit.

The electrophysiological effects of nicardipine-HCl, a new calcium antagonist and potent vasodilator, were studied in the isolated sinoatrial (SA) and atrio-ventricular (AV) nodes of the rabbit in an oxygenated Tyrode solution at 35 degrees C using an intracellular microelectrode technique. Nicardipine-HCl decreased the spontaneous rate of the SA node and prolonged sinus recovery time, dose-dependently. The effective refractory period (ERP) and functional refractory period (FRP) of the AV node and AV conduction time (A-H interval) were also prolonged by nicardipine-HCl in a dose-dependent manner. In conclusion, nicardipine-HCl has electrophysiological effects on the SA and the AV node similar to those of other calcium antagonists in the excised and superfused rabbit heart.