[Effect of verapamil on chronotropic autoregulation in rabbit atria]

With continuous perfusion at defined intraluminal pressures of 0.1 and 0.5 kPa, the effect of the calcium ion antagonist verapamil on the chronotropic autoregulation mediated by stretch was investigated in right atrial preparations. At both intraluminal pressures verapamil at a concentration of 4 X 10(-7) mol/l decreased the atrial rate progressively with increasing duration of verapamil perfusion. Time-dependent the stretch acceleration was also inhibited significantly at 50-72% of the control values. The findings of the present study support the hypothesis of the participation of a calcium current in the origin of stretch-induced chronotropic autoregulation.