1995 Volume 36 Issue 4 Pages 465-476
The lack of currently available data stimulated us to investigate the electrophysiological effects of ajmaline, a classical class Ia antiarrhythmic agent, on various currents responsible for the action potential plateau and repolarization phases. The whole cell patch clamp recording technique was applied to guinea pig ventricular myocytes. Ajmaline suppressed the Ca2+ current (ICa) in a dosedependent manner (K∂=1.2×10-5M) without affecting the steady-state inactivation kinetics and the voltage dependency of the currentvoltage relationship. Ajmaline inhibited the inward portion of the inward rectifying K+ current (IK1). Ajmaline decreased the delayed rectifier K+ current (IK) without altering the activation or deactivation time courses. All these inhibitory effects of ajmaline prolonged the action potential duration in a dose dependent manner. The inhibitory actions of ajmaline on the action potential upstroke and various currents responsible for the plateau and repolarization may contribute to the observed suppression of depolarizationinduced abnormal automaticities by this agent.
