Effects of amiodarone on barium-induced automatic activity in guinea pig ventricular muscle

Abstract

1. 1. The electrophysiological effects of a potent antiarrhythmic agent, amiodarone, on BaCl 2-induced automaticity of guinea pig ventricular papillary muscle were studied by means of conventional microelectrode techniques. 2. 2. BaCl 2 (5 × 10 −4 M) depolarized the maximum diastolic potential of muscle preparation to about -62 mV and induced the spontaneous activity at rate of about 62 beats/min. 3. 3. The application of amiodarone (4.4 × 10 −5 M to 1.1 × 10 −3 M) to the BaCl 2-induced automatic muscle fibers decreased the spontaneous rate and slope of slow diastolic depolarization in a dose-dependent manner, associated with insignificant changes in action potential duration. 4. 4. Amiodarone may exert the inhibitory effects on BaCl 2-induced automaticity by decreasing steady-state conductance for the Na + and Ca 2+, probably thereby permitting the manifestation of antiarrhythmic properties in combination of its other actions.