Effects of amiodarone on barium-induced automatic activity in guinea pig ventricular muscle.
1. The electrophysiological effects of a potent antiarrhythmic agent, amiodarone, on BaCl2-induced automaticity of guinea pig ventricular papillary muscle were studied by means of conventional microelectrode techniques. 2. BaCl2 (5 x 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. The application of amiodarone (4.4 x 10(-5) M to 1.1 x 10(-3) M) to the BaCl2-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. Amiodarone may exert the inhibitory effects of BaCl2-induced automaticity by decreasing steady-state conductance for the Na+ and Ca2+, probably thereby permitting the manifestation of antiarrhythmic properties in combination of its other actions.
Aomine
M
M
Department of Physiology, Medical College of Oita, Japan.
D000200:Action Potentials / Q000187:drug effects; D000638:Amiodarone / Q000494:pharmacology*; D000818:Animals; D001464:Barium / Q000494:pharmacology*; D005260:Female; D006168:Guinea Pigs; D006321:Heart / Q000187:drug effects*; D066298:In Vitro Techniques; D008297:Male; D008839:Microelectrodes; D010210:Papillary Muscles / Q000187:drug effects
D001464:Barium; D000638:Amiodarone