Effects of Propranolol on the Transmembrane Potentials of Ventricular Muscle and Purkinje Fibers of the Dog

摘要: Papillary muscle-false tendon tissue preparations isolated from dog hearts were perfused with Tyrode's solution containing propranolol in concentrations ranging 0.1 to 20.0 mg/liter. Transmembrane action potentials of both ventricular muscle fibers and Purkinje recorded. With sufficient concentration drug, the velocity upstroke overshoot fiber types decreased. The curve relating level membrane potential for was displaced right down. ability respond rapid frequencies stimulation Repolarization accelerated by propranolol, but repolarization unaffected. Duration effective refractory period decreased; that unchanged. Graded responses decremental impulse conduction abolished presence propranolol. Low doses which caused no change transmembrane completely blocked increase diastolic depolarization normally induced epinephrine. possible mechanisms might exert its antiarrhythmic actions on arrhythmias discussed.