Electrophysiological Effects of Isoproterenol on Purkinje Fibers of the Heart

Publisher Website
Google Scholar
Abstract
The effects of isoproterenol on resting and action potentials, automaticity and conduction velocity in isolated Purkinje fibers of sheep hearts were studied with microelectrode recording techniques. In quiescent Purkinje fibers, local application of isoproterenol to the site of microelectrode recording caused depolarization to a potential level from which repetitive discharge occurred. During the acceleration in beat frequency, the threshold and maximum diastolic potentials increased. When isoproterenol was applied to the pacemaker of beating fibers, the steepness of the pacemaker potential increased and the rate accelerated. Threshold and maximum diastolic potentials were affected variably in the beating preparation. Isoproterenol did not change conduction velocity in isolated, stimulated Purkinje fibers. The electrophysiological effects of isoproterenol resemble those described previously for epinephrine. The observations do not permit definition of the mechanism of action.