SINGLE FIBER RECORDING OF THE EFFECTS OF QUINIDINE AT ATRIAL AND PACEMAKER SITES IN THE ISOLATED RIGHT ATRIUM OF THE RABBIT

¹ Department of Pharmacoloqy, School of Medicine, University of Washington, Seattle, Washington

The effects of quinidine were studied its isolated atrial preparations from rabbits. Quinidine was administered in the concentration of 6 µg per ml. The environmental temperature was 37°C. Atrial segments deprived of the normal pacemaker were driven electrically. Action potential configuration was observed over a wide range of stimulation rates, both under control and experimental conditions. Quinidine was shown to depress the rate of repolarization at all frequencies, but depressed the rate of depolarization only at the higher frequencies of the range. In spontaneously beating right atria, or in isolated sinoatrial node preparations, quinidine retarded the rate of repolarization in pacemaker cells and reduced the spontaneous discharge rate of such cells. It was concluded that the effect of quinidine on the depolarization process was secondary to its effect on the processes of repolarization and recovery.