Abstract
In the course of studies in this laboratory on the mode of action of catecholamines on the transmembrane potential of the extirpated atrium of rabbit (1), some of the potentials recorded from the pacemaker area (West) responded differently to reserpine and adrenaline from the typical pacemaker potentials. The potential under this study was recorded from the area which was somewhat wider than the triangular pacemaker area shown schematically by West (2). This potential was characteristic in a notching of the upstroke and a slow rate of depolarization, and was very sensitive to reserpine and adrenaline. The notched potential in the sinoatrial node of rabbit's heart was at first reported by West (2), who studied the distribution of the potential. Although the similar notched potentials have been reported in the atrioventricular node of mammalian heart (3, 4), the smooth muscle of uterus (5) and the sinoauricular funnel of amphibian heart (6), the exact nature of the potentials remains to be settled. In the present report the responses of the notched potential recorded from the sinoatrial node of rabbit's heart were studied. It is expected that the responses of the potential to reserpine and adrenaline might have some contribution to elucidate the mechanism of the pacemaker activity.
