Resolution of Two Components in the Upstroke of the Action Potential in Atrioventricular Fibers of the Rabbit Heart

Abstract

A preparation is described which allows recording of unaltered intracellular potentials from different regions of the perfused heart (atrium, interventricular septum, and atrioventricular junction). Two components were identified in the upstroke of action potentials from nodal (A.V.) cells. In low sodium medium, a time lag between the two components becomes evident. Amplitude and slope of the first one decrease and the characteristics of the second one remain unaltered. It is concluded that the first component is sodium-dependent, while another not yet identified ion determines the second component.