Nonsyncytial nature of cardiac muscle: membrane resistance of single cells

Abstract

Previous work suggested that the myocardium is not a functional syncytium. In the present study of isolated frog ventricle, constant-current pulses were used to estimate the d.c. resistance between two microelectrodes when: a) both were extracellular, b) one was intracellular, and c) both were intracellular. A resistance of 12.4 ± 0.5 megohms was obtained for single cells. This large resistance indicates that the cells are functionally small units. The resistance between two cells was about twice that of one cell and was independent of the distance between the cells. Hence there are no low resistance pathways between cells. The results support the hypothesis that conduction in the heart does not involve a functional syncytium; rather junctional transmission may occur from cell to cell. Myocardial cells which had been previously punctured generally showed a much lower resistance, even though the resting and action potentials were normal.