Weak electrotonic interaction between contiguous cardiac cells

¹ Department of Physiology, Western Reserve University School of Medicine, Cleveland, Ohio

Electrotonic spread of current was studied by double microelectrodes cemented at various distances. A bridge circuit enabled transmembrane potentials to be recorded at zero distance from injected current. At interelectrode distances of 60 µ or greater, current flow of 16 x 10^–9 amp through one intracellular electrode produced no change in potential at the second electrode. At interelectrode distances of 45 µ or less, similar currents through a given electrode pair produced either a substantial or no change in potential depending on the impalement. Various criteria, including simultaneous subthreshold oscillations, indicated when both electrodes impaled the same cell. The degree of electrotonic spread did not increase during the plateau of the action potential and did not depend on the interelectrode distance per se at close interelectrode distances. Thus, current flow through one cell does not have substantial effect on the membrane potentials of adjacent cells; hence the intercalated discs may be high resistance.

Key Words: cardiac muscle electrophysiology • nonsyncytial nature • role of intercalated discs • electrotonic spread of current • space constant measurements • transmembrane potentials • voltage/current curves • membrane resistance • cell-to-cell interaction

Submitted on January 6, 1964