Voltage clamp of cardiac muscle. A theoretical analysis of early currents in the single sucrose gap.

A theoretical model is presented for the early currents in the voltage clamp of cardiac muscle using the single sucrose gap technique. The preparation is represented by a single one-dimensional active cable with modified Hodgkin-Huxley membrane and the interent imperfections in the technique are also included, e.g., leakage through the sucrose gap and resistance in series with the membrane in the test compartment. The stability of the control system was found to depend on the position of the control point with respect to the sucrose gap border. Computed currents for a stable system closely resembled those in the literature and those from a near-ideal system (e.g., squid axon.) The potential immediately across the membrane, however (not including potential drops across the series resistance external to the membrane), was found to be essentially uncontrolled and the "current-voltage" relationship was shown to be almost independent of membrane properties.