[Inactivation of fast sodium current across the membrane of isolated cardiocytes]

Inactivation of sodium conduction across the membrane of rat single heart cells was studied by the patch-voltage-clamp method. The development of sodium channel inactivation was found to be double-exponential. Dependence of both time constants on the membrane potential was measured. The time course of the recovery of the sodium conduction from inactivation was sigmoidal in shape with marked retardation at the beginning. The data obtained are not covered by the Hodgkin-Huxley formalismus.