Comparison of two-pulse sodium inactivation with reactivation in Myxicola giant axons.

Values for the time constant of reactivation of the sodium conductance following depolarization sufficient to completely inactivate GNa have been compared over a 15 mV range of membrane potential with the time constants of inactivation during a depolarization prepulse. Over this range the reactivation time constants were consistently 30-50% larger than the inactivation time constants determined simultaneously at the same potential in the same axon. The data suggests that inactivation and reactivation do not occur by identical mechanisms, and therefore implies that there are at least three kinds of experimental procedures necessary to fully characterize the sodium inactivation process in any particular system.