THE THEORETICAL BASIS FOR NONEXPONENTIAL TIME-COURSE OF THE RECOVERY FROM INACTIVATION OF HODGKIN-HUXLEY-TYPE IONIC CURRENTS

In this paper, we have carried out a theoretical analysis of the recov ery process of inactivating currents whose voltage-dependent conductan ces obey the Hodgkin-Huxley equations. We demonstrate that the recover y process is complex, and, in particular, is non-exponential. Conseque ntly, it cannot be characterized by a single-time constant. Neverthele ss, its time-course is completely determined by the properties of the activation and inactivation kinetics at the membrane potential at whic h the deinactivation of the current takes place. Moreover, we show tha t the recovery asymptotically approaches an exponential time-course wh ose time-constant, in turn, is found to be identical to that of the in activation at the membrane potential of deinactivation. The method com monly used to reconstruct the recovery process can, therefore, provide a way of estimating the inactivation time-constant at membrane potent ials where a measurement with the usual voltage-clamp protocol would n ot be possible. The conclusions of our analysis are discussed with reg ard to recent theoretical and experimental results.