Single-ion electrodiffusion models of the late sodium and potassium currents in the giant axon of the squid

Single-ion electrodiffusion has been studied theoretically as a possible mechanism responsible for K super(+) activation and Na super(+) inactivation i.e., the processes constituting the late current following a voltage clamp potential step in the Hodgkin-Huxley axon. Nonsteady-state conductance changes under voltage clamp have been computed in the nonlinear range, assuming a constant electric field. The results show a general agreement with the Hodgkin Huxley equations. The shapes, sigmoidal or exponential, of the conductance transients are well reproduced in the electrodiffusion models. The behavior of the time constant is also compatible with squid axon data. Some discrepancies are present and possible theoretical explanations of them are discussed.