Periodicity in Na⁺ channel properties alters excitability of a model neuron

Abstract

The voltage gated Na channels play vital role in action potential waveform shaping and propagation. We have shown earlier that the duration and amplitude of a prolonged depolarization alter all the steady state and kinetic parameters of rNa_ν1.2a voltage gated Na channel in a pseudo-oscillatory fashion. In the present study, we show that the Hodgkin-Huxley voltage and time dependent rate constants of activation (α_m and β_m) and fast inactivation (α_hand β_h), obtained from the analyses of Na currents and steady state activation and inactivation plots, following application of prepulses in both slow (1-100 s) and fast (100-1000 ms) ranges, vary with the duration of a prepulse in a pseudo-oscillatory manner. Using these Hodgkin-Huxley kinetic parameters in simulation, the excitability and firing pattern of a model neuron are shown to vary in a history dependent periodic fashion.