The role of nonlinear axonal membrane capacitance in modulating ion channel cooperativity in action potential dynamics: Studies on Hodgkin-Huxley's model.

Hodgkin-Huxley's (HH) model of action potential (AP) has been modified in view of the nonlinear membrane capacitance of the axon of a neuron as well as the cooperation among the participating ion channels in the axon. Previous studies of action potential behavior based on computational analysis of modified HH models with either nonlinear axonal membrane capacitance or ion channel cooperativity show significant changes in action potential dynamics, e.g. AP peak, hyperpolarization amplitude, spike threshold, rapid onset, etc. As shown in the present paper, the combined effect of the nonlinear capacitance and ion channel cooperativity displays qualitatively similar results that are quantitatively different. For example, the nonlinear membrane capacitance leads to a reduction in the ion channel cooperativity effect on the action potential dynamics. The reason for this combined effect is thought to be axonal membrane distortion and depolarization caused by the varying membrane potential.