Spike-forming model of the neural membrane: computer simulation of some perfused axon experiments.

This paper is an attempt to account for the action potential spikes observed when the normal axoplasm of a squid giant neuron is replaced by a postassium-free, sodium-rich fluid, and the axon is immersed in a potassiumand sodium-free, calcium-rich bath. For this purpose a recently described model of the neural membrane [Wooldridge, D. E. (1975) Proc. Nat. Acad. Sci. USA 72, 3468-3471] is extended. Allowances are made for the flow of Ca++, Cl-, and Na+ ions through some of the membrane pore configurations, as well as for some electron conductance, all of amounts too small to be significant in the normal neuron. It is also postulated that the nature of the perfusing fluid affects the rates of some of the reactions that change the convertible gates from one configuration to another, as well as the ionic permeabilities of the resulting configurations. The result of the modifications is a single membrane model that accounts for the 3-sec, 15 muA/cm2 action potential spikes of the perfused axon as well as for the 0.5-msec, 1 mA/cm2 spikes of the normal neuron.