Steady state inactivation of sodium permeability in myelinated nerve fibres of Xenopus laevis

Previous experiments (Dodge & Frankenhaeuser, 1958, 1959) have shown that the permeability changes at the node of Ranvier are qualitatively similar to those in the squid giant axon (Hodgkin & Huxley, 1952a-d). When the membrane is depolarized the sodium permeability rises rapidly to a peak and then falls as a result of inactivation. The aim of the present paper is to determine the relation between membrane potential and the extent to which the sodium conducting system is inactivated or refractory.