SLOW ACTIONS OF HYPERPOLARIZATION ON SODIUM-CHANNELS IN THE MEMBRANE OF MYELINATED NERVE

The mean sodium current, I, and the variance of sodium current fluctuations, var, were measured in myelinated nerve during a depolarization to V = 40 mV applied from the resting potential (VH = 0) or from a hyperpolarizing holding potential VH = -28 mV. From I and var the relative variations in the number N and the conductance γ of sodium channels following changes of the holding potential were calculated. Hyperpolarizing the membrane from VH = 0 to -28 mV increased N by a factor of 3.7, whereas γ decreased by a factor of 0.53. These actions of holding potential on sodium channels develop slowly since 500 ms prepulses to 0 or -28 mV do not alter the values of N and γ. © 1979.