Abstract

Electrical signaling in nerve, muscle, and endocrine cells depends on the initiation of action potentials by voltage-gated sodium channels, as described by Hodgkin and Huxley using the voltage-clamp technique (Hodgkin and Huxley, 1952a,b,c,d). By imposing a rapid depolarization upon the membrane of the giant nerve axon of the squid, they showed that sodium channels rapidly activate (within 1 ms) and then rapidly inactivate (within 5 ms). The brief pulse of inward sodium current produced by the activation of sodium channels is responsible for the rapidly rising (depolarizing) phase of the action potential and for its rapid conduction along nerve and muscle fibers. These studies first revealed the transient sodium currents as the mechanism of initiation and propagation of action potentials.