A SIMPLE-MODEL OF K+ CHANNEL ACTIVATION IN NERVE MEMBRANE

A model is proposed for activation of potassium ion channel current, I K, in squid giant axons, which consists of two closed states and one o pen state. The rate parameter in the forward direction between the two closed states depends upon previous history. That is, it relaxes expo nentially to its steady-state value appropriate to the membrane potent ial of a voltage clamp step rather than change instantaneously as in t raditional models of channel gating. The model successfully describes both the enhancement of the delay in activation of IK With relatively negative prepulse potentials, i.e. the Cole-Moore effect, and the time -dependent rising phase of ''on'' gating current, which has been repor ted recently for several types of potassium channels. (C) 1995 Academi c Press Limited