VGL K DR [native]: ‘Delayed rectifier’ type K+ currents in native cell types of vertebrates

Abstract

This chapter discusses the delayed rectifier (DR) type K+ currents in native cell types of vertebrates. DR potassium channels in native cells were originally named because of the delayed or sigmoidal change in the membrane conductance that they induced following the application of voltage steps. A primary function of potassium-selective delayed rectifiers in nerve and muscle cells is the repolarization of action potentials propagated by Ca2+ and Na+ influx. In the Hodgkin–Huxley model for electrical propagation in the squid giant axon, activation of IK (repolarizing) was slow as compared to the INa (depolarizing) component. Consequently, the delayed rectifier component is frequently considered to be the final voltage-gated conductance that is activated following the depolarization of native cells. Activity of delayed rectifiers can therefore regulate the degree of Ca2+ influx with each action potential, and hence the action potential duration. In excitable cells, neurotransmitter modulation of IK can markedly affect presynaptic neurotransmitter release thresholds and/or development of postsynaptic potentials and muscular tone. A large number of separate genes that encode K+ channels with delayed rectifying properties can contribute to the heterogeneity.