GATING KINETICS OF THE Ca CHANNEL

Abstract

Gating kinetics of the Ca channel have been studied recently by applying a cell attached patch clamp and a whole cell recording techniques to the rat pituitary cell line, GH₃, and to the hair cells dissociated from a chick vestibular organ. In both preparations, Ca channels were gated open by depolarizing command pulses and were not inactivated. The activation kinetics were reasonably fitted by the mm² kinetic model, while the steady-state noise analysis indicated a presence of much faster opening-closing kinetics in the gating mechanism. The fast opening-closing gating mechanism was observed in the Ba cullents passing through a single Ca channel. Steady-state noise analyses and single channel Ba currents suggest a presence of dual gates in the Ca channel; the one may be a voltage dependent slow gate which operates on a reaction scheme analogous to the mm² process, and the other may be a less voltage dependent fast gate which seems operating independent of the slow gate.