TEMPERATURE DEPENDENCE OF THE SODIUM CHANNEL GATING KINETICS IN THE NODE OF RANVIER

Abstract

Temperature dependence of the Na+ channel gating kinetics was measured from the ionic and charge displacement currents in the node of Ranvier of Xenopus laevis. m3h kinetics was applied, assuming a delay, δt, in the activation process. The rate constants for the m‐ and h‐process showed Arrhenius temperature‐dependence with Q10 of 2·34 and 2·9 respectively, while δt exhibited non‐Arrhenius temperature‐dependence. Q10 for [unknown]PNa, measured as 1·6, was smaller than for the rate constants and similar to that for a diffusion process. A negative shift and decrease in voltage sensitivity of the steady‐state curves, h∞ and m∞, occurred with decreasing temperature. The maximum time constant obtained from a single exponential fit to the displacement currents during the pulse for times greater than 90 µs exhibited Q10 of 2·01, which lies between that for [unknown]PNa and that for τm. © 1982 The Physiological Society