Temperature dependence of the sodium channel gating kinetics in the node of Ranvier

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, delta t, 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 delta t exhibited non-Arrhenius temperature-dependence. Q10 for 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 infinity and m infinity, 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 microseconds exhibited Q10 of 2.01, which lies between that for PNa and that for tau m.