Figure 4
Effect of temperature on WT, R1451C and R1451L channels. (A) Representative whole-cell traces recorded at −10 mV of WT, R1451L and R1451C channels at 10 °C (blue), 15 °C (purple), 22 °C (black/orange/green) and 28 °C (red). The dashed line represents zero current. (B) Voltage dependence of inactivation time constants of WT (n = 9), R1451C (n = 8) and R1451L (n = 7) channels recorded at 10 °C. The time course of the current decay elicited at depolarized voltages was best fitted to a single exponential function, and the resulting time constants (τh) were plotted against voltage. The kinetics of fast inactivation were slower for all channels at all voltages by cooling to 10 °C. The statistical significances of the differences between the WT and R1451C/L channels (*P < 0.05, **P < 0.001, ***P < 0.001) are shown. (C) Arrhenius plots showing the temperature sensitivities of WT and R1451C/L channels. Unlike R1451C, the slope of the R1451L was significantly different from that of the WT as revealed by ANCOVA statistical test (**P < 0.005). The R1451 Each data point is a mean of 6–15 cells. (D) Steady-state inactivation (left curves) after a 500-ms prepulse was left-shifted for WT (n = 10), R1451C (n = 8) and R1451L (n = 7) by 7, 8 and 5 mV, respectively, whereas that of steady-state activation (right curves) was right-shifted by 5, 12 and 16 mV for WT (n = 11), R1451C (n = 8) and R1451L (n = 9), respectively. The V1/2, kv, and n values are given in Table 2. The protocols are the same as those in Fig. 2C. (E) Recovery from inactivation of WT (n = 5), R1451C (n = 8) and R1451L (n = 5) channels. The resulting curves were fitted to a single exponential equation, yielding one time constant (τ). The τ of R1451L (3.3 ± 0.3 ms) was slightly smaller than the τ of WT channel (4.4 ± 0.3 ms). The values of the time constants are given in Table 2. For clarity, the grey curves in (B,D and E) represent the experiments performed at 22 °C (see Fig. 2).
