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. 2010 Jan 27;285(13):9402–9409. doi: 10.1074/jbc.M109.068205

FIGURE 1.

FIGURE 1.

Membrane depolarization augments the amplitude, but does not affect the kinetics of KCNQ2/Q3 currents expressed in Xenopus oocytes. KCNQ2/Q3 currents expressed in Xenopus oocytes were recorded under TEVC. A, KCNQ2/Q3 current was elicited by the voltage protocol shown above. The protocol was repeated with a minimum time interval of 65 ms. The arrow indicates the increase of the current with time. The dashed line shows the zero current level. B, membrane potential-dependence of KCNQ2/Q3 current amplitudes. KCNQ2/Q3 currents were increased by a continuous depolarization (+20 mV) with the time constant shown; the increased currents recovered when the membrane was repolarized (−80 mV) with the time constant shown. Brief depolarization pulses (+20 mV, 10 s) during the repolarization were applied to assess the changes of the current amplitudes. C, voltage-dependence of the depolarization-induced increase of KCNQ2/Q3 currents. The depolarization-induced current increases were assessed by the voltage protocol shown. I1 is the control current amplitude; I2 is the current amplitude after a 15 min conditioning voltages at different level. The ratio of I2 and I1 was plotted against the conditioning potentials. The data were fitted with the Boltzmann function, and V1/2 is −26.1 ± 0.5 mV. D, depolarization did not affect the activation and deactivation of KCNQ2/Q3 currents. Time constants of activation and deactivation of KCNQ2/Q3 currents before and after a 15-min depolarization (0 mV) were compared. The upper panel shows the voltage protocol used, and the activation and deactivation of KCNQ2/Q3 currents elicited by I1 and I2 are summarized and compared in the lower panel. E, conductance-voltage relationship (G-V) of KCNQ2/Q3 currents before (open squares) and after a 15-min depolarization (filled squares). The whole cell conductance was measured from the tail currents at −60 mV. Conductance at each depolarizing voltage was normalized to the Gmax. The data were fitted with the Boltzmann function, and V1/2 is −28.7 ± 0.5 mV and −29.6 ± 0.4 mV, respectively, for before and after the depolarization (n = 6). F, summary of fold increases for KCNQ currents induced by the depolarization. **, p < 0.01.