FIGURE 6.

Extracellular acidification does not significantly affect gating transitions within bursts. Unitary current from cell-attached patches recorded at pH 7.4 and 6.4 with 2- or 3-min depolarizing pulses to 100 mV were idealized using a half-amplitude method. (A) The open duration histogram obtained from the current trace shown in Fig. 5 A was fitted to a biexponential distribution to give time constants of 0.5 and 2.6 ms, and an area of 0.30 and 0.70, respectively. (B) The closed duration histogram obtained at pH 7.4 was fitted to a four-component exponential distribution, and the fastest three time constants were 0.2, 0.5, and 4.8 ms, with a respective area of 0.63, 0.36, and 0.02. The slowest component (time constant 0.48 s) is thought to represent one or more inactivated states. It has a relative area <1% of the total closed events. (C) The open duration histogram generated from the current trace shown in Fig. 5 B at pH 6.4. The fast and slow time constants are 0.5 and 2.1 ms with an area of 0.2 and 0.8, respectively. (D) The closed duration histogram at pH 6.4 was fitted to a four-component exponential distribution. The three fastest components have time constants 0.2, 0.4, and 2.6 ms and an area 0.81, 0.18, and 0.01, respectively. The slowest component (time constant 5.5 s) represents <1% of the total nonconducting events.