Figure 9. Recovery of VONa conductance from inactivation.

A, protocol used to examine recovery from inactivation. Pericytes were held at −100 mV and depolarized to −10 mV for 50 ms to elicit the baseline Na⁺ current (I_Na,BL) and inactivate the associated Na⁺ conductance. Subsequently, the cells were repolarized to a specified interpulse potential (V_ip). Pericytes were maintained at V_ip for 1, 2, 5, 10, 20, 50, 100, 200 or 500 ms (separate sweeps, not all values are shown in the illustration). Subsequently, a repeat test pulse to −10 mV for 10 ms was performed to obtain a measurement of I_Na after the interpulse recovery period at V_ip. Intersweep intervals of 5 s were employed. Using separate executions of similar protocols, V_ip was varied between −60 and −120 mV. B, example of I_Na traces elicited at baseline (BL) and then again, following various interpulse intervals (1–500 ms, V_ip, −120 mV). Upward deviations are cell capacitance transients and downward deviations are I_Na. C, the mean (± s.e.m.) I_Na, normalized to I_Na,BL, is plotted against the interpulse interval. Results obtained at the various interpulse potentials (V_ip) are superimposed to illustrate the effect on the rate of recovery from inactivation. D, the mean (± s.e.m.) time constant for recovery of I_Na (τ) is plotted for n = 8–10 cells tested at each V_ip. Exponential fits to the data are superimposed (see text).