Fig. 4.

Time course of inactivation of the currents through recombinant calcium channels expressed inXenopus oocytes. A, Normalized representative currents for oocytes coexpressing the α_1Aand the β₄ subunits in the absence or in the presence of the full-length α₂δ or the chimeric α₂Ad subunits. In all cases the decay of the currents was poorly fit by a single exponential. The sum of two exponential functions was necessary:I_Ba = I_∞+A_f(exp(−t/τ_f) +A_s(exp(−t/τ_s) + c, where I_∞ is the steady-state inward current, A is the amplitude,t is time, and τ_f and τ_s are time constants for the fast and slow components, respectively.B, Pooled data comparing the average time constants (τ_fast and τ_slow) and relative contribution of the slow component of inactivation amplitude (Amp) at 0 mV from various oocytes in the three groups (n = 6). Asterisks denote significant differences (p < 0.05).