Figure 7.

Simulations of stochastic gating of 120 channels of two different single-channel currents mixed in different proportions. (A) Variance–mean plot for mixing 90 7-pA and 30 14-pA channels, fit to Eq. 1, gave i = −4.8 pA. (B) Variance–mean plot for mixing of 30 7-pA and 90 14-pA channels, fit to Eq. 1, gave i = −6.5 pA. In A and B, both 7-pA and 14­-pA channels have the same activation time constants τ_Act = 10 μs. (C) Variance–mean plot for mixing 90 7-pA and 30 14-pA channels, fit to Eq. 1, gave i = −4.2 pA. (D) Variance–mean plot for mixing of 30 7-pA and 90 14-pA channels, fit to Eq. 1, gave i = −3.9 pA. In C and D, 7-pA and 14-pA channels have activation time constants τ_Act = 16 μs and 4 μs, respectively. In all conditions, both channel currents were filtered at 10 kHz. (E) Plot of apparent channel current versus proportion that were 14-pA channels [N₁₄ / (N₇ + N₁₄)]. Currents unfiltered (raw, open circles), channels with identical kinetics (τ_Act = 10 μs), filtered at 10 kHz (filled circles), and channels with different kinetics (7-pA channel τ_Act = 16 μs; 14-pA channel τ_Act = 4 μs) all filtered at 10 kHz (crosses). Note that with mixing of 7-pA slow channels and 14-pA fast channels, the apparent conductance is virtually unchanged.