Figure 4.

The β₁ subunit exerts its characteristic effects on gating in 0 Ca²⁺ _i from +30 to +100 mV. Data are plotted for α channels (○) and α+β₁ channels (•). All data were obtained in 0 Ca²⁺ _i. (A–F) Plots of the indicated kinetic parameters versus membrane potential. The β₁ subunit increased P _o (A), mean burst duration (B), the mean duration of gaps between bursts (C), mean open time (D), and the mean numbers of openings per bursts (F) over the examined range of membrane potentials by shifting the parameters on the double logarithmic plots, while having little effect on the mean closed times (E). The data for α channels are from eight patches containing 1–12 channels and the data for α+β₁ channels are from nine patches containing 1–13 channels. Multichannel patches were used only when the P _o was sufficiently low that bursts did not overlap. Parameters from multichannel patches were corrected for the number of channels in each patch. Data are plotted as the mean ± SEM.