Open and closed dwell-time distributions for BK_B channel DM4 at the indicated voltages in saturating Ca²⁺_i. Lines are mixtures of exponential components fitted to the dwell times. Open time histograms were described by one to two significant exponential components, and closed time histograms were described by two to five significant exponential components. The time constants and areas of the exponentials for the four studied channels are given in Tables S1 and S2. A moving bin mean of three consecutive bins was used for the data at negative potentials because of the small numbers of intervals at the low Po. Channel DM4 is presented in Figs. 3–7,⁴⁵⁶⁷ as a representative channel. Similar conclusions were reached with channels DM1–DM3.