Fig. 1.

Presence of the β1 subunit decreases the sensitivity of BK channels to penitrem. A and B, representative traces of BK current at +100 mV in HEK 293 cells transfected with hSlo α (A) or hSlo α + β1 (B). Whole-cell current was measured before (control) and after the addition of penitrem A (100 nM). C, group data (n = 4–16 cells at each concentration) show the effect of BK channel subunit composition on sensitivity to block by penitrem A. *, p < 0.05 between the two groups as determined by two-way ANOVA. D and E, group data (n = 3–9) show time- and concentration-dependent block of BK α (D) and α + β1 (E) by penitrem A. Note that compared with α a 10× higher concentration of penitrem A is required to achieve a similar time-dependent block in α + β1.