bbTBA and sucrose each slow paxilline inhibition. (A) Blockade of Slo1 current by 100 nM paxilline is displayed with and without simultaneous application of 100 µM bbTBA. The equilibration conditions were 0 mV with 10 µM Ca²⁺, and BK current availability was monitored by voltage steps to 160 mV applied at 1 Hz. Blocker applications are shown with horizontal bars, with all measurements from the same patch. Block and unblock with 100 µM bbTBA alone (black) is rapid, whereas block by 100 nM paxilline (red) alone exhibits slow onset and recovery. After simultaneous application of paxilline with 100 µM bbTBA, the amount of paxilline inhibition is reduced about half. (B) BK currents were activated with 300 µM Ca²⁺ with the indicated voltage protocol without and with the addition of 2 M sucrose to the cytosolic solution. Insets show currents with a red trace at −20 mV. Sucrose markedly reduces outward current, whereas tail currents at −120 mV are reduced a little more than half. For control solutions, V_h = −16.3 ± 7.2 mV, whereas with 2 M sucrose, V_h = −12.8 ± 3.3 mV. (C) 100 nM paxilline strongly inhibits BK current, whereas in 2 M sucrose, both outward and inward currents are only slightly affected by paxilline. Top traces are single sweeps. Bottom traces correspond to an average of 15 sweeps before, during, and after washout of 100 nM paxilline. (D) Plot of time course of paxilline inhibition without and with 2 M sucrose suggests that sucrose slows the development of inhibition by paxilline.