Effect of inhibition of Ca²⁺ channels on BK currents from β2 KO SCN neurons. (A–C) BK currents recorded from β2 KO SCN neurons during the day. (A) Representative BK current traces in control (n = 22), 10 µM Nim (n = 18), and 10 µM Dan (n = 13). (B) The percentage of cells with a detectable BK current was reduced with Nim and Dan. *, Fisher's exact test (control vs. Nim, P = 0.01 and Dan, P = 0.04). (C) Peak daytime BK current density versus voltage from only those cells with a BK current in β2 KO control (n = 22), Nim (n = 13), Dan (n = 10), or a cocktail of 10 µM Nim, 10 µM Dan, and 3 µM MVIIC (n = 4). In β2 KO neurons, both Nim and Dan decreased BK current magnitude compared with control. Unlike with WT neurons (Fig. 3 D), the Ca²⁺ cocktail did not completely inhibit all BK current. *, One-way ANOVA with Bonferroni post hoc test at 90 mV: control versus Nim, P = 10⁻³; Dan, P = 10⁻³; and Ca²⁺ cocktail, P = 10⁻⁴). At 30 mV, only Nim significantly decreased the BK current (P = 0.03). (D–F) BK currents recorded from β2 KO SCN neurons during the night. (D) Representative BK current traces. (E) The percentage of cells with a detectable BK current was decreased with Dan at night. *, Fisher's exact test (control vs. Dan, P = 10⁻⁴). β2 KO Control, n = 17; Dan, n = 8; Nim, n = 12; and Ca²⁺ cocktail, n = 5. (F) Peak daytime BK current density versus voltage from only those cells with a BK current in control (n = 17), Nim (n = 12), Dan (n = 5), or cocktail (n = 5). Dan, but not Nim, produced a large decrement in BK current at night, similar to WT neurons (Fig. 4 D). *, One-way ANOVA with Bonferroni post hoc test at 90 mV: control vs. Dan, P = 10⁻⁴ or Ca²⁺ cocktail, P = 10⁻⁴. At 30 mV, Dan and the Ca²⁺ cocktail, but not Nim, significantly decreased the BK current (P = 0.001 and 0.002, respectively). All data are mean ± SE.