Whole-cell Ca²⁺ currents in islet cells from WT and CaV2.3^–/– mice. (A) Whole-cell Ca²⁺ currents (i) evoked by a 300-ms voltage-clamp depolarization (V) in WT CaV2.3^+/+ (black) and CaV2.3^–/– (gray) β cells. β cells were identified by exhibiting half-maximal Na⁺ channel inactivation at membrane potentials (V) lower than –100 mV (half-maximal inactivation at –102 mV; inset). (B) Average integrated current-voltage (Q-V) relationships. Data are mean values ± SEM in 10 WT (filled circles) and 10 CaV2.3^–/– (shaded circles) β cells. *P < 0.05. (C) Whole-cell Ca²⁺ currents were recorded as in A, but using CaV2.3^–/– β cells. The recordings were made under control conditions (lower gray line) in the presence of R-type Ca²⁺ channel blocker SNX482 (100 nM; black line) and after addition of L-type Ca²⁺ channel inhibitor isradipine (isr) (2 μM; upper gray line). (D) Average Q-V relationships representing mean values ± SEM in 4 CaV2.3^–/– β cells under control conditions (shaded circles), in the presence of SNX482 (filled circles), and after addition of isradipine (open circles). *P < 0.05, **P < 0.01, control versus SNX482 plus isradipine. (E) Whole-cell Ca²⁺ currents were recorded as in A, but in α cells identified by Na⁺ channel inactivation at membrane potentials greater than –100 mV (half-maximal inactivation at –49 mV; inset). (F) Q-V relationships in α cells. Data represent average values ± SEM in 8 WT (filled circles) and 4 CaV2.3^–/– (shaded circles) α cells. pC, picocoulombs.