Fig. 1. Mitochondrial depolarization slowed the rate of [Ca²⁺]_c decline following I_Ca activation and decreased the amplitude of the Ins(1,4,5)P₃-induced [Ca²⁺]_c rise. Plasmalemmal depolarization (–70 mV to +10 mV, 500 ms, A), local photolysis of caged Ins(1,4,5)P₃ (UV-flash release at , B) and carbachol (CCh, 100 µM by pressure ejection, C) each transiently increased [Ca²⁺]_c, as indicated by an increase in Fluo-4 fluorescence (controls, thin line). Inhibition of mitochondrial Ca²⁺ uptake by _m depolarization with CCCP plus oligomycin (1 µM and 6 µM, respectively, A), increased the time for [Ca²⁺]_c to decline to resting values (thick line), compared with vehicle-treated control (0.2% DMSO, thin line). The peak [Ca²⁺]_c rise evoked by Ins(1,4,5)P₃ release was decreased by _m depolarization (B, thick line), as was the peak [Ca²⁺]_c evoked by CCh (C, thick line), each compared with vehicle-treated control (0.2% DMSO, thin lines). By contrast, _m depolarization did not alter the amplitude or rate of decline of [Ca²⁺]_c increases evoked by caffeine (CAF; 10 mM by pressure ejection, D).