FIGURE 6.

Depolarization of ΔΨ_M with CCCP/oligomycin inhibits Ca²⁺ puffs. At −70 mV, locally photolyzed caged InsP₃ (25 μm) (↑, C) in a ∼20-μm diameter region (A, bright spot in left-hand panel, see also whole cell electrode, left side) evoked Ca²⁺ puffs in an EGTA (300 μm)-buffered colonic myocyte (B and C). Note: there are two individual Ca²⁺ puff sites in response to photorelease of InsP₃; one site releases Ca²⁺ just before the other site. Flash photolysis of InsP₃ every ∼60 s generated approximately comparable [Ca²⁺]_c increases (C). Superfusion of CCCP and oligomycin (1 and 6 μm, respectively) while continuing to photolyze InsP₃ at ∼60 intervals, decreased the amplitude of InsP₃-mediated Ca²⁺ puffs (B and C). The [Ca²⁺]_c images (B) are derived from the time points indicated by the corresponding numbers in C. [Ca²⁺]_c changes in B are expressed by color: dark blue, low and light blue, high [Ca²⁺]_c. Measurements were made from a 3 × 3 pixel box (A, right-hand panel, white square). The large increase in fluorescence at time 0 is the flash artifact.