FIGURE 4.

InsP₃-mediated Ca²⁺ puffs and global Ca²⁺ increases. At −70 mV, locally photolyzed caged InsP₃ (6.25 μm) (↑, B) in a ∼20-μm diameter region (A, bright spot in left-hand panel, see also whole cell electrode, left side) evoked a Ca²⁺ puff that was preceded by a Ca²⁺“blip”-like event (A and B). Flash photolysis of caged InsP₃ in the area is indicated by the circle, in A each ∼60 s generated Ca²⁺ puffs (B, black line). When photolysis energy was increased to photolyze more InsP₃ a larger amount of Ca²⁺ release occurred throughout the region (B, red line). The Ca²⁺ puff was overlaid (B, right panel) for comparison. The [Ca²⁺]_c images (A) are derived from the time points indicated by the corresponding numbers in B. [Ca²⁺]_c changes in A are expressed by color: dark blue, low and light blue, high [Ca²⁺]_c. Measurements were made from a 3 × 3 pixel box located at the center of each Ca²⁺ release event (not shown). The large increase in fluorescence at time 0 is the flash artifact.