Fig. 6. Effect of uncaging inositol-trisphosphate (IP₃) on cytosolic Ca²⁺ and Na⁺. (A) Uncaging IP₃ with a UV pulse elicited a cytosolic Ca²⁺ rise (F) but no membrane potential change. A second UV pulse changed neither cytosolic Ca²⁺ nor membrane potential, and membrane depolarization in 40 mmol l^–1 K⁺ still evoked a normal transient Ca²⁺ rise. (B,C) Summary of effects of uncaging IP₃ and of 40 mmol l^–1 K⁺ on cytosolic Ca²⁺ (B) and on the membrane potential (C). (D,E) Uncaging of IP₃ elicited a reversible intracellular Na⁺ rise but no membrane potential change. A second UV pulse had no effect on either Na⁺ or membrane potential. ^*P<0.05.