Figure 2.

In forskolin-treated beta cells, caffeine released Ca²⁺ from an Ins(1,4,5)P₃-insensitive pool. Conditions of experiments were as in the legend to Fig. 1. Forskolin (5 μM) was added before the addition of caffeine. Caffeine (10 mM), in the continued presence of forskolin, induced Ca²⁺ spikes in 13 of 21 cells examined. Carbachol (10 μM) released further Ca²⁺ from the Ins(1,4,5)P₃-sensitive pool.