Figure 4. The relationship between extracellular cation levels, the intracellular Ca²⁺ concentration and responses to carbachol (CCh).

A, mean calibrated change in [Ca²⁺]_i on exposure to carbachol (10 μm; 90 s) for a range of extracellular Ca²⁺ and K⁺ concentrations. B, normalized intracellular Ca²⁺ level (relative to that in 5.4 mM K⁺, 1.8 mM Ca²⁺) at the time of the carbachol exposure under the various conditions. Pooled data were obtained from experiments where carbachol was applied under at least 2 separate conditions, without prior depolarization, and includes all cells that were responsive to carbachol.