Figure 1. Simultaneous force (top) and intracellular [Ca²⁺] (bottom) measurements before, during and after cyanide application to guinea-pig ureter.

A, phasic contractions produced by action potentials following electrical stimulation. B, tonic contraction produced by high K⁺ depolarization. The Ca²⁺ measurements were made from the ratio of the fluorescence signals of indo-1 emitted at 400 and 500 nm. Adapted from Bullock & Wray, 1998.