Fig. 1. Changes in intracellular concentration of free Ca²⁺(indicated by R^340/380) and muscle tension during contractions induced by high K⁺(72.7 mm) and carbachol (1 μm). Low temperature (34°C) was introduced during the contractions. Exposure to low temperature reduced the carbachol-induced increase in Ca²⁺, but it enhanced the muscle contraction.