Fig. 3. Effects of 1 μm nifedipine on muscle tension and intracellular concentration of free Ca2+([Ca2+]i) (indicated by R340/380) in carbachol-stimulated tracheal and bronchial smooth muscles. The inhibitory effects on the muscle tension and [Ca2+]iwere significantly greater in tracheal smooth muscles than in bronchial smooth muscles. Bars represent the mean ± SD; n = 7; * P < 0.05 versus tracheal smooth muscle.