Fig. 2. Relations between anesthetic potencies (minimum alveolar concentration [MAC]) and percentage of response of muscle tension or intracellular concentration of free Ca²⁺([Ca²⁺]ⁱ) (indicated by R^340/380) in tracheal and bronchial smooth muscles. The volatile anesthetics tested had significantly greater inhibitory effects on bronchial smooth muscles than on tracheal smooth muscles. Symbols represent the mean ± SD; n = 7; * P < 0.05 versus  0 MAC anesthetic; †P < 0.05 versus  tracheal smooth muscle.