The effect of ISO and forskolin on Ca²⁺ sensitivity in airway SMCs. The relaxation of airways, contracted with 0.1 µM 5-HT, induced by (A) 1 µM ISO or (B) 1 µM forskolin in lung slices before and after Ca²⁺ permeabilization with 20 mM caffeine and 50 µM ryanodine. ISO and forskolin strongly relaxed airways before and after Ca²⁺ permeabilization. Data are representative of at least three different slices from two mice.