Figure 2.

Involvement of Ca²⁺ dynamics and Ca²⁺ sensitization in the relaxant effect of β₂-adrenoceptor agonists. (a,b) Typical samples of continuous recording of tension and F340/F380 demonstrating the inhibitory effect of procaterol (0.1–30 nM) (a) and salbutamol (1–100 nM) (b) on MCh (1 µM)-induced smooth muscle contraction; (c,d) Concentration–response curve for procaterol (0.1–10 nM) (c) and salbutamol (1–100 nM) (d) in tension (□) and F340/F380 (■) in 1 µM MCh-precontracted smooth muscle. Resting state tension and F340/F380 were taken as 0%, and those in each MCh-stimulated state were taken as 100%. MCh, methacholine; PRO, procaterol; SB, salbutamol. **** p < 0.0001; *** p < 0.001; ** p < 0.01; * p < 0.05.