Fig. 2.

Concentration-response curves for the effects of isoproterenol (0.1 nM–100 μM) on the phasic contraction amplitude (A), phasic contraction frequency (B), muscle force integral (C), and muscle tone (D) in UBSM strips isolated from WT mice under control conditions and after the BK channel was blocked with IBTX (200 nM). In the presence of IBTX, the concentration-response curves were shifted to the right. Data are normalized to the 20 mM K⁺-induced contractions. Values are means ± SE (n = 4). *P < 0.05; **P < 0.01; ***P < 0.005 (paired test).