Fig. 3.

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 and BK-KO mice. Surprisingly, there was no rightward shift in the concentration-response curves for the contraction amplitude (A), frequency (B), and muscle force (C) such as that observed in the WT animals in the presence of IBTX (see Fig. 2), and even a leftward shift was noted on the effects on the phasic contraction amplitude (A). Data are normalized to the 20 mM K⁺-induced contractions. Values are means ± SE (n = 14–21). *P < 0.05 (unpaired test).