Fig. 4. Effects of nifedipine on norepinephrine (NE)- and KCl-induced increases in force and R^340/380in the presence of ryanodine (+ryanodine). (A ) Examples of steady-state (i.e. , maximal) effects of nifedipine on the responses to either norepinephrine (left ) or KCl (right ). (B ) Analyzed data (left , force; right , R^340/380) (n = 4). *P < 0.05 versus  control (100%) within each group. The IC⁵⁰values for the inhibitions of norepinephrine-induced increases in force and R^340/380were 3.4 and 6.8 nm, respectively, whereas those for the inhibitions of KCl-induced increases in force and R^340/380were 0.016 and 0.12 μm, respectively.