Fig. 3. Effect of bupivacaine on maximal Ca2+-activated tension in skinned ventricular trabeculae obtained at pCa 4.8. The concentration of bupivacaine was changed from 1 to 100 μm. Control = in the absence of bupivacaine. The values were significantly different as follows (P < 0.01 for all): 10 μm versus control, 10 μm versus 1 μm, 100 μm versus control, 100 μm versus 1 μm, and 100 μm versus 10 μm. Asterisks indicate the significant difference compared with control (P < 0.01). Tension at pCa 4.8 was regarded as the maximum because a further increase in the Ca2+concentration had no effect on isometric tension in the presence of 100 μm bupivacaine. Vertical bars are SEM of eight data points.