Figure 5. Effects of isoflurane, ouabain, and isoflurane plus ouabain on the force of contraction at different stimulation frequencies. Mean +/- SEM (n = 7). C, control; I, isoflurane (1.5%); O, ouabain (1 micro Meter); O + I, ouabain (1 micro Meter) + isoflurane (1.5%). *P < 0.05 compared with the corresponding control value at the same frequency.