Figure 4. (A) Peak force induced by Ca2+release. Comparison between sevoflurane (black square, n = 4–6), isoflurane (dark gray square, n = 4–6) and halothane (light gray square, n = 4–7) at 7.6 mM and 3.5 mM (to evaluate the extent and direction of the effects) and in a lower concentration (0.6 mM equivalent to 5.87 vol% for sevoflurane, 2.68 vol% for isoflurane, and 2.28 vol% for halothane). Caffeine (30 mM) is shown as a standard and as a control (open square, n = 11). The relative force induced by caffeine was significantly greater than 3.5 mM and 0.6 mM of volatile anesthetics (P < 0.05, significance not indicated). (B) Peak Ca2+transients derived from force transients based on the [Ca2+]-force relation. The peak calcium transients induced by caffeine were significantly greater than those induced by 0.6 mM sevoflurane and isoflurane (significance not indicated). Results are mean +/- SD. *P < 0.05.