Fig. 4. Effects of volatile anesthetics on Ca²⁺uptake by SR. (A ) Effects of halothane (HAL), enflurane (ENF), isoflurane (ISO), and sevoflurane (SEV), applied during the Ca²⁺loading, on the caffeine (20 mm)-induced contraction, an estimate for the amount of stored Ca²⁺, in either absence (left ) or presence (right ) of procaine (P; 10 mm for halothane, 1 mm for enflurane) in the fura-2–nonloaded strips (n = 4). * P < 0.05 versus  control (100%) within each group. #P < 0.05 versus  the enflurane group at each concentration. ‡P < 0.05 versus  the procaine-treated group at each concentration in each anesthetic group. (B ) Effects of halothane (HAL), enflurane (ENF), isoflurane (ISO), and sevoflurane (SEV), applied during Ca²⁺loading, on the caffeine (20 mm)-induced increases in R^340/380(open column) and force (gray column), estimates for the amount of stored Ca²⁺, in either absence or presence of procaine (PROC; 10 mm for halothane, 1 mm for enflurane) in the fura-2–loaded strips. Effects of procaine alone, applied during Ca²⁺loading phase, on the caffeine response are also shown (n = 4 or 5). * P < 0.05 versus  control (100%).