Fig. 3. Concentration dependence of volatile anesthetic preconditioning. ( A ) Isoflurane (Iso) concentration-dependence curve. Age-matched adult wild-type Caenorhabditis elegans were exposed to various concentrations of isoflurane for 4 h at 20°, were allowed to recover for 1 h in air at 20°, and were subsequently challenged for 20 h in a hypoxia chamber (<0.3% O 2 ) and were then allowed to recover for 24 h in air at 20° before scoring as alive or dead. The data points represent the mean ± SEM of five trials with more than 50 animals/trial. * P < 0.01 after Bonferroni correction versus 0% by Fisher exact chi-square test for A-B . ( B ) Halothane (Hal) concentration-dependence curve. Identical to A except with various concentrations of halothane. The data points represent the mean ± SEM of five trials with more than 50 animals/trial.