Fig. 3. Time course (A ) and dose–response relation (B ) of isoflurane-increased extracellular signal–regulated kinase (ERK1/2) phosphorylation. pERK1/2 = phosphorylated ERK at molecular weight of 44 kDa (p44 or ERK1) and 42 kDa (p42 or ERK2); tERK1/2 = total ERK1/2; Iso (%) = isoflurane, concentrations in percent of partial pressure. Mean ± SD (n = 9). pERK1/2 levels are expressed as a percentage of the control (100%, vehicle without isoflurane). *P < 0.05 compared with the control. Isoflurane increased pERK1/2 (A and B ), which was a direct function of isoflurane concentrations (B ). However, the tERK1/2 (A ) values were relatively constant throughout each experiment to confirm the amount of total proteins administered and changes of pERK1/2 by isoflurane.