Fig. 4. Effects of the inhibitor of mitogen-activated protein kinase kinase (MEK), PD98059, on isoflurane-increased phosphorylated ERK1/2 (pERK1/2) level. PD98059 = 10 μm; Iso = 3% isoflurane; pERK1/2 = phosphorylated ERK1/2. Mean ± SD (n = 3–8). pERK1/2 levels are expressed as a percentage of the control (vehicle, 100%). *P < 0.05 compared with control containing vehicle. #P < 0.05 compared with 3% isoflurane. The MEK inhibitor, PD98059, significantly decreased pERK1/2 levels, and the isoflurane-increased pERK1/2 levels were completely blocked.