Objective To investigate the ability of once and twice isoflurane preconditioning against oxygen and glucose deprivation（OGD） injury in rats brain in vitro.Methods Rat hippocampal slices were exposed to 1vol%,2vol% and 3vol% isoflurane for 30 min under normoxic condition（95% O2/5% CO2） once and twice（n=12 for each group） respectively before OGD.At the end of each exposure,the slices were set with a 15-min washout period interspersed,then slices were exposed to 13-min OGD period（95% N2/5%CO2,glucose-free） followed by 30min reoxygenation.The amplitude CA1 population spikes（PS,neuronal function） was measured and used to quantify the degree of recovery of neuronal function at post OGD period.To assess the role of the mitogen-activated protein kinases（MAPKs） in preconditioning,U0126,an inhibitor of extracellular signal-regulated protein kinase（MEK-ERK1/2）,and SB203580,an inhibitor of p38 MAPK,were used during isoflurane exposure.Results Isoflurane-preconditioning with 1vol%,2vol% and 3vol% once increased the degree of recovery from 4.8%±1.4%（control） to 41.9%±9.2%,55.1%±11.0% and 63.2%±10.8%,respectively,and twice to 53.8%±12.0%,63.5%±11.1% and 76.3%±12.3%, respectively.The effect of twice exposure to 3vol% isoflurane was blocked by U0126（6.1%±1.5%）.Conclusion It is concluded that twice isoflurane preconditioning could achieve better neuroprotection than once via activation of extracellular signal-regulated protein kinase（MEK-ERK1/2）.
