Abstract: Objective To evaluate the therapeutic efficacy of two kinds of large dose hyperbaric oxygenation protocol on super-early acute permanent middle cerebral artery occlusion and their effects on oxidative stress of ischemic brain tissue in rats.Methods Rat'sintraluminal middle cerebral artery permanent occlusion models(MCAO) were randomly divided into two HBO groups(9 h and 18 h) and a control group.Main Outcome Measures:1) The Garcia neurological grading systems were used to assess the therapeutic efficacy of HBO.2) Twenty-four hours and 5 days after MCAO,the infarct volume was calculated with the TTC pathological staining and NIH Image J software.3) The animals of the three groups were separately examined for SOD,MDA and NO levels of ischemic brain tissue at the 18h,48 h and 5 day with spectrophotometric device.Results 1) There was significant improvement in neurobehavioral outcome of rats in 9 h and 18 h groups compared with the control group(P<0.01).2) Cerebral infarct volume decreased 63%～64% in rats of 9 h group and 66%～51% in rats of 18 h group respectively at 24 h and 5 d compared with the control group.3) The SOD level of 18 h group was remarkably lower than that of the control group at 18 h and 48 h(P<0.01 and P<0.05 respectively).4) The MDA level of the 9 h and 18 h groups were both remarkably lower than the controls,especially at the 18 h point(P<0.05).Meanwhile,the level of the 9 h group was remarkably lower than both of the 18 h group and the control group(P<0.01 & P<0.05 respectively).5) The levels of NO in both HBO groups were remarkably higher than that of the control at 18 h and 48 h time points(P<0.01);while the level in 18 h group was remarkably lower than that of 9 h group at 18 h time point(P<0.05).On the 5th day,the levels of NO were basically the same in all three groups.Conclusion 1) The two kinds large dose HBO is highly efficient in reducing infarct volume and improving neurobehavioral outcome in permanent middle cerebral artery occlusion at super-early stage.2) The dosage of HBO is not the longer the better,it may aggravate the oxidative stress of the ischemic tissue.

Key words: hyperbaric oxygenation, cerebral infarction, neurobehavioral outcome, infarct volume, oxidative stress