Abstract: Background The underlying mechanism of early neurobiological impairment after subarachnoid hemorrhage (SAH) is not well understood,but the system of reactive oxygen superoxide (ROS) might be involved.Edaravone (MC1-186),a potent free radical scavenger that prevents apoptosis of neurons,was thus used in this study to see its possible therapeutic effect in early brain injury due to SAH in a rat model.Methods One hundred and twenty male Sprague-Dawley rats were randomly assigned to four groups:group 1,control rats receiving sham operation only;group 2,rats with SAH treated by saline;group 3,rats with SAH treated with 1 mg/kg MCI-186 injected intraperitoneally;and group 4,rats with SAH treated with 3 mg/kg MC1-186.Treated with either saline or MC1-186 twice daily for two consecutive days after SAH,the rats were sacrificed for measurements of malondialdehyde (MDA) and activity of superoxide dismutase (SOD) and histological analysis of caspase-3 protein by Western blotting and immunohistochemical staining.In addition,mortality and neurological scores were statistically analyzed by the chi-square test and Dunn's procedure respectively for each group.One-way analysis of variance followed by the Tukey's procedure was also used in data analysis.Results The rats in group 2 that received saline only showed neurological impairment as well as elevated mortality,and were found to have significantly increased levels of MDA and caspase-3,but reduced SOD activities in brain tissues (P<0.05).When treated with MC1-186 at two different dosages,the rats in groups 3 and 4 had markedly decreased levels of MDA and caspase-3 but increased SOD activities in the brain tissue (P<0.05),along with improved scores of neurological evaluation (P<0.05).Conclusions This study sheds some lights on the therapy of SAH-induced early brain injury by providing the promising data indicating that MC1-186,a radical scavenger,can efficiently diminish apoptosis of neurons and thus prevent the function loss of the brain in rats with SAH.