Neuroprotection induced by Estrogen Against Focal Cerebral Ischemic-reperfusion Injury in Ovariectomized Rats

Objective:To study the neuroprotection and its mechanism by estrogen after cerebral ischemic reperfusion in ovariectomized rats.Methods:Female SD rats bilaterally ovariectomized two weeks before were subjected to 2-hour middle cerebral artery(MCA)occlusion by intraluminal filament,followed by a reperfusion of 70 hours.The neurological status of each rat was evaluated after reperfusions of 2 hours and 70 hours.At the reperfusion 70 hours after administration of estrodiol benzoate,the cerebral pathology, change in cerebral infarct volume ratio and edema volume were investigated under microscope;immunohistochemistry technique was applied to study the expression of estrogen-receptor(ER)of cerebral cortex;the serum levels of IL-1 and TNF were measured.Results:The neurological deficit scores,cerebral infarct volume ratio,cerebral edema volume,serum levels of IL-1 and TNF at reperfusion 70 hours in the group treated with estrogen were significantly reduced than that of control group(P0.01)except neurological deficit scores after reperfusion 2 hours (P0.05).Furthermore,the number of ER-labeled positive cortical neurons after estrogen injection was significantly increased than that in control group.Conclusion:Estrogen provides significantly neuroprotective effect for ovariectomized rat with focal infarction.A possible mechanism of neuroprotection is by means of inhibiting inflammatory cytokines(IL-1、TNF) releasing.Potential interaction between estrogen and ER might be involved in neuroprotection induced by estrogen against cerebral ischemic injury.