Aim To explore the expression and significance of cyclooxygenase(COX-2)during the focal ischemic reperfusion injury of middle cerebral artery in rats.Methods The model of focal ischemic reperfusion injury of middle cerebral artery was built in rats by placing an intraluminal suture.80rats were divided into8groups,which were control group,ischemia for2hours,ischemic reperfusion for3hours,6hours,12hours,24hours,48hours,72hours.The nerve function was evaluated and the change of brain tissue injury was observed by HE stain.Northern blot,Western blot and immunohistoche-mistry were used to dectect the expression of COX-2.Results Manifestation of neurologic impairment gradually aggravatedwith the extension of reperfusion time.The mRNA and protein expression of COX-2increased significantly after ischemia for2hours,and gradually reinforced after reperfusion,which reached the peak from12hours to24hours after reperfusion(p<0.01).Conculsion The expression of COX-2gene in focal cerebral iscliemia reperfusion injury was dynamic changing process.The expression of COX-2protein may be involved in the delayed neuronal death after ischemic reperfusion injury.