Objective To observe the distributive characteristics of glial cell line-derived neurotrophic factor(GDNF)in brain tissue during cerebral ischemia-reperfusion in rats,and its role in ischemic brain damage.Methods The model of focal cerebral ischemia was made by occluding middle cerebral artery(MCA) for 2 h and reperfusion for 0.5～48 h, HE Staining was used to investigate the histological features of ischemic cerebral damage,the immunohistochemical method was used to observe the distributive characteristics of GDNF in brain tissue in rats. Results The focal ischemic areas (including preoptic area, striatum and cortex) presented at 0.5 h of reperfusion and peaked at 24 h. The neurons presented irreversible degeneration at 6 h of reperfusion. At 24 h, the ischemic area in the preoptic area developed into infarct form. At 0.5 h of reperfusion, neurons in ischemic cortex showed GDNF weak positive, neurons in peri-ischemic regions showed GDNF moderate positive. During reperfusion 3～48 h, neurons in ischemic regions showed GDNF negative. Up to 48 h of reperfusion, the active microglias or macroglias in periinfart area strongly expressed GDNF.The number of GDNF positive cells in all groups decreased (P