Microglias play a dual role in the induction of cerebral ischemic tolerance

Abstract

Objective To investigate the effect of focal cerebral ischemic preconditioning (IPC)on the activation of microglias to explore the endogenous neuroprotection of microglias. Methods SD rats were divided into 4 groups, in which the IPC (10 minutes)+MCAO group and SS (without IPC)+MCAO group received middle cerebral artery occlusion (MCAO, 2 h) followed by reperfusion (22 h),and the other 2 groups received SS+SS (blank controls) or IPC+SS (without MCAO). The infarct volume,ultrastructure and activation changes of microglias were evaluated in each group by riphenyltetrazolium chloride (TTC) staining, electron microscope and immunohistochemical staining, respectively. Results Compared with SS+MCAO group, the further reduction of infarct volume and slight ultrastructure changes were observed in the IPC+MCAO group. More severe pathological changes in the SS+MCAO group were observed than those in the IPC+MCAO group. In contrast with that in the IPC+SS group, the activation of microglias further increased in the SS+MCAO and IPC+MCAO group; while that in the SS+MCAO was significantly higher than that in the IPC+MCAO group (P＜0.05). Conclusion Microglias play a dual role in the induction of ischemic tolerance, and inflammation mediated by activation of microglias might be a key event in the mechanism of endogenous neuroprotection induced by focal IPC. Key words: Ischemic preconditioning; Ischemic tolerance; Cerebral infarction; Microglia