The distributive characteristics of inducible nitric oxide synthase(iNOS)in cerebraltissue of rats subjected to cerebral ischemia-reperfusion

Objective To observe the distributive characteristics of inducible nitric oxide synthase(iNOS)in cerebral tissue of rats subjected to cerebral Ischemia-reperfusion,and its role in ischemic brain damage.Methods The model of focal cerebral ischemia was made by occluding middle cerebral artery(MCA)for 2h and reperfusion for 3～120h.HE staining was used to investigate the histological features of ischemic cerebral damage,the immunohistochemical method was used to observe the expression of iNOS in brain tissue in rats.Results The neurons presented irreversible degeneration at 12h of reperfusion.At 24h,the ischemic area in the preoptic area,striatum and cortex developed into infarct form iNOS positive cells were not detected in normal and sham-operated and 3h of reperfusion rats.At 12、24、48、72、120h of reperfusion,the number of iNOS positived cells appeared at 12h of reperfusion,then peaked at 24h of reperfusion,and then gradually decreased.Quantitation analysis reveals that the number of iNOS immunoreactive cells in the ipsilateral-ischemic area significantly decreased(P0.01) at 48、72h,and 120h after MCA occlusion reperfusion compared with that of 24 after MCA occlusion reperfusion.Moreover,the number of Inos immunostaining cell in ischemic area significantly increased(P0.01) at 24h after MCA occlusion compared with that of control groups.Conclusion iNOS expression appears at 12h of reperfusion,peaked at 24h of reperfusion and then decreased gradually,mainly expressed in activated microglias or macrophages.iNOS had a siginificancy correlation to neuron injury in the late phase of cerebral ischemia reperfusion.The study provides a certain referance value to use iNOS inhibitor in early phase of cerebral ischemic to decrease cerebral injury.