Effect Of Thrombin On Microglial Activation And Inducible Nitric Oxide Synthase Expression After Intracerebral Injection In Rats

Objective To observe the effect of thrombin on microglial activation and inducible nitric oxide synthase(iNOS) expression after intracerebral injection in rats, and explore the possible mechanisms of thrombin-induced brian injury after intracerebral hemorrhage(ICH).Methods Sixty Sprague-Dawley rats were seperated randomly into a experiment group(n=50) and a control group(n=10). Ten Units of thrombin were stereotaxically injected into the right caudate putamen of the rats in the experimental group. The rats were sacrificed at 6h,24h,48h,72h,and7d(n=10 at each time point) for immunohistochemistry and RT-PCR measurements of microglia and iNOS. Animals of control group recerved an injection of 50ul saline.Results Microglia began to increase at 6h(18.2±1.6)after intracerebral injection of thrombin in rats.It reached the peak at 24h(66.7±2.4) and continued for 72h(61.1±2.0).The positive expression could still be observed at day 7(26.1±1.9). Moveover,the iNOS protein began to express at 6h after the injection(14.8±1.8). The expression increased significantly at 24h(40.0±1.8).It reached the peak at about 48h(64.6±2.2).It decreased slightly at 72h(45.0±2.0),and then decreased almost to the baseline at day 7(16.3±1.9). The change trend of iNOS mRNA expression was similar to the level of iNOS protein expression.There was statistical difference between the experimental group and control group(P<0.05).Conclusions Intracerebral injection of thrombin induces microglial proliferation and activation,inducing iNOS expression.The excessive activation of microglia and overexpression of iNOS may be one of the mechanisms of thrombin neurotoxicity .They may participate in the pathophysiological procession of second brain injury after intracerebral hemorrhage.