Effects of mild hypothermia on the iNOS expression in different brain regions following focal cerebral ischemia-reperfusion in rats

Objective To investigate the effect of mild hypothermia on inducible nitric oxide synthase (iNOS) expression in different brain regions following focal cerebral ischemia-reperfusion in rats. Methods The Male Sprague-Dawley rats were randomly assigned to sham-operated group,normthermic group and intraischemic hypothermia group. The middle cerebral artery of rat was occluded by using the intraluminal suture method and then recirculated. At 48h postischemia,The histological morphological damage were investigated and iNOS proteins,iNOS activity,nitric oxide (NO) concent were measured in the different brain regions. Results The increase of iNOS activity and iNOS immunoreactivity were detected in striatum and cortex at 48h postischemia in normthermic group. iNOS immunoreactivity in cortical penumbra was significantly higher than that in the striatum and the cortical core. Mild hypothermia significantly reduced the infarct area. Furthermore,Mild hypothermia reduced iNOS protein expression in the different brain regions,especially in the cortical penumbra,as well as suppressed iNOS activity and NO generation in the cortex and striatum. Conclusion It is assumed that the decrease of iNOS protein expression in the ischemic penumbra and the inhibition of iNOS activity,resulting in reduction of NO production,may be one of the mechanisms of hypothermic neuroprotection.