Objective To detect the expression of iNOS gene in brain tissues from limb ischemia\|reperfused SD rats.Method SD rats were randomly divided into three groups:limb ischemia\|reperfusion group(I\|R), simple ischemia group(I) and normal control group(N).The expression of iNOS mRNA in brain was semiquantitatively detected by using of RT\|PCR.The distribution and the expression of iNOS and peroxynitrite protein in brain were measured by immunohistochemistry.Results iNOS mRNA was not detected in brain from control rats,while it was detected in both I and I\|R groups.After I\|R, the expression of iNOS mRNA gradually increased at 2h and peaked at 6h( P <0.01 vs I group),then decreased,but there was also a little expression at 24h.The morphologic results showed that there were more iNOS positive cells and more dispersal NT positive neurons in I\|R group than I group.Conclusion The expression of iNOS mRNA in brain significantly increased after limb ischemia\|reperfusion in a time\|dependent manner.