Abstract: AIM: To investigate the effects of postconditioning on neuron apoptosis and expression of endothelial nitric oxide synthase (eNOS) and inducible nitric oxide synthase (iNOS) protein in local cerebral ischemic reperfusion rats via middle cerebral artery occlusion(MCAO).METHODS: Fifty male Sprague-Dawley rats were randomized into five groups (n =10, each group) ,sham-operated group, MCAO group, preconditioning combined MCAO group, postconditioning combined MCAO grouPand nimodipine combined MCAO group.In the preconditioning groups animals were subject to 2 cycles of 2-min ischemia and 20-min reperfusion of the bilateral carotid arteries 24 h before middle cerebral artery occlusion.In the postconditioning groups animals were subject to 3 cycles of 20-second ischemia and 20-second reperfusion of the MCAO before reperfusion.At the 24^th hour after reperfusion, the rat brains were obtained for detecting eNOS and iNOS protein expression by immunohistochemistry method.RESULTS: In the postconditioning groups, the apoptotic cells were significantly decreased(P<0.05) ;the expression of eNOS protein was significantly increased (P<0.05) ;on the contrary, that of iNOS protein was significantly decreased (P<0.01).CONCLUSION: The postconditioning can prevent apoptosis in local cerebral ischemic reperfusion model rats due to the enhanced expression of eNOS protein and decreased expression of iNOS protein.

Key words: postconditioning, preconditioning, cerebral ischemia reperfusion, apoptosis, eNOS, iNOS