| Objective Focal cerebral ischemia-reperfusion was induced by middle cerebral artery occlusion (MCAO). To investigate whether sevoflurane preconditioning could protect Sprague-Dawley rat’s brain from injury induced by focal cerebral ischemia-reperfusion and whether the mechanism of brain protection is related to CCAAT/enhancer binding protein (C/EBP) homologous protein (CHOP) expression in cerebral cortex.Methods One hundred and eight male Sprague-Dawley rats weighing250～280g were randomly divided into3groups:sham operation group (group S), ischemia-reperfusion group (group I/R) and sevoflurane preconditioning group (group Sevo-pc). The rats in each group were furtherly divided into three subgroups at12h,24h and72h after reperfusion. The rats were anesthetized with intraperitoneal chloral hydrate. The right common carotid artery and external carotid artery were exposed and then were ligatured. A suture used as an occluder was inserted into right internal carotid artery and threaded cranially until resistance was met. MCAO was maintained for1h followed by reperfusion. The rats in group Sevo-pc inhaled2.7%sevoflurane for1h before ischemia. No nylon suture was inserted in group S. Neurological deficits were assessed and scored at the end of12h,24h and72h reperfusion. Six rates in each subgroup were decapitated and then their brains were immediately removed. Cerebral infarct size was determined by TTC staining. The rest of rats in each subgroup were anesthetized and then their hearts were perfused with4%paraformaldehyde solution. After receiving brain tissue, immediately placed in4%paraformaldehyde solution fixed, then dehydrated, transparent, dipping wax and embedded. Morphologic characteristics of ischemic cerebral cortex was observed by HE staining. The CHOP protein expression in ischemic cerebral cortex was determined by immunohistochemistry staining. Apoptosis neurons were counted by TUNEL staining.Results1. The model of focal cerebral ischemia-reperfusion in rats was produced successfully.2. neurological deficit scores:No neurological deficit was found in group S. The neurological deficit scores were significantly higher in group I/R and group Sevo-pc than in group S (P<0.01). The neurological deficit scores were lower in group Sevo-pc than in group I/R (P<0.05).3. HE staining:The structure and hierarchy of cerebral cortex were clear, cellular morphous was normal in group S. In group I/R, different degrees of cellular swelling and degeneration were found at12h after reperfusion. Neurons were found deformed and shrunken, nucleus and cytoplasm were concentrated at24h after reperfusion.Cellular nuclear fragmentation and solution became apparent.At72h after reperfusion, cellular necrosis was more significant and gliocyte proliferation was observed. In group Sevo-pc, pathological changes of cerebral cortex lessened significantly compared with group I/R, neurons were arranged regularly.4. TTC staining:No cerebral infarct was found in group S. Cerebral infarct size was significantly larger in group I/R and Sevo-pc than in group S(P<0.01). Cerebral infarct size was smaller in group Sevo-pc than in group I/R (P<0.05). Cerebral infarct size in group I/R and group Sevo-pc became the largest at24h after reperfusion (P<0.05).5. immunohistochemistry staining:The CHOP protein expression was up-regulated in group I/R and group Sevo-pc than in group S (P<0.05). The CHOP protein expression was down-regulated in group Sevo-pc than in group I/R (P<0.05). The level of CHOP protein expression in group I/R and group Sevo-pc became the highest at24h after reperfusion (P<0.05).6. TUNEL staining: The number of apoptosis neurons was significantly higher in group I/R and group Sevo-pc than in group S (P<0.01). The number of apoptosis neurons was lower in group Sevo-pc than in group I/R (P<0.05or0.01). The number of apoptosis neurons in group I/R and group Sevo-pc were the highest at24h after reperfusion (P<0.05).Conclusion1. Neuronal apoptosis plays an important role in cerebral ischemia-reperfusion injury.2. Sevoflurane preconditioning can provide neuroprotection by inhibiting neuron apoptosis induced by focal cerebral ischemia-reperfusion.3. Sevoflurane preconditioning may protect the brain against focal cerebral ischemia-reperfusion injury by down-regulating CHOP protein expression in cerebral cortex. |
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