The Protecting Effect Of Adrenomedullin In The Process Of Ischemia Tolerance Induced By Global Cerebral Ischemia Preconditioning Of The Adult Rat

Objective: To explore the the protecting effect of adrenomedullin in the process of ischemia tolerance induced by global cerebral ischemia preconditioning (IP) in the adult rat and its expression changes in this process.Materials and methods: we have used Modified four-vessel occlusion rat models was used in this study, 78 healthly Sprague-Dawley (SD) rats were divided randomly into 13 groups: Group A : blank. Group B: sham opreation. Group C1:(IP for 3 min and reperfusion for 24 hours). Group C2:(IP for 3 min and reperfusion for 48 hours). Group C3(IP for 3 min and reperfusion for 72 hours). Group C4 :(IP for 3 min and reperfusion for 7 days). GroupC5:(IP for 3 min and reperfusion for 14 days). Group D1:(IP for 3 min and reperfusion for 24 hours-----ischemia for 9 min). Group D2:(IP for 3 min and reperfusion for 48hours-----ischemia for 9 min). Group D3:(IP for 3 min and reperfusion for72 hours-----ischemia for 9 min). Group D4:(IP for 3 min and reperfusionfor 7 days------ischemia for 9 min). Group D5(IP for 3 min andreperfusion for 14 days------ischemia for 9 min). Group E:(cerebralischemia for 9 min directly).All rats were decapitated after 7 days and the brains were taken out.The histopathological changes and ultrastructure of cerebral hippocampus CA1 subarea are exmined by HE staining and the expressions of ADM are studied by immunohistochemistry. SPSS13.0 software has been adopted to analyze and make drawings.Results: HE-stained slices were observed by microscope, all results showed: There were no significant chances of cell death in groups of A,B,C1—C5; Mass cell death were observed in groups of E,D1,D5; Partly cell death were observed in groups of D2,D3,D4, especially in the group of D3 ; ADM immunohistochemical staining: The hippocampus were slightly stained in groups of A,B,C4,D4; deeply stained in the groups of D2,C3,E; partly stained in the groups of C2,D5; significantly stained in groups of C1,C5,D3. After ischemia pretreatment the neuron and the expression of ADM of every groups are different significantly.Conclusions: (1)after single cerebral ischemia for 3 min , brain can get the protective effect against the following deadly cerebral ischemia; (2) after single cerebral ischemia for 3 min and reperfusion for 24h,48h,72h,7d, the expression of ADM have a decline tendency; (3)ADM plays a role in the mechanism of ischemic tolerant effect, and the level of ADM' s expression is related to the protective effect on nerves.