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BACKGROUND: Activation of N-methyl-D-aspartate receptor(NMDAR)is a key link of exitotoxictiy at the phase of cerebral ischemic injury.Because NMDAR is a main way to mediate intal flow of Ca2+ among glutamic acid receptors,over-excitation can cause neuronal apoptosis.Calcitonin gene related peptide has a strongly biological activity.On one hand,it can play the protective effect through inhibiting the expression of NMDAR1 mRNA;on the other hand,it can play the protective effect through down-regulating the expression of NMDAR1 mRNA by exogenous calcitonin gene related peptide.OBJECTIVE: To observe the expression of NMDAR1 and the regulatory effect of calcitonin gene related peptide on the expression of NMDAR1 mRNA and protein in the cerebral cortex of rats with focal cerebral ischemia/reperfusion(I/R).DESIGN: Randomized controlled animal study.SETTING: China Medical University.MATERIALS: A total of 216 healthy male Wistar rats,general grade,weighing 250-280 g,were selected in this study.Twelve rats were randomly selected to regard as control group;meanwhile,other 204 rats were used to establish middle cerebral artery occlusion/reperfusion (MACO)models.The main reagents were detailed as follows:calcitonin gene related peptide (Sigma Company);calcitonin gene related peptide kit (Boster Company);antibodyⅠ,Ⅱand antibody β-actin Ⅰ,Ⅱ of NMDAR1 mRNA and chemiluminescence reagent (Santa Cruz Company,USA)METHODS:The experiment was carried out in the Laboratory of Neurobiology of China Medical University from August 2005 to June 2006. ①Right MCAO models of rats were established to cause focal ischemia and scored based on Zea Longa five-grade scale. If the scores were 1,2 and 3 after wakefulness,the MACO models were established successfully and involved in the experiment. A total of 120 rats with successful modeling were randomly divided into I/R group and administration group with 60 in each group.All rats in the both groups were observed at five time points,including 6,12,24,48 and 72 hours after reperfusion and after 2-hour ischemia,with 12 experimental animals at each time point. Six rats were prepared for detection of hybridization in situ,and the other 6 were used for West blotting histochemical detection.Rats in the control group were opened their skin to separate common carotid artery and not treated with line and drugs. In addition,rats in the I/R group were treated with 1 mL saline at 2 hours after focal cerebral ischemia,and then,rats in the administration group were treated with 1 mL(1 g/L)calcitonin gene related peptide at 2 hours after focal cerebral ischemia.②The expression of NMDAR1 mRNA was detected with hybridization in situ at various time points; moreover,the expression of NMDAR1 protein was measured with West blotting method at various time points.The results were analvzed with Metamoph imaging analytical system.MAIN OUTCOME MEASURES:The expression of NMDAR1 mRNA and its protein in cortical neurons of rats at various time points.RESULTS:A total of 84 rats were excluded because of non-symptoms,exanimation or death;and then,132 rats were involved in the final analysis.The expression of NMDAR1 mRNA and its protein in cortical neurons of rafs in the control group was 0.205±0.001 and 0.184±0.001,respectively;after I/R,expression of NMDAR1 mRNA and its protein was up-regulated,especially,expression of mRNA at 6,12,24,48 and 72 hours was 0.245±0.003,0.287 ± 0.004,0.354±0.008,0.284±0.002 and 0.217±0.006,respectively;moreover,expression of protein at 6,12,24,48 and 72 hours was 0.222±0.003,0.261±0.028,0.311±0.004,0.259±0.013 and 0.210±0.008,respectively.There was significant difference between the two groups(0.205±0.001,P＜0.01).The expression was up-related in the former 24 hours, reached peak at 24 hours,down-regulated, and decreased to the level of control group at 72 hours.Except 72 hours.the expression of NMDAR1 mRNA and its protein was lower in administration group than that in I/R group at other four time points. In addition.the expression of mRNA at 6,12,24,48 and 72 hours was 0.223±0.005,0.243±0.001,0.292±0.002,0.250±0.003 and 0.213±0.003,respectively;moreover,the expression of protein at 6,12.24,48 and 72 hours was 0.216±0.006,0.245±0.025,0.276±0.003,0.241±0.045 and 0.202±0.013, respectively.There was significant difference at various time points(P＜0.05).CONCLUSION:The expressions of NMDAR1 mRNA and its protein of peripheral cortical neurons are up-related in ischemic area after focal cerebral I/R.Meanwhile,exogenous calcitonin gene related peptide can protect cortical neurons through inhibiting expression of NMDAR1 mRNA and its protein after focal cerebral I/R.