中文摘要：

目的基于大脑中动脉栓塞（MCAO）模型,探讨褪黑素（MT）对局灶性脑缺血大鼠脑DWI及脑组织中Fas、FasL、活性Caspase-3蛋白表达的影响。方法将80只SD大鼠随机分为Sham组（n=16）、MCAO组（n=32）及MT组（n=32）。MCAO组及MT组建立大鼠MCAO模型后,于脑缺血再灌注（IR）前后30min,分别腹腔注射生理盐水与MT;Sham组进行假手术操作,腹腔注射生理盐水。对各组大鼠进行行为学评分,于MCAO组及MT组中选取评分为1-3分者纳入研究。分别于假手术或IR后6h、24h、72h、7天,行大鼠脑DWI扫描,计算相对DWI信号强度（rDWI-SI）;并于每一时间点各组随机选取大鼠进行Fas、FasL及活性Caspase-3免疫组化染色观察,并比较各组Fas、FasL、活性Caspase-3阳性细胞数（个/mm^2）。结果最终Sham组16只、MCAO组29只、MT组30只大鼠纳入研究。3组间大鼠行为学评分差异具有统计学意义（χ^2=50.125,P〈0.01）,MT组及MCAO组行为学评分均高于Sham组（P均〈0.01）,MT组行为学评分低于MCAO组（P〈0.01）。IR后6h、24h、72h、7天,MCAO组及MT组rDWI-SI值均高于Sham组假手术后相应时间rDWI-SI值（P均〈0.01）;IR后6h、24h、72h,MCAO组rDWI-SI值均高于MT组（P均〈0.05）;IR后7天MT组与MCAO组间rDWI-SI值差异无统计学意义（P〉0.05）。IR后6h、24h、72h,MT组及MCAO组Fas、FasL染色及活性Caspase-3染色阳性细胞数均较Sham组增多（P均〈0.01）,MT组较MCAO组减少（P〈0.05）;IR后7天,3组间阳性细胞数差异无统计学意义（P〉0.05）。结论在大鼠局灶性脑缺血损伤模型中,MT可有效减低rDWI-SI值,并可抑制Fas、FasL、活性Caspase-3蛋白表达。

英文摘要：

Objective Based on middle cerebral artery occlusion（MCAO）model,to investigate the effects of melatonin（MT）on DWI and expression of Fas,FasL and cleaved Caspase-3proteins in rat model with focal cerebral ischemia.Methods Eighty SD rats were randomly divided into Sham group（n=16）,MCAO group（n=32）and MT group（n=32）.The rats in sham group were treated with sham-operation.And the rats in MCAO and MT groups were peritoneally injected with saline and MT respectively.The behavioral scores were assessed in the three groups.The rats in MCAO and MT group with the behavioral scores of 1—3points were selected in the study.The DWI relative signal intensity（rDWI-SI）,Fas,FasL and cleaved Caspase-3proteins were respectively examined by MR scaning and immunohistochemical staining in all rats of each group at 6h,24 h,72hand 7days after ischemia reperfusion（IR）or sham-operation.And the DWI and immunohistochemical results for each group were compared.Results At last,there were 16 rats in sham group,29 rats in MCAO group and 30 rats in MT group,respectively.There was significant difference of the behavioral scores among the three groups（χ^2=50.125,P〈0.01）.The behavioral scores of MT and MCAO groups were higher than those of sham group（all P 0.05）.And the behavior scores of the MT group were lower compared with MCAO group after IR.Compared with the rDWI-SI values measured at 6h,24 hand 72h,7days in sham group,the rDWI-SI values of MT and MCAO groups were significantly higher（all P〈0.01）.And the rDWI-SI was higher in MCAO group than those in MT group at 6h,24 hand 72hafter IR（all P〈0.01）.And there was no significant difference of rDWI-SI at 7days after IR between MT and MCAO groups（P〉0.05）.The immunohistochemical staining results showed that the number of Fas,FasL and cleaved Caspase-3positive cells in MCAO and MT groups were significantly higher than those in sham group（all P〈0.01）.And there were less Fas,FasL and cleaved Caspase-3positive cells in MT groups compared with