中文摘要：

目的 采用DWI观察N-乙酰-5-羟色胺（NAS）对急性局灶性脑缺血再灌注（IR）大鼠脑水肿的神经保护作用。方法 将66只大鼠随机分为假手术组（n=10）、大脑中动脉阻塞（MCAO）组（n=28）和NAS组（n=28）。对MCAO组和NAS组大鼠IR后6h、24h、72h、7天,对假手术组于72h,分别行DWI和病理学检查,比较3组不同时间点脑梗死区相对ADC值（rADC）、相对指数ADC值（reADC）、水通道蛋白4（AQP4）阳性细胞数的变化。IR后72h,测量各组脑组织含水量的变化。结果 假手术组大鼠MRI检测未见异常信号。NAS组与MCAO组大鼠DWI图均可见损伤侧大脑皮层及纹状体异常高信号,ADC图为低信号,eADC图为高信号。IR后6、24、72h,NAS组rADC值均高于MCAO组（P均〈0.05）,reADC值和AQP4阳性细胞数低于MCAO组（P均〈0.05）;IR后7天,各组rADC值、reADC值及AQP4阳性细胞数差异无统计学意义（P均〉0.05）。IR后72h,NAS组大鼠脑组织水含量低于MCAO组（P〈0.05）。结论 NAS可减轻急性IR脑损伤大鼠脑水肿,其机制可能与下调AQP4蛋白的表达有关;DWI对评价NAS的神经保护作用具有重要价值。

英文摘要：

Objective To observe the protective effect of N-acetylserotonin （NAS） on brain edema induced by focal cerebral ischemia reperfusion （IR） in rats using DWI.Methods Sixty-six rats were divided randomly into Sham-operation group （n=10）, middle cerebral artery occlusion （MCAO） group （n=28） and NAS group （n=28）. The rats of NAS and MCAO groups were performed DWI and pathological examination at 6 h, 24 h, 72 h and 7 days after IR, performed at 72 h for sham-operation group. And the relative apparent diffusion coefficient （rADC）, relative exponential apparent diffusion coefficient （reADC） and AQP4 positive cells in cerebral infarction area were measured. 72 h after IR, the changes of brain water content were measured in all the three groups.Results In Sham-operation group, no abnormal signal was seen on DWI. In the NAS and MCAO groups, abnormal high signals in the cerebral cortex and striatum in the injured side on DWI, low signal on ADC map and high signal on eADC map were shown respectively. 6 h, 24 h and 72 h after IR, the value of rADC in NAS group was significantly higher than that in MCAO group （all P〈0.05）, while the value of reADC and AQP4 positive cells were significantly lower than those in MCAO group （all P〈0.05）. 7 days after IR, there were no significant differences of rADC, reADC, and AQP4 positive cells in all groups （all P〉0.05）. The water content of the NAS group was much lower than that in the MCAO group （P〈0.05）.Conclusion NAS can reduce brain edema and down-regulated the AQP4 expression in IR rats. DWI plays an important role in the evaluation of the neuroprotective effect of NAS.