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目的利用MRI-DWI动态观察褪黑素(MT)对急性脑缺血再灌注(IR)大鼠的保护作用。方法将96只雄性Sprangue Dawley大鼠随机分为假手术组(分离血管后缝合,并于分离前30 min腹腔注入生理盐水)、模型组(造模前后30 min腹腔注射生理盐水)、MT组(造模前后30 min腹腔注射10 ml/kg MT),每组32只。采用改良Longa线栓法制作局灶性脑IR模型。于缺血2 h再灌注后6 h、24 h、72 h、7天行头颅T2WI、DWI扫描,测量脑梗死区的相对T2信号强度(r SI-T_2WI)、相对表观扩散系数(r ADC);HE染色观察组织病理形态改变。结果假手术组大鼠MRI未见异常信号,脑神经细胞排列密集,形态规则,间质无水肿。MT组与模型组大鼠T_2WI、DWI图均可见右侧大脑皮层及纹状体出现异常高信号,ADC图为低信号,脑梗死区r ADC值逐渐上升,而r SI-T2WI 24 h内逐渐上升,随后开始下降,脑梗死区神经细胞皱缩、溶解、坏死,间质水肿。MT组与模型组比较,脑梗死区r ADC值明显升高(P<0.05),r SI-T_2WI明显降低(P<0.05),脑水肿减轻,神经细胞凋亡数减少,形态较规则。结论 MT预处理能在一定程度上减轻大鼠IR后脑水肿及脑神经细胞损伤,MRI-DWI对评价MT的神经保护作用具有重要价值。
Objective To observe the protective effect of melatonin (MT) on acute cerebral ischemia-reperfusion (IR) rats by MRI-DWI. Methods Ninety-six male Sprangue Dawley rats were randomly divided into sham operation group (sutured after separation of blood vessels and injection of normal saline 30 min before separation), model group (intraperitoneal injection of normal saline 30 min before and after modeling), MT group 30 min before and after model injection by intraperitoneal injection of 10 ml / kg MT), 32 in each group. Focal brain IR model was made by modified Longa thread method. The relative T2 signal intensity (r SI-T_2WI) and relative apparent diffusion coefficient (r ADC) were measured at 6 h, 24 h, 72 h and 7 d after 2 h of reperfusion. ); HE staining observed histopathological changes. Results There was no abnormal signal in the sham-operation group, but dense neurons in the brain. In the MT group and the model group, the right cerebral cortex and striatum showed abnormally high signal in T_2WI and DWI, the ADC showed low signal, the r ADC in cerebral infarction increased gradually, and gradually increased within 24 hours after r SI-T2WI Increased, then began to decline, cerebral infarction nerve cell shrinkage, dissolution, necrosis, interstitial edema. Compared with the model group, the r ADC value in cerebral infarction area was significantly increased (P <0.05), r SI-T 2WI was significantly decreased (P <0.05), the brain edema was reduced and the number of apoptotic neurons was decreased. Conclusion MT pretreatment can relieve cerebral edema and neuronal damage after IR in rats. MRI-DWI is of great value in evaluating the neuroprotective effect of MT.