不同剂量17β-雌二醇对血管性痴呆大鼠的神经保护作用

Neuroprotective effects of different doses of 17β-estradiol on vascular dementia in rats

目的探讨不同剂量17β-雌二醇对血管性痴呆(vascular dementia,VD)大鼠认知功能及海马CA1区神经胶质纤维酸性蛋白(glial fibrillary acidic protein,GFAP)、神经型一氧化氮合酶(neuronal nitric oxide synthase,nNOS)表达的影响。方法取健康雄性Wistar大鼠50只,随机分成假手术组、模型组、治疗组(又分为80、200、400μg/kg组),每组10只大鼠。采用结扎双侧颈总动脉方法制备VD模型,治疗组于术后第2天予以腹腔注射17β-雌二醇,假手术组和模型组给予等量消毒花生油。连续给药30次,隔天1次,共60d。手术后60d应用Y迷宫法检测大鼠学习、记忆能力(测试30次的正确次数);采用免疫组化法检测大鼠海马CA1区GFAP、nNOS的表达情况。结果假手术组,模型组,治疗组中80、200、400μg/kg组学习能力的正确次数分别为25.8±1.8、15.5±2.0、21.2±2.2、23.7±2.0、20.5±2.1;记忆能力的正确次数为26.2±1.7、16.0±1.9、21.3±1.7、23.4±2.1、21.6±2.0。GFAP阳性细胞数分别为16.5±1.7、28.8±1.6、23.4±1.4、20.2±1.6、27.6±2.0;nNOS阳性细胞数为30.3±2.5、17.8±1.7、22.1±1.9、25.8±1.7、21.4±1.8。模型组与其他组比较,学习、记忆能力、GFAP及nNOS阳性细胞表达,差异均有统计学意义(F=37.620,P=0.000;F=39.112,P=0.000;F=91.484,P=0.000;F=58.839,P=0.000)。200μg/kg组与80、400μg/kg组比较差异亦有统计学意义(F=4.983,P=0.000;F=16.718,P=0.000)。结论17β-雌二醇能够明显改善慢性缺血后大鼠的认知功能障碍,其机制可能与降低GFAP、提高nNOS阳性细胞表达有关;其疗效与剂量有关,200μg/kg的雌二醇对大鼠神经保护作用优于80μg/kg及400μg/kg。

Objective To explore the effects of different doses of 17β-estradiol on cognitive function and the expressions of glial fibrillary acidic protein （GFAP） in hippocampal CA1 region and neuronal nitric oxide synthase （nNOS） in rats with vascular dementia （VD）. Methods A total of 50 healthy male Wistar rats were randomly allocated into sham operation, model and treatment groups （80, 200 and 400 μg/kg dose groups）, 10 in each group. The VD model was established by ligating bilateral common carotid arteries. The treatment group was injected 17β-estradiol intraperitoneally at the second day after the procedure, once every other day; the sham operation and model groups were injected equivalent volume of sterilized peanut oil, and successively injected 30 times for 60 days. The abilities of learning and memory in rats were assessed by Y maze test after 60 days. The expressions of GFAP and nNOS in rat hippocampal CA1 region were detected by immunohistochemical assay. Results The correct times of learning ability were tested for30 times in the sham operation, model and treatment （80, 200 and 400 μg/kg） groups, they were 25.8 ± 1.8, 15.5 ± 2. 0, 21.2 ± 2. 2, 23.7 ± 2. 0, and 20. 5 ± 2. 1, respectively ; the correct times of memory ability were 26. 2 ± 1.7, 16.0 ± 1.9, 21.3 ± 1.7, 23.4 ±2. 1, and 21.6 ±2. 0, respectively; the number of GFAP positive cells were 16. 5 ± 1.7, 28.8 ± 1.6, 23.4 ± 1.4, 20. 2 ± 1.6, and 27.6 ± 2. 0, respectively ; the number of nNOS positive cells were 30. 3 ± 2. 5, 17.8 ± 1.7, 22. 1 ± 1.9, 25.8 ± 1.7, and 21.4 ± 1.8, respectively. There was statistical significance in the abilities of learning and memory, and the expressions of GFAP and nNOS positive cells in the model group as compared with other groups（F = 37.620, P = 0.000;F = 39. 112, P = 0.000;F =91.484, P = 0.000;F = 58.839, P = 0. 000 ）. There were also statistical significance between the 200 μg/kg dose group and the 80 and 400 μg/kg dose groups （ F =4. 983, P =0. 000 ;F = 16. 718, P =0. 000. Conclusions 17β-estradiol may significantly improve the cognitive impairment in rats after chronic ischemia. Its mechanism may be associated with the expressions of decreasing GFAP and increasing nNOS positive cells, and the efficacy was associated with the dosage of estradiol.