NG-硝基精氨酸甲酯对慢性脑缺血大鼠记忆及诱导型一氧化氮合酶的影响

Effect of NG-nitro-L-arginine methyl ester on the spatial learning and memory function and expression of inducible nitric oxide synthase in hippocampus in rats with chronic cerebral ischemia

目的研究一氧化氮合酶抑制剂——NG-硝基-L-精氨酸甲酯(L-NAME)对慢性脑缺血大鼠学习空间记忆能力及海马区诱导型一氧化氮合酶(iNOS)表达的影响。方法3～4个月龄健康雄性Wistar大鼠54只,随机分为假手术组、模型组及L-NAME组,每组18只。采用双侧颈总动脉永久结扎法制备慢性脑缺血大鼠模型。L-NAME组在造模后第3周开始每日给予L-NAME(20mg.kg-1.d-1配入每日饮用水中)。造模后2、4、6个月,利用Morris水迷宫方法检测各组大鼠学习空间记忆能力;观察海马区的组织病理学改变和iNOS的表达。结果①造模后2、4、6个月,模型组、L-NAME组的逃避潜伏期、搜索路径长度均比假手术组明显增多,差异有统计学意义(P<0.01,P<0.05),L-NAME组比模型组明显缩短(P<0.01,P<0.05)。②HE染色显示,模型组和L-NAME组随着缺血时间的延长,海马区的锥体细胞损伤程度逐渐加重;L-NAME组各相应时间点损伤程度较模型组明显减轻。③模型组和L-NAME组海马CA1区iNOS阳性细胞数目随着缺血时间的延长而逐渐增多,均高于假手术组(P<0.01,P<0.05);与模型组比较,L-NAME组的iNOS阳性细胞数目相对减少(P<0.01,P<0.05)。结论L-NAME可减轻慢性脑缺血所致的脑组织损伤,改善脑缺血所致的进行性学习空间记忆能力的下降;其可能的机制为通过抑制iNOS的表达而发挥神经保护作用。

Objective To study the effect of nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester （L-NAME） on the spatial learning and memory and the expression of inducible nitric oxide synthase （iNOS） in hippocampus in rats with chronic cerebral ischemia. Methods Fifty-four healthy male Wistar rats were randomly assigned to sham-operation, model and L-NAME groups （n = 18 in each group）. A rat model of chronic cerebral ischemia was induced by permanent ligation of bilateral common carotid arteries. L-NAME （20 mg · kg-1 · d- 1 in drinking water daily） was administrated daily in the L-NAME group 3 weeks after modeling. Morris water maze was used to detect the spatial learning and memory of the rats 2, 4, and 6 months after modeling; the histopathological changes and the iNOS expression in hippocampal region were observed. Results ①The escape latency and the search path length in the mod- el and L-NAME groups were significantly longer than those in the control group 2, 4, and 6 months after modeling, and the difference was statistically significant （ P 〈 0. 01, P 〈 0. 05 ） , while they were significantly shorter in the L-NAME group than those in the model group （P 〈 0.01, P 〈 0.05 ）. ②Hematoxylineosin （HE） staining showed that with the extension of ischemic time the damage degree of pyramidal cells in hippocampal region aggravated gradually in the model and L-NAME groups, while the damage degree at all corresponding time points in the L-NAME group was significantly milder than that in the model group. ③The numbers of iNOS positive ceils in hippocampal CA1 region increased gradually with the extension of ischemic time in the model group and the L-NAME group, and they were all higher than the sham-operation group （P 〈0.01, P 〈0.05）; the numbers of iNOS positive cells in the L-NAME group were reduced as compared to the model group （P 〈 0.01, P 〈 0.05）. Conclusion L-NAME may alleviated brain tissue injury caused by chronic cerebral ischemia and improve the progressively declined in spatial learning and memory fumction caused by cerebral ischemia. Its possible mechanism is to exert neuroprotective effect through inhibiting the expression of iNOS.