Objectives: To observe the effects of electroacupuncture(EA) on memory, cognitive impairment, and the brain-derived neurotrophic factor(BDNF)/N-methyl-D-aspartate receptor subtype 1(NMDAR1) pathway in the brains of offspring rat with intrauterine growth restriction(IUGR) induced by perinatal nicotine exposure(PNE), so as to explore the underlying mechanism.
Methods: SD rats were randomly divided into normal, model, and EA groups, with 4 mothers and 10 offspring rats of each mother in each group. The IUGR model was established by subcutaneous injection of nicotine during pregnancy and lactation. From the 6th day of pregnancy in the mothers until the 21st day after birth of the offspring rats, EA (2 Hz/15 Hz, 1 mA) was administered bilaterally at the "Zusanli"(ST36) of mothers, once daily for 20 min. The brain organ coefficient was used to evaluate the brain development of the offspring rats. The Y-maze test and novel object recognition experiments were performed to assess memory and cognitive function. HE staining was used to observe the development and cellular morphology of the hippocampus and prefrontal cortex in the offspring rats. UV spectrophotometry was used to measure the glutamate(Glu) content in the hippocampus. ELISA was used to detect the BDNF content in the hippocampus. Western blot was performed to measure the protein expression of NMDAR1 in the hippocampus. Immunohistochemistry was used to count the number of BDNF-positive cells in the hippocampus and prefrontal cortex.
Results: Compared with the normal group, the brain organ coefficient, exploration time of the novel arm, spontaneous alternation rate, and novel object recognition index, contents of BDNF and expression of NMDAR1 proteins in the hippocampus, the number of BDNF-positive cells in the CA1 and CA3 regions of the hippocampus and prefrontal cortex were significantly reduced(P<0.01), while the Glu content in the hippocampus was significantly increased(P<0.01) in the model group of offspring rats；decreased cell number, scattered arrangement, and disrupted cellular structure were observed in the hippocampus and prefrontal cortex of offspring rats in the model group. Compared with the model group, the brain organ coefficient, exploration time of the novel arm, spontaneous alternation rate, and novel object recognition index, the BDNF contents and NMDAR1 protein expression in the hippocampus, the number of BDNF-positive cells in the hippocampal CA1 and CA3 regions and prefrontal cortex significantly increased(P<0.01, P<0.05), while the Glu content in the hippocampus was significantly decreased (P<0.01) in offspring rats of the EA group；increased cell number, neat arrangement, and reduced cellular damage were observed in the hippocampus and prefrontal cortex in the EA group.
Conclusions: EA has an improving effect on memory and cognitive function impairment in offspring rats with IUGR induced by PNE, and this mechanism may be associated with the regulation of BDNF/NMDAR1 pathway, thereby improving the neuronal quantity and structure of the hippocampus and prefrontal cortex in offspring rats.
目的: 通过观察电针对围产期尼古丁暴露（PNE）诱发子代大鼠宫内生长受限（IUGR）后记忆、认知损伤和脑组织脑源性神经营养因子（BDNF）/N-甲基-D-天冬氨酸受体Ⅰ型（NMDAR1）通路的影响，探讨电针的作用机制。方法: SD大鼠随机分为正常组、模型组、电针组，每组4只母鼠，40只子鼠。采用母鼠孕期哺乳期皮下注射尼古丁制备IUGR模型。从母鼠受孕第6天一直到子代大鼠出生后第21天，电针母鼠双侧“足三里”，每日1次，每次20 min。采用脑脏器系数检测子代大鼠脑发育情况，用Y迷宫和新物体识别实验检测子代大鼠记忆和认知功能，HE染色法观察子代大鼠海马和前额叶皮质发育情况及细胞形态，紫外线比色法检测子代大鼠海马谷氨酸（Glu）含量，ELISA法检测子代大鼠海马BDNF含量，Western blot法检测子代大鼠海马NMDAR1蛋白表达量，免疫组织化学法检测子代大鼠海马和前额叶皮质BDNF阳性细胞数。结果: 与正常组比较，模型组子代大鼠脑脏器系数显著降低（P<0.01）；新异臂探索时间、自发交替率和新物体识别指数均显著降低（P<0.01）；HE染色示海马和前额叶皮质的神经元数量减少，排列散乱，细胞整体结构遭到破坏；海马中Glu蛋白含量显著升高（P<0.01），BDNF蛋白含量和NMDAR1蛋白表达量均显著降低（P<0.01）；海马CA1区、CA3区和前额叶皮质BDNF阳性细胞数减少（P<0.01）。与模型组比较，电针组子代大鼠脑脏器系数显著升高（P<0.01）；新异臂探索时间、自发交替率和新物体识别指数均显著升高（P<0.05，P<0.01）；HE染色示海马和前额叶皮质的神经元数量增多，排列整齐，细胞整体结构损伤减轻；海马中Glu蛋白含量显著降低（P<0.01），BDNF蛋白含量和NMDAR1蛋白表达量均显著升高（P<0.05）；海马CA1区、CA3区和前额叶皮质BDNF阳性细胞数增多（P<0.05，P<0.01）。结论: 电针对PNE所导致的IUGR子代大鼠记忆和认知功能损伤具有改善作用，其机制可能与通过调节BDNF/NMDAR1通路进而改善子代大鼠海马和前额叶皮质神经元数量和结构有关。.
Keywords: Cognitive memory; Electroacupuncture; Hippocampus; Intrauterine growth restriction; Nicotine exposure; Perinatal period; Prefrontal cortex; Zusanli(ST36).