Mechanism of effects of electroacupuncture on memory and cognitive impairment in offspring rats with perinatal nicotine exposure.

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 6^th day of pregnancy in the mothers until the 21^st 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.