Objective: To investigate the effects of electroacupuncture (EA) on the expression of related proteins in the brain-derived neurotrophic factor (BDNF)/mammalian target of rapamycin complex 1 (mTORC1) signaling pathway and synapse-associated proteins and the density of dendrite spines in the prefrontal cortex (PFC) of depression model rats, and to reveal the underlying mechanism by which EA regulates the synaptic plasticity to improve depressive symptoms.
Methods: Thirty-six healthy male Sprague-Dawley (SD) rats were randomly divided into normal group, model group, EA group, and scopolamine (SCOP) group, with 9 in each group. The depression model was established by exposing rats to chronic unpredictable mild stress (CUMS) combined with isolated feeding. Rats in the EA group were treated with EA (2 Hz/100 Hz, 1-1.2 mA) at "Baihui" (GV20), "Yintang" (EX-HN3), "Hegu" (LI4), and "Taichong" (LR3), 20 min each time, once per day, for 14 d, while those in the SCOP group treated with intraperitoneal injection of 25 μg/kg SCOP, once every 16 h, for 14 d. The sucrose preference and feeding latency of rats in each group were observed in the sucrose preference test (SPT) and novelty-suppressed feeding test. The expression levels of proteins in the BDNF/mTORC1 signaling pathway and synapse-associated proteins PSD95, Synapsin Ⅰ, and GluR1 were assayed by Western blot. Golgi-Cox staining was conducted for exploring the total density of dendritic spines on the apical dendrites of layer Ⅴ pyramidal neurons in PFC as well as the densities of mature, immature, and filopodial-like dendritic spines.
Results: Compared with the normal group, the model group exhibited significantly decreased sucrose preference (P<0.001), prolonged feeding latency (P<0.001), down-regulated BDNF, mTORC1, phosphorylated mTORC1 (p-mTORC1), PSD95, Synapsin Ⅰ, and GluR1 expression (P<0.001，P<0.01), and diminished total, mature, and immature spine dendritic densities (P<0.001). Compared with the model group, both EA and SCOP remarkably increased the sucrose preference (P<0.001), shortened the feeding latency (P<0.001), up-regulated the BDNF, mTORC1, p-mTORC1, PSD95, Synapsin Ⅰ, and GluR1 expression in PFC(P<0.05，P<0.01，P<0.001), and elevated the total and immature spine dendritic densities (P<0.001,P<0.01). The density of filopodial-like dendritic spine in the EA group was obviously enhanced (P<0.01), whereas the mature dendritic spine density in the SCOP group rose sharply (P<0.001). However, there were no significant differences between the EA group and SCOP group (P>0.05).
Conclusion: EA alleviates the depressive symptoms of CUMS model rats possibly by up-regulating the expression of proteins in the BDNF/mTORC1 signaling pathway and synapse-asso-ciated proteins PSD95, Synapsin Ⅰ, and GluR1, increasing the dendritic spine density, and enhancing the synaptic plasticity in PFC.
目的：观察电针对抑郁大鼠前额叶脑源性神经营养因子/哺乳动物雷帕霉素复合物1(BDNF/mTORC1)通路蛋白、突触相关蛋白表达和树突棘密度的影响，探讨电针促进突触可塑性改善抑郁的可能机制。方法：健康SPF级雄性SD大鼠随机分为正常组、模型组、电针组和东莨菪碱组，每组9只。以慢性不可预测温和应激联合孤养的方法构建抑郁大鼠模型。电针组予电针“百会”“印堂”“合谷”“太冲”，20 min/次，每日1次，持续14 d；东莨菪碱组予腹腔注射东莨菪碱(25 μg/kg)，每16 h 注射1次，持续14 d。采用糖水偏好实验、新环境抑制进食实验观察各组大鼠的糖水偏好率、延迟进食时间；Western blot法检测前额叶BDNF/mTORC1通路蛋白和突触相关蛋白PSD95、Synapsin I和谷氨酸受体1(GluR1)的表达水平；高尔基染色法检测前额叶第Ⅴ层椎体神经元顶树突棘总密度以及成熟型、不成熟型和丝状伪足型树突棘密度。结果：与正常组比较，模型组大鼠糖水偏好率显著降低(P<0.001)，延迟进食时间明显延长(P<0.001)，前额叶BDNF、mTORC1、磷酸化mTORC1(p-mTORC1)和突触相关蛋白PSD95、Synapsin I和GluR1表达水平明显降低(P<0.001，P<0.01)，树突棘总密度、成熟型和不成熟型树突棘密度显著减小(P<0.001)；与模型组比较，电针组和东莨菪碱组大鼠糖水偏好率显著升高(P<0.001)，延迟进食时间明显缩短(P<0.001)，前额叶BDNF、mTORC1、p-mTORC1和突触相关蛋白PSD95、Synapsin I和GluR1表达水平显著增加(P<0.05，P<0.01，P<0.001)，树突棘总密度和不成熟型树突棘密度显著增高(P<0.001,P<0.01)，电针组丝状伪足型树突棘密度显著增高(P<0.01)，东莨菪碱组成熟型树突棘密度显著增高(P<0.001)；电针组和东莨菪碱组比较，各指标差异均无统计学意义(P>0.05)。结论：电针可能通过上调BDNF/mTORC1通路蛋白，促进突触相关蛋白PSD95、Synapsin I和GluR1表达，增加树突棘密度，调节突触可塑性，改善抑郁大鼠的抑郁症状。.
Keywords: Brain-derived neurotrophic factor; Depression; Electroacupuncture; Mammalian target of rapamycin complex 1; Synaptic plasticity.