右美托咪定对抑郁症大鼠行为及海马BDNF和mTOR蛋白表达的影响

目的:观察右美托咪定(DEX)对抑郁症大鼠行为及海马脑源性神经营养因子(BDNF)和哺乳动物雷帕霉素靶蛋白(mTOR)表达的影响并探讨其机制。方法:实验设5组,即假手术(sham)组、抑郁症模型(model)组及DEX(2.5、5和10μg/kg)组,每组12只大鼠。抑郁症动物模型采用卵巢摘除加慢性不可预知性温和应激法制备。DEX各剂量组大鼠连续腹腔注射给药21 d。强迫游泳及旷场实验观察大鼠行为变化。Morris水迷宫实验评价大鼠空间学习和记忆能力。海马神经元病理变化采用尼氏染色法检测。大鼠海马白细胞介素1β(IL-1β)、IL-6和肿瘤坏死因子α(TNF-α)mRNA的表达水平采用RT-qPCR法检测。Western blot检测海马IL-1β、IL-6、TNF-α和BDNF蛋白表达水平及蛋白激酶A(PKA)、cAMP反应元件结合蛋白(CREB)、原肌球蛋白相关激酶B(TrkB)、磷脂酰肌醇3-激酶(PI3K)、蛋白激酶B(Akt)和mTOR蛋白的磷酸化水平。结果:与model组相比,DEX各剂量组大鼠强迫游泳不动时间明显降低,自发活动明显增加,逃避潜伏期明显降低,穿越平台次数明显增加(P<0.05或P<0.01),海马神经元损伤显著减轻,IL-1β、IL-6和TNF-α的表达水平明显降低,PKA、CREB及TrkB的磷酸化水平和BDNF表达水平均明显升高,同时PI3K/Akt/mTOR信号通路蛋白磷酸化水平明显上调(P<0.01)。结论:右美托咪定可改善抑郁症大鼠行为及空间学习和记忆能力,其机制可能与其抗炎、调节海马BDNF蛋白表达及TrkB磷酸化水平、进而激活PI3K/Akt/mTOR信号通路有关。

Effects of dexmedetomidine on behaviors and expression of BDNF and mTOR in hippocampus of depressive rats

AIM:To investigate the effects of dexmedetomidine(DEX)on the behaviors and the expression of brain-derived neurotrophic factor(BDNF)and mammalian target of rapamycin(mTOR)in the hippocampus of depressive rats.METHODS:Sprague-Dawley(SD)rats were randomly divided into 5 groups:sham operation group,model group,and DEX(2.5,5 and 10μg/kg)groups.The rats were randomly selected in each group(n=12).The rat depression model was established by chronic unpredictable mild stress and ovariectomy.The rats in DEX groups received daily DEX treatment via intraperitoneal injection for 21 d.The forced swimming immobility time(FSIT)and open-field test were used to evaluate the antidepressant effect of DEX.Escape latency and times of crossing the flat were evaluated by Morris water maze.The histological changes of hippocampal neurons were determined by Nissl staining.The mRNA levels of interleukin-1β(IL-1β),IL-6 and tumor necrosis factor-α(TNF-α)were detected by RT-qPCR.The protein expression of IL-1β,IL-6,TNF-αand BDNF,and the phosphorylation levels of protein kinase A(PKA),cAMP response element-binding protein(CREB),tropomyosin-related kinase B(TrkB),phosphatidylinositol 3-kinase(PI3K),protein kinase B(Akt)and mTOR in hippocampus were evaluated by Western blot.RESULTS:Compared with model group,the FSIT was significantly reduced and the spontaneous activity was markedly increased in DEX groups.The damage of the hippocampal neurons was obviously attenuated,the escape latency was obviously decreased,and times of crossing the flat were markedly increased(P<0.05 or P<0.01).The levels of IL-1β,IL-6 and TNF-αwere obviously decreased,and the protein levels of p-PKA,p-CREB,BDNF,p-TrkB and p-PI3K,p-Akt,p-mTOR in hippocampal tissues were obviously increased(P<0.05 or P<0.01).CONCLUSION:Dexmedetomidine improves the behaviors and the spatial learning and memory ability of depressive model rats,which may be related to its anti-inflammatory effects,as well as up-regulating the protein levels of BDNF and p-TrkB,and activating PI3K/Akt/mTOR signaling pathway in the hippocampus.