BDNF/TrkB信号通路在预先注射青年大鼠血浆减轻七氟烷诱发老龄大鼠认知功能障碍中的作用

Role of BDNF/TrkB signaling pathway in pre-injection of young rat plasma-induced reduction of sevoflurane-caused cognitive dysfunction in aged rats

目的评价脑源性神经营养因子(BDNF)/原肌球蛋白相关激酶B(TrkB)信号通路在预先注射青年大鼠血浆减轻七氟烷诱发老龄大鼠认知功能障碍中的作用。方法SPF级健康雄性SD大鼠80只,18月龄,体重550~650 g,采用随机数字表法分为4组(n=20):对照组(C组)、七氟烷麻醉组(S组)、青年大鼠血浆组(Y组)和BDNF/TrkB信号通路抑制剂K252a组(K组)。Y组和K组尾静脉注射经过处理的3月龄青年大鼠血浆100μl/次,C组和S组尾静脉注射等容量生理盐水,2次/周,共4周。处理结束后S组、Y组和K组吸入3%七氟烷麻醉3 h,麻醉前K组尾静脉注射K252a 25 mg/kg。于麻醉后3 d时行旷场试验及Morris水迷宫实验评估大鼠自发运动能力和认知功能;随后处死大鼠分离海马组织,采用Western blot法测定BDNF、磷酸化TrkB(p-TrkB)、突触后致密蛋白-95(PSD-95)和突触囊泡蛋白(SYN)的表达,行高尔基染色记录海马CA1区神经元树突长度和树突棘密度,透射电镜下记录突触数量并测量突触活性区长度。结果与C组比较,S组逃避潜伏期延长,穿越原平台次数减少,海马p-TrkB、BDNF、PSD-95和SYN表达下调,海马神经元树突长度、树突棘密度、突触数量及突触活性区长度降低(P<0.05)。与S组比较,Y组逃避潜伏期缩短,穿越原平台次数增加,海马p-TrkB、BDNF、PSD-95和SYN表达上调,海马神经元树突长度、树突棘密度、突触数量及突触活性区长度升高(P<0.05)。与Y组比较,K组逃避潜伏期延长,穿越原平台次数减少,海马p-TrkB、BDNF、PSD-95和SYN表达下调,海马神经元树突长度、树突棘密度、突触数量及突触活性区长度降低(P<0.05)。结论预先注射青年大鼠血浆减轻七氟烷诱发老龄大鼠认知功能障碍的机制与激活BDNF/TrkB信号通路,改善海马突触可塑性有关。

Objective To evaluate the role of brain-derived neurotrophic factor(BDNF)/tropomyosin-related kinase B(TrkB)signaling pathway in pre-injection of young rat plasma-induced reduction of sevoflurane-caused cognitive dysfunction in aged rats.Methods Eighty SPF healthy male Sprague-Dawley rats,aged 18 months,weighing 550-650 g,were divided into 4 groups(n=20 each)using a random number table method:control group(group C),sevoflurane anesthesia group(group S),young rat plasma group(group Y)and BDNF/TrkB signaling pathway inhibitor K252a group(group K).The plasma 100μl obtained from 3-month-old young rats was injected via the tail vein in group Y and group K,while the equal volume of normal saline was given via the tail vein in group C and group S,twice a week,for 4 weeks.In S,Y and K groups,3%sevoflurane was inhaled for 3 h starting from the end of treatment,and BDNF/TrkB signaling pathway inhibitor K252a was injected via the tail vein before anesthesia in group K.The open field test and Morris water maze test were performed at 3 days after anesthesia to assess the spontaneous motor ability and cognitive function.Then the rats were sacrificed,and the hippocampal tissues were isolated for determination of the expression of BDNF,phosphorylated TrkB(p-TrkB),postsynaptic dense protein-95(PSD-95)and synaptic vesicle protein(SYN)(by Western blot),dendritic length and dendritic ridge density of neurons in hippocampal CA1 area(by Golgi staining),and the number of synapses and length of synaptic active area(with a transmission electron microscope).Results Compared with group C,the escape latency was significantly prolonged,the number of crossing the original platform was reduced,the expression of p-TrkB,BDNF,PSD-95 and SYN was down-regulated,and the dendritic length,dendritic ridge density,the number of synapses and length of synaptic active area were decreased in group S(P<0.05).Compared with group S,the escape latency was significantly shortened,the number of crossing the original platform was increased,the expression of p-TrkB,BDNF,PSD-95 and SYN was up-regulated,and the dendritic length,dendritic ridge density,the number of synapses and length of synaptic active area were increased in group Y(P<0.05).Compared with group Y,the escape latency was significantly prolonged,the number of crossing the original platform was reduced,the expression of p-TrkB,BDNF,PSD-95 and SYN was down-regulated,and the dendritic length,dendritic ridge density,the number of synapses and length of synaptic active area were decreased in group K(P<0.05).Conclusions The mechanism by which pre-injection of young rat plasma reduces sevoflurane-induced cognitive dysfunction is related to activation of BDNF/TrkB signaling pathway and improvement in synaptic plasticity in the hippocampus of aged rats.