GABAA受体激活BDNF—TrkB—ERK信号通路在脑缺血中的作用

目的探讨γ-氨基丁酸（GABA）A受体激活后在大鼠脑缺血模型中是否能通过激活BDNF—TrkB—ERK信号通路而延缓海马神经元的死亡。方法制备sD大鼠大脑四动脉结扎全脑缺血模型，采用末端脱氧核苷酸转移酶（TdT）介导的d—UTP缺口末端标记（TUNEL）技术观察GABA。受体激动剂蝇蕈醇对缺血后海马神经元凋亡的影响；采用免疫印迹法检测蝇蕈醇和GABA受体的拮抗剂荷包牡丹碱对缺血后海马神经元脑源性神经营养因子（BDNF）表达和下游蛋白ERKI／2磷酸化水平的影响；采用免疫沉淀检测蝇蕈醇和荷包牡丹碱对BD—NF的受体TrkB磷酸化水平的影响。结果蝇蕈醇对缺血后海马CA1区神经元具有保护作用（P〈0．05）；而且，在缺血15min复灌1天蝇蕈醇提高了BDNF表达水平、TrkB和ERK1／2磷酸化水平（P〈0．05），而荷包牡丹碱可以降低三者升高的水平（P〈0．05）。结论蝇蕈醇对缺血后神经元有保护作用，可能的分子机制是激活了BDNF—TrkB—ERK信号通路。

The role of the GABAA receptor-activated BDNF-TrkB-ERK pathway in ischemic brain injury

Objective To investigate whether the activation of γ- aminobutyric acid （GABA） A receptor agonist muscimol could retard the hippoeampal neuronal death via the activation of BDNF - TrkB - ERK pathway in rat model of ischemie brain injury. Methods Transient brain ischemia was induced by the four - vessel ligation in Sprague - Dawley rats. The effect of muscimol on the neuronal apoptosis of CA1 pyramidal neurons in rat hippocampus was first examined by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling （TUNEL） , and the effect of museimol and GABAA receptor antagonist bicucullin on the expression of brain - derived neurotrophic factor （BDNF） receptor TrkB and the phosphorylation of down - stream protein ERK1/2 in eytosol extracts of CA1 region was detected by Western blotting, and immunoprecipitation was employed to detect the effect of muscimol and bicueullin on the phosphorylation level of TrkB. Results Muscimol had protective effect on the neurons of hippocampal CAI region following ischemia （ P 〈 0.05）. Furthermore, following 15 rain of ischemia and 1 day of reperfusion, museimol enhanced the expression of BDNF and the phosphorylation of TrkB and ERK1/2 （P 〈 0.05 ） , which were reversed by bicueullin. Conclusion Museimol exerts the neuroprotective effect via the possible molecular mechanism of the activation of BDNF - TrkB - ERK1/2 path- way.