胞内Ca^(2+) 、Na^+ 和ATP的稳定性介导NMDA诱导兴奋保护作用(英文)

Intracellular Ca^(2+) , Na^+, and ATP Homeostasis Mediated NMDA induced Excitoprotection in Rat Cerebellar Granule Neurons

目的:研究N甲基D天冬氨酸(NMDA)诱导大鼠小脑颗粒神经元兴奋毒性保护作用的机制。方法:分别用Ca2+和Na+敏感的染料Fura2/AM和SBFI/AM测定胞内Ca2+和Na+浓度[(Ca2+)i,(Na+)i]。并用反向高效液相色谱法测定胞内三磷酸腺苷(ATP)的含量。结果:①在NMDA预处理组与非处理组,谷氨酸均迅速触发胞内Ca2+反应高峰,两者无显著性差异。而后在NMDA处理组,胞内Ca2+迅速下降,并维持在高于静息Ca2+水平的平台状,撤离谷氨酸后,[Ca2+]i迅速下降并恢复至静息水平;而NMDA非处理组则相反。②谷氨酸均诱发上述两组神经元[Na+]i升高,在NMDA非处理组,[Na+]i均高于NMDA预处理组。③谷氨酸消耗胞内ATP,而NMDA预处理组则减少胞内ATP的耗竭。结论:NMDA诱导兴奋毒性保护作用是通过减少ATP的消耗而增强胞内Ca2+和Na+的自稳态。

Objective:To study the mechanisms underlying N methyl D aspartate (NMDA) induced excitoprotection in cultured rat cerebellar granule neurons. Methods: Intracellular Ca 2+ ([Ca 2+ ]i) and intracellular Na +([Na +]i) were measured microspectrofluorimetrically with the Ca 2+ sensitive dye fura 2/Am and the Na + sensitive indicator SBFI/AM respectively. Cytosolic denosine triphosphate(ATP) was quantified by means of reverse phase HPLC. Results: First. Glutamate rapidly induced a peak [Ca 2+ ]i response in both untreated and NMDA treated neurons. In NMDA treated neurons, [Ca 2+ ]i then rapidly dropped to a stable plateau concentration above that of the basal condition. Thirty minutes later, with the removal of glutamate, [Ca 2+ ]i rapidly returned to near basal concentrations. In contrast, with NMDA untreated neurons, prolonged glutamate exposure resulted in a heterogeneous [Ca 2+ ]i response in many neurons,with [Ca 2+ ]i either gradually or abruptly increasing. Upon glutamate removal, many untreated neurons failed to return to basal levels. Second,Glutamate rapidly induced a peak [Na +]i response in both untreated and NMDA treated neurons. However, the glutamate induced [Na +]i peaks, during and after glutamate were all higher in untreated neurons, compared with NMDA pretreated neurons. Third, Glutamate induced the consumption of ATP stores in the neurons. However,ATP consumption in the neurons pretreated with NMDA was significantly reduced,compared with neurons not pretrect. Conclusions:NMDA induced excitoprotection in cerebellar granule neurons is associated with enhanced [Ca 2+ ]i and [Na +]i homeostasis by reducing ATP consumption.