Pharmacological study on neurogenesis enhancing factors expressed by neuronal death

纵观历史，N-甲基-D-天冬氨酸(NMDA)受体的激活在体内和体外都能诱导神经细胞死亡。除了这一作用外，我们还发现NMDA受体对海人酸致小鼠海马神经元兴奋性毒性损伤具有保护作用。最近的研究表明，NMDA受体对海马齿状回的神经发生有调节作用。为了阐明NMDA信号的作用，我们研究了NMDA受体在神经元退化和再生中的作用。NMDA拮抗剂(MK-801、SM31900或ifenprodil)可显著抑制TMT诱导的小鼠齿状回颗粒下区BrdU掺入的增加。在含有生长因子的DMEM/F12培养液中培养胚胎小鼠海马神经前体细胞，以评估这些拮抗剂的存在与否对细胞增殖的影响。使用这些拮抗剂中的任何一种都可以减少存活的神经球的数量和大小。用抗α蛋白抗体进行的Western blotting分析表明，SM31900处理显著减少了由Calain切割的150kD的产物。钙蛋白酶抑制剂显著减少培养的神经前体细胞中神经球的形成。这些结果表明，NMDA信号在神经元的存活和再生中起着积极的作用。

Throughout history, the activation of N-methyl-D-asparate (NMDA) receptors has been well known to induce neuronal cell death in vivo and in vitro. In addition to this role, we showed that NMDA receptors have the protective role against excitotoxic injury induced by kainic acid in mouse hippocampus in vivo. Recent studies have shown that NMDA receptor modulates neurogenesis in dentate gyrus of hippocampus. To elucidate roles of NMDA signals, we investigated the involvement of NMDA receptors in degeneration and regeneration of neurons. Treatment with NMDA antagonists (MK-801, SM31900 or ifenprodil) significantly suppressed TMT-induced enhancement of BrdU incorporation in the dentate subgranular zone of mice. Nerual progenitor cells from embryonic mouse hippocampus were cultured in DMEM/F12 medium containing growth factors for assessment of cell proliferation in either the presence or absence of these antagonists. Treatment with any of these antagonists led to a decrease in the number and the size of surviving neurospheres. Western blotting analysis by using anti-α-fodrin antibody showed that treatment with SM31900 produces a significant reduction in a 150 kD product cleaved by calpain. Calpain inhibitors markedly decreased the neurosphere formation in cultured neural progenitor cells. These results suggest that NMDA signals would play positive roles in survival and regeneration of neurons.