GLUTAMATE, EXCITOTOXINS & NEURONAL-GLIAL INTERACTIONS

这个实验室的总体目标是阐述机制。 潜藏着几种神经退行性变的模型。在这项建议中，我们将 继续我们对神经元-胶质氨基酸相互作用的研究 代谢，因为它与兴奋性毒性现象有关。这些研究 应主要利用鸡的胚胎视网膜和组织培养 大鼠大脑皮层星形胶质细胞和视网膜Muller细胞。所有这些建议 研究是在前一次拨款期间进行的实验的直接结果 句号。作为一种缺血/缺氧模型，鸡视网膜将在 各种代谢的无糖或含糖培养液 抑制剂(碘乙酸酯或脱氧葡萄糖抑制糖酵解，KCN至 抑制线粒体电子传递，二硝基苯酚解偶联 氧化磷酸化)。我们之前的研究表明，新陈代谢 抑制会导致兴奋性损伤，而兴奋性毒性损伤可以通过抑制 NMDA受体。将深入研究这些调查结果，试图 了解代谢抑制和表观代谢抑制之间的联系 激活NMDA受体。参数，如时间参数 三磷酸腺苷耗竭与急性神经毒性的关系及游离的作用 自由基的产生，胞外镁离子水平，可能的增强 细胞内碱中毒的兴奋性毒性及其影响 细胞外pH和温度的变化也将被评估。这个 这一效应的个体发育将被检查并与 糖酵解和有氧代谢的发展。多胺在人类免疫系统中的作用 NMDA介导的毒性也将被用不同的多胺作为 嗯，抗缺血药物伊芬地尔和SL82.0715已经被 据报道，该基因与NMDA受体上的一个“多胺”位点相互作用。在我们的 Hands ifenprodil对雏鸡视网膜的NMDA毒性有保护作用，然而， 神经元的子集不受保护。我们将进一步研究这一点，并 试图确定无保护者的神经递质表型 神经元。星形胶质细胞氨基酸代谢的研究还将继续 关注兴奋性氨基酸和代谢的直接影响 对糖酵解和氨基酸等各种参数的抑制作用 新陈代谢、能量电荷和细胞肿胀。到那时，类似的研究将 视网膜的初级神经胶质细胞，即穆勒细胞。这些 研究应回答一些与心力衰竭发病机制有关的基本问题 神经退行性疾病的兴奋性毒性及胶质细胞的特殊作用 可能在这种毒性中起作用。

The overall aim of this laboratory has been the elaboration of mechanisms underlying several models of neurodegeneration. In this proposal we shall continue our studies of the interaction of neuronal-glial amino acid metabolism as it relates to the phenomenon of excitotoxicity. These studies shall make use primarily of the embryonic chick retina and tissue culture of rat cortical astrocytes and retinal Muller cells. All of these proposed studies are the direct outcome of experiments done during previous grant periods. As a model of ischemia/hypoxia, chick retina will be incubated in glucose-free medium or glucose-containing medium with various metabolic inhibitors (iodoacetate or deoxyglucose to inhibit glycolysis, KCN to inhibit mitochondrial electron transport, dinitrophenol to uncouple oxidative phosphorylation). Our previous work has shown that metabolic inhibition causes an excitotoxic lesion which is prevented by inhibitors of the NMDA receptor. These findings will be pursued in depth in an attempt to understand the connection between metabolic inhibition and apparent activation of the NMDA receptor. Parameters such as the temporal relationship of ATP depletion and acute neurotoxicity, the role of free radical generation, extracellular Mg2+ levels, the possible potentiation of the excitotoxicity by intracellular alkalinosis and the effects of extracellular pH and temperature changes will also be assessed. The ontogeny of this effect will be examined and correlated with the development of glycolysis and aerobic metabolism. The role of polyamines in NMDA-mediated toxicity will also be examined using various polyamines as well the anti-ischemic agents ifenprodil and SL82.0715 which have been reported to interact with a "polyamine" site on the NMDA receptor. In our hands ifenprodil protects against NMDA toxicity in chick retina, however, a subset of neurons is not protected. This will be further examined and attempts made to identify the neurotransmitter phenotype of the unprotected neurons. Studies on astrocyte amino acid metabolism will be continued focusing on direct effects of exciatory amino acids and metabolic inhibition on various parameters such as glycolytic and amino acid metabolism, energy charge and cellular swelling. Similar studies will then be done with the primary glial cell of the retina, the Muller cell. These studies should answer some basic questions concerning the mechanism of excitotoxicity in neurodegenerative disorders and the special role glia might play in that toxicity.