NEUROTRANSMITTER TRANSPORTERS IN THE RETINA

描述(摘自申请者的摘要)：作为首屈一指的兴奋 突触递质谷氨酸有可能影响神经元的功能。 视网膜中的大多数神经元回路。此外，谷氨酸还可以作为一种 当视网膜微环境中存在高水平的神经毒素时，会产生强烈的神经毒素。 因此，胞外谷氨酸需要维持在较低的水平，以 确保谷氨酸能神经传递的高信噪比，并 保护神经元免受兴奋性损伤和细胞死亡。长期目标 拟议项目的目的是确定运行机制以维持 视网膜中的谷氨酸水平。胞外谷氨酸水平通常保持在 视网膜神经元和视网膜中存在的有效摄取系统的作用 穆勒(神经胶质)细胞和谷氨酸清除不足可能导致 兴奋性毒性神经元丢失。尽管已知胶质谷氨酸转运体 在谷氨酸摄取中起主要作用，它们对谷氨酸的特殊贡献 动态平衡还没有被直接检测，因为胶质细胞特有的谷氨酸 摄取抑制剂是不可用的。靶向破坏神经胶质细胞的小鼠 谷氨酸转运蛋白基因GLT-1和GLAST提供了一种替代手段 研究神经胶质谷氨酸转运体的功能。目前的建议 与神经化学和免疫定位研究有关 GLAST基因敲除小鼠，并验证了GLAST发挥关键作用的假设 在调节视网膜谷氨酸水平，以及在代谢运输中 视网膜。 该提案的具体目标是确定正常代谢是否 信号和代谢产物从穆勒细胞转移到光感受器是 被GLAST的丢失扰乱；检查GLAST缺乏是否会引发 其他谷氨酸转运体的代偿性变化；以确定 GLAST基因敲除后细胞内和细胞外谷氨酸水平发生改变 确定NMDA和AMPA谷氨酸受体的表达是否 在GLAST缺失的小鼠中进行修改；最后检查GLAST导联的丢失 视网膜中GABA能神经元的主要变化。因为胞外 据报道，青光眼和糖尿病患者的谷氨酸水平升高。 视网膜病变，建议的研究对于阐明细胞 视网膜谷氨酸水平升高的机制，以及 考虑将谷氨酸转运体作为潜在的治疗靶点。

DESCRIPTION (Adapted from applicant's abstract): As the premier excitatory synaptic transmitter, glutamate has the potential to influence the function of most neuronal circuits in the retina. In addition, glutamate can also act as a potent neurotoxin when present at a high level in the retinal microenvironment. Therefore, extracellular glutamate needs to be maintained at a low level to ensure a high signal-to-noise ratio for glutamatergic neurotransmission and to protect neurons from excitoxic damage and cell death. The long-term objective of the proposed project is to identify mechanisms that operate to maintain glutamate levels in the retina. Extracellular glutamate level is normally kept low by the action of potent uptake systems present in retinal neurons and Muller (glial) cells, and inadequate clearance of glutamate may result in excitotoxic neuronal loss. Although glial glutamate transporters are known to play a major role in glutamate uptake, their specific contribution to glutamate homeostasis has not been directly examined because glial-specific, glutamate uptake inhibitors are not available. Mice with targeted disruption of glial glutamate transporter genes, GLT-1- and GLAST, provide an alternative means to investigate the function of glial glutamate transporters. The present proposal is concerned with neurochemical and immunolocalization studies in GLAST-knockout mice, and tests the hypothesis that GLAST plays a crucial role in regulating retinal glutamate levels, and in metabolic trafficking in the retina. The specific goals of the proposal are to determine whether normal metabolic signaling, and metabolite transfer from Muller cells to photoreceptors is disrupted by loss of GLAST; to examine whether GLAST-deficiency provokes compensatory changes in other glutamate transporters; to determine whether intracellular and extracellular glutamate levels are altered in GLAST-knockout mice; to determine whether NMDA and AMPA glutamate receptor expression is modified in GLAST-null mice; and finally to examine whether loss of GLAST leads to major changes in GABAergic neurons in the retina. Because extracellular glutamate levels have been reported to be elevated in glaucoma and diabetic retinopathy, the proposed studies are crucial for elucidating the cellular mechanisms responsible for elevation in glutamate levels in the retina, and for considering glutamate transporters as potential therapeutic targets.