NEUROTRANSMITTER TRANSPORTERS IN THE RETINA

描述（改编自申请人的摘要）：作为首要的兴奋性 作为突触递质，谷氨酸有可能影响 视网膜中的大多数神经回路。此外，谷氨酸还可以作为一种 当在视网膜微环境中以高水平存在时，是一种有效的神经毒素。 因此，细胞外谷氨酸需要维持在低水平， 确保高信噪比的神经递质， 保护神经元免受兴奋性毒性损伤和细胞死亡。长期目标 一个重要的任务是确定运作机制， 视网膜中的谷氨酸水平细胞外谷氨酸水平通常保持在 通过视网膜神经元中存在的有效摄取系统的作用降低， Muller（神经胶质）细胞，谷氨酸清除不足可能导致 兴奋毒性神经元丧失虽然已知神经胶质谷氨酸转运蛋白 在谷氨酸摄取中起主要作用，它们对谷氨酸的特定贡献 由于神经胶质细胞特异性谷氨酸 没有摄取抑制剂。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，提供了一种替代方法， 研究胶质细胞谷氨酸转运体的功能。现时的建议 与神经化学和免疫定位研究有关， GLAST基因敲除小鼠，并测试的假设，GLAST起着至关重要的作用， 在调节视网膜谷氨酸水平，并在代谢运输中， 视网膜。 该提案的具体目标是确定是否正常代谢 信号传导和代谢物从Muller细胞转移到光感受器， 因GLAST丢失而中断;检查GLAST缺乏是否引起 其他谷氨酸转运蛋白的代偿性变化;以确定是否 GLAST敲除后细胞内和细胞外谷氨酸水平改变 小鼠;以确定是否NMDA和AMPA谷氨酸受体的表达， 在GLAST缺失小鼠中进行修饰;最后检查GLAST缺失是否导致 视网膜中GABA能神经元的主要变化。因为细胞外 据报道，谷氨酸水平在青光眼和糖尿病患者中升高， 视网膜病变，拟议的研究是至关重要的阐明细胞 负责视网膜中谷氨酸水平升高的机制，以及 认为谷氨酸转运蛋白是潜在的治疗靶点。

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.