TROPHIC INTERACTIONS DURING VISUAL SYSTEM DEVELOPMENT

视觉系统发育过程中的营养相互作用

• 批准号: 2888583
• 负责人: SUSANA COHEN-CORY
• 金额: $ 22.87万
• 依托单位: UNIVERSITY OF CALIFORNIA LOS ANGELES
• 依托单位国家: 美国
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-08-01 至 2002-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2888583
• 关键词: Xenopus; axon; confocal scanning microscopy; electron microscopy; electrophysiology; green fluorescent proteins; microinjections; neurogenesis; neurotrophic factors; retinal bipolar neuron; synaptogenesis; video microscopy

DESCRIPTION: (Adapted From The Applicant's Abstract) The proposed studies will examine the mechanisms by which retinal projection neurons make precise and functional connections with their central targets. The hypothesis that neuronal activity and neurotrophic factors interact synergistically to modulate axon terminal arborization, as well as synapse formation and stabilization will be tested in the live developing brain. Specifically, the roles and interactions between neurotrophins, and pre- and post-synaptic activity during the dynamic elaboration of optic axon terminal arbors and formation of synaptic contracts will be examined in live, anesthetized tadpoles. The Xenopus laevis visual system is a uniquely accessible vertebrate model in which the development of neuronal connections between retinal ganglion cells and their tecta target neurons can be followed over time in the intact embryo. The mechanisms controlling axon growth, arborization, and complexity will be studied in connections with target neurons. Growth and arborization patterns of individual, fluorescently labeled retinal ganglion cell axons will be followed over time using low-light level video microscopy and laser scanning confocal microscopy. The interactions between neurotrophins and pre- and post-synaptic neuronal activity in the dynamics of axon arborization (axon branch addition and withdrawal) and the final complexity of axonal arbors will be examined by perturbing endogenous neurotrophic factor levels and the activity patterns of projection or target neurons. Neurotrophic factor levels will be altered by direct microinjection of neurotrophins, function- blocking antibodies, or control solutions into the tecta of live, anesthetized tadpoles. The contributions of neuronal activity to the dynamics of axon arborization and refinement will be tested by selectively altering pre- or post-synaptic activity by direct microinjection of pharmacological agents into the retina (sodium channel blocks) or rectum (glutamate receptor agonists or antagonists) of the anesthetized tadpole. A combination of in vivo microscopic imaging of individual retinal ganglion cell axon arbors, and targeted expression and in vivo imaging of chimeric, fluorescently labeled synaptic proteins will be used to determine the correlates between axon morphology and synaptic structure. This will provide simultaneous, single cell observation of axon arborization dynamics and refinement, and synapse formation and stabilization. The roles of activity and neurotrophic signals during synapse formation and stabilization will be examined by combining pharmacologic perturbations of neurotrophic factor levels and activity signaling with simultaneous in vivo imaging of axonal arbors and synaptic proteins. The results of these studies will provide valuable insights into fundamental mechanisms of synaptogenesis in the living brain, and will further our understanding of the mechanisms that control the development of regeneration of the visual pathways, that are critically important in the maintenance of normal visual function.

描述：（根据申请人的摘要改编）提议 研究将研究视网膜投影神经元的机制 与其中心目标建立精确的功能连接。这 神经元活性和神经营养因子相互作用的假设 协同地调节轴突末端均匀化以及 突触形成和稳定将在现场测试 发展大脑。具体而言，角色和互动 动态期间神经营养蛋白以及前后突触的活性 阐述光轴末端轴和突触的形成 合同将在现场，麻醉t的现场检查中检查。 Xenopus Laevis Visual System是一种独特的脊椎动物模型 视网膜神经节细胞之间神经元连接的发展 随着时间的流逝，可以遵循其TECTA靶神经元的完整性神经元 胚胎。控制轴突生长，树博化和 将在与目标神经元的连接中研究复杂性。生长 和荧光标记的视网膜的树木化模式 随着时间的推移，将使用弱光水平随时间遵循神经节细胞轴突 视频显微镜和激光扫描共聚焦显微镜。这 神经营养蛋白与突触后神经元之间的相互作用 轴突动力学的活性（轴突分支添加和 撤回）和轴突乔木的最终复杂性将被检查 通过扰动内源性神经营养因子水平和活性 投影或靶神经元的模式。神经营养因子水平 将通过直接显微注射神经营养蛋白而改变，功能 - 阻止抗体或控制溶液到实时的结构中， 麻醉t。神经活性对 轴突树木化和精炼的动力学将通过 通过直接选择性改变突触前或突触后活性 将药理学剂显微注射到视网膜（钠通道） 块）或直肠（谷氨酸受体激动剂或拮抗剂） 麻醉t。体内微观成像的组合 单个视网膜神经节细胞轴突轴和靶向表达 和嵌合，荧光标记的突触蛋白的体内成像 将用于确定轴突形态和 突触结构。这将提供同时的单个单元格 观察轴突树木化动力学和改进和突触 形成和稳定。活性和神经营养的作用 突触形成和稳定期间的信号将通过 结合神经营养因子水平和 与轴突乔木的体内成像同时进行活性信号 和突触蛋白。这些研究的结果将提供 对突触发生的基本机制的宝贵见解 活着的大脑，并将进一步了解我们对机制的理解 控制视觉途径再生的发展 对于维持正常视觉功能至关重要。