Neurotrophin and Synaptic Plasticity

描述（由申请人提供）：神经营养因子（NT）是发育中神经元存活和分化所必需的蛋白质家族，已显示参与活性依赖性突触可塑性。在这个项目中，我们建议测试的假设，即分泌的NT在发育中的突触是由突触活动触发的尖峰模式依赖的方式和本地化的突触活动分泌的NT反过来产生长期的功能和结构的修改发展中的突触连接。我们将集中我们的注意力在脑源性神经营养因子（BDNF），NT广泛表达在发育中的神经系统，使用生理学，分子生物学和光学成像方法相结合。本研究共分三个部分。在第一部分中，我们将使用大鼠或小鼠海马神经元的培养物来研究外源性BDNF对海马能和GABA能突触的功能和可塑性以及轴突/树突形态和突触发生的急性突触前和突触后效应。我们也将研究BDNF的突触特异性局部作用和潜在的信号传导机制。在第二部分中，我们将研究内源性分泌的BDNF在海马培养物中活动诱导的突触功能和形态改变、活动依赖性BDNF分泌以及BDNF的神经元内和神经元间运输中的作用。在第三部分中，使用正在发育的非洲爪蟾蝌蚪，我们将研究BDNF对视网膜顶盖突触的功能和可塑性、顶盖中轴突/树突动力学和突触发生以及内源性BDNF的运输和分泌的体内作用。最后，我们将探讨BDNF在顶盖神经元视网膜定位图和方向选择性感受野发育中的作用。两者合计，这些在体外和体内的研究提供了独特的机会，以解决几个基本的细胞生物学问题的神经营养因子的调节功能，在活动依赖性完善发展中的神经连接，并可能产生新的信息，我们的基本了解生理和病理学的发展中的神经系统。

DESCRIPTION (provided by applicant): Neurotrophins (NTs), a family of proteins essential for the survival and differentiation of developing neurons, have been shown to participate in activity-dependent synaptic plasticity. In this project, we propose to test the hypothesis that secretion of NTs at developing synapses is triggered by synaptic activity in a spike pattern-dependent manner and localized synaptic actions of secreted NTs in turn produce long-term functional and structural modification of developing synaptic connections. We will focus our attention on brain-derived neurotrophic factor (BDNF), a NT widely expressed in the developing nervous system, using a combination of physiological, molecular biological, and optical imaging methods. The proposed research consists of three parts. In PART I, we will use cultures of rat or mouse hippocampal neurons to examine the acute pre- and postsynaptic effects of exogenously-applied BDNF on the function and plasticity of glutamatergic and GABAergic synapses and on axon/dendrite morphology and synaptogenesis. The synapse-specific local actions of BDNF and underlying signaling mechanisms will also be investigated. In PART II, we will study the role of endogenously-secreted BDNF in activity-induced modifications of synaptic function and morphology in hippocampal cultures, activity-dependent BDNF secretion, and intra- and interneuronal trafficking of BDNF. In PART Ill, using developing Xenopus tadpoles, we will examine the in vivo effect of BDNF on the function and plasticity of retinotectal synapses, axon/dendrite dynamics and synaptogenesis in the tectum, and the trafficking and secretion of endogenous BDNF. Finally, we will investigate the role of BDNF in the development of retinotopic map and direction-selective receptive field of tectal neurons. Taken together, these in vitro and in vivo studies provide unique opportunities to address several fundamental cell biological issues concerning the modulatory function of neurotrophins in activity-dependent refinement of developing neural connections, and are likely to yield new information relevant to our basic understanding of physiology and pathology of the developing nervous system.