Mechanisms Regulating Synaptic Function in the Developing Auditory System

 描述（由申请人提供）：本研究的目的是确定产生对正常听觉功能至关重要的声音的快速神经编码的机制。然而，发展机制知之甚少，在脑干，在快速神经编码赤字的基础方面的听觉时间处理障碍。在成熟的听觉突触中，快速神经编码是由AMPA型谷氨酸受体（AMPA-R）介导的，这在很大程度上是由于它们的亚基排列，这与其他脑区不同。它们独特的亚基排列提出了重要的生物学问题：调节听觉系统中专门AMPA-R特性的发展的机制与调节大脑其他地方AMPA-R的机制相似吗？如果是这样的话，是什么机制控制着AMPA-R亚基的这种不同排列？如果不是，那么调节AMPA-R的替代机制是否仅限于听觉系统？本研究将通过研究鸟类听觉脑干中突触AMPA-Rs特性的调节来解决这些问题。 在发育中的大脑中的其他地方，NMDA-R有助于调节正常的AMPA-R特性和特定的疾病状态; NMDA-R被认为是控制突触AMPA-R功能障碍的分子靶标。NMDA-R还在听觉系统疾病中起负面作用，包括耳鸣、噪声诱导的听力损失和神经性老年性耳聋。然而，NMDA-Rs在调节突触AMPA-Rs中的因果作用以及它们在发育中的听觉脑干中对声音的快速神经编码的贡献程度尚不清楚。这项研究将测试的假设，即建立快速神经编码需要NMDA-R依赖性调节突触AMPA-R的属性在发育中的脑干，精确的听觉时间处理能力的关键。研究NMDA-Rs对AMPA-Rs的调节作用将是理解与听觉时间加工障碍相关的病理学的重要第一步。使用创新的方法，该项目旨在确定NMDA-Rs（1）调节发育中的鸟类大细胞核（NM）中突触AMPA-R的数量和亚基组成的程度，以及（2）确定在NMDA-Rs的遗传操作后，AMPA-Rs在功能成熟的NM突触中介导的时间速度和精度的程度。我将结合联合收割机卵内遗传操作、药理学/生化测定和体外膜片钳电生理学，在对应于突触形成、听力开始和功能成熟的发育时间段内测试上述目标。了解NMDA-Rs对突触发育和完善的贡献，将有助于了解亚单位特异性AMPA-Rs在听觉系统中的作用。更好地了解分子水平的NMDA-R机制，可以确定药理学靶点，以改善其中突触AMPA-R功能障碍在与听觉时间处理相关的病理中具有直接或因果作用的疾病。

 DESCRIPTION (provided by applicant): The goal of this research is to identify mechanisms that give rise to fast neural encoding of sound critical for normal auditory function. However, developmental mechanisms are poorly understood in the brainstem, where deficits in fast neural encoding underlie aspects of auditory temporal processing disorders. At mature auditory synapses, fast neural encoding is mediated by AMPA-type glutamate receptors (AMPA-Rs) due largely in part to their subunit arrangement, which is distinct from other brain regions. Their unique subunit arrangement raises important biological questions: are the mechanisms that regulate the development of specialized AMPA- R properties in the auditory system similar to mechanisms that regulate AMPA-Rs elsewhere in the brain? If so, what mechanisms govern this different arrangement of AMPA-R subunits? If not, are alternative mechanisms regulating AMPA-Rs exclusive to the auditory system? This study will address these questions by investigating the regulation of synaptic AMPA-Rs properties in the avian auditory brainstem. Elsewhere in the developing brain, NMDA-Rs assist in regulating normal AMPA-R properties and during specific diseased states; NMDA-Rs are implicated as a molecular target in controlling synaptic AMPA-R dysfunction. NMDA-Rs also play a negative role in diseases of the auditory system, including tinnitus, noise- induced hearing loss and neural presbycusis. However, the causal role NMDA-Rs plays in regulating synaptic AMPA-Rs and the extent to which they contribute to fast neural encoding of sound in the developing auditory brainstem are not known. This study will test the hypothesis that the establishment of fast neural encoding requires NMDA-R dependent regulation of synaptic AMPA-R properties in the developing brainstem, critical for precise auditory temporal processing abilities. Investigating the regulator role of NMDA-Rs on AMPA-Rs will be a significant first step in understanding pathologies associated with auditory temporal processing disorders. Using innovative methods, the project aims to determine the extent to which NMDA-Rs (1) regulate the number and subunit composition of synaptic AMPA-R in the developing avian nucleus magnocellularis (NM) and (2) to determine the extent to which temporal speed and precision are mediated by AMPA-Rs at functionally mature NM synapses following genetic manipulation of NMDA-Rs. I will combine in-ovo genetic manipulations, pharmacological/biochemical assays, and in-vitro patch clamp electrophysiology to test the above Aims during developmental time periods corresponding to synapse formation, hearing onset, and functional maturation. Gaining an understanding of NMDA-Rs contribution to synaptic development and refinement should shed light on the role of subunit-specific AMPA-Rs in the auditory system. A better understanding of molecular-level NMDA-R mechanisms may identify pharmacological targets to improve disorders in which synaptic AMPA-R dysfunction has either a direct or causal role in pathologies related to auditory temporal processing.