Anatomical and Functional Properties of Auditory Nerve Synapses

听神经突触的解剖和功能特性

• 批准号: 9207101
• 负责人: Maria Eulalia Rubio
• 金额: $ 47.21万
• 依托单位: UNIVERSITY OF PITTSBURGH AT PITTSBURGH
• 依托单位国家: 美国
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-03-01 至 2018-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9207101
• 关键词: AMPA Receptors; Acoustic Nerve; Acute; Adult; Anatomy; Applications Grants; Auditory; Auditory Brainstem Responses; Auditory system; Binaural; Brain; Brain Stem; Cells; Characteristics; Clinical; Cochlea; Cochlear Implants; Cochlear nucleus; Code; Complex; Conductive hearing loss; Cues; Data; Earplug; Electrophysiology (science); Freeze Fracturing; Fusiform Cell; Glutamate Receptor; Glutamates; Goals; Hearing; Hearing Aids; Hearing Tests; Hearing problem; Inferior Colliculus; Kinetics; Knock-out; Knockout Mice; Label; Lead; Light; Mediating; Molecular; Morphology; Mus; Nerve Fibers; Neurons; Pharmacology; Population; Population Projection; Procedures; Property; Quantitative Reverse Transcriptase PCR; Research; Reverse Transcriptase Polymerase Chain Reaction; Role; Slice; Sound Localization; Stimulus; Synapses; Synaptic Transmission; Techniques; Testing; Therapeutic; Whole-Cell Recordings; auditory processing; base; cell type; density; dorsal cochlear nucleus; experience; genetic approach; hearing impairment; in vivo; novel; postsynaptic; public health relevance; response; sound

DESCRIPTION (provided by applicant): The auditory nerve (AN) transmits all auditory information from the cochlea to the brain. In the cochlear nucleus (CN), AN fibers bifurcate to innervate multiple cell populations, including bushy cells (BCs) in the ventral CN, and fusiform cells (FCs) in the dorsal CN. These two cell types differ significantly in their ability to encode temporal properties of sound stimuli. BCs project to binaural circuits in the superior olivary complex and encode spectral and temporal characteristics that allow sounds to be localized in the horizontal plane. FCs project to monaural circuits in the inferior colliculus and detect spectrl cues for localizing sounds in the vertical plane. AN synapses on BCs and FCs are both glutamatergic and involve AMPARs as major postsynaptic glutamate receptors. At AN-BC synapses, synaptic transmission is extremely fast and reliable to preserve information contained in the timing of AN spikes. At AN-FC synapses, synaptic transmission is significantly slower than at AN-BC synapses. Understanding the synaptic mechanisms that make AN-BC synapses faster than AN-FC synapses has been an important question that has been intensely studied. However, which specific AMPAR subunits actually mediate fast synaptic transmission at AN synapses is still unresolved. The goal of the proposed studies is to provide understanding of the functional role of GluA3 AMPAR subunits at AN synapses on brainstem neurons and the sensitivity of AN synapses to auditory experience. Data obtained from this proposal will advance understanding of the cellular mechanisms underlying the temporal precision of sound coding in the normal and in the hearing impaired. Thus in Aim 1 we will test the hypothesis that GluA3 in AN-BC synapses is the AMPAR subunit that determines fast AMPAR kinetics. Aim 2 will test the hypothesis that increase in expression and localization within the PSD of GluA3 AMPAR subunits mediates the experience-dependent plasticity of AN-BC and AN-FC synapses. To achieve these goals, we will combine hearing tests (auditory brainstem responses, ABRs) to analyze the ability of the brainstem to respond to sound stimuli in vivo, quantitative ultrastructural and molecular techniques, genetic approaches (knockouts) and electrophysiology in acute brainstem slices of adult normal hearing and monaurally earplugged mice. Specifically, we will use freeze-fracture and postembedding immunogold labeling, qRT-PCR together with whole-cell recording to identify morphological, molecular and functional alterations at AN synapses. The results of our studies can be applied to efforts to optimize strategies for treating hearing loss and other hearing disorders. A large body of evidence indicates that the auditory system is highly specialized. Systematic, rigorous studies of the synaptic mechanisms underlying the specializations will both suggest and inform rational therapeutic approaches.

描述（由申请人提供）：听神经（AN）将所有的听觉信息从耳蜗传递到大脑。在耳蜗核（CN）中，AN纤维分叉并支配多个细胞群，包括位于CN腹侧的丛状细胞（BCs）和位于CN背侧的梭状细胞（FCs）。这两种类型的细胞在编码声音刺激的时间特性的能力上有很大的不同。BCs投射到上橄榄复合体的双耳回路，并编码频谱和时间特征，使声音定位在水平面上。FCs投射到下丘的单耳回路，并检测光谱线索，以定位垂直平面上的声音。BCs和FCs上的AN突触都是谷氨酸能突触，并涉及ampar作为主要的突触后谷氨酸受体。在AN- bc突触中，突触传输非常快速和可靠，以保存AN尖峰时间所包含的信息。在AN-FC突触，突触传递明显慢于AN-BC突触。了解使an - bc突触比an - fc突触更快的突触机制一直是一个被深入研究的重要问题。然而，具体是哪些AMPAR亚基在AN突触中介导快速突触传递仍未明确。本研究的目的是了解脑干神经元上的AN突触中GluA3 AMPAR亚基的功能作用以及AN突触对听觉体验的敏感性。从该提案中获得的数据将促进对正常和听力受损的声音编码时间精度的细胞机制的理解。因此，在Aim 1中，我们将测试AN-BC突触中的GluA3是决定AMPAR快速动力学的AMPAR亚基的假设。目的2将验证GluA3 AMPAR亚基在PSD内表达和定位的增加介导AN-BC和AN-FC突触的经验依赖可塑性的假设。为了实现这些目标，我们将结合听力测试（听觉脑干反应，ABRs）来分析脑干在体内对声音刺激的反应能力，定量超微结构和分子技术，遗传方法（敲除）以及成年正常听力小鼠和单耳小鼠急性脑干切片的电生理学。具体来说，我们将使用冷冻断裂和包埋后免疫金标记，qRT-PCR以及全细胞记录来鉴定AN突触的形态，分子和功能变化。我们的研究结果可以应用于努力优化治疗听力损失和其他听力障碍的策略。大量证据表明，听觉系统是高度专业化的。系统的，严格的研究突触机制的基础专业化将建议和告知合理的治疗方法。