Anatomical and Functional Properties of Auditory Nerve Synapses

听神经突触的解剖和功能特性

• 批准号: 8810723
• 负责人: Maria Eulalia Rubio
• 金额: $ 8.85万
• 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 2018-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8810723
• 关键词: AMPA Receptors; Acoustic Nerve; Acute; Adult; Applications Grants; Auditory; Auditory Brainstem Responses; Auditory system; 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; Genetic Techniques; Glutamate Receptor; Glutamates; Goals; Health; Hearing; Hearing Aids; Hearing Tests; Hearing problem; Inferior Colliculus; Kinetics; Knock-out; Knockout Mice; Label; Lead; Light; Long-Term Effects; Mediating; Molecular; Mus; Nerve Fibers; Neurons; Population; Population Projection; Procedures; Process; Property; Research; Reverse Transcriptase Polymerase Chain Reaction; Role; Slice; Stimulus; Synapses; Synaptic Transmission; Testing; Therapeutic; Time; Whole-Cell Recordings; base; cell type; density; dorsal cochlear nucleus; experience; hearing impairment; in vivo; novel; postsynaptic; 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）：听觉神经（AN）将所有听觉信息从耳蜗传递到大脑。在耳蜗核（CN）中，AN纤维分叉以支配多个细胞群，包括腹侧CN中的丛状细胞（BC）和背侧CN中的梭形细胞（FC）。这两种细胞类型在编码声音刺激的时间特性的能力上显着不同。BC投射到上级橄榄复合体中的双耳电路，并编码频谱和时间特性，使声音定位在水平面中。FC投射到下丘中的单耳回路，并检测用于在垂直平面中定位声音的spectrl线索。BC和FC上的AN突触都是谷氨酸能的，并且涉及AMPAR作为主要的突触后谷氨酸受体。在AN-BC突触处，突触传递非常快速和可靠，以保存包含在AN尖峰的定时中的信息。在AN-FC突触处，突触传递明显慢于AN-BC突触处。了解使AN-BC突触比AN-FC突触快的突触机制一直是一个重要的问题，一直在深入研究。然而，具体的AMPAR亚基实际上介导在AN突触的快速突触传递仍然没有解决。本研究的目的是了解GluA 3 AMPAR亚基在脑干神经元AN突触中的功能作用以及AN突触对听觉体验的敏感性。从这一建议获得的数据将促进理解的细胞机制的时间精度的声音编码在正常和听力受损。因此，在目标1中，我们将测试的假设，在AN-BC突触的GluA 3是AMPAR亚基，决定快速AMPAR动力学。目的2：验证神经元突触后皮层中GluA 3 AMPAR亚基表达和定位的增加介导了AN-BC和AN-FC突触的经验依赖性可塑性。为了实现这些目标，我们将结合联合收割机听力测试（听觉脑干反应，ABR），以分析脑干的能力，在体内的声音刺激，定量超微结构和分子技术，遗传方法（敲除）和电生理学在急性脑干切片的成年正常听力和单耳耳塞小鼠。具体而言，我们将使用冷冻断裂和植入后免疫金标记，qRT-PCR与全细胞记录一起，以确定AN突触的形态，分子和功能改变。我们的研究结果可用于优化治疗听力损失和其他听力障碍的策略。大量的证据表明，听觉系统是高度专业化的。对这些特化背后的突触机制进行系统、严格的研究，将为合理的治疗方法提供建议和信息。