Anatomical and Functional Properties of Auditory Nerve Synapses

听神经突触的解剖和功能特性

• 批准号: 8477668
• 负责人: Maria Eulalia Rubio
• 金额: $ 47.07万
• 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/8477668
• 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; 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; 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）：听觉神经（AN）将所有听觉信息从耳蜗传输到大脑。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方面存在显着差异。 BC 投射到上橄榄复合体中的双耳回路，并编码频谱和时间特性，使声音能够在水平面上定位。 FC 投射到下丘的单耳回路并检测用于在垂直平面中定位声音的光谱线索。 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 突触中，突触传输极其快速且可靠，可以保存 AN 尖峰时序中包含的信息。在 AN-FC 突触处，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人们深入研究的一个重要问题。然而，哪些特定的 AMPAR 亚基实际上介导 AN 突触的快速突触传递仍悬而未决。拟议研究的目的是了解 GluA3 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。从该提案中获得的数据将促进对正常人和听力受损者声音编码时间精度背后的细胞机制的理解。因此，在目标 1 中，我们将检验以下假设：AN-BC 突触中的 GluA3 是决定快速 AMPAR 动力学的 AMPAR 亚基。目标 2 将检验以下假设：GluA3 AMPAR 亚基的 PSD 内表达和定位的增加介导 AN-BC 和 AN-FC 突触的经验依赖性可塑性。为了实现这些目标，我们将结合听力测试（听觉脑干反应，ABR）来分析脑干在体内对声音刺激做出反应的能力，定量超微结构和分子技术，遗传方法（敲除）和急性脑干切片中的电生理学。成年正常听力小鼠和单耳耳塞小鼠。具体来说，我们将使用冷冻断裂和嵌入后免疫金标记、qRT-PCR 以及全细胞记录来识别 AN 突触的形态、分子和功能变化。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。大量证据表明听觉系统是高度专业化的。对专业化背后的突触机制进行系统、严格的研究将提出合理的治疗方法并为合理的治疗方法提供信息。