Anatomical and Functional Properties of Auditory Nerve Synapses

听神经突触的解剖和功能特性

• 批准号: 8804940
• 负责人: Maria Eulalia Rubio
• 金额: $ 55.14万
• 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 2016-02-29
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8804940
• 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; 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; Techniques; Testing; Therapeutic; Time; Whole-Cell Recordings; base; cell type; density; dorsal cochlear nucleus; experience; genetic approach; 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(申请人提供)：听神经(AN)将所有的听觉信息从耳蜗处传输到大脑。在耳蜗核(CN)，纤维分支支配多种细胞群，包括腹侧CN的丛状细胞(BCS)和背侧CN的梭形细胞(FCS)。这两种细胞类型在编码声音刺激的时间属性的能力上有很大的不同。BCS投射到上橄榄复合体中的双耳回路，并编码频谱和时间特征，使声音能够在水平面上定位。FCS投射到下丘的单耳回路，并检测光谱信号，以定位垂直平面上的声音。BCS和FCS上的突触都是谷氨酸能的，AMPAR是主要的突触后谷氨酸受体。在AN-BC突触，突触传输极其快速和可靠，以保存包含在棘波计时中的信息。在An-Fc突触，突触传输明显慢于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广泛研究的重要问题。然而，哪些特定的AMPAR亚基实际上介导了突触的快速突触传递仍未解决。这项拟议研究的目的是了解突触上GluA3 AMPAR亚单位在脑干神经元上的功能作用，以及突触对听觉体验的敏感性。从这项建议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确度背后的细胞机制的理解。因此，在目标1中，我们将检验这样的假设，即AN-BC突触中的GluA3是决定快速AMPAR动力学的AMPAR亚单位。目的2验证GluA3AMPAR亚基在PSD内表达和定位增加介导An-BC和An-Fc突触经验依赖性可塑性的假设。为了实现这些目标，我们将结合听力测试(听觉脑干反应，ABR)来分析脑干对体内声音刺激的反应能力，定量超微结构和分子技术，遗传方法(基因敲除)和成年正常听力和单耳耳塞小鼠急性脑干切片的电生理学。具体地说，我们将使用冷冻断裂和包埋后的免疫金标记法、qRT-PCR结合全细胞记录来识别突触的形态、分子和功能变化。我们的研究结果可用于优化听力损失和其他听力障碍的治疗策略。大量证据表明，听觉系统高度专门化。对突触机制的系统、严谨的研究将为合理的治疗方法提供建议和信息。