Preservation of timing in plastic auditory pathways

保留可塑性听觉通路的时序

• 批准号: 8765714
• 负责人: HENRIQUE Prado VON GERSDORFF
• 金额: $ 32.2万
• 依托单位: OREGON HEALTH & SCIENCE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-03-01 至 2016-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8765714
• 关键词: Accounting; Acoustic Nerve; Action Potentials; Adult; American; Amphibia; Auditory; Biological Assay; Biological Preservation; Buffers; Bypass; Cell physiology; Cells; Cellular biology; Characteristics; Chemicals; Cochlea; Cytoplasm; Data; Dependence; Electric Capacitance; Electron Microscopy; Electrophysiology (science); Event; Exhibits; Exocytosis; Fatigue; Fiber; Frequencies; Glutamates; Grant; Hair Cells; Health; Hearing; Impairment; In Vitro; Inner Hair Cells; Ion Channel; Kinetics; Labyrinth; Lead; Mammals; Measurement; Measures; Membrane; Membrane Potentials; Mental Depression; National Institute on Deafness and Other Communication Disorders; Nerve; Nerve Fibers; Neurotransmitters; Pattern; Phase; Physiological; Physiology; Plastics; Play; Preparation; Primates; Property; Protocols documentation; Rana catesbeiana; Recovery; Recruitment Activity; Refractory; Resolution; Role; Stimulus; Structure; Synapses; Synaptic Transmission; Synaptic Vesicles; Testing; Time; Vesicle; afferent nerve; auditory pathway; hearing impairment; implantable device; insight; novel; patch clamp; postsynaptic; premature; reconstruction; response; ribbon synapse; sound; sound frequency; tongue papilla; vector; vesicular release; voltage clamp

DESCRIPTION (provided by applicant): Auditory hair cells release the excitatory neurotransmitter glutamate at their basal pole where they form synapses with afferent fibers. The underlying mechanisms that control and regulate the release of glutamate from hair cells, and how this release elicits action potential spikes in the afferent fibers, are still poorly understood. Part of the reason for this is the small size, fragility, and inaccessibility of adult mammalian inner hair cells and their afferent fibers. We propose here to study fundamental aspects of synaptic transmission from auditory hair cells in the adult bullfrog amphibian papilla. This unique in vitro preparation allows us to routinely access single hair cells and their afferent fibers for high-time-resolution patch-clamp electrophysiology and structure/function studies. We propose to use paired recordings of the hair cell and its connected afferent fiber to study multiquantal glutamate release and simultaneously to measure membrane capacitance changes from the hair cell to assay the exocytosis of synaptic vesicles. We will pursue three Specific Aims: First, we hypothesize that hair cells contain three distinct readily releasable pools of synaptic vesicles that have morphological correlates. Electrophysiological and serial electron microscopy reconstruction studies will be undertaken to determine the size, efficiency of release, Ca-dependence, recruitment and recovery rates, and short-term plasticity of these vesicle pools. Second, we hypothesize that the depletion of a small but fast releasing pool of vesicles accounts for the rapid phase of spike firing adaptation, whereas the second and slower phase of spike adaptation depends on vesicle recruitment from the synaptic ribbon and cytoplasm. Paired recordings will be used to determine vesicle release rates, which will then be compared to afferent fiber spike rates evoked by the same hair-cell stimulus protocol. We will also determine the identity and properties of the ionic currents present at the afferent fiber to better understand how afferent fibers trigger spikes. Finally, we hypothesize that evoked multiquantal EPSC amplitudes become effectively Ca-independent when hair cells are stimulated by sinusoidal-like stimuli that mimic pure tone sounds. We propose that this regime of Ca-independent multiquantal release allows spike synchronization to occur at a given characteristic sound frequency even as stimulus intensity changes. This grant will thus lead to fundamental insights on how the hair cell synapse encodes information about the timing and intensity of sound via the rate, latency, and timing of action potential spikes in the afferent fibers.

描述（由申请人提供）：听觉毛细胞在其基极处释放兴奋性神经递质谷氨酸，在那里它们与传入纤维形成突触。控制和调节毛细胞谷氨酸释放的潜在机制，以及这种释放如何引起传入纤维中的动作电位峰值，仍然知之甚少。造成这种情况的部分原因是成年哺乳动物内毛细胞及其传入纤维体积小、脆弱且难以接近。我们在这里建议研究成年牛蛙两栖动物乳头中听觉毛细胞突触传递的基本方面。这种独特的体外制备使我们能够常规地获取单个毛细胞及其传入纤维，以进行高时间分辨率膜片钳电生理学和结构/功能研究。我们建议使用毛细胞及其连接的传入纤维的配对记录来研究多量子谷氨酸释放，同时测量毛细胞的膜电容变化以测定突触小泡的胞吐作用。我们将追求三个具体目标：首先，我们假设毛细胞包含三个不同的易于释放的具有形态相关性的突触小泡池。将进行电生理学和连续电子显微镜重建研究，以确定这些囊泡池的大小、释放效率、Ca依赖性、募集和恢复率以及短期可塑性。其次，我们假设少量但快速释放的囊泡池的耗尽导致了尖峰放电适应的快速阶段，而尖峰适应的第二个和较慢的阶段取决于突触带和细胞质中的囊泡招募。配对记录将用于确定囊泡释放速率，然后将其与相同毛细胞刺激方案引起的传入纤维尖峰速率进行比较。我们还将确定传入纤维中存在的离子电流的特性和特性，以更好地了解传入纤维如何触发尖峰。最后，我们假设当毛细胞受到模拟纯音的正弦曲线刺激时，诱发的多量子 EPSC 振幅实际上变得与 Ca 无关。我们提出，这种与 Ca 无关的多量子释放机制允许在给定的特征声音频率下发生尖峰同步，即使刺激强度发生变化。因此，这项资助将带来关于毛细胞突触如何通过传入纤维中动作电位尖峰的速率、潜伏期和时间来编码有关声音的时间和强度的信息的基本见解。