Preservation of timing in plastic auditory pathways

保留可塑性听觉通路的时序

• 批准号: 8042234
• 负责人: HENRIQUE Prado VON GERSDORFF
• 金额: $ 32.52万
• 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 2015-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8042234
• 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; 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; 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. PUBLIC HEALTH RELEVANCE: More than thirty million Americans suffer from significant hearing deficits and most of these impairments are due to damaged hair cells in the inner ear. Our ability to treat this hearing loss, however, has been greatly impaired by a poor understanding of hair cell synapses, and of the mechanisms that generate action potential spikes in the auditory nerve fibers. This proposal uses a novel adult auditory hair cell synapse preparation to study fundamental aspects of hair cell synaptic physiology, so it will further our basic understanding of how to excite different auditory nerve fibers artificially with cochlea implants (devices that can partially restore hearing by bypassing the damaged hair cells to directly stimulate the auditory nerve) by using more physiologically relevant patterns of stimulation that match the original information rates of healthy adult hair cells.

描述（由申请人提供）：听觉毛细胞释放兴奋性神经递质的谷氨酸在其基底极，在那里它们用传递的纤维形成突触。控制和调节从毛细胞中释放和调节谷氨酸的基本机制，以及该释放如何引起传入纤维中的动作电位尖峰，但仍知之甚少。原因的一部分是成年哺乳动物内毛细胞及其传入纤维的尺寸小，脆弱性和无法访问的原因。我们在这里建议研究成人牛蛙两栖乳头中听觉毛细胞的突触传播的基本方面。这种独特的体外制备使我们能够常规地访问单毛细胞及其传入纤维，以进行高空分辨率贴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，同时研究多功能谷氨酸释放，以测量毛细胞中膜电容的变化，以测定突触小囊泡的胞吞作用。我们将追求三个特定目标：首先，我们假设毛细胞包含三个不同易于释放的突触囊泡的池，它们具有形态学相关。将进行电生理和串行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，募集和恢复速率以及短期可塑性。其次，我们假设一个小但快速释放的囊泡的耗竭是尖峰放电适应的快速阶段，而峰值适应的第二个且较慢的阶段取决于突触色带和细胞质中的囊泡募集。配对的记录将用于确定囊泡释放速率，然后将其与相同的发型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上存在的离子电流的身份和特性，以更好地了解传入纤维如何触发尖峰。最后，我们假设诱发的多功能EPSC振幅在模仿纯音的声音时被正弦样刺激刺激毛细胞被刺激时，有效地独立于CA不依赖。我们建议，这种独立于CA的多功能释放制度允许即使刺激强度变化，也可以在给定的特征声频率下出现尖峰同步。因此，这项赠款将导致有关毛细胞突触如何通过传入纤维中的速率，延迟和动作潜在尖峰的声音的时间和强度编码有关声音的时间和强度的信息的基本见解。 公共卫生相关性：超过300万美国人患有严重的听力障碍，其中大多数障碍是由于内耳内部的毛细胞受损。然而，我们治疗这种听力损失的能力受到了对毛细胞突触的不良理解以及在听觉神经纤维中产生动作潜在尖峰的机制的严重损害。该建议使用一种新型的成人听觉毛细胞突触准备来研究毛细胞突触生理学的基本方面，因此，它将进一步进一步了解如何用耳蜗植入物人为地激发不同听觉神经纤维的基本理解（可以通过绕开绕过听力来绕开听力的设备通过使用更多与健康成人毛细胞的原始信息速率相匹配的刺激模式，损坏了毛细胞直接刺激听觉神经）。