High-fidelity synaptic transmission from hair cells to auditory afferent fibers

从毛细胞到听觉传入纤维的高保真突触传递

• 批准号: 9310778
• 负责人: Geng-Lin Li
• 金额: $ 33.36万
• 依托单位: UNIVERSITY OF MASSACHUSETTS AMHERST
• 依托单位国家: 美国
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-03-02 至 2022-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9310778
• 关键词: AMPA Receptors; Acoustic Stimulation; Activities of Daily Living; Address; Adrenergic alpha-Antagonists; Adult; Affinity; Amphibia; Auditory; Auditory system; Binding; Biological Models; Birth; Brain; Buffers; Bypass; Cells; Charge; Clinical Treatment; Cochlea; Code; Computer Simulation; Coupling; Data; Diffusion; Egtazic Acid; Electric Capacitance; Event; Exocytosis; Explosion; Fiber; Fire - disasters; Fluorescence; Glutamates; Hair Cells; Hearing; In Vitro; Kinetics; Knowledge; Labyrinth; Lead; Length; Light; Mediating; Membrane Potentials; Mental Depression; Modeling; Molecular; Nerve Fibers; Neurotransmitters; Noise-Induced Hearing Loss; Pattern; Performance; Pharmaceutical Preparations; Phase; Physiologic pulse; Physiological; Physiology; Preventive measure; Property; Rana catesbeiana; Rest; Role; Signal Transduction; Site; Synapses; Synaptic Transmission; Synaptic Vesicles; Testing; Time; Toxic effect; afferent nerve; biophysical properties; cyclothiazide; desensitization; experimental study; hearing impairment; improved; in vivo; insight; mature animal; patch clamp; postsynaptic; presynaptic; prevent; response; ribbon synapse; sensor; sound; synaptic depression; synaptic function; synaptic inhibition; tongue papilla; transmission process; vesicular release; voltage

Project Summary Auditory hair cells connect to afferent nerve fibers through ribbon synapses, where auditory signals are converted from graded membrane potentials in hair cells into spikes in afferent nerve fibers. In vivo studies conducted in adult animals have shown that in response to sound afferent fibers fire spikes with remarkable temporal precision, but the underlying synaptic mechanisms are still poorly understood. A major hurdle is the lack of a fully mature model system for dual patch-clamp analysis in vitro. The afferent fiber terminals in the adult mammalian cochlea are small and mostly inaccessible to patch-clamp analysis, and results from the immature cochlea are insufficient to explain in vivo findings. Here we propose to examine auditory transmission in the amphibian papilla of adult bullfrogs, which is a unique model system where spiking patterns of afferent fibers in vivo have been recapitulated with paired patch-clamp experiments in vitro. Using this model system, we will combine dual patch-clamp recording, glutamate uncaging and computer modeling to address a central and fundamental question in hearing: how small and fast-changing signals in auditory hair cells are transmitted to afferent fibers precisely and tirelessly. First, we will examine the desensitization properties of AMPA receptors in afferent fiber terminals, and determine how these properties allow the ribbon synapses to maintain synaptic strength under continuous glutamate release from hair cells. Second, we will demonstrate that Ca2+ influx caused by pre-depolarization leads to rapid priming of synaptic vesicles and makes them releasable in response to brief voltage changes. We will test the hypothesis that this priming of synaptic vesicles is mediated by a second Ca2+ sensor with biophysical properties distinct from the one for synaptic vesicle fusion. Lastly, we will elucidate the cellular mechanisms for multivesicular release, a hallmark of hair cell ribbon synapses. We will test three major candidate mechanisms: fusion pore flickering, nanodomain coupling of synaptic vesicles and Ca2+ channels, and coordination of synaptic ribbons. The results obtained through this project will answer several long-standing questions of inner ear physiology, and expand our knowledge of the fundamental rules governing synaptic transmission at auditory hair cell synapses.

项目摘要 听觉毛细胞通过色带突触连接到传入的神经纤维，其中听觉 信号从毛细胞中的分级膜电位转换为传入中的尖峰 神经纤维。在成年动物中进行的体内研究表明，响应声音 具有显着的时间精确度的传入纤维火峰值，但基础突触 机制仍然很了解。一个主要障碍是缺乏完全成熟的模型 体外双重贴片钳分析的系统。成人的传入纤维终端 哺乳动物的耳蜗很小，大多数是对斑块夹的分析，并且来自 未成熟的耳蜗不足以解释体内发现。在这里我们建议检查 成人牛蛙的两栖动物乳头上的听觉传输，这是一个独特的模型系统 其中已经用配对贴片钳概括了体内传入纤维的尖刺模式 体外实验。使用此模型系统，我们将结合双贴片框架记录， 谷氨酸分离和计算机建模，以解决一个中心和基本问题 听力：听觉毛细胞中的小且快速变化的信号传输到传入 纤维精确，不懈。首先，我们将检查AMPA的脱敏特性 传入纤维端子中的受体，并确定这些特性如何允许色带 在连续的谷氨酸释放毛细胞下，突触以保持突触强度。 其次，我们将证明由前偏度引起的Ca2+流入导致快速启动 突触囊泡，使其可响应短暂的电压变化。我们将 检验以下假设，即这种突触囊泡的启动是由第二个Ca2+传感器介导的 具有与突触囊泡融合的生物物理特性不同。最后，我们会的 阐明了多个释放的细胞机制，这是毛细胞色带的标志 突触。我们将测试三种主要候选机制：融合孔闪烁，纳米域 突触囊泡和Ca2+通道的耦合，以及突触色带的配位。这 通过该项目获得的结果将回答几个长期存在的内耳问题 生理学，并扩大我们对掌管突触的基本规则的了解 听觉毛细单元突触的传输。