Mechanisms of Transmitter Release by Cochlear Hair Cells

耳蜗毛细胞释放递质的机制

• 批准号: 6782358
• 负责人: THOMAS D PARSONS
• 金额: $ 35.53万
• 依托单位: UNIVERSITY OF PENNSYLVANIA
• 依托单位国家: 美国
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-08-01 至 2007-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6782358
• 关键词: adenosine triphosphate; auditory stimulus; buffers; calcium binding protein; calcium flux; calcium indicator; chickens; cochlea; computational neuroscience; ear hair cell; electrophysiology; electrostimulus; exocytosis; flash photolysis; fluorescence microscopy; neural transmission; neuropharmacology; neurotransmitter receptor; neurotransmitter transport; neurotransmitters; potassium channel; sound frequency; synapses; synaptic vesicles; voltage /patch clamp

DESCRIPTION (provided by applicant): Frequency components of sound are encoded in the temporal pattern of auditory nerve discharges - and thus by inference also encoded by the hair cell synapse. In particular, auditory afferent fibers fire at a particular phase of a low-frequency pure tone stimulus. As stimulus frequency increases, this 'phase locking' or 'synchrony' is maintained until it falls off with a corner frequency, fc ranging from 1-3 kHz in guinea pig and cat to 6 kHz in the barn owl. Synaptic latency and variability in that latency (called jitter) are typically on the order of 1-2 ms at many conventional synapses. Thus, it is unclear what underlying mechanisms maintain the temporal precision associated with phase locking at the cochlear hair cell afferent fiber (CHC-AF) synapse, especially when acoustic stimuli occur with periodicity less than 1 ms. We propose to use a variety of experimental preparations from a single species to: 1. Characterize the temporal precision of the chick CHC-AF synapse. Phase locking, synaptic latency and synaptic jitter are measured in vivo and their fc determined. 2. Tests the hypothesis that calcium-dependent steps in depolarization-exocytosis coupling behave as additional low pass-filters to limit the temporal precision of the CHC, AF synapse. Intracellular calcium transients and endogenous buffering are assayed with Kca, channels while exocytic latency and rate are examined with electrical measures of cell surface area. A computational model then incorporates these in vitro physiological parameters to predict the interactions of experimentally dissected low pass filter components. 3. Tests the hypothesis that the synaptic ribbon functions to improve temporal precision at the CHC-AF synapse. Dual-wave length total internal reflection fluorescent microscopy simultaneously images localized calcium influx at synaptic ribbons and exocytosis of spryly dye-labeled synaptic vesicles. We propose that the synaptic ribbon tethers synaptic vesicles in mutual contact and facilitates multivesicular release by compound exocytosis. However, direct evidence for vesicles tethered to hair cell synaptic ribbons in exocytosis is lacking. Therefore the preferential release of vesicles tethered to the synaptic ribbon is tested. fc values for the different pre-synaptic mechanisms are measured in vitro and compared with fc determined for the neural responses in vivo. A computational model allows us to probe their relative contribution to the underlying mechanisms that maintain or degrade the temporal precision of phase locking by the CHC-AF synapse.

描述（由申请人提供）：声音的频率成分以听觉神经放电的时间模式编码 - 因此，通过推断也由毛细胞突触编码。特别是，听觉传入纤维在低频纯音刺激的特定阶段发射。随着刺激频率的增加，这种“相位锁定”或“同步”将保持不变，直到它以角频率下降为止，FC从几内亚猪中的1-3 kHz和猫cat到谷仓猫头鹰的6 kHz。该潜伏期（称为抖动）的突触潜伏期和可变性通常在许多常规突触下为1-2 ms的顺序。因此，目前尚不清楚哪种基本机制保持了与耳蜗毛细胞传入纤维（CHC-AF）突触相关的时间精度，尤其是在周期性小于1 ms的声学刺激发生时。我们建议使用从单个物种到： 1。表征Chick CHC-AF突触的时间精度。相位锁定，突触潜伏期和突触抖动在体内测量及其FC。 2。检验以下假设：钙依赖性步骤在去极化 - 胞毒性耦合中的行为是额外的低通滤波器，以限制CHC的时间精度，即AF Synapse。细胞内钙瞬变和内源性缓冲用KCA，通道测定，而胞外潜伏期和速率则通过细胞表面积的电测量来检查。然后，计算模型结合了这些体外生理参数，以预测实验解剖的低通滤波器成分的相互作用。 3。检验了突触色带功能以提高CHC-AF突触时时间精度的假设。双波长长度总内反射荧光显微镜同时图像突触丝带处局部钙涌入，并在旋转染料标记的突触囊泡的胞吐作用。我们建议在相互接触中的突触带突触囊泡，并通过复合胞吐作用促进多囊性释放。但是，缺乏囊泡囊泡的直接证据。因此，测试了系绳上的囊泡的优先释放。 在体外测量了不同突触前机制的FC值，并与确定体内神经反应的FC进行了比较。计算模型使我们能够探究其对维持或降低CHC-AF突触锁定时间锁定时间精度的基本机制的相对贡献。