PRESYNAPTIC MECHANISMS IN HAIR CELLS

描述：这项工作的长期目标是了解 钙介导的神经递质胞吐作用机制 突触传递。化学突触是许多毒素的目标， 治疗药物和通过改变大脑影响大脑的滥用药物 突触传递。化学突触传递的可塑性 基础是某些形式的学习和记忆，以及特定的 神经递质系统构成了许多精神病学、神经病学和 神经肌肉疾病。更好地理解突触传递 从而促进人类健康。拟议中的实验将调查 青蛙球囊毛细胞的突触前生理学。毛细胞 是听觉和前庭的特殊感觉感受器 系统。它们独特的解剖学和生理学结合 它们的特性使其非常适合于研究突触前机制。 这些特性包括：(A)单个毛细胞可以分离和 在体外研究；(B)其紧凑的形状允许快速控制 用全细胞和穿孔贴片记录突触的膜电位 方法：(C)突触前钙电流可以很容易地从 其他电流并记录在电压钳实验中；(D) 突触前钙离子浓度可由脑组织中 突触前KCA通道；(E)电容测量可用于 监测胞吐作用；(F)已知浓度的外源物质可 通过记录吸管快速添加到细胞质中。这些 这些特征将使我们能够详细分析钙结合的作用 突触传递中的蛋白质(Calbindin-D28k和synaptopagmin)。这个 该项目的具体目标是：(1)检验假设 Calbindin-D28k对青蛙球囊短程钙信号的影响 毛细胞。(二)优化快速变化的测算方法 膜电容。(3)检验去极化诱发的假设 膜电容的增加是由于突触小泡的融合 质膜位于活跃区。(4)检验假设 只有沿着一排排突触前突触的突触小泡 钙离子通道可以立即释放，而且最大 可持续的胞吐速率受到这一速率的限制 释药准备池可从其他囊泡池(S)供应。 利用荧光显微镜和电子显微镜进行形态研究 将用于将生理测量与突触相关联 结构。这些研究将提供新的、定量的信息 钙信号和神经递质释放应适用于 神经系统中的其他突触。

DESCRIPTION: The long-term objective of this work is to understand the mechanisms underlying calcium-mediated exocytosis of neurotransmitter during synaptic transmission. Chemical synapses are the targets of many toxins, therapeutic drugs, and drugs of abuse that affect the brain by altering synaptic transmission. Plasticity of chemical synaptic transmission underlies some forms of learning and memory, and disorders of specific neurotransmitter systems underlie a number of psychiatric, neurological, and neuromuscular diseases. A better understanding of synaptic transmission will thus advance human health. The proposed experiments will investigate the presynaptic physiology of hair cells from the frog saccules. Hair cells are the specialized sensory receptors of the auditory and vestibular systems. Their unique combination of anatomical and physiological properties make them ideally suited for studies of presynaptic mechanisms. These properties include: (a) individual hair cells can be isolated and studied in vitro; (b) their compact shape allows rapid control of the membrane potential at synapses, using the whole-cell and perforated-patch methods; (c) the presynaptic calcium current can easily be separated from other currents and recorded in voltage clamp experiments; (d) the presynaptic calcium concentration can be estimated from the activity of presynaptic Kca channels; (e) capacitance measurements can be used to monitor exocytosis; (f) known concentrations of exogenous substances can be rapidly added to the cytoplasm through the recording pipette. These features will allow a detailed analysis of the roles of calcium-binding proteins (calbindin-D28k and synaptotagmin) in synaptic transmission. The specific aims of the project are: (1) To test the hypothesis that calbindin-D28k influences short-range calcium signaling ion frog saccular hair cells. (2) To optimize the method for measuring rapid changes in membrane capacitance. (3) To test the hypothesis that depolarization-evoked increases in membrane capacitance are due to the fusion of synaptic vesicles with the plasma membrane at active zones. (4) To test the hypothesis that only the synaptic vesicles that lie alongside the rows of presynaptic calcium channels are available for immediate release, and that the maximum sustainable exocytotic rate is limited by the rate at which this release-ready pool can be supplied from other pool(s) of vesicles. Morphological studies using fluorescence microscopy and electron microscopy will be used to correlate the physiological measurements with synaptic structures. These studies will provide new, quantitative information about calcium signaling and neurotransmitter release that should be applicable to other synapses in the nervous system.