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的机制 突触传递 化学突触是许多毒素的目标， 治疗药物和滥用药物，通过改变大脑， 突触传递 化学突触传递的可塑性 是某些形式的学习和记忆的基础， 神经递质系统是许多精神病学、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。 拟议的实验将调查 青蛙囊毛细胞的突触前生理学。 毛细胞 是听觉和前庭的专门感觉感受器 系统. 他们独特的解剖学和生理学的结合 这些特性使它们非常适合于突触前机制的研究。 这些特性包括：（a）可以分离单个毛细胞， （B）它们的紧凑形状允许快速控制细胞的生长。 突触处的膜电位，使用全细胞和穿孔贴片 方法;（c）突触前钙电流可以很容易地分离， 其他电流和记录在电压钳实验;（d） 突触前钙离子浓度可以从 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 通过记录移液管快速加入到细胞质中。 这些 功能将允许详细分析钙结合的作用， 突触传递中的蛋白质（钙结合蛋白-D28 k和突触结合蛋白）。 的 该项目的具体目标是：（1）检验假设， calbindin-D28 k对蛙囊膜细胞钙信号转导的影响 毛细胞 (2)为了优化测量快速变化的方法， 膜电容 (3)为了验证去极化诱发的 膜电容的增加是由于突触囊泡的融合 质膜位于活性区。 (4)为了验证这个假设， 只有位于突触前神经元排列旁边的突触囊泡 钙通道可立即释放，最大的 可持续的胞吐速率受到这一速率的限制， 可释放池可以由其他囊泡池提供。 使用荧光显微镜和电子显微镜进行形态学研究 将用于将生理测量与突触 结构. 这些研究将提供新的定量信息， 钙信号传导和神经递质释放，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.