Analysis of MEPSC shape at photoreceptor ribbon synapses

光感受器带状突触 MEPSC 形状分析

• 批准号: 6559586
• 负责人: BRUCE R MAPLE
• 金额: $ 15.05万
• 依托单位: BAYLOR COLLEGE OF MEDICINE
• 依托单位国家: 美国
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-05-01 至 2006-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6559586
• 关键词: Urodela; calcium flux; computer program /software; cone cell; electrodes; exocytosis; fluorescence microscopy; glutamate receptor; mathematical model; molecular shape; neural transmission; neurotransmitter transport; osmotic pressure; receptor binding; retina; retinal ganglion; rod cell; synapses; visual photoreceptor; voltage /patch clamp

DESCRIPTION (provided by applicant): The ultimate goal of this work is to develop a comprehensive understanding of how glutamate is released and eliminated at ribbon synapses of the retina. The mechanisms underlying vesicular release of glutamate at these synapses remain largely unknown. Miniature excitatory postsynaptic currents (MEPSCs) have traditionally been thought to arise from the exocytosis of single presynaptic vesicles, but preliminary results of this investigator suggest that at photoreceptor ribbon synapses they actually arise from the exocytosis of a cluster of vesicles. Furthermore, the contents of vesicles within such a cluster appear to be released in a series of sequential bursts, and multidimensional analysis of MEPSC shape suggests that the effects of individual vesicles within a cluster sum in a highly nonlinear and cooperative manner. The initial focus of the proposed research will be to gather additional evidence in support of these hypotheses. This work will use MEPSCs observed in off-center bipolar cells as an assay for transmitter release from rods and cones. The shapes of MEPSCs will be analyzed in a novel manner in order to determine an underlying subunit structure. The effects of agents such as calcium and osmotic pressure, which may affect the timing of subunit release, will be examined. The processes of glutamate uptake and glutamate receptor desensitization will also be studied by examining how agents that block these processes affect MEPSC time course. These data, plus data from an analysis of light-suppressed current fluctuations in bipolar cells will be used to generate a detailed model of synaptic transmission at photoreceptor ribbon synapses. Although the proposed work is primarily basic research, focused towards solving a fundamental problem in neurobiology, it could also have important implications for clinical ophthalmology Glutamate excitotoxicity is thought to contribute to degenerative conditions such as glaucoma. A better understanding of the unknown steps between presynaptic calcium influx and neurotransmitter exocytosis could lead to new approaches for limiting the rate of glutamate release at ribbon synapses, such as the synapse between bipolar cells and ganglion cells. A better understanding of the dynamics of glutamate diffusion, uptake, and binding to postsynaptic receptors within the synaptic cleft might also suggest better strategies to prevent glutamate-induced retinal degeneration.

描述（由申请人提供）：这项工作的最终目标是对视网膜的色带突触中如何释放和消除谷氨酸的全面了解。谷氨酸在这些突触上谷氨酸的囊泡释放的机制仍然很大未知。传统上认为，微型兴奋性突触后电流（MEPSC）是由单个突触前囊泡的胞吐作用引起的，但是该研究者的初步结果表明，在光感受器的丝带突触上，它们实际上是由囊泡簇的胞吞作用而产生的。此外，这种簇中的囊泡的内容似乎以一系列顺序爆发释放，并且对MEPSC形状的多维分析表明，单个囊泡在聚类中以高度非线性和合作方式的影响。拟议研究的最初重点是收集更多证据以支持这些假设。 这项工作将使用在中心双极细胞中观察到的MEPSC作为从杆和锥体释放发射器的测定法。将以新颖的方式分析MEPSC的形状，以确定潜在的亚基结构。将检查可能影响亚基释放时间的钙和渗透压等药物的影响。还将研究谷氨酸摄取和谷氨酸受体脱敏的过程，还可以通过检查阻断这些过程的试剂影响MEPSC时间过程。这些数据以及来自双极细胞中光抑制电流波动的分析的数据将用于在光感受器色带突触上生成详细的突触传播模型。 尽管拟议的工作主要是基础研究，专注于解决神经生物学中的基本问题，但它对临床眼科谷氨酸兴奋性兴奋性也可能具有重要意义，被认为有助于诸如青光眼等退化性疾病。更好地理解突触前钙的流入和神经递质胞吐作用之间的未知步骤可能会导致新的方法来限制色带突触处的谷氨酸释放速率，例如双极细胞和神经节细胞之间的突触。更好地理解谷氨酸扩散，摄取和与突触裂缝内突触后受体的结合的动力学可能还提出了预防谷氨酸引起的视网膜变性的更好策略。