BIOPHYSICAL MECHANISMS OF SINGLE PHOTON DETECTION

单光子检测的生物物理机制

• 批准号: 6843135
• 负责人: FREDERICK M RIEKE
• 金额: $ 28.92万
• 依托单位: UNIVERSITY OF WASHINGTON
• 依托单位国家: 美国
• 财政年份: 1997
• 资助国家: 美国
• 起止时间: 1997-08-01 至 2006-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6843135
• 关键词: Urodela; behavioral /social science research tag; calcium flux; calcium indicator; chemical kinetics; electrodes; electrophysiology; guinea pigs; membrane potentials; neural transmission; retinal adaptation; retinal bipolar neuron; rhodopsin; rod cell; single cell analysis; synapses; tissue /cell culture; visual perception; visual photosensitivity; visual phototransduction

DESCRIPTION (provided by applicant): The ability of the dark-adapted visual system to count absorbed photons has been known for many years; however, the biophysical mechanisms which make photon detection and counting possible are not understood. Much of rod vision occurs at light levels where photon absorptions occur rarely; thus, failure of either transduction of single photons or transmission of the resulting signals to bipolar cells severely impairs rod vision. Visual sensitivity places strict constraints on how absorbed photons are transduced into electrical signals and how these electrical signals are transmitted across the rod-bipolar synapse. Current understanding of signal transduction and synaptic transmission cannot account for this level of performance. Experiments proposed here will determine how accurately information about the number and timing of photon absorptions is represented in the rod signals, what source of noise limits this accuracy and what mechanisms permit reliable transmission of these responses to bipolar cells. Studies of phototransduction will investigate the functional significance of the rod's ability to produce a nearly identical response to each absorbed photon. In particular, we will test the idea that this reproducibility is critical for the temporal sensitivity of rod vision - that is the ability to represent the time of photon absorption accurately. These studies will also characterize the other noise sources in the rod signals and determine their contribution to limiting the detection and temporal sensitivity of the rod's signals. These are requisite measurements to further understanding of the relationship between photoreceptor signal and noise and visual sensitivity. Studies of synaptic transmission will determine how single photon responses are reliably transmitted to bipolar cells in the retina. Two issues will receive particular attention: (1) separation of single photon response from other noise sources in the rods by a thresholding nonlinearity in signal transfer; and (2) changes in the kinetics of the dim flash response in signal transfer from rods to bipolars. Signal transfer will be studied directly by controlling the rod voltage while recording the resulting bipolar response. These experiments will further the general understanding of how synapses in non-spiking cells work and the relation between synaptic mechanisms and visual sensitivity.

描述（由申请人提供）：暗适应视觉的能力 计数吸收的光子的系统已经已知多年;然而， 使光子探测和计数成为可能的生物物理机制是 不理解。大部分视杆细胞的视觉发生在光水平上， 流产很少发生;因此，单个细胞的转导失败， 光子或产生的信号传输到双极细胞严重 损害视杆细胞的视力。视觉敏感性严格限制了 吸收的光子被转换成电信号， 电信号通过杆-双极突触传输。电流 对信号转导和突触传递的理解不能解释 对于这种水平的表现。这里提出的实验将确定如何 关于光子发射的数量和时间的准确信息是 表示在杆信号中，什么噪声源限制了这种精度， 什么机制允许这些反应可靠地传递给双相情感障碍 细胞 光转导的研究将探讨的功能意义， 视杆细胞对每一种吸收的 光子特别是，我们将测试这种可重复性是 视杆视觉的时间敏感性的关键-这是能力， 准确地表示光子吸收的时间。这些研究还将 表征棒信号中的其他噪声源，并确定它们的 对限制杆的检测和时间灵敏度的贡献 信号.这些都是进一步了解 光感受器信号和噪声与视觉灵敏度的关系。 对突触传递的研究将确定单光子反应是如何 可靠地传递到视网膜中的双极细胞。两个问题将得到 特别注意：（1）从其他噪声中分离单光子响应 通过信号传递中的阈值非线性来检测杆中的源;以及（2） 在从棒传递信号时暗闪光响应的动力学变化 到两极。通过控制棒直接研究信号传递 电压，同时记录产生的双极响应。这些实验将 进一步了解非尖峰细胞中的突触如何工作， 突触机制与视觉敏感性的关系。