Mechanisms of Synaptic Processing in the Retina

视网膜突触处理机制

• 批准号: 6671434
• 负责人: William Rowland Taylor
• 金额: $ 33.98万
• 依托单位: OREGON HEALTH & SCIENCE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-07-01 至 2007-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6671434
• 关键词: biological signal transduction; dendrites; evoked potentials; interneurons; laboratory rabbit; neural conduction; neural information processing; neural inhibition; neural initiation; neurophysiology; neurotransmitter metabolism; retina; synapses; voltage /patch clamp

DESCRIPTION (provided by applicant): How the brain resolves the direction of external motion from the pattern of light passing across the retina has puzzled neuroscientists for decades. Neurons that encode the direction of image motion are first encountered in the retina. The neurons are the on-off direction-selective ganglion cells (DSGCs). We will examine in isolation the convergent synaptic mechanisms that generate direction selectivity, and determine how they arise, and how they are integrated by the DSGC. Comparison of the results obtained from this system, with those in other brain regions and other species, will provide new insights into how neural circuits remove redundant information, and extract specific features or patterns from the barrage of incoming synaptic activity. Each DSGC determines the direction of image motion in a small region of visual space. These cells are most selective for movement along a preferred-null axis. Their responses are largest for movement in the preferred direction and smallest for movement in the opposite, null direction. Our preliminary recordings indicate that a mix of synaptic mechanisms generate direction-selective responses. The excitatory and inhibitory inputs to DSGCs are directional, indicating that there is presynaptic modulation of neurotransmitter release from interneurons. Directional responses are also generated within the dendrites of the DSGC, and arise from the postsynaptic integration of excitatory and inhibitory synaptic inputs. A striking finding is that the two distinct dendritic arbors of DSGCs use different synaptic mechanisms to generate a directional signal. The proposed research will use whole-cell patch-clamp recording techniques to analyse the visually evoked synaptic responses in DSGCs in an in vitro rabbit retina preparation. The first aim will determine the origin and nature of the lateral inhibition that is critical for generating direction-selective responses. The second aim will be to determine the synaptic mechanisms that generate directional excitatory inputs to the DSGCs. The third aim will further test the hypothesis that the two dendritic strata generate directional signals using different synaptic mechanisms.

描述（由申请人提供）：大脑如何从穿过视网膜的光的模式中分辨出外部运动的方向，这困扰了神经科学家几十年。编码图像运动方向的神经元首先出现在视网膜中。神经元是开关方向选择性神经节细胞（DSGCs）。我们将单独研究产生方向选择性的会聚突触机制，并确定它们是如何产生的，以及它们是如何被DSGC整合的。将该系统的结果与其他大脑区域和其他物种的结果进行比较，将为神经回路如何去除冗余信息，并从传入的突触活动中提取特定特征或模式提供新的见解。 每个DSGC确定视觉空间的小区域中的图像运动的方向。这些单元格对于沿首选空轴沿着移动是最有选择性的。他们的反应是最大的运动在首选方向和最小的运动在相反的方向，零。我们的初步记录表明，突触机制的混合产生方向选择性反应。对DSGCs的兴奋性和抑制性输入是定向的，表明中间神经元的神经递质释放存在突触前调制。定向反应也在DSGC的树突内产生，并且由兴奋性和抑制性突触输入的突触后整合引起。一个引人注目的发现是，DSGCs的两个不同的树突状乔木使用不同的突触机制来产生方向信号。 本研究拟采用全细胞膜片钳技术分析离体兔视网膜DSGCs的视觉诱发突触反应。第一个目标是确定侧抑制的起源和性质，侧抑制对产生方向选择性反应至关重要。第二个目标将是确定产生定向兴奋性输入的DSGCs的突触机制。第三个目标将进一步测试这两个树突层使用不同的突触机制产生定向信号的假设。