RETINAL SYNAPTIC TRASMISSION--CA++ AND NEUROTRASMITTERS

视网膜双极细胞终末递质释放的调节 对从视网膜外到视网膜的视觉信号处理很重要 脊椎动物的内侧视网膜。尽管Ca~(2+)在细胞内的核心作用 突触前终末的递质释放是确定的， 细胞内钙浓度([Ca~(2+)]i)的动态调节 突触前终末及其对递质释放的影响 很大程度上还不清楚。这项建议的目标是研究 钙离子通道和GABA受体在钙离子动力学调节中的作用 在哺乳动物双极细胞的轴突末端。实验将是 在单独的大鼠和小鼠双极细胞中进行。对钙离子敏感 将使用荧光染料。荧光信号将被监测 通过基于高分辨率共焦显微镜的成像系统。细胞的 膜电位将由膜片钳方法控制， 或者，高K+也会引起细胞去极化。这个 具体目标是：i)确定 双极细胞内不同类型的钙通道；2)表征 钙激活过程中双极细胞终末的钙瞬变 不同的钙离子通道和在细胞去极化过程中 双极光响应波形；3)表征不同的 GABAA和GABAC受体在钙调节中的作用 双极电池端子上的瞬变；4)确定空间 γ-氨基丁酸受体的分布及其可能的共定位 特定类型的γ-氨基丁酸受体与特定类型的钙(S) 频道。我们从这些研究中获得的知识不仅将导致 为了更好地理解基本的视觉信号处理 哺乳动物的视网膜也将有助于我们对其作用的了解 钙离子和抑制性神经递质在突触传递中的作用 中枢神经系统。

The regulation of transmitter release at retinal bipolar cell terminals is important for visual signal processing from the outer retina to the inner retina in vertebrates. Although the central role of Ca2+ in transmitter release at presynaptic terminals is well established, the dynamic regulation of intracellular Ca2+ concentrations ([Ca2+]i) at presynaptic terminals and its effect on transmitter release is still largely unclear. The objective of this proposal is to study the roles of Ca2+ channels and GABA receptors in the regulation of Ca2+ dynamics at the axon terminal of mammalian bipolar cells. Experiments will be performed in solitary rat and mouse bipolar cells. Ca2+-sensitive fluorescence dyes will be used. Fluorescence signals will be monitored by a high resolution confocal microscope based imaging system. Cell's membrane potential will be controlled by patch-clamp methods and, alternatively, cell depolarization will be evoked by high K+. The specific aims are: I) to determine the spatial distribution of different types of Ca2+ channels in bipolar cells; 2) to characterize the Ca2+ transients at bipolar cell terminals during the activation of different Ca2+ channels and during cell depolarization that mimics bipolar light response waveforms; 3) to characterize the distinct effects of GABA A and GABA C receptors on the regulation of the Ca2+ transients at bipolar cell terminals; 4) to determine the spatial distribution of GABA receptors and the possible co-localization of specific types of GABA receptors with specific type(s) of Ca2+ channels. The knowledge we gain from these studies will not only lead to a better understanding of basic visual signal processing in mammalian retina but will also contribute to our knowledge of the roles of Ca2+ and inhibitory neurotransmitters in synaptic transmission in the CNS.