Dopamine Regulation of GABA(A) Receptors Contributes to Light/Dark Modulation of the ON-Cone Bipolar Cell Receptive Field Surround in the Retina.
Dopamine Regulation of GABA(A) Receptors Contributes to Light/Dark Modulation of the ON-Cone Bipolar Cell Receptive Field Surround in the Retina.
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DOI：
10.1016/j.cub.2017.07.063
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发表时间：
2017-09-11
期刊：
影响因子：
--
通讯作者：
Mangel SC
中科院分区：
文献类型：
--
作者：
Chaffiol A;Ishii M;Cao Y;Mangel SC
视锥双极细胞是中间神经元，接收来自视锥感光细胞的突触输入并提供视网膜第一突触层的输出。这些细胞表现出中心-环绕感受野，这是相邻感觉细胞之间横向抑制的原型，其中感受野中心的刺激使细胞兴奋，而周围区域的刺激横向抑制细胞。这种基本的感觉编码机制有利于空间辨别和刺激边缘的检测。然而，尽管众所周知，当环境或背景照明最强烈时（例如在中午），感受野环绕最强，并且在持续黑暗后环绕最小，但产生和调节环绕的突触机制尚未得到解决。在细胞表现出周围光反应的实验条件下，使用双极细胞的电记录以及光和电子显微镜免疫细胞化学，我们在兔视网膜中显示，位于ON中心视锥双极细胞树突上的多巴胺D1受体的亮光诱导激活增加了细胞树突上GABAA受体的表达和活性，并且周围光反应依赖于内源性GABAA受体激活。我们还表明，在维持光照和 D1 受体激活后维持黑暗和 D1 受体阻断会导致 GABAA 受体表达和活性最小，并且周围环境大大减弱。环境光水平对 ON-cBC 树突 D1/GABAA 受体信号通路的调节有助于检测明亮白天的空间细节和无月夜晚的大昏暗物体。
Cone-bipolar cells are interneurons that receive synaptic input from cone photoreceptor cells and provide the output of the first synaptic layer of the retina. These cells exhibit center-surround receptive fields, a prototype of lateral inhibition between neighboring sensory cells in which stimulation of the receptive field center excites the cell whereas stimulation of the surrounding region laterally inhibits the cell. This fundamental sensory coding mechanism facilitates spatial discrimination and detection of stimulus edges. However, although it is well established that the receptive field surround is strongest when ambient or background illumination is most intense, e.g., at midday, and that the surround is minimal following maintained darkness, the synaptic mechanisms that produce and modulate the surround have not been resolved. Using electrical recording of bipolar cells under experimental conditions in which the cells exhibited surround light responses, and light and electron microscopic immunocytochemistry, we show in the rabbit retina that bright light-induced activation of dopamine D1 receptors located on ON-center cone-bipolar cell dendrites increases the expression and activity of GABAA receptors on the dendrites of the cells and that surround light responses depend on endogenous GABAA receptor activation. We also show that maintained darkness and D1 receptor blockade following maintained illumination and D1 receptor activation result in minimal GABAA receptor expression and activity and greatly diminished surrounds. Modulation of the D1/GABAA receptor signaling pathway of ON-cBC dendrites by the ambient light level facilitates detection of spatial details on bright days and large dim objects on moonless nights.
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