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Abstract：
In the vertebrate retina, several dozens of parallel channels relay information about the visual world to the brain. These channels are represented by the different types of retinal ganglion cells (RGCs), whose responses are rendered selective for distinct sets of visual features by various mechanisms. These mechanisms can be roughly grouped into synaptic interactions and cell-intrinsic mechanisms, with the latter including dendritic morphology as well as ion channel complement and distribution. Here, we investigate how strongly ion channel complement can shape RGC output by comparing two mouse RGC types, the well-described ON alpha cell and a little-studied ON cell that is EGFP-labelled in the Igfbp5 mouse line and displays an unusual selectivity for stimuli with high contrast. Using patch-clamp recordings and computational modelling, we show that a higher activation threshold and a pronounced slow inactivation of the voltage-gated Na+ channels contribute to the distinct contrast tuning and transient responses in ON Igfbp5 RGCs, respectively. In contrast, such a mechanism could not be observed in ON alpha cells. This study provides an example for the powerful role that the last stage of retinal processing can play in shaping RGC responses.
摘要：
在脊椎动物的视网膜上，几十个平行通道将视觉世界的信息传递给大脑。这些通道由不同类型的视网膜神经节细胞（RGCs）代表，其响应通过各种机制对不同的视觉特征集进行选择性渲染。这些机制可以大致分为突触相互作用和细胞内在机制，后者包括树突状形态以及离子通道的互补和分布。这里,我们通过比较两种小鼠RGC类型来研究离子通道补体对RGC输出的影响，良好描述的ONα细胞和很少研究的ON细胞在Igfbp5小鼠品系中被EGFP标记，并且对高对比度的刺激显示出异常的选择性。使用膜片钳记录和计算建模，我们表明，较高的激活阈值和电压门控Na+通道的明显缓慢失活有助于ONIgfbp5RGC的明显对比调谐和瞬态响应，分别。相比之下,在ONα细胞中无法观察到这种机制。这项研究为视网膜处理的最后阶段在塑造RGC反应中可以发挥的强大作用提供了一个例子。
