Local Signals in Mouse Horizontal Cell Dendrites
Local Signals in Mouse Horizontal Cell Dendrites
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DOI：
10.1016/j.cub.2017.10.050
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发表时间：
2017-12-04
期刊：
影响因子：
9.2
通讯作者：
Schubert, Timm
中科院分区：
文献类型：
--
作者：
Chapot, Camille A.;Behrens, Christian;Schubert, Timm
小鼠视网膜包含单一类型的水平细胞，即 GABA 能中间神经元，它从可及范围内的所有视锥细胞中采样，并通过并行反馈机制调节其谷氨酸输出。由于水平单元形成电耦合网络，因此它们涉及全局信号处理，例如大规模对比度增强。最近，有人提出水平细胞也可以在单个视锥光感受器水平上局部发挥作用。为了从生理学角度测试这种可能性，我们使用双光子显微镜记录了锥体轴突末端和水平细胞树突中光刺激诱发的 Ca2+ 信号以及外丛状层中谷氨酸的释放。通过用绿光和紫外光选择性刺激两个小鼠视锥细胞视蛋白，我们评估了来自单个视锥细胞的信号是否在水平细胞树突尖端内保持隔离，或者它们是否遍布树突乔木。与小鼠的视蛋白表达梯度一致，我们发现背侧水平细胞树突记录的Ca2+信号以M-视蛋白为主，腹侧水平细胞的Ca2+信号以S-视蛋白激活为主。在相邻水平细胞树突尖中测量的信号在其色彩偏好上显着变化，这与全局处理相矛盾。相反，我们的实验数据和生物物理现实建模的结果支持水平细胞可以局部处理锥体输入的想法，扩展了水平细胞功能的经典观点。从药理学上去除电路中的水平细胞降低了视锥细胞信号对低频的敏感性，这表明局部水平细胞反馈塑造了视锥细胞输出的时间特性。
The mouse retina contains a single type of horizontal cell, a GABAergic interneuron that samples from all cone photoreceptors within reach and modulates their glutamatergic output via parallel feedback mechanisms. Because horizontal cells form an electrically coupled network, they have been implicated in global signal processing, such as large-scale contrast enhancement. Recently, it has been proposed that horizontal cells can also act locally at the level of individual cone photoreceptors. To test this possibility physiologically, we used two-photon microscopy torecord light stimulus-evoked Ca2+ signals in cone axon terminals and horizontal cell dendrites as well as glutamate release in the outer plexiform layer. By selectively stimulating the two mouse cone opsins with green and UV light, we assessed whether signals from individual cones remain isolated within horizontal cell dendritic tips or whether they spread across the dendritic arbor. Consistent with the mouse's opsin expression gradient, we found that the Ca2+ signals recorded from dendrites of dorsal horizontal cells were dominated by M-opsin and those of ventral horizontal cells by S-opsin activation. The signals measured in neighboring horizontal cell dendritic tips varied markedly in their chromatic preference, arguing against global processing. Rather, our experimental data and results from biophysically realistic modeling support the idea that horizontal cells can process cone input locally, extending the classical view of horizontal cell function. Pharmacologically removing horizontal cells from the circuitry reduced the sensitivity of the cone signal to low frequencies, suggesting that local horizontal cell feedback shapes the temporal properties of cone output.