Department of Cell & Developmental Biology, University of Colorado School of Medicine, Aurora, CO 80045, USA.
Department of Neuroscience, Brown University, Providence, RI 02912, USA.
Neuron. 2018 Jan 3;97(1):150-163.e4. doi: 10.1016/j.neuron.2017.11.030. Epub 2017 Dec 14.
Intrinsically photosensitive retinal ganglion cells (ipRGCs) combine direct photosensitivity through melanopsin with synaptically mediated drive from classical photoreceptors through bipolar-cell input. Here, we sought to provide a fuller description of the least understood ipRGC type, the M5 cell, and discovered a distinctive functional characteristic-chromatic opponency (ultraviolet excitatory, green inhibitory). Serial electron microscopic reconstructions revealed that M5 cells receive selective UV-opsin drive from Type 9 cone bipolar cells but also mixed cone signals from bipolar Types 6, 7, and 8. Recordings suggest that both excitation and inhibition are driven by the ON channel and that chromatic opponency results from M-cone-driven surround inhibition mediated by wide-field spiking GABAergic amacrine cells. We show that M5 cells send axons to the dLGN and are thus positioned to provide chromatic signals to visual cortex. These findings underscore that melanopsin's influence extends beyond unconscious reflex functions to encompass cortical vision, perhaps including the perception of color.
内在光敏视网膜神经节细胞（ipRGC）通过黑视蛋白将直接光敏性与经典光感受器通过双极细胞输入介导的突触驱动相结合。在这里，我们试图更全面地描述最不为人知的 ipRGC 类型 M5 细胞，并发现了一个独特的功能特征——色相对抗（紫外线兴奋，绿色抑制）。连续的电子显微镜重建显示，M5 细胞从 9 型视锥双极细胞接收选择性的 UV-视蛋白驱动，但也从双极细胞类型 6、7 和 8 接收混合视锥信号。记录表明，兴奋和抑制都是由 ON 通道驱动的，色相对抗是由 M-锥体驱动的宽场放电 GABA 能无长突细胞介导的环绕抑制引起的。我们表明，M5 细胞向 dLGN 发送轴突，因此能够向视皮层提供色觉信号。这些发现强调了黑视蛋白的影响不仅限于无意识的反射功能，还包括皮层视觉，可能包括颜色感知。
