生物钟'看到'光的视觉基础——内在光感受性视网膜神经节细胞

摘要

Mammalian eyes mediate both image-forming and non-image-forming visual functions. Non-image-forming vision provides a measure of the ambient light for the purposes of synchronization of circadian clocks to light/dark cycles and regulation of pupil size,pineal melatonin production and other functions. Traditionally,people used to believe that the classical photoreceptors (rods and cones) regulate both image-forming and non-image-forming visual pathways. However,a small subset of retinal ganglion cells called intrinsically photosensitive RGCs ( ipRGCs) has been identified to be a third type of mammalian photoreceptor and determined to be photosensitive, recently. The discovery of ipRGCs has allowed for rapid progress in the past decade toward understanding the non-image-forming visual system,especially about how the circadian clock complete the synchronization with the light/dark cycle. The anatomical and developmental characteristics of ipRGCs, as well as its biological functions and regulation were reviewed in this paper.%哺乳动物眼除了调节图形视觉功能外,还负责调节非形觉视觉功能.非形觉功能主要是指眼可以将外部光信息传递到机体生物钟,调节昼夜节律、激素分泌、瞳孔大小变化等功能.传统理论认为,无论图形视觉功能还是非形觉功能都由经典的光感受器(视杆、视锥细胞)启动的.近年发现一类特殊的视网膜神经节细胞(RGCs)具有内在光感受性,称为内在光感受性视网膜神经节细胞( ipRGCs),被认为是第三类光感受器.此类细胞的出现为理解非形觉视觉系统,特别是生物钟如何依据外部光信号调节机体节律功能带来了长足进展.就ipRGCs的解剖学、发育特点,以及生物功能和相关调控作用进行综述.