Foster Russell G, Hankins Mark, Lucas Robert J, Jenkins Aaron, Muñoz Marta, Thompson Stewart, Appleford Joanne M, Bellingham James
Department of Integrative and Molecular Neuroscience, Division of Neuroscience and Psychological Medicine, Imperial College Faculty of Medicine, Charing Cross Hospital, Fulham Palace Road, London W6 8RF, UK.
Novartis Found Symp. 2003;253:3-23; discussion 23-30, 52-5, 102-9.
Until recently, all ocular photoreception was attributed to the rods and cones of the retina. However, studies on mice lacking rod and cone photoreceptors (rd/rd cl), has shown that these mice can still use their eyes to detect light to regulate their circadian rhythms, suppress pineal melatonin, modify locomotor activity and modulate pupil size. In addition, action spectra for some of these responses have characterized a novel opsin/vitamin A-based photopigment with a lambda(max) approximately 480 nm. Electrophysiological studies have shown that a subset of retinal ganglion cells are intrinsically photosensitive, and melanopsin has been proposed as the photopigment mediating these responses to light. In contrast to mammals, an inner retinal photopigment gene has been identified in teleost fish. Vertebrate ancient (VA) opsin forms a photopigment with a lambda(max) between 460-500 nm, and is expressed in a sub-set of retinal horizontal cells, and cells in the amacrine and ganglion cell layers. Electrophysiological analysis suggests that VA opsin horizontal cells are intrinsically photosensitive and encode irradiance information. In contrast to mammals, however, the function of these novel ocular photoreceptors remains unknown. We compare non-rod, non-cone ocular photoreceptors in mammals and fish, and examine the criteria used to place candidate photopigment molecules into a functional context.
直到最近，所有的眼部光感受器都被认为是视网膜中的视杆细胞和视锥细胞。然而，对缺乏视杆和视锥光感受器的小鼠（rd/rd cl）的研究表明，这些小鼠仍然能够利用眼睛检测光线，以调节其昼夜节律、抑制松果体褪黑素、改变运动活动并调节瞳孔大小。此外，其中一些反应的作用光谱已表征出一种基于视蛋白/维生素A的新型光色素，其最大吸收波长（λmax）约为480纳米。电生理研究表明，一部分视网膜神经节细胞具有内在光敏性，并且有人提出黑视蛋白是介导这些对光反应的光色素。与哺乳动物不同，硬骨鱼中已鉴定出一种视网膜内光色素基因。脊椎动物古老（VA）视蛋白形成一种最大吸收波长在460 - 500纳米之间的光色素，并在一部分视网膜水平细胞以及无长突细胞层和神经节细胞层中的细胞中表达。电生理分析表明，VA视蛋白水平细胞具有内在光敏性并编码辐照度信息。然而，与哺乳动物不同的是，这些新型眼部光感受器的功能仍然未知。我们比较了哺乳动物和鱼类中的非视杆、非视锥眼部光感受器，并研究了用于将候选光色素分子置于功能背景下的标准。
