Diverse types of ganglion cell photoreceptors in the mammalian retina.
Diverse types of ganglion cell photoreceptors in the mammalian retina.
复制标题
哺乳动物视网膜中不同类型的神经节细胞感光器。
DOI：
10.1016/j.preteyeres.2012.03.003
复制
发表时间：
2012
影响因子：
17.8
通讯作者：
Kofuji,Paulo
中科院分区：
文献类型：
--
作者：
Sand,Andrea;Schmidt,TiffanyM;Kofuji,Paulo
光感受器通过捕捉光线并将其转化为电信号来执行视觉的第一步。杆状和锥状感光器通过光激活视蛋白类感光材料，有效地将光子捕获转化为电信号。直到最近，中心的教义是，对于哺乳动物来说，所有的光传导都发生在杆状和锥状细胞中。然而，最近在视网膜内部发现的一种新的光感受器类型从根本上挑战了这一观点。这些视网膜神经节细胞本质上是光敏性的，并介导一系列广泛的生理反应，如生物钟的光携带、睡眠的光调节、瞳孔光反射和光抑制褪黑激素的分泌。从本质上讲，对光敏的视网膜神经节细胞表达黑素，这是一种新的基于视蛋白的信号机制，类似于无脊椎动物横纹体光感受器中发现的机制。表达黑素的视网膜神经节细胞将环境辐射信息直接传递到大脑中心，如下丘脑、视前核和外侧膝状核。初步研究表明，这些表达黑素的光感受器在解剖和功能上是同质的群体。然而，在过去十年左右的时间里，很明显，根据它们的形态、分子标记、功能特性和传出投射，这些光感受器可以区分为单独的亚型。这些结果提供了一种新的分类方案，包括哺乳动物视网膜中的五种黑色素感受器亚型，每种亚型可能具有不同的输入和输出特性。在这篇综述中，我们总结了黑素光感受器亚型结构和功能多样性的证据以及目前该领域的争议。
Photoreceptors carry out the first step in vision by capturing light and transducing it into electrical signals. Rod and cone photoreceptors efficiently translate photon capture into electrical signals by light activation of opsin-type photopigments. Until recently, the central dogma was that, for mammals, all phototransduction occurred in rods and cones. However, the recent discovery of a novel photoreceptor type in the inner retina has fundamentally challenged this view. These retinal ganglion cells are intrinsically photosensitive and mediate a broad range of physiological responses such as photoentrainment of the circadian clock, light regulation of sleep, pupillary light reflex, and light suppression of melatonin secretion. Intrinsically photosensitive retinal ganglion cells express melanopsin, a novel opsin-based signaling mechanism reminiscent of that found in invertebrate rhabdomeric photoreceptors. Melanopsin-expressing retinal ganglion cells convey environmental irradiance information directly to brain centers such as the hypothalamus, preoptic nucleus, and lateral geniculate nucleus. Initial studies suggested that these melanopsin-expressing photoreceptors were an anatomically and functionally homogeneous population. However, over the past decade or so, it has become apparent that these photoreceptors are distinguishable as individual subtypes on the basis of their morphology, molecular markers, functional properties, and efferent projections. These results have provided a novel classification scheme with five melanopsin photoreceptor subtypes in the mammalian retina, each presumably with differential input and output properties. In this review, we summarize the evidence for the structural and functional diversity of melanopsin photoreceptor subtypes and current controversies in the field.