Circadian Rhythms and Sleep Disorders Program, Neuroscience Institute, Morehouse School of Medicine, Atlanta, GA 30310, USA.
Exp Eye Res. 2012 Oct;103:82-9. doi: 10.1016/j.exer.2012.08.009. Epub 2012 Aug 31.
In the vertebrate retina, melatonin is synthesized by the photoreceptors with high levels of melatonin at night and lower levels during the day. Melatonin exerts its influence by interacting with a family of G-protein-coupled receptors that are negatively coupled with adenylyl cyclase. Melatonin receptors belonging to the subtypes MT(1) and MT(2) have been identified in the mammalian retina. MT(1) and MT(2) receptors are found in all layers of the neural retina and in the retinal pigmented epithelium. Melatonin in the eye is believed to be involved in the modulation of many important retinal functions; it can modulate the electroretinogram (ERG), and administration of exogenous melatonin increases light-induced photoreceptor degeneration. Melatonin may also have protective effects on retinal pigment epithelial cells, photoreceptors and ganglion cells. A series of studies have implicated melatonin in the pathogenesis of age-related macular degeneration, and melatonin administration may represent a useful approach to prevent and treat glaucoma. Melatonin is used by millions of people around the world to retard aging, improve sleep performance, mitigate jet lag symptoms, and treat depression. Administration of exogenous melatonin at night may also be beneficial for ocular health, but additional investigation is needed to establish its potential.
在脊椎动物的视网膜中，褪黑素由感光器合成，夜间褪黑素水平较高，白天水平较低。褪黑素通过与一组 G 蛋白偶联受体相互作用发挥其影响，这些受体与腺苷酸环化酶呈负偶联。在哺乳动物的视网膜中已经鉴定出属于亚型 MT(1)和 MT(2)的褪黑素受体。MT(1)和 MT(2)受体存在于神经视网膜的所有层和视网膜色素上皮中。人们认为眼睛中的褪黑素参与调节许多重要的视网膜功能；它可以调节视网膜电图 (ERG)，并且外源性褪黑素的给药会增加光诱导的感光细胞变性。褪黑素对视网膜色素上皮细胞、感光细胞和节细胞也可能具有保护作用。一系列研究表明褪黑素与年龄相关性黄斑变性的发病机制有关，褪黑素的给药可能代表一种预防和治疗青光眼的有用方法。全世界有数百万人使用褪黑素来延缓衰老、改善睡眠质量、缓解时差症状和治疗抑郁症。夜间给予外源性褪黑素也可能对眼部健康有益，但需要进一步研究以确定其潜在作用。
