Melanopsin, a G family coupled receptor, found within the ganglion cell layer in the retina, plays an important role in non-image-forming visual functions, including hormone secretion, entrainment of circadian rhythms, cognitive and affective processes. Diffuse projections of melanopsin-containing cells to many brain areas suggest that different responses may involve different neural projections, thus different melanopsin cells. Considering the complexity of the melanopsin system, its contribution to so many different biological functions is not surprising. In this review, we summarize the current knowledge about melanopsin in terms of its photophysics, photochemistry, mechanisms of activation, cell signaling, morphology, and physiology. In the last part, the role of melanopsin in image and non-image forming processes and cognitive and affective functioning of animals and humans, are discussed. Although in recent years considerable insight has been gained into the melanopsin system, it still remains an open question of how one protein expressed by several thousand cells in the retina, could be responsible for so many diverse functions and what activation mechanism(s) it uses.

中文翻译：

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黑色素：从小分子到脑功能。

黑素菌素，一种G家族偶联受体，存在于视网膜神经节细胞层中，在非图像形成的视觉功能（包括激素分泌，昼夜节律的夹带，认知和情感过程）中起着重要作用。含黑色素的细胞向许多大脑区域的扩散投影表明，不同的反应可能涉及不同的神经投影，因此黑色素的细胞也不同。考虑到黑视蛋白系统的复杂性，其对许多不同生物学功能的贡献不足为奇。在这篇综述中，我们从黑素蛋白的光物理，光化学，激活机制，细胞信号转导，形态学和生理学方面总结了有关黑素蛋白的当前知识。在最后一部分，讨论了黑色素在图像和非图像形成过程中的作用以及动物和人类的认知和情感功能。尽管近年来已经对黑素视蛋白系统获得了相当多的见识，但仍然是一个悬而未决的问题，即视网膜中数千个细胞表达的一种蛋白质如何负责这么多种功能以及其使用的激活机制。