Light influences diverse aspects of human physiology and behaviour including neuroendocrine function, the circadian system and sleep. A role for melanopsin-expressing intrinsically photosensitive retinal ganglion cells (ipRGCs) in driving such effects is well established. However, rod and/or cone signals routed through ipRGCs could also influence “non-visual” spectral sensitivity. In humans, this has been most extensively studied for acute, light-dependent, suppression of nocturnal melatonin production. Of the published action spectra for melatonin suppression, one demonstrates a spectral sensitivity consistent with that expected for melanopsin while our own (using briefer 30 minute light exposures) displays very high sensitivity to short wavelength light, suggesting a contribution of S-cones. To clarify that possibility, six healthy young male participants were each exposed to 30 minutes of five irradiances of 415 nm monochromatic light (1-40 µW/cm²) across different nights. These data were then combined with the original action spectrum. The aggregated data are incompatible with the involvement of any single-opsin and multi-opsin models based on the original action spectrum (including Circadian Stimulus) fail to predict the responses to 415 nm stimuli. Instead, the extended action spectrum can be most simply approximated by an ~2:1 combination of melanopsin and S-cone signals. Such a model also better describes the magnitude of melatonin suppression observed in other studies using an equivalent 30 minute mono- or polychromatic light paradigm but not those using longer (90 minute) light exposures. In sum, these data provide evidence for an initial S-cone contribution to melatonin suppression that rapidly decays under extended light exposure.

中文翻译：

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S-锥体对人类急性褪黑激素抑制反应的贡献

光会影响人类生理和行为的各个方面，包括神经内分泌功能、昼夜节律系统和睡眠。已经很好地确定了表达黑视素的内在光敏视网膜神经节细胞 (ipRGC) 在驱动这种效果中的作用。然而，通过 ipRGC 路由的杆状和/或锥状信号也可能影响“非视觉”光谱灵敏度。在人类中，这已被最广泛地研究用于急性、依赖光、抑制夜间褪黑激素的产生。在已发表的褪黑激素抑制作用光谱中，一个表现出与黑视素预期一致的光谱敏感性，而我们自己的（使用更短的 30 分钟曝光）对短波长光显示出非常高的敏感性，表明 S 锥的贡献。为了澄清这种可能性，²）跨越不同的夜晚。然后将这些数据与原始动作谱相结合。聚合数据与基于原始动作谱（包括昼夜节律刺激）的任何单视蛋白和多视蛋白模型的参与不兼容，无法预测对 415 nm 刺激的反应。相反，扩展的动作谱可以最简单地通过黑视蛋白和 S 锥信号的 ~2:1 组合来近似。这样的模型还更好地描述了在其他研究中观察到的褪黑激素抑制程度，使用等效的 30 分钟单色或多色光范式，而不是那些使用更长（90 分钟）曝光的研究。总之，这些数据为初始 S 锥体对褪黑激素抑制的贡献提供了证据，褪黑激素在长时间曝光下会迅速衰减。