Hashimoto S, Nakamura K, Honma S, Tokura H, Honma K
Department of Physiology, Hokkaido University School of Medicine, Sapporo, Japan.
Am J Physiol. 1996 May;270(5 Pt 2):R1073-7. doi: 10.1152/ajpregu.1996.270.5.R1073.
Effects of a single light exposure on the circadian rhythm in plasma melatonin were, examined in young males to obtain the threshold of light intensity for suppressing the nocturnal melatonin level on the one hand and to understand the relationship between the light-induced phase shift of melatonin rhythm and the melatonin suppression on the other hand. Eight subjects spent 3 days in an experimental living facility where light intensity was set below 200 lx and were exposed to light for 3 h in the early morning on the 2nd day. The same procedure was repeated five times in each subject with an interval of at least 3 wk, and one of five light intensities was tested in each trial. As a result, nocturnal melatonin level was not suppressed by light of 200 lx but significantly suppressed by light of intensity > or + 500 lx. On the other hand, the circadian melatonin rhythm was not shifted by any light intensity up to 10,000 lx. It is concluded that the threshold of light intensity for suppressing the melatonin level is located between 200 and 500 lx in young Japanese males, and the threshold for phase shifting the circadian melatonin rhythm was much greater than that for suppressing the nocturnal melatonin level in humans under entrained conditions.
在年轻男性中研究了单次光照对血浆褪黑素昼夜节律的影响，一方面是为了获得抑制夜间褪黑素水平的光照强度阈值，另一方面是为了了解光照引起的褪黑素节律相位偏移与褪黑素抑制之间的关系。八名受试者在一个光照强度设定低于200勒克斯的实验生活设施中度过3天，并在第2天清晨接受3小时光照。每个受试者以至少3周的间隔重复该过程5次，每次试验测试五种光照强度之一。结果，200勒克斯的光照未抑制夜间褪黑素水平，但强度>或+500勒克斯的光照显著抑制了夜间褪黑素水平。另一方面，高达10000勒克斯的任何光照强度都未使昼夜褪黑素节律发生偏移。得出结论，在年轻日本男性中，抑制褪黑素水平的光照强度阈值位于200至500勒克斯之间，并且在昼夜节律固定条件下，使昼夜褪黑素节律发生相位偏移的阈值远高于抑制夜间褪黑素水平的阈值。
