Kozaki Tomoaki, Hidaka Yuki, Takakura Jun-Ya, Kusano Yosuke
Department of Environment Science, Fukuoka Women's University, 1-1-1 Kasumigaoka, Higashi-ku, Fukuoka, Japan.
Graduate School of Design, Kyushu University, 4-9-1 Shiobaru, Minami-ku, Fukuoka, Japan.
Neurosci Lett. 2020 Mar 23;722:134857. doi: 10.1016/j.neulet.2020.134857. Epub 2020 Feb 22.
Bright light at night has been known to suppress melatonin secretion. Photoreceptors, known as intrinsically photosensitive retinal ganglion cells (ipRGCs), project dark/bright information into the superchiasmatic nucleus, which regulates the circadian system. Electroretinograms of ipRGCs show fluctuation that is synchronized with light ON-OFF stimulation. This finding suggests that the flickering condition of light may have an impact on our circadian system. In this study, we evaluate light-induced melatonin suppression under flickering and non-flickering light conditions. Fifteen male subjects between the ages of 20 and 23 years (mean ± SD, 21.9 ± 1.9) were exposed to three light conditions (dim, 100-Hz flickering and non-flickering light) from 1:00 a.m. to 2:30 a.m. Saliva samples were taken just before 1:00 and at 1:15, 1:30, 2:00, and 2:30 a.m. Repeated-measure t-test with Bonferroni correction showed a significant decrease in melatonin levels under both 100-Hz and non-flickering light conditions compared to dim light conditions after 2:00 a.m. Moreover, at 2:30 a.m., the rate of change in melatonin level under 100 Hz of flickering light was significantly lower than that under non-flickering light. Our present findings suggest that 100-Hz flickering light may suppress melatonin secretion more than non-flickering light.
已知夜间强光会抑制褪黑素的分泌。一种被称为内在光敏视网膜神经节细胞（ipRGCs）的光感受器会将明暗信息投射到视交叉上核，而视交叉上核会调节昼夜节律系统。ipRGCs的视网膜电图显示出与光开关刺激同步的波动。这一发现表明，光的闪烁状态可能会对我们的昼夜节律系统产生影响。在本研究中，我们评估了闪烁光和非闪烁光条件下光诱导的褪黑素抑制情况。15名年龄在20至23岁之间的男性受试者（平均±标准差，21.9±1.9）在凌晨1点至2点30分期间暴露于三种光照条件下（暗光、100赫兹闪烁光和非闪烁光）。在凌晨1点前以及凌晨1点15分、1点30分、2点和2点30分采集唾液样本。采用Bonferroni校正的重复测量t检验显示，与暗光条件相比，在凌晨2点之后，100赫兹闪烁光和非闪烁光条件下的褪黑素水平均显著下降。此外，在凌晨2点30分，100赫兹闪烁光下褪黑素水平的变化率显著低于非闪烁光下的变化率。我们目前的研究结果表明，100赫兹闪烁光可能比非闪烁光更能抑制褪黑素的分泌。
