Cleary-Gaffney Michael, Coogan Andrew N
Department of Psychology, Maynooth University, National University of Ireland, Maynooth, Ireland.
Department of Psychology, Maynooth University, National University of Ireland, Maynooth, Ireland.
Physiol Behav. 2018 May 15;189:78-85. doi: 10.1016/j.physbeh.2018.03.010. Epub 2018 Mar 11.
Circadian rhythms are recurring patterns in a range of behavioural, physiological and molecular parameters that display periods of near 24 h, and are underpinned by an endogenous biological timekeeping system. Circadian clocks are increasingly recognised as being key for health. Environmental light is the key stimulus that synchronises the internal circadian system with the external time cues. There are emergent health concerns regarding increasing worldwide prevalence of electric lighting, especially man-made light-at-night, and light's impact on the circadian system may be central to these effects. A number of previous studies have demonstrated increased depression-like behaviour in various rodent experimental models exposed to dim light-at-night. In this study we set out to study the impact of dim light-at-night on circadian and affective behaviours in C57Bl/6 mice. We set out specifically to examine the impact of sex on light at night's effects, as well as the impact of housing conditions. We report minimal impact of light-at-night on circadian and affective behaviours, as measured by the tail suspension test, the forced swim test, the sucrose preference test and the elevated plus maze. Light-at-night was also not associated with an increase in body weight, but was associated with a decrease in the cell proliferation marker Ki-67 in the dentate gyrus. In summary, we conclude that experimental contextual factors, such as model species or strain, may be considerable importance in the investigation of the impact of light at night on mood-related parameters.
昼夜节律是一系列行为、生理和分子参数中反复出现的模式，其周期接近24小时，并由一个内源性生物计时系统支撑。昼夜节律时钟越来越被认为是健康的关键。环境光是使内部昼夜节律系统与外部时间线索同步的关键刺激因素。全球范围内，电气照明尤其是人造夜间光的普及引发了新的健康担忧，而光对昼夜节律系统的影响可能是这些影响的核心。此前的一些研究表明，在各种暴露于夜间昏暗灯光的啮齿动物实验模型中，抑郁样行为有所增加。在本研究中，我们着手研究夜间昏暗灯光对C57Bl/6小鼠昼夜节律和情感行为的影响。我们特别旨在研究性别对夜间光照影响的作用，以及饲养条件的影响。通过悬尾试验、强迫游泳试验、蔗糖偏好试验和高架十字迷宫试验测量，我们发现夜间光照对昼夜节律和情感行为的影响极小。夜间光照也与体重增加无关，但与齿状回中细胞增殖标志物Ki-67的减少有关。总之，我们得出结论，在研究夜间光照对情绪相关参数的影响时，实验背景因素，如模型物种或品系，可能具有相当重要的意义。
