Chabot Christopher C, Connolly Devin M, Waring Brenda B
Department of Biological Sciences, Plymouth State University, Plymouth, NH 03264, UK.
J Circadian Rhythms. 2012 Sep 9;10(1):6. doi: 10.1186/1740-3391-10-6.
An endogenous circadian clock controls locomotor activity in common spiny mice (Acomys cahirinus). However, little is known about the effects of constant light (LL) on this activity or about the existence of an additional food entrainable clock. A series of experiments were performed to investigate the effects of LL and DD on tau and activity levels.
Spiny mice were housed individually and their running wheel activity monitored. One group of mice was exposed to LD, DD and several intensities of LL. Another group was exposed to a restricted feeding (RF) paradigm in light: dark (LD) during one hour before the L to D transition. Significance of rhythmicity was assessed using Lomb-Scargle periodograms.
In LD all animals exhibited nocturnal activity rhythms that persisted in DD. When animals were exposed to RF (during L), all of these animals (n = 11) demonstrated significant food anticipatory activity as well as an increase in diurnal activity. This increase in diurnal activity persisted in 4/11 animals during subsequent ad libitum conditions. Under LL conditions, the locomotor rhythms of 2/11 animals appeared to entrain to RF. When animals were exposed to sequentially increasing LL intensities, rhythmicity persisted and, while activity decreased significantly, the free-running period was relatively unaffected. In addition, the period in LL was significantly longer than the period in DD. Exposure to LL also induced long-term changes (after-effects) on period and activity when animals were again exposed to DD.
Overall these studies demonstrate clear and robust circadian rhythms of wheel-running in A. cahirinus. In addition, LL clearly inhibited activity in this species and induced after-effects. The results also confirm the presence of a food entrainable oscillator in this species.
内源性昼夜节律时钟控制着普通刺毛鼠（埃及刺毛鼠）的运动活动。然而，关于持续光照（LL）对这种活动的影响或是否存在额外的食物诱导时钟，人们知之甚少。进行了一系列实验来研究LL和持续黑暗（DD）对昼夜节律周期（tau）和活动水平的影响。
将刺毛鼠单独饲养，并监测它们的转轮活动。一组小鼠暴露于光照-黑暗循环（LD）、持续黑暗（DD）和几种强度的持续光照（LL）环境中。另一组小鼠在光照-黑暗循环（LD）中，在光照转为黑暗前一小时接受限时进食（RF）模式。使用 Lomb-Scargle 周期图评估节律性的显著性。
在光照-黑暗循环（LD）条件下，所有动物都表现出夜间活动节律，这种节律在持续黑暗（DD）条件下依然存在。当动物在光照期间接受限时进食（RF）时，所有这些动物（n = 11）都表现出显著的食物预期活动以及日间活动增加。在随后的自由进食条件下，11只动物中有4只的日间活动增加持续存在。在持续光照（LL）条件下，11只动物中有2只的运动节律似乎被限时进食（RF）所诱导。当动物依次暴露于强度逐渐增加的持续光照（LL）时，节律性持续存在，并且虽然活动显著减少，但自由运行周期相对未受影响。此外，持续光照（LL）条件下的周期明显长于持续黑暗（DD）条件下的周期。当动物再次暴露于持续黑暗（DD）时，暴露于持续光照（LL）也会对周期和活动产生长期变化（后效应）。
总体而言，这些研究表明埃及刺毛鼠的转轮运动存在清晰且稳健的昼夜节律。此外，持续光照（LL）明显抑制了该物种的活动并诱导了后效应。结果还证实了该物种中存在食物诱导振荡器。
