Dattolo T, Coomans C P, van Diepen H C, Patton D F, Power S, Antle M C, Meijer J H, Mistlberger R E
Department of Psychology, Simon Fraser University, BC, Canada.
Leiden University Medical Center, Leiden, Netherlands.
Neuroscience. 2016 Feb 19;315:91-103. doi: 10.1016/j.neuroscience.2015.12.014. Epub 2015 Dec 14.
Circadian rhythms in mammals are regulated by a system of circadian oscillators that includes a light-entrainable pacemaker in the suprachiasmatic nucleus (SCN) and food-entrainable oscillators (FEOs) elsewhere in the brain and body. In nocturnal rodents, the SCN promotes sleep in the day and wake at night, while FEOs promote an active state in anticipation of a predictable daily meal. For nocturnal animals to anticipate a daytime meal, wake-promoting signals from FEOs must compete with sleep-promoting signals from the SCN pacemaker. One hypothesis is that FEOs impose a daily rhythm of inhibition on SCN output that is timed to permit the expression of activity prior to a daytime meal. This hypothesis predicts that SCN activity should decrease prior to the onset of anticipatory activity and remain suppressed through the scheduled mealtime. To assess the hypothesis, neural activity in the SCN of mice anticipating a 4-5-h daily meal in the light period was measured using FOS immunohistochemistry and in vivo multiple unit electrophysiology. SCN FOS, quantified by optical density, was significantly reduced at the expected mealtime in food-anticipating mice with access to a running disk, compared to ad libitum-fed and acutely fasted controls. Group differences were not significant when FOS was quantified by other methods, or in mice without running disks. SCN electrical activity was markedly decreased during locomotion in some mice but increased in others. Changes in either direction were concurrent with locomotion, were not specific to food anticipation, and were not sustained during longer pauses. Reduced FOS indicates a net suppression of SCN activity that may depend on the intensity or duration of locomotion. The timing of changes in SCN activity relative to locomotion suggests that any effect of FEOs on SCN output is mediated indirectly, by feedback from neural or systemic correlates of locomotion.
哺乳动物的昼夜节律由昼夜振荡器系统调节，该系统包括视交叉上核（SCN）中的光可调节起搏器以及大脑和身体其他部位的食物可调节振荡器（FEO）。在夜行性啮齿动物中，SCN促进白天睡眠和夜间觉醒，而FEO则在预期可预测的每日进食时促进活跃状态。对于夜行性动物来说，要预期白天的进食，来自FEO的促觉醒信号必须与来自SCN起搏器的促睡眠信号竞争。一种假设是，FEO对SCN输出施加每日抑制节律，其时间安排是为了在白天进食前允许活动的表达。该假设预测，SCN活动应在预期活动开始前下降，并在预定用餐时间内保持受抑制状态。为了评估该假设，使用FOS免疫组织化学和体内多单位电生理学方法测量了在光照期预期每天有4 - 5小时进食的小鼠SCN中的神经活动。与自由进食和急性禁食的对照组相比，通过光密度定量的SCN FOS在能够使用跑步盘的食物预期小鼠的预期用餐时间显著降低。当通过其他方法定量FOS时，或者在没有跑步盘的小鼠中，组间差异不显著。在一些小鼠中，SCN电活动在运动期间显著降低，但在其他小鼠中则增加。向任一方向的变化都与运动同时发生，并非食物预期所特有，并且在较长的停顿期间不会持续。FOS降低表明SCN活动受到净抑制，这可能取决于运动的强度或持续时间。SCN活动相对于运动的变化时间表明，FEO对SCN输出的任何影响都是通过运动的神经或全身相关反馈间接介导的。
