Rapid Adjustment of Circadian Clocks to Simulated Travel to Time Zones across the Globe
Rapid Adjustment of Circadian Clocks to Simulated Travel to Time Zones across the Globe
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DOI：
10.1177/0748730415598875
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发表时间：
2015-12-01
影响因子：
3.5
通讯作者：
Gorman, Michael R.
中科院分区：
文献类型：
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作者：
Harrison, Elizabeth M.;Gorman, Michael R.
哺乳动物生理和行为的日常节律是由位于下丘脑视交叉上核（SCN）的中央起搏器产生的，其时间由环境光线决定。当周围的光暗周期发生变化时，就像穿越时区时发生的那样，SCN及其输出节律必须重置或重新调整它们的阶段以匹配新的时间表——一个缓慢的过程，每小时轮班大约需要1天。通过对6个等距时区子午线的昼夜节律重置的全球分析，我们记录了叙利亚仓鼠在模拟夏季白昼长度的典型实验室照明条件下的这种特征缓慢且距离依赖的重置。然而，昼夜节律起搏器的波形（即24小时振荡的形状）允许跟踪季节性变化的白天长度。我们在这里展示了一种前所未有的，基于光照的加速，在两次昼夜节律波形操作后进行相位重置。昼夜节律波形对长冬夜（8小时光照，16小时黑暗）的适应使倒班后的前3天的倒班反应增加了一倍。此外，暴露于一个新的24小时光-暗-光-暗循环中引起的分叉波形允许几乎瞬间重置相移从4到12小时的幅度，这表明活动节奏和新的光循环之间的不匹配减少了71%。因此，通过对哺乳动物昼夜节律模式物种的昼夜节律起搏器波形进行非药物、非侵入性操作，可以诱导相移的显著增强。鉴于人类起搏器波形保持灵活性的证据，这些发现提出了灵活重置的希望，适用于轮班工人、频繁的时区旅行者和任何被迫适应具有挑战性的时间表的个人。
Daily rhythms in mammalian physiology and behavior are generated by a central pacemaker located in the hypothalamic suprachiasmatic nuclei (SCN), the timing of which is set by light from the environment. When the ambient light-dark cycle is shifted, as occurs with travel across time zones, the SCN and its output rhythms must reset or re-entrain their phases to match the new schedulea sluggish process requiring about 1 day per hour shift. Using a global assay of circadian resetting to 6 equidistant time-zone meridians, we document this characteristically slow and distance-dependent resetting of Syrian hamsters under typical laboratory lighting conditions, which mimic summer day lengths. The circadian pacemaker, however, is additionally entrainable with respect to its waveform (i.e., the shape of the 24-h oscillation) allowing for tracking of seasonally varying day lengths. We here demonstrate an unprecedented, light exposure-based acceleration in phase resetting following 2 manipulations of circadian waveform. Adaptation of circadian waveforms to long winter nights (8 h light, 16 h dark) doubled the shift response in the first 3 days after the shift. Moreover, a bifurcated waveform induced by exposure to a novel 24-h light-dark-light-dark cycle permitted nearly instant resetting to phase shifts from 4 to 12 h in magnitude, representing a 71% reduction in the mismatch between the activity rhythm and the new photocycle. Thus, a marked enhancement of phase shifting can be induced via nonpharmacological, noninvasive manipulation of the circadian pacemaker waveform in a model species for mammalian circadian rhythmicity. Given the evidence of conserved flexibility in the human pacemaker waveform, these findings raise the promise of flexible resetting applicable to circadian disruption in shift workers, frequent time-zone travelers, and any individual forced to adjust to challenging schedules.