Circadian effects of light no brighter than moonlight
Circadian effects of light no brighter than moonlight
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DOI：
10.1177/0748730407301988
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发表时间：
2007-08-01
影响因子：
3.5
通讯作者：
Gorman, Michael R.
中科院分区：
文献类型：
--
作者：
Evans, Jennifer A.;Elliott, Jeffrey A.;Gorman, Michael R.
在哺乳动物中，光通过最近在视网膜神经节细胞中发现的光感受器机制诱导每日相移，从而携带内源性昼夜节律起搏器。与月光强度相当的光线通常在诱导相移或抑制褪黑素分泌方面无效，这促使人们认为，昼夜光敏感度已被滴定，因此中央起搏器不受自然夜间照明的影响。然而，作者在几个不同的夹带范例中表明，完全黑暗的夜晚在功能上并不等同于昏暗的夜晚，即使夜间照度低于昼夜视觉系统的假定阈值。目前的研究扩展了这些发现。在这里，昏暗的照明既不是一个与已发表的光通量响应曲线一致的强烈的变色剂，也不是其他变色剂的增强剂。然而，昏暗的光线明显改变了自由运行的昼夜节律起搏器的行为。将叙利亚仓鼠从刺激条件下释放到持续黑暗或暗淡的窄带绿色照明(类似于0.01IX，1.3×10~(-9)W/cm(2)，峰值波长=560 nm)中。相对于完全黑暗，恒定的暗光使该周期延长约0.3h，并改变昼夜节律性的波形。在从长日照(L 14章：10节)进入恒定条件的动物中，相对于完全黑暗，暗淡的光照使活动期的持续时间(Cc)增加了类似3h。短日夹带(L 8：16D)最初产生长的(X)，在恒定的暗光下进一步增加，在完全黑暗下减少。相反，微弱的光脉冲2小时或更长时间对昼夜节律和褪黑激素的分泌产生影响，但影响幅度很小。此外，在暗光和暗背景下，对强光和非光刺激的相位重置幅度相似，表明前者不直接放大昼夜节律输入。昏暗的光照通过对(X)的影响显著地改变了昼夜节律的波形，这表明昏暗的光影响了振荡器之间的耦合，理论上是为了编程主观夜晚的开始和结束。负责将微弱的光刺激传递到起搏器的生理机制以及对时间疗法的影响值得进一步研究。
In mammals, light entrains endogenous circadian pacemakers by inducing daily phase shifts via a photoreceptor mechanism recently discovered in retinal ganglion cells. Light that is comparable in intensity to moonlight is generally ineffective at inducing phase shifts or suppressing melatonin secretion, which has prompted the view that circadian photic sensitivity has been titrated so that the central pacemaker is unaffected by natural nighttime illumination. However, the authors have shown in several different entrainment paradigms that completely dark nights are not functionally equivalent to dimly lit nights, even when nighttime illumination is below putative thresholds for the circadian visual system. The present studies extend these findings. Dim illumination is shown here to be neither a strong zeitgeber, consistent with published fluence response curves, nor a potentiator of other zeitgebers. Nevertheless, dim light markedly alters the behavior of the free-running circadian pacemaker. Syrian hamsters were released from entrained conditions into constant darkness or dim narrowband green illumination (similar to 0.01 Ix, 1.3 x 10-(9) W/cm(2), peak lambda = 560 nm). Relative to complete darkness, constant dim light lengthened the period by similar to 0.3 h and altered the waveform of circadian rhythmicity. Among animals transferred from long day lengths (14 L:10 D) into constant conditions, dim illumination increased the duration of the active phase (cc) by similar to 3 h relative to complete darkness. Short day entrainment (8 L:16 D) produced initially long (x that increased further under constant dim light but decreased under complete darkness. In contrast, dim light pulses 2 h or longer produced effects on circadian phase and melatonin secretion that were small in magnitude. Furthermore, the amplitude of phase resetting to bright light and nonphotic stimuli was similar against dimly lit and dark backgrounds, indicating that the former does not directly amplify circadian inputs. Dim illumination markedly alters circadian waveform through effects on (x, suggesting that dim light influences the coupling between oscillators theorized to program the beginning and end of subjective night. Physiological mechanisms responsible for conveying dim light stimuli to the pacemaker and implications for chronotherapeutics warrant further study.