Department of Cellular and Structural Biology, UT Health Science Center San Antonio, Texas, USA.
J Physiol Pharmacol. 2011 Jun;62(3):269-74.
The current scientific literature is replete with investigations providing information on the molecular mechanisms governing the regulation of circadian rhythms by neurons in the suprachiasmatic nucleus (SCN), the master circadian generator. Virtually every function in an organism changes in a highly regular manner during every 24-hour period. These rhythms are believed to be a consequence of the SCN, via neural and humoral means, regulating the intrinsic clocks that perhaps all cells in organisms possess. These rhythms optimize the functions of cells and thereby prevent or lower the incidence of pathologies. Since these cyclic events are essential for improved cellular physiology, it is imperative that the SCN provide the peripheral cellular oscillators with the appropriate time cues. Inasmuch as the 24-hour light:dark cycle is a primary input to the central circadian clock, it is obvious that disturbances in the photoperiodic environment, e.g., light exposure at night, would cause disruption in the function of the SCN which would then pass this inappropriate information to cells in the periphery. One circadian rhythm that transfers time of day information to the organism is the melatonin cycle which is always at low levels in the blood during the day and at high levels during darkness. With light exposure at night the amount of melatonin produced is compromised and this important rhythm is disturbed. Another important source of melatonin is the gastrointestinal tract (GIT) that also influences the circulating melatonin is the generation of this hormone by the entero-endocrine (EE) cells in the gut following ingestion of tryptophan-containing meal. The consequences of the altered melatonin cycle with the chronodisruption as well as the alterations of GIT melatonin that have been linked to a variety of pathologies, including those of the gastrointestinal tract.
目前的科学文献中充斥着大量的研究，这些研究提供了有关神经元调节视交叉上核（SCN）昼夜节律的分子机制的信息，SCN 是主生物钟。实际上，生物体的每一个功能在每 24 小时内都以高度规律的方式发生变化。这些节律被认为是 SCN 通过神经和体液途径调节内在时钟的结果，而这些内在时钟可能存在于生物体的所有细胞中。这些节律优化了细胞的功能，从而预防或降低了病理学的发生。由于这些周期性事件对改善细胞生理学至关重要，因此 SCN 必须为周围细胞振荡器提供适当的时间线索。由于 24 小时光照：黑暗周期是中央生物钟的主要输入，因此很明显，光周期环境的干扰，例如夜间光照，会破坏 SCN 的功能，从而将这种不适当的信息传递给周围的细胞。一种将白天时间信息传递给生物体的昼夜节律是褪黑素节律，它在白天的血液中水平始终较低，而在黑暗中水平较高。夜间光照会使褪黑素的产生量减少，从而扰乱这种重要的节律。褪黑素的另一个重要来源是胃肠道（GIT），它也会影响循环中的褪黑素，因为肠道中的肠内分泌（EE）细胞在摄入含色氨酸的食物后会产生这种激素。褪黑素周期的改变以及与各种病理学相关的 GIT 褪黑素的改变所导致的生物钟紊乱的后果，包括胃肠道的病理学。
