Basic aspects of melatonin action.
Basic aspects of melatonin action.
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DOI：
10.1016/s1087-0792(98)90020-x
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发表时间：
1998-08-01
影响因子：
10.5
通讯作者：
Pevet, P
中科院分区：
文献类型：
--
作者：
Cardinali, D P;Pevet, P
褪黑素是在光-暗周期的黑暗时期合成和分泌的。因此，褪黑素与睡眠有明显的联系，至少在昼行性动物中是这样。有节奏的夜间褪黑激素分泌是由昼夜节律时钟直接产生的，位于哺乳动物的视交叉上核（SCN）内，并被光-暗循环以24小时为周期。褪黑激素的周期性分泌可能被用作任何系统的昼夜节律介质，而不是“读取”信息。此外，这种激素对SCN的直接作用可以解释褪黑素对昼夜节律系统的一些影响。褪黑素夜间分泌的持续时间与夜晚的长度成正比，实验证明它是光周期整合的关键参数。解释褪黑激素作用的两个主要假设是持续时间假设（支持夜晚长度由褪黑激素分泌阶段的持续时间编码）和巧合假设（认为生理反应与对褪黑激素敏感性的昼夜节律的存在有关）。褪黑素在昼夜节律和光周期反应中的作用位点和机制还远未被阐明，但通过特定的膜受体位点的作用是有充分记录的。鉴于褪黑素的亲脂性，与特定的细胞内蛋白如钙调蛋白或微管蛋白或与核受体位点的相互作用也被考虑，而已记录的褪黑素抗氧化作用的生理意义仍有待解决。褪黑素似乎充当了生物钟的“手臂”，向一些身体功能发出与时间相关的信号；其中之一，生物防御的昼夜节律组织，作为一个例子进行了一些详细的讨论。
Melatonin is synthesized and secreted during the dark period of the light-dark cycle. Thus, melatonin has an obvious association with sleep, at least in diurnal animals. Rhythmic nocturnal melatonin secretion is directly generated by the circadian clock, located in mammals within the suprachiasmatic nuclei (SCN), and is entrained to a 24-h period by the light-dark cycle. The periodic secretion of melatonin may be used as a circadian mediator to any system than can "read" the message. In addition, direct effects of the hormone on the SCN could explain some of melatonin effects on the circadian system. Duration of melatonin nocturnal secretion is directly proportional to the length of the night and it has been demonstrated experimentally to be the critical parameter for photoperiod integration. The two main hypotheses to explain the action of melatonin are the duration hypothesis (supporting that night length is coded by the duration of the melatonin secretory phase) and the coincidence hypothesis (holding that physiological responses are linked to the existence of a diurnal rhythm in sensitivity to melatonin). The sites and mechanisms of action of melatonin for circadian and photoperiodic responses are far from being elucidated, but action through specific membrane receptor sites is well documented. In view of melatonin s lipophilic nature, interactions with specific intracellular proteins like calmodulin or tubulin, or with nuclear receptor sites, have also been considered, whereas the physiological significance of the documented antioxidant effect of melatonin remains to be settled. Melatonin seems to act as an "arm" of the circadian clock, giving a time-related signal to a number of body functions; one of these, the circadian organization of an organism's defence, is discussed in some detail as an example.