Arendt J
School of Biological Sciences, University of Surrey, Guildford, UK.
Therapie. 1998 Sep-Oct;53(5):479-88.
The primary function of melatonin in mammals is to transmit information concerning light-dark cycles for the organization of day length dependent on seasonal functions. There is little evidence for an essential role in circadian organization in mammals, in contrast with lower vertebates. It does, however, appear to reinforce physiological functions associated with darkness. Free-running blind and indeed sighted subjects show a close correlation between maximum sleepiness, minimum temperature and peak melatonin secretion. In humans exogenous melatonin will lower core body temperature and induce transient sleepiness in suitable doses and conditions. Similarly it will shift circadian phase, as assessed by a number of marker rhythms. These phase-shifting properties may not be sufficient to synchronize all circadian rhythms in the absence of other time cues. In most normal sighted subjects and a number of blind subjects the sleep-wake cycle can be 'stabilized' to a 24 h period by daily melatonin administration in free-running conditions. However, anomalous results have also been obtained. Daily administration of melatonin (5 mg) appears to fragment sleep in some subjects treated in dim light conditions. This observation requires further investigation since it may compromise the therapeutic potential of both melatonin and its agonists.
褪黑素在哺乳动物中的主要功能是传递有关昼夜循环的信息，以协调依赖于季节功能的白昼时长。与低等脊椎动物不同，几乎没有证据表明褪黑素在哺乳动物的昼夜节律组织中起关键作用。然而，它似乎确实能增强与黑暗相关的生理功能。自由运转的盲人以及视力正常的受试者在最大困倦程度、最低体温和褪黑素分泌峰值之间显示出密切的相关性。在人类中，外源性褪黑素在适当剂量和条件下会降低核心体温并诱发短暂的困倦感。同样，通过多种标记节律评估，它会改变昼夜节律相位。在没有其他时间线索的情况下，这些相位改变特性可能不足以同步所有昼夜节律。在大多数视力正常的受试者以及一些盲人受试者中，在自由运转条件下，每天服用褪黑素可使睡眠 - 清醒周期“稳定”到24小时。然而，也得到了一些异常结果。在暗光条件下接受治疗的一些受试者中，每天服用褪黑素（5毫克）似乎会使睡眠碎片化。这一观察结果需要进一步研究，因为它可能会损害褪黑素及其激动剂的治疗潜力。
