MELATONIN - A CHRONOBIOTIC AND SOPORIFIC HORMONE

In this report we review evidence that melatonin, a hormone produced b y the pineal gland during the hours of darkness, plays a major role in the synchronization of the sleep/wake cycle. The production of melato nin is regulated by a structure located in the hypothalamus called the suprachiasmatic nucleus (SCN). The activity of the SCN is strongly af fected by changes in illumination and, as a consequence, melatonin lev els are high during darkness and low in the light and it, therefore, r eflects the cycle. Changes in sleep/wake patterns are among the hallma rks of biological aging. Complaints of difficulty in initiating and ma intaining sleep, and daytime drowsiness, are more common in the elderl y than in any other age group. In this report, we review evidence that impaired meltonin secretion is associated with sleep disorders in old age. Circulating melatonin levels have been found to be significantly lower in elderly insomniacs than ill age-matched controls, and their onset and peak times delayed. In view of these findings, we investigat ed the effects of melatonin treatment on melatonin-deficient insomnia in the elderly. From the results of our study, it seems likely that me latonin replacement therapy may be beneficial in the initiation and ma intenance of sleep in this population. Copyright (C) 1997 Elsevier Sci ence Ireland Ltd.