Melatonin: perspectives in the life sciences.

The pineal gland hormone melatonin is now considered an important neuroendocrine component of animal physiology. Although the functional status of melatonin has been well described for subhuman species, there is a paucity of data concerning the physiological role of this hormone in man. This paucity of data has much to do with the limitations of experimental design imposed by the practical and ethical difficulties associated with the study of a nocturnally secreted hormone. The recent advent of salivary melatonin assay has provided a very practical means of monitoring melatonin secretion in long-term longitudinal type community based studies of pineal gland function in human health and disease. The efforts to describe key chronobiological changes in melatonin secretion of possible functional significance have been accompanied by a seemingly less enthusiastic search to describe the nature of the melatonin receptor, another highly important component of the 'melatonin message'. The functional relevance of specific chronobiological changes in melatonin secretion cannot be completely understood without an increased knowledge of melatonin action at the receptor level. The present work describes the recent methodological advance in the investigation of human pineal gland physiology represented by salivary melatonin assay, and discusses the present status of our knowledge of the melatonin receptor.