ABSTRACT
This chapter attempts to bring together most of the available information on steroidmediated regulation of pineal melatonin synthesis, both from experimental animals and clinical observations. In addition, the potential cellular sites for steroid hormone influences are considered. According with data reported, the influence of estrogens on melatonin binding sites seems to be region specific, since ovariectomy produces a large estradiol-reversible reduction of melatonin binding sites in the medulla pons and hypothalamus, but not in the hippocampus, cerebellum, striatum, or parietal cortex. In summary, the reported effects of gonadal steroids on melatonin binding sites clearly support an interconnection between melatonin and steroid target neurons in central neuroendocrine regions of the rat. In the context of this work, it would imply that the rise in circulating levels of gonadal hormones, preceding or accompanying pubertal development, may cause a feedback modulation of pineal melatonin synthesis and secretion.
