Circadian melatonin and young-to-old pineal grafting postpone aging and maintain juvenile conditions of reproductive functions in mice and rats

Chronic, night administration of melatonin to aging mice and transplantation of a young pineal gland into the thymic rudiment of older mice and rats have been studied with the aim of evaluating their effects on aging of gonadal, sexual, and reproductive functions. Both melatonin administration and young-to-old pineal grafting positively affect size and function of testes and maintenance of juvenile hippocampal and testicular LHRH-receptors and β-adrenergic receptors in the testes of old rats and mice. These results demonstrate that a pineal-directed circadian function and cyclicity is fundamental for the regulation of sexual reproductive physiology, and that proper intervention with melatonin may potentially postpone aging of both neural and gonadal sexual function.