Melatonin and animal reproduction: implications on ovarian physiology

Abstract

The reproductive activity of mammalian species can be related to the most propitious time of the year to the birth of offspring. The light period duration (photoperiod) is strongly related to this mechanism through the secretion of melatonin by pineal gland. Melatonin is the neurotransmitter responsible for mediate the daily information of light/dark cycle, informing the night duration to the body and, consequently the corresponding time of the year. The presence of melatonin receptor sites in the hypothalamus and the pituitary gland explain its effects on the secretion of pituitary hormones (Follicle stimulating hormone-FSH and Luteinizing hormone-LH) and seasonal rhythm organization. In addition to its systemic action, reports have demonstrated an influence in the ovarian physiology, since high levels in follicular fluid were detected and the presence of melatonin receptors in the ovarian cells has been found. Also, its important function as an antioxidant can influence follicular growth, oocyte maturation, ovulation and luteal function. The purpose of this article is to review the melatonin influence in the animal reproduction, especially in the ovarian physiology. Keywords: Photoperiod, folliculogenesis, antioxidant.