Prolactin (PRL) is known for the diverse role it plays in the preparation, maintenance and secretor activity of the mammary glands during lactation. It plays a role in processes such reproduction, fat metabolism, hair shedding and immune response. In humans, prolactin is able to inhibit GnRH secretion and has an antagonistic activity on ovarian function in comparison to GnRH. The role of prolactin during the estrous cycle has not been established, although there are few reports on increased follicular growth in anestrous mares, which have been administered prolactin. In mares, prolactin concentration is related to the length of daylight photoperiod periods, and its highest concentrations coincide with periods of maximum reproductive activity.
Secretion of melatonin by the pineal gland is a biochemical signal which informs the organism about changes in the duration of day and night. The possibility to read this information determines the synchronization of the fertility period in animals at the time of the year typical for a given species. Melatonin binding sites were localized in different areas of the central nervous system and in the pars tuberalis of the pituitary gland. The use of micro-implants containing melatonin allowed to establish that the mediobasal hypothalamus is a site of melatonin action on sexual activity. Because in large mammals a melatonin receptors are absent from this area, it is supposed that regulation of the reproductive functions by melatonin takes place on the level of neurons which control LHRH release from the hypothalamus.
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.