Melatonin is involved in the modulation of the hypothalamic and pituitary activity in the South American plains vizcacha, Lagostomus maximus

AbstractMelatonin, the key messenger of photoperiodic information, is synthesized in the pineal gland by arylalkylamineN-acetyltransferase enzyme (AANAT). It binds to specific receptors MT1 and MT2 located in the hypothalamus and pituitary gland. Melatonin can modulate the reproductive axis affecting the secretion of gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH). The South American plains vizcacha,Lagostomus maximus, shows natural poliovulation of up to 800  oocytes per estrous cycle, a 154-day long pregnancy, and reactivation of the reproductive axis at mid-gestation with pre-ovulatory follicular recruitment, presence of active corpora lutea, and variations of the endocrine status. Here we analyzed the involvement of melatonin in the modulation of th e hypothalamic and pituitary gland physiology of vizcacha thorough several approaches, including histological localization of melatoninergic system components, assessment of melatoninergic components expression throughout the reproductive cycle, and evaluation of the effect of melatonin on hypothala mic and pituitary activities during the follicular and luteal phases of the estrous cycle. AANAT and melatonin receptors were localized in the pineal gland and preoptic area of the hypothalamus. Increase in pineal AANAT and serum melatonin expression was observed as pregnancy progressed, with the lo west hypothalamic MT1 and MT2 levels at mid-pregnancy. Pulsatility assays demonstrated that melatonin induces GnRH...
Source: Journal of Comparative Physiology B: Biochemical, Systemic, and Environmental Physiology - Category: Physiology Source Type: research