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Effects of melatonin absence on lactation and maternal behavior

Grant number: 16/24956-4
Support type:Scholarships in Brazil - Scientific Initiation
Effective date (Start): March 01, 2017
Effective date (End): December 31, 2017
Field of knowledge:Biological Sciences - Physiology
Principal Investigator:José Cipolla Neto
Grantee:Rafaela Panaiotta Parthimos
Home Institution: Instituto de Ciências Biomédicas (ICB). Universidade de São Paulo (USP). São Paulo, SP, Brazil
Associated research grant:14/50457-0 - Melatonin and the control of energy metabolism: basic, clinical and epidemiological research, AP.TEM

Abstract

Introduction: Childhood is a critical period due to development of most human potentialities. Absence of lactation, early weaning and/or changing breastfeeding by toddler formulas is prejudicial to children and mother's health. Maternal behaviour and lactation are physiological phenomena that occur due to significant hormonal changes. The main hormones related to maternal behaviour and lactation are progesterone, estradiol, prolactin and oxytocin. Among these, prolactin is the key hormone for development of mammary gland and maternal behaviour expression. Another important hormone to the reproductive physiology of the females is melatonin. Melatonin is synthetized mainly by pineal gland and its secretion is synchronized to the light/dark cycle, so the highest concentrations of melatonin are in the dark phase and the lowest concentrations are in the light phase. Evidences suggest that melatonin acts on pituitary gland, regulating the secretion of prolactin and oxytocin. Besides that, it is known that melatonin is a maternal hormone that crosses the placenta and is found in the milk, neuro-protecting and regulating the circadian rhythms of the fetus and newborn. So, melatonin acts directly on the hormonal axis that controls maternal behaviour and lactation, besides that the maintenance of circadian rhythms and the profile of synthesis and secretion of melatonin are essentials to ensure a reproductive adaptative physiology in female mammals. Aim: The aim of the project is to investigate if melatonin absence affects mammogenesis, lactogenesis and maternal behaviour by physiological, behavioural and molecular analysis in lactating female rats pinealectomized (PINX group) or not (control group). Material and methods: Wistar female rats (250g) maintained on 12h light/dark cycle, temperature of 24 ±2°C and food/water ad libitum will be pinealectomized or not, and four weeks after the surgery they will be mated. After confirmation of pregnancy females will be isolated and weighted daily to determine the exact day of delivery, which will be consider the first day of lactation (L1). The maternal behaviour and lactation tests will be performed at day 5 (L5) and day 8 (L8) of lactation. On day 10 of lactation (L10) the female will be euthanized and the tissues (hypothalamus, mammary gland and serum) collected for histological, biochemical and molecular analysis. (AU)