The existence of neurogenesis during the lactation period - multiuser equipment approved in Fapesp Grant number 2016/02224-1: confocal microscope, brand Zeiss, model LSM 800

Abstract

The melanin-concentrating hormone [MCH] is an important neuropeptide, implied in a plethora of functions. Exclusively during the lactation period MCH-ir neurons and ppMCH mRNA are detected in new hypothalamic territories, as the ventromedial preoptic area [MPOAvm]. MCH synthesis in this region rises as the lactation progresses, reaching its peak at the final stage [around the 19th - 21st days] when it then disappears. The origin of these cells is still unknown. A possible explanation to this phenomenon is the de novo appearance of cells in this region, which would characterize neurogenesis in the adult hypothalamus of lactating female rats. Goal: to identify the origin of MCH-ir cells that appear in the MPOAvm during the lactation period, making a global evaluation of neurogenesis occurrence in the maternal brain. Additionally, to study the impact that MCH has over feeding and maternal behavior of lactating females. Rationale: Since both the ppMCH mRNA and the MCH peptide are detected in new loci of the rat CNS at later stages of lactation, we would like to unravel the role played by this neuropeptide over a possible control of hormonal/neuronal aspects of lactation termination, besides other possible neurogenic niches in the maternal brain. Material and Methods: to evaluate MCH participation in the lactation period: 1) female rats will receive sequential BrdU injections and will be sacrificed in different lactation stages. Their brains will then be used in immunohistochemistry for the identification of multiple markers of neurogenesis and neuronal maturation; 2) through osmotic minipumps, lactating females will receive chronic infusions of MCH during the entire lactation period and its effects will be evaluated through immunohistochemistry, in situ hybridization, western blotting, qRT-PCR, behavioral analysis and milk withdraw; 3) RNA interference [RNAi] will be used to inhibit the Pmch gene function, both in the LHA and in the MPOA of lactating females and, through that, we will analyze its effects on maternal and feeding behavior. (AU)