title: Chemical identity and connections of medial preoptic area neurons expressing melanin-concentrating hormone during lactation.
abstract: Lactation is an energy-demanding process characterized by massive food and water consumption, cessation of the reproductive cycle and induction of maternal behavior. During lactation, melanin-concentrating hormone (MCH) mRNA and peptide expression are increased in the medial preoptic area (MPO) and in the anterior paraventricular nucleus of the hypothalamus. Here we show that MCH neurons in the MPO coexpress the GABA synthesizing enzyme GAD-67 mRNA. We also show that MCH neurons in the MPO of female rats are innervated by neuropeptides that control energy homeostasis including agouti-related protein (AgRP), alpha-melanocyte stimulating hormone (alphaMSH) and cocaine- and amphetamine-regulated transcript (CART). Most of these inputs originate from the arcuate nucleus neurons. Additionally, using injections of retrograde tracers we found that CART neurons in the ventral premammillary nucleus also innervate the MPO. We then assessed the projections of the female MPO using injections of anterograde tracers. The MPO densely innervates hypothalamic nuclei related to reproductive control including the anteroventral periventricular nucleus, the ventrolateral subdivision of the ventromedial nucleus (VMHvl) and the ventral premammillary nucleus (PMV). We found that the density of MCH-ir fibers is increased in the VMHvl and PMV during lactation. Our findings suggest that the expression of MCH in the MPO may be induced by changing levels of neuropeptides involved in metabolic control. These MCH/GABA neurons may, in turn, participate in the suppression of cyclic reproductive function and/or sexual behavior during lactation through projections to reproductive control sites.
authors.affiliation: Laboratory of Chemical Neuroanatomy, Department of Anatomy, Institute of Biomedical Sciences, University of São Paulo - USP, 05508-900 São Paulo, SP, Brazil.
authors.forename: Tatiane Araujo
authors.initials: TA
authors.lastname: Rondini
authors.forename: José
authors.initials: J
authors.lastname: Donato
authors.forename: Bruno de Crudis
authors.initials: Bde C
authors.lastname: Rodrigues
authors.forename: Jackson Cioni
authors.initials: JC
authors.lastname: Bittencourt
authors.forename: Carol Fuzeti
authors.initials: CF
authors.lastname: Elias
mesh_terms: D000818:Animals; D005260:Female; D007028:Hypothalamic Hormones / Q000378:metabolism*; D007091:Image Processing, Computer-Assisted; D017403:In Situ Hybridization; D007774:Lactation; D008543:Melanins / Q000378:metabolism*; D009434:Neural Pathways / Q000378:metabolism*; D009474:Neurons / Q000737:chemistry / Q000378:metabolism*; D010907:Pituitary Hormones / Q000378:metabolism*; D011301:Preoptic Area / Q000737:chemistry / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D007028:Hypothalamic Hormones; D008543:Melanins; D010907:Pituitary Hormones; D012333:RNA, Messenger; C019463:melanin-concentrating hormone