title: Suckling-induced Fos activation and melanin-concentrating hormone immunoreactivity during late lactation.
abstract: OBJECTIVE
  Melanin-concentrating hormone (MCH) is implicated in the control of food intake, body weight regulation and energy homeostasis. Lactation is an important physiological model to study the hypothalamic integration of peripheral sensory signals, such as suckling stimuli and those related to energy balance. MCH can be detected in the medial preoptic area (MPOA), especially around the 19th day of lactation, when this hormone is described as displaying a peak synthesis followed by a decrease after weaning. The physiological significance of this phenomenon is unclear. Therefore, we aimed to investigate hypothalamic changes associated to sensory stimulation by the litter, in special its influence over MCH synthesis.
  
  
  METHODS
  Female Wistar rats (n=56) were euthanized everyday from lactation days 15-21, with or without suckling stimulus (WS and NS groups, respectively). MCH and Fos immunoreactivity were evaluated in the MPOA and lateral and incerto-hypothalamic areas (LHA and IHy).
  
  
  RESULTS
  Suckling stimulus induced Fos synthesis in all regions studied. An increase on the number of suckling-induced Fos-ir neurons could be detected in the LHA after the 18th day. Conversely, the amount of MCH decreased in the MPOA from days 15-21, independent of suckling stimulation. No colocalization between MCH and Fos could be detected in any region analyzed.
  
  
  CONCLUSIONS
  Suckling stimulus is capable of stimulating hypothalamic regions not linked to maternal behavior, possibly to mediate energy balance aspects of lactation. Although dams are hyperphagic before weaning, this behavioral change does not appear to be mediated by MCH.
authors.affiliation: Department of Pathology, School of Veterinary Medicine, University of São Paulo, São Paulo 05508-270, Brazil.
authors.forename: R D
authors.initials: RD
authors.lastname: Alvisi
authors.affiliation: Laboratory of Chemical Neuroanatomy, Department of Anatomy, Institute of Biomedical Sciences, University of São Paulo, São Paulo 05508-000, Brazil.
authors.forename: G B
authors.initials: GB
authors.lastname: Diniz
authors.affiliation: Laboratory of Chemical Neuroanatomy, Department of Anatomy, Institute of Biomedical Sciences, University of São Paulo, São Paulo 05508-000, Brazil.
authors.forename: J M
authors.initials: JM
authors.lastname: Da-Silva
authors.affiliation: Laboratory of Chemical Neuroanatomy, Department of Anatomy, Institute of Biomedical Sciences, University of São Paulo, São Paulo 05508-000, Brazil; Center for Neuroscience and Behavior, Institute of Psychology, University of São Paulo, Sao Paulo 05508-030, Brazil.
authors.forename: J C
authors.initials: JC
authors.lastname: Bittencourt
authors.affiliation: Department of Pathology, School of Veterinary Medicine, University of São Paulo, São Paulo 05508-270, Brazil. Electronic address: lfelicio@usp.br.
authors.forename: L F
authors.initials: LF
authors.lastname: Felicio
mesh_terms: D000818:Animals; D000833:Animals, Suckling; D005260:Female; D007028:Hypothalamic Hormones / Q000032:analysis / Q000096:biosynthesis*; D007031:Hypothalamus / Q000378:metabolism*; D007774:Lactation / Q000378:metabolism*; D008543:Melanins / Q000032:analysis / Q000096:biosynthesis*; D008547:Melanophores / Q000378:metabolism*; D010907:Pituitary Hormones / Q000032:analysis / Q000096:biosynthesis*; D016760:Proto-Oncogene Proteins c-fos / Q000032:analysis / Q000096:biosynthesis*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D007028:Hypothalamic Hormones; D008543:Melanins; D010907:Pituitary Hormones; D016760:Proto-Oncogene Proteins c-fos; C019463:melanin-concentrating hormone
keywords: Fos; Incerto-hypothalamic area; Lateral hypothalamic area; Maternal behavior; Medial preoptic area; Suckling stimulus