title: Altered feeding and body weight following melanocortin administration to the ventral tegmental area in adult rats.
abstract: BACKGROUND
  The melanocortin system is an important component of the brain circuitry controlling feeding and body weight, and most of the effects of melanocortins are attributed to their actions in hypothalamic and brainstem nuclei. The mesolimbic dopamine system is another component of the central circuitry controlling feeding, and there is evidence that melanocortins can act on mesolimbic dopamine pathways. It is unknown, however, whether melanocortins can act on the mesolimbic dopamine system to regulate feeding.
  
  
  OBJECTIVE
  These studies tested whether injection of melanocortin receptor agonists and antagonists directly into the ventral tegmental area (VTA) of adult rats affects feeding and body weight.
  
  
  METHODS
  Varying doses of the melanocortin receptor agonist, MTII, or the melanocortin receptor antagonist, SHU9119, were injected directly into the VTA, and food intake was measured at specific intervals. In addition, melanocortin receptors in the VTA were chronically blocked through repeated daily injections of SHU9119 into the VTA, and the resulting effects on food intake and body weight were determined.
  
  
  RESULTS
  Injection of MTII into the VTA dose-dependently inhibited feeding for up to 24 h, while injection of SHU9119 into the VTA dose-dependently stimulated feeding for up to 24 h. In addition, chronic blockade of melanocortin receptors in the VTA increased feeding, body weight, and caloric efficiency.
  
  
  CONCLUSIONS
  These studies demonstrate that melanocortins can control feeding and body weight by acting in the VTA and suggest that endogenous melanocortins control feeding in part through actions on the mesolimbic dopamine system in vivo.
authors.affiliation: Department of Biology, Georgia State University, 24 Peachtree Center Ave NE, Suite 430SA, Atlanta, GA 30303, USA. aroseberry@gsu.edu
authors.forename: Aaron G
authors.initials: AG
authors.lastname: Roseberry
mesh_terms: D000818:Animals; D001835:Body Weight / Q000187:drug effects*; D001931:Brain Mapping; D004305:Dose-Response Relationship, Drug; D005247:Feeding Behavior / Q000187:drug effects*; D008297:Male; D053486:Melanocortins / Q000378:metabolism; D009074:Melanocyte-Stimulating Hormones / Q000008:administration & dosage / Q000494:pharmacology*; D008845:Microinjections; D051381:Rats; D017207:Rats, Sprague-Dawley; D044101:Receptors, Melanocortin / Q000819:agonists / Q000037:antagonists & inhibitors; D013997:Time Factors; D017557:Ventral Tegmental Area / Q000187:drug effects* / Q000378:metabolism; D000521:alpha-MSH / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology
chemical_list: D053486:Melanocortins; D044101:Receptors, Melanocortin; C081720:alpha-MSH (4-10)amide, Ac-Nle(4)-cyclo(Asp(5)-Phe(7)-Lys(10))-; C103272:SHU 9119; D000521:alpha-MSH; D009074:Melanocyte-Stimulating Hormones