title: Melatonin Receptor 1 Deficiency Affects Feeding Dynamics and Pro-Opiomelanocortin Expression in the Arcuate Nucleus and Pituitary of Mice.
abstract: METHODS
  Melatonin, the neurohormone for darkness, mediates photoperiod-dependent changes in physiology and behavior by targeting specific membrane-bound receptors (MT1 and MT2). In the present study, we investigated the impact of MT1 receptor deficiency on feeding behavior, locomotor activity and mRNA expression levels encoding for the polypeptide pro-opiomelanocortin (Pomc) and neuropeptide Y (Npy) in the hypothalamic arcuate nucleus (ARC) and the adenohypophysis [pars distalis (PD) and pars intermedia (PI)] in a comparison between wild-type (WT) and MT1-deficient (MT1-/-) mice.
  
  
  RESULTS
  The MT1-/- mice spent significantly more time feeding than the WT mice, while the general locomotor behavior, body weight and the total amount of food consumed did not differ between both genotypes. The nocturnal expression levels of Pomc in the ARC and PD were significantly higher in WT as compared to MT1-/- mice and exogenous melatonin administered during the light phase stimulated Pomc expression in WT mice only. No differences were found between WT and MT1-/- mice with regard to Pomc expression levels in the PI.
  
  
  CONCLUSIONS
  Thus, the MT1-mediated signaling stimulates Pomc expression in a region-specific pattern. Since the MT1-mediated changes in Pomc expression do not elicit direct orexigenic or anorexigenic effects, such effects are obviously mediated by regulatory systems downstream of the Pomc mRNA (e.g. cleavage and release of POMC derivatives), which are independent of MT1 signaling.
authors.affiliation: Dr. Senckenbergische Anatomie, Institut für Anatomie II, Frankfurt/Main, Germany.
authors.forename: Claudia
authors.initials: C
authors.lastname: Fischer
authors.forename: Tanja
authors.initials: T
authors.lastname: Mueller
authors.forename: Martina
authors.initials: M
authors.lastname: Pfeffer
authors.forename: Helmut
authors.initials: H
authors.lastname: Wicht
authors.forename: Charlotte
authors.initials: C
authors.lastname: von Gall
authors.forename: Horst-Werner
authors.initials: HW
authors.lastname: Korf
mesh_terms: D000818:Animals; D001111:Arcuate Nucleus of Hypothalamus / Q000187:drug effects / Q000378:metabolism*; D002940:Circadian Rhythm / Q000187:drug effects / Q000235:genetics; D004435:Eating / Q000187:drug effects / Q000235:genetics; D005247:Feeding Behavior / Q000187:drug effects / Q000502:physiology*; D005786:Gene Expression Regulation / Q000235:genetics*; D008124:Locomotion / Q000187:drug effects / Q000235:genetics; D008297:Male; D008550:Melatonin / Q000494:pharmacology; D051379:Mice; D018345:Mice, Knockout; D009478:Neuropeptide Y / Q000378:metabolism; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism*; D011333:Pro-Opiomelanocortin / Q000235:genetics / Q000378:metabolism*; D044122:Receptor, Melatonin, MT1 / Q000172:deficiency* / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics
chemical_list: D009478:Neuropeptide Y; D044122:Receptor, Melatonin, MT1; D011333:Pro-Opiomelanocortin; D008550:Melatonin
keywords: Arcuate nucleus; Melatonin; Melatonin receptor 1; Neuropeptide Y; Pro-opiomelanocortin