title: A potential role for hypothalamomedullary POMC projections in leptin-induced suppression of food intake.
abstract: Melanocortin-3/4 receptor ligands administered to the caudal brain stem potently modulate food intake by changing meal size. The origin of the endogenous ligands is unclear, because the arcuate nucleus of the hypothalamus and the nucleus of the solitary tract (NTS) harbor populations of proopiomelanocortin (POMC)-expressing neurons. Here we demonstrate that activation of hypothalamic POMC neurons leads to suppression of food intake and that this suppression is prevented by administration of a melanocortin-3/4 receptor antagonist to the NTS and its vicinity. Bilateral leptin injections into the rat arcuate nucleus produced long-lasting suppression of meal size and total chow intake. These effects were significantly blunted by injection of SHU-9119 into the fourth ventricle, although SHU-9119 increased meal size and food intake during the first, but not the second, 14-h observation period. Leptin effects on meal size and food intake were abolished throughout the 40-h observation period by injection of SHU-9119 into the NTS at a dose that by itself had no effect. Neuron-specific tracing from the arcuate nucleus with a Cre-inducible tract-tracing adenovirus in POMC-Cre mice showed the presence of labeled axons in the NTS. Furthermore, density of alpha-melanocyte-stimulating hormone-immunoreactive axon profiles throughout the NTS was decreased by approximately 70% after complete surgical transection of connections with the forebrain in the chronic decerebrate rat model. The results further support the existence of POMC projections from the hypothalamus to the NTS and suggest that these projections have a functional role in the control of food intake.
authors.affiliation: Neurobiology of Nutrition Laboratory, Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, Louisiana, USA.
authors.forename: Huiyuan
authors.initials: H
authors.lastname: Zheng
authors.forename: Laurel M
authors.initials: LM
authors.lastname: Patterson
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Rhodes
authors.forename: Gwendolyn W
authors.initials: GW
authors.lastname: Louis
authors.forename: Karolina P
authors.initials: KP
authors.lastname: Skibicka
authors.forename: Harvey J
authors.initials: HJ
authors.lastname: Grill
authors.forename: Martin G
authors.initials: MG
authors.lastname: Myers
authors.forename: Hans-Rudolf
authors.initials: HR
authors.lastname: Berthoud
mesh_terms: D000818:Animals; D001111:Arcuate Nucleus of Hypothalamus / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D001369:Axons / Q000378:metabolism; D003655:Decerebrate State; D004435:Eating / Q000187:drug effects* / Q000502:physiology; D020546:Fourth Ventricle; D049452:Green Fluorescent Proteins / Q000235:genetics; D020738:Leptin / Q000494:pharmacology*; D008297:Male; D009074:Melanocyte-Stimulating Hormones / Q000494:pharmacology; D051379:Mice; D008822:Mice, Transgenic; D009434:Neural Pathways / Q000166:cytology / Q000502:physiology; D011333:Pro-Opiomelanocortin / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D044105:Receptor, Melanocortin, Type 4 / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D017552:Solitary Nucleus / Q000166:cytology* / Q000502:physiology*; D014630:Vagus Nerve / Q000166:cytology / Q000502:physiology; D000521:alpha-MSH / Q000378:metabolism
chemical_list: D020738:Leptin; D044105:Receptor, Melanocortin, Type 4; D049452:Green Fluorescent Proteins; C103272:SHU 9119; D000521:alpha-MSH; D011333:Pro-Opiomelanocortin; D009074:Melanocyte-Stimulating Hormones