Melanocortin-3 receptor mRNA expression in pro-opiomelanocortin neurones of the rat arcuate nucleus.
The melanocortins alpha- and gamma-melanocyte-stimulating hormones (alpha- and gamma-MSH) derive from the pro-opiomelanocortin (POMC) precursor. Melanocortins exert a wide range of biological activities in the brain through activation of at least three distinct melanocortin receptor (MC-R) subtypes. In order to determine whether POMC neurones can modulate their own activity, we looked for the possible expression of the MC3-R gene in POMC-positive cell bodies in the rat hypothalamus. In situ hybridization experiments revealed that the density of MC3-R mRNA is particularly high in the arcuate nucleus which contains the main population of POMC neurones in the brain. The occurrence of MC3-R mRNA in POMC-positive cell bodies was demonstrated using a double-labelling in situ hybridization technique. The proportion of POMC neurones expressing MC3-R mRNA was significantly higher in the most rostral (43.5%) than in the most posterior part of the arcuate nucleus (8.2%). These results indicate that melanocortins likely exert a direct regulatory feedback on POMC neurones through activation of MC3-R receptors. Our data also suggest that MC3-R may be involved in the neuroendocrine responses induced by centrally administered melanocortins.
Jégou
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European Institute for Peptide Research (IFRMP 23), Laboratory of Cellular and Molecular Neuroendocrinology, INSERM U413, UA CNRS, University of Rouen, Rouen, France. sylvie.jegou@univ-rouen.fr
Boutelet
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Vaudry
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D000818:Animals; D001111:Arcuate Nucleus of Hypothalamus / Q000166:cytology / Q000378:metabolism*; D017403:In Situ Hybridization; D008297:Male; D008969:Molecular Sequence Data; D009474:Neurons / Q000378:metabolism*; D011333:Pro-Opiomelanocortin / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D044104:Receptor, Melanocortin, Type 3; D018043:Receptors, Corticotropin / Q000235:genetics*
D012333:RNA, Messenger; D044104:Receptor, Melanocortin, Type 3; D018043:Receptors, Corticotropin; D011333:Pro-Opiomelanocortin