title: Characterization of melanocortin receptor ligands on cloned brain melanocortin receptors and on grooming behavior in the rat.
abstract: Since the melanocortin MC3 and melanocortin MC4 receptors are the main melanocortin receptor subtypes expressed in rat brain, we characterized the activity and affinity of nine melanocortin receptor ligands using these receptors in vitro, as well as their activity in a well-defined melanocortin-induced behavior in the rat: grooming behavior. We report here that [D-Tyr4]melanotan-II and RMI-2001 (Ac-cyclo-[Cys4, Gly5, D-Phe7, Cys10]alpha-MSH-NH2) have significantly higher affinity and potency on the rat melanocortin MC4 receptor as compared to the rat melanocortin MC3 receptor. Nle-gamma-MSH (melanocyte-stimulating hormone) was the only ligand with higher affinity and potency on the rat melanocortin MC3 receptor. The potency order of melanocortin MC4 receptor agonists, but not that of melanocortin MC3 receptor agonists, fitted with the potency of these ligands to stimulate grooming behavior, when administered intracerebroventricularly. SHU9119 (Ac-cyclo-[Nle4, Asp5, D-Nal(2)7, Lys10]alpha-MSH-(4-10)-NH2) and RMI-2005 (Ac-cyclo-[Cys4, Gly5, D-Na](2)7, Nal(2)9, Cys10]alpha-MSH-(4-10)-NH2) were able to inhibit alpha-MSH-induced melanocortin receptor activity in vitro, as well as alpha-MSH-induced grooming behavior. Melanotan-II, [Nle4-D-Phe7]alpha-MSH and RMI-2001 were also effective in inducing grooming behavior when administered intravenously. In the absence of purely selective melanocortin MC(3/4) receptor ligands, we demonstrated that careful comparison of ligand potencies in vitro with ligand potencies in vivo, could identify which melanocortin receptor subtype mediated alpha-MSH-induced grooming behavior. Furthermore, blockade of novelty-induced grooming behavior by SHU9119 demonstrated that this physiological stress response is mediated via activation of the melanocortin system.
authors.affiliation: Department of Medical Pharmacology, Rudolf Magnus Institute for Neurosciences, Utrecht University, The Netherlands. adan@med.uu.nl
authors.forename: R A
authors.initials: RA
authors.lastname: Adan
authors.forename: A W
authors.initials: AW
authors.lastname: Szklarczyk
authors.forename: J
authors.initials: J
authors.lastname: Oosterom
authors.forename: J H
authors.initials: JH
authors.lastname: Brakkee
authors.forename: W A
authors.initials: WA
authors.lastname: Nijenhuis
authors.forename: W M
authors.initials: WM
authors.lastname: Schaaper
authors.forename: R H
authors.initials: RH
authors.lastname: Meloen
authors.forename: W H
authors.initials: WH
authors.lastname: Gispen
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001667:Binding, Competitive; D002404:Catheterization; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D006120:Grooming / Q000187:drug effects*; D006801:Humans; D007275:Injections, Intravenous; D007276:Injections, Intraventricular; D008024:Ligands; D009074:Melanocyte-Stimulating Hormones / Q000494:pharmacology; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000494:pharmacology; D011869:Radioligand Assay; D051381:Rats; D017208:Rats, Wistar; D044104:Receptor, Melanocortin, Type 3; D044105:Receptor, Melanocortin, Type 4; D018043:Receptors, Corticotropin / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D044101:Receptors, Melanocortin; D011993:Recombinant Fusion Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013997:Time Factors; D000519:alpha-Galactosidase / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D000521:alpha-MSH / Q000378:metabolism / Q000494:pharmacology
chemical_list: D008024:Ligands; D010446:Peptide Fragments; C122006:RMI 2001; C122008:RMI 2004; C122007:RMI 2005; D044104:Receptor, Melanocortin, Type 3; D044105:Receptor, Melanocortin, Type 4; D018043:Receptors, Corticotropin; D044101:Receptors, Melanocortin; D011993:Recombinant Fusion Proteins; C103272:SHU 9119; D000521:alpha-MSH; D009074:Melanocyte-Stimulating Hormones; D000519:alpha-Galactosidase