Characterization of melanocortin receptor ligands on cloned brain melanocortin receptors and on grooming behavior in the rat

• Published in: European journal of pharmacology Vol. 378; no. 3; pp. 249 - 258
• Main Authors: Adan, Roger A.H, Szklarczyk, Arkadiusz W, Oosterom, Julia, Brakkee, Jan H, Nijenhuis, Wouter A.J, Schaaper, Wim M.M, Meloen, Rob H, Gispen, Willem Hendrik
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 13-08-1999; Elsevier
• Subjects: ACTH (adrenocorticotrope hormone); alpha-Galactosidase - drug effects; alpha-Galactosidase - genetics; alpha-Galactosidase - metabolism; alpha-MSH - metabolism; alpha-MSH - pharmacology; Amino Acid Sequence; Animals; Behavioral psychophysiology; Binding, Competitive; Biological and medical sciences; Catheterization; Cell Line; Dose-Response Relationship, Drug; Drug Interactions; Fundamental and applied biological sciences. Psychology; Grooming - drug effects; Grooming behavior; Hormones and behavior; Humans; Injections, Intravenous; Injections, Intraventricular; Ligands; Ligand–receptor interaction; Melanocortin receptor; Melanocyte-Stimulating Hormones - pharmacology; Molecular Sequence Data; MSH (melanocyte-stimulating hormone); Peptide Fragments - pharmacology; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Radioligand Assay; Rats; Rats, Wistar; Receptor, Melanocortin, Type 3; Receptor, Melanocortin, Type 4; Receptors, Corticotropin - antagonists & inhibitors; Receptors, Corticotropin - drug effects; Receptors, Corticotropin - genetics; Receptors, Corticotropin - metabolism; Receptors, Melanocortin; Recombinant Fusion Proteins - drug effects; Recombinant Fusion Proteins - genetics; Recombinant Fusion Proteins - metabolism; Sequence Homology, Amino Acid; Stress; Time Factors; Grooming behavior; ACTH (adrenocorticotrope hormone); MSH (melanocyte-stimulating hormone); Melanocortin receptor; Ligand–receptor interaction; Stress; Human; Agonist; Intravenous administration; Rat; Rodentia; Central nervous system; Molecular interaction; Melanocyte stimulating hormone; In vitro; In vivo; Vertebrata; Mammalia; Adrenocorticotropic hormone; Animal; Intracerebral administration; Subtype; Brain (vertebrata); Hormonal receptor
• ISSN: 0014-2999; 1879-0712
• DOI: 10.1016/S0014-2999(99)00465-3

Since the melanocortin MC
3 and melanocortin MC
4 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-Tyr
4]melanotan-II and RMI-2001 (Ac-cyclo-[Cys
4, Gly
5,
d-Phe
7, Cys
10]α-MSH-NH
2) have significantly higher affinity and potency on the rat melanocortin MC
4 receptor as compared to the rat melanocortin MC
3 receptor. Nle-γ-MSH (melanocyte-stimulating hormone) was the only ligand with higher affinity and potency on the rat melanocortin MC
3 receptor. The potency order of melanocortin MC
4 receptor agonists, but not that of melanocortin MC
3 receptor agonists, fitted with the potency of these ligands to stimulate grooming behavior, when administered intracerebroventricularly. SHU9119 (Ac-cyclo-[Nle
4, Asp
5,
d-Nal(2)
7, Lys
10]α-MSH-(4–10)-NH
2) and RMI-2005 (Ac-cyclo-[Cys
4, Gly
5,
d-Nal(2)
7, Nal(2)
9, Cys
10]α-MSH-(4–10)-NH
2) were able to inhibit α-MSH-induced melanocortin receptor activity in vitro, as well as α-MSH-induced grooming behavior. Melanotan-II, [Nle
4-
d-Phe
7]α-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 α-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.