Melanin-concentrating hormone signaling systems in fish

Peptides

Volumn 25, Issue 10 SPEC. ISS., 2004, Pages 1577-1584

  Kawauchi, Hiroshi ^a   Baker, Bridget I ^b  

^a KITASATO UNIVERSITY   (Japan)

^b University of Bath   (United Kingdom)

Author keywords

Food intake signaling; Gene expression; MCH receptor (MCH R); Melanin concentrating hormone (MCH); Melanocortin; Melanotropic signaling; Orexigenic peptide; Melanophore stimulating hormone ( MSH)

Indexed keywords

AGOUTI PROTEIN; AGOUTI RELATED PROTEIN; ALPHA INTERMEDIN; ANOREXIGENIC AGENT; APPETITE STIMULANT; G PROTEIN COUPLED RECEPTOR; MELANIN; MELANIN CONCENTRATING HORMONE; NEUROPEPTIDE; RECEPTOR BLOCKING AGENT;

CALORIC INTAKE; CELL AGGREGATION; FISH; FOOD INTAKE; GENE EXPRESSION; GENETIC MANIPULATION; HOMEOSTASIS; HORMONAL REGULATION; HUMAN; HYPOTHALAMUS; MAMMAL; MELANOPHORE; NONHUMAN; PRIORITY JOURNAL; PROTEIN BINDING; PROTEIN FUNCTION; REVIEW; SIGNAL TRANSDUCTION; TELEOST; VERTEBRATE;

MAMMALIA; MELANOPHORA; VERTEBRATA;

EID: 5444226515     PISSN: 01969781     EISSN: None     Source Type: Journal    
DOI: 10.1016/j.peptides.2004.03.025     Document Type: Review

References (98)

1. C.R. Abbott, A.R. Kennedy, A.M. Wren, M. Rossi, K.G. Murphy, and L.J. Seal Identification of hypothalamic nuclei involved in the orexigenic effect of melanin-concentrating hormone Endocrinology 44 2003 3943 3949
2. M. Amano, A. Takahashi, Y. Oka, T. Yamanome, H. Kawauchi, and K. Yamamori Immunocytochemical localization and ontogenic development of melanin-concentrating hormone in the brain of a pleuronectiform fish, the barfin flounder Cell Tissue Res. 311 2003 71 77
3. S. An, G. Cutler, J.J. Zhao, S.G. Huang, H. Tian, and W. Li Identification and characterization of a melanin-concentrating hormone receptor Proc. Natl. Acad. Sci. USA 98 2001 7576 7581
4. B.I. Baker Melanin-concentrating hormone: a general vertebrate neuropeptide Int. Rev. Cytol. 126 1991 1 147
5. B.I. Baker The role of melanin-concentrating hormone in colour change Ann. NY Acad. Sci. 680 1993 279 289
6. B.I. Baker, D.J. Bird, and J.C. Buckingham Salmonid melanin-concentrating hormone inhibits corticotropin release J. Endocrinol. 106 1985 R5 R8
7. B.I. Baker, and D.J. Bird Neuronal organization of the melanin-concentrating hormone system in primitive actinopterygians: evolutionary changes leading to teleosts J. Comp. Neurol. 442 2002 99 114
8. B. Baker, A. Levy, L. Hall, and S. Lightman Cloning and expression of melanin-concentrating hormone genes in the rainbow trout brain Neuroendocrinology 61 1995 67 76
9. Balm PHM, and D. Groneveld The melanin-concentrating hormone system in fish Ann. NY Acad. Sci. 839 1988 205 209
10. L.D. Barber, B.I. Baker, J.C. Penny, and A.N. Eberle Melanin- concentrating hormone inhibits the release of α-MSH from teleosts pituitary glands Gen. Comp. Endocrinol. 65 1987 79 86
11. G.S. Barsh, and M.W. Schwartz Genetic approach to studying energy balance: perception and integration Nat. Rev. 3 2002 589 600
12. V. Berberian, M.S. Sanchez, and M.E. Celis Participation of the cholinergic system in the excessive grooming behavior induced by neuropeptide (N) glutamic acid (E) isoleucine (I) amide (NEI) Neurochem. Res. 27 2002 1713 1717
13. D.J. Bird, I.C. Potter, S.A. Sower, and B.I. Baker The distribution of melanin-concentrating hormone in the lamprey brain Gen. Comp. Endocrinol. 121 2001 232 241
14. B. Borowsky, M.M. Durkin, K. Ogozalek, M.R. Marzabadi, J. DeLeon, and B. Lagu Antidepressant, anxiolytic and anorectic effects of a melanin-concentrating hormone-1 receptor antagonist Nat. Med. 7 2002 297 303
15. R.L. Bradley, J.P. Mansfield, E. Maratos-Flier, and B. Cheatham Melanin-concentrating hormone activates signaling pathways in 3T3-L1 adipocytes Am. J. Physiol. Endocrinol. Metab. 283 2002 E584 E592
16. C. Breton, F. Presse, G. Hervieu, and J.L. Nahon Structure and regulation of the mouse melanin concentrating hormone mRNA and gene Mol. Cell. Neurosci. 42 1993 71 84
17. J.M. Cerda-Reverter, and R.E. Peter Endogenous melanocortin antagonist in fish: structure, brain mapping, and regulation by fasting of the goldfish agouti-related protein gene Endocrinology 144 2003 4552 4561
18. J.M. Cerda-Reverter, A. Ringholm, H.B. Schioth, and R.E. Peter Molecular cloning, pharmacological characterization, and brain mapping of the melanocortin 4 receptor in the goldfish: involvement in the control of food intake Endocrinology 144 2003 2336 2349
19. J. Chambers, R.S. Ames, D. Bergsma, A. Muir, L.R. Fitzgerald, and G. Hervieu Melanin-concentrating hormone is the cognate ligand for the orphan G-protein-coupled receptor SLC-1 Nature 400 1999 261 265
20. Y. Chen, C. Hu, C.K. Hsu, Q. Zhang, C. Bi, and M. Asnicar Targeted disruption of the melanin-concentrating hormone receptor-1 results in hyperphagia and resistance to diet-induced obesity Endocrinology 143 2002 2469 2477
21. S.R. Chiocchio, M.G. Gallardo, P. Louzan, V. Gutnisky, and J.H. Tramezzani Melanin-concentrating hormone stimulates the release of luteinizing hormone-releasing hormone and gonadotropins in the female rat acting at both median eminence and pituitary levels Biol. Reprod. 64 2001 1466 1472
22. D.J. Clegg, E.L. Air, S.C. Benoit, R.S. Sakai, R.J. Seeley, and S.C. Woods Intraventricular melanin-concentrating hormone stimulates water intake independent of food intake Am. J. Physiol. Regul. Integr. Comp. Physiol. 284 2003 R494 R499
23. Crowley VEF, Yeo GSH, and S. O'Rahilly Obesity therapy: altering the energy intake-and-expenditure balance sheet Nat. Rev. 1 2002 276 286
24. O. Della-Zuana, F. Presse, C. Ortola, J. Duhault, J.L. Nahon, and N. Levens Acute and chronic administration of melanin-concentrating hormone enhances food intake and body weight in Wistar and Sprague-Dawley rats Int. J. Obes. Relat. Metab. Disord. 26 2002 1289 1295
25. G. Duarte, M.M. Segura-Noguera, M.P. Martin del Rio, and J.M. Mancera The hypothalamo-hypophyseal system of the white seabream Diplodus sargus: immunocytochemical identification of arginine-vasotocin, isotocin, melanin-concentrating hormone and corticotropin-releasing factor Histochem. J. 33 2001 569 578
26. C. Forray The MCH receptor family: feeding brain disorders? Curr Opin 3 2003 85 89
27. X.B. Gao, and A.N. van den Pol Melanin-concentrating hormone depresses L-, N-, and P/Q-type voltage-dependent calcium channels in rat lateral hypothalamic neurons J. Physiol. 542 2002 273 286
28. M.L. Gonzalez, B.I. Baker, and C.A. Wilson Stimulatory effect of melanin-concentrating hormone on LH release Neuroendocrinology 66 1997 254 262
29. R.V. Gottumukkala, E.A. Waterman, L.M. Herd, D.J. Gawkrodger, P.F. Watson, and A.P. Weetman Autoantibodies in vitiligo patients recognize multiple domains of the melanin-concentrating hormone receptor J. Invest. Dermatol. 121 2003 765 770
30. B. Griffond, and B.I. Baker Cell and molecular cell biology of melanin-concentrating hormone Int. Rev. Cytol. 213 2002 233 277
31. D. Gröneveld, P.H. Balm, and S.E. Wendelaar Bonga Biphasic effect of MCH on alpha-MSH release from the tilapia (Orechromis rnossambicus) pituitary Peptides 16 1995 945 949
32. D. Gröneveld, E.R. Eckhardt, A.J. Coenen, G.J. Martens, P.H. Balm, and S.E. Wendelaar Bonga Expression of tilapia prepro-melanin-concentrating hormone mRNA in hypothalamic and neurohypophysial cells J. Mol. Endocrinol. 14 1995 199 207
33. D. Gröneveld, P.H. Balm, G.J. Martens, and S.E. Wendelaar Bonga Differential melanin-concentrating hormone gene expression in two hypothalamic nuclei of the teleost tilapia in response to environmental changes J. Neuroendocrinol. 7 1995 527 533
34. J. Harris, and D.J. Bird Supernatants from leucocytes treated with melanin-concentrating hormone (MCH) and alpha-melanocyte stimulating hormone (alpha-MSH) have a stimulatory effect on rainbow trout (Oncorh. ynchus mykiss) phagocytes in vitro Vet. Immunol. Immunopathol. 76 2000 117 124
35. J. Harris, D.J. Bird, and L.A. Yeatman Melanin-concentrating hormone (MCH) stimulates the activity of rainbow trout (Oncorhynchus mykiss) head kidney phagocytes in vitro Fish Shelfish Immunol. 8 1998 639 642
36. B.E. Hawes, E. Kil, B. Green, K. O'Neill, S. Fried, and M.P. Graziano The melanin-concentrating hormone receptor couples to multiple G proteins to activate diverse intracellular signaling pathways Endocrinology 141 2000 4524 4532
37. G. Hervieu, and J.L. Nahon Pro-melanin concentrating hormone messenger ribonucleic acid and peptides expression in peripheral tissues of the rat Neuroendocrinology 61 1995 348 364
38. J. Hill, M. Duckworth, P. Murdock, G. Rennie, C. Sabido-David, and R.S. Ames Molecular cloning and functional characterization of MCH2, a novel human MCH receptor J. Biol. Chem. 276 2001 20125 20129
39. A. Hinney, A. Schmidt, K. Nottebom, O. Heibult, I. Becker, and A. Ziegler Several mutations in the melanocortin-4 receptor gene including a nonsense and a frame shift mutation associated with dominantly inherited obesity in humans J. Clin. Endocrinol. Metab. 84 1999 1483 1486
40. E. Hintermann, H. Tanner, C. Talke-Messerer, S. Schlumberger, U. Zumsteg, and A.N. Eberle Expression of the melanin-concentrating hormone receptor in porcine and human ciliary epithelial cells Invest. Ophthalmol. Vis. Sci. 42 2001 206 209
41. M.J. Hoogduijn, J. Ancans, I. Suzuki, S. Estdale, and A.J. Thody Melanin-concentrating hormone and its receptor are expressed and functional in human skin Biochem. Biophys. Res. Commun. 296 2002 698 701
42. D. Huszar, C.A. Lynch, V. Fairchild-Huntress, J.H. Dunmore, Q. Fang, and L.R. Berkemeier Targeted disruption of the melanocortin-4 receptor results in obesity in mice Cell 88 1997 131 141
43. M. Ito, A. Gomori, A. Ishihara, M. Ito, S. Mashiko, and H. Matsushita Chronic intracerebroventricular infusion of MCH causes obesity in mice Am. J. Physiol. Endocrinol. Metab. 284 2003 E583 E588
44. D. Jezova, V. Bartanusz, I. Westergren, B.B. Johansson, J. Rivier, and W. Vale Rat melanin-concentrating hormone stimulates adrenocorticotropin secretion: evidence for a site of action in brain regions protected by the blood brain barrier Endocrinology 130 1992 1024 1029
45. H. Kawano, S. Honma, A. Honma, M. Horie, Y. Kawano, and S. Hayashi Melanin-concentrating hormone neuron system: the Wide Web that controls the feeding Anat. Sci. Int. 77 2002 149 160
46. H. Kawauchi Melanin concentrating hormone. II. Structure and biosynthesis of melanin-concentrating hormone Life Sci. 45 1989 1133 1140
47. H. Kawauchi, I. Kawazoe, M. Tsubokawa, M. Kishida, and B.I. Baker Characterization of melanin-concentrating hormone in chum salmon pituitaries Nature 305 1983 321 323
48. H. Kawauchi, N. Naito, and M. Ono Chemistry of melanin-concentrating hormone Ann. NY Acad. Sci. 680 1993 64 77
49. J. Kela, P. Salmi, R. Rimondini-Giorgini, M. Heilig, and C. Wahlestedt Behavioural analysis of melanin-concentrating hormone in rats: evidence for orexigenic and anxiolytic properties Regul. Pept. 114 2003 109 114
50. A.R. Kennedy, J.F. Todd, W.S. Dhillo, L.J. Seal, M.A. Ghatei, and C.P. O'Toole Effect of direct injection of melanin-concentrating hormone into the paraventricular nucleus: further evidence for a stimulatory role in the adrenal axis via SLC-1 J. Neuroendocrinol. 15 2003 268 272
51. A.R. Kennedy, J.F. Todd, S.A. Stanley, C.R. Abbott, C.J. Small, and M.A. Ghatei Melanin-concentrating hormone (MCH) suppresses thyroid stimulating hormone (TSH) release, in vivo and in vitro, via the hypothalamus and the pituitary Endocrinology 142 2001 3265 3268
52. M. Kishida, B.I. Baker, and A.N. Eberle The measurement of melanin-concentrating hormone in trout blood Gen. Comp. Endocrinol. 74 1989 221 229
53. B. Lakaye, A. Minet, W. Zorzi, and T. Grisar Cloning of the rat cDNA encoding for the SLC-1 G protein-coupled receptor reveals the presence of an intron in the gene Biochim. Biophys. Acta 1401 1998 216 220
54. P.M. Lembo, E. Grazzini, J. Cao, D.A. Hubatsch, M. Pelletier, and C. Hoffert The receptor for the orexigenic peptide melanin-concentrating hormone is a G-protein-coupled receptor Nat. Cell Biol. 1 1999 267 271
55. X. Lin, H. Volkoff, Y. Narnaware, N.J. Bernier, P. Peyon, and R.E. Peter Brain regulation of feeding behavior and food intake in fish Comp. Biochem. Physiol. Part A 126 2000 415 434
56. D.W. Logan, R.J. Bryson-Richardson, K.E. Pagan, M.S. Taylor, P.D. Currie, and I.J. Jackson The structure and evolution of the melanocortin and MCH receptors in fish and mammals Genomics 81 2003 184 191
57. D.W. Logan, R.J. Bryson-Richardson, M.S. Taylor, P. Currie, and I.J. Jackson Sequence characterization of teleost fish melanocortin receptors Ann. NY Acad. Sci. 994 2003 319 330
58. D.S. Ludwig, K.G. Mountjoy, J.B. Tatro, J.A. Gillette, R.C. Frederich, and J.S. Flier Melanin-concentrating hormone: a functional melanocortin antagonist in the hypothalamus Am. J. Physiol. 274 1998 E627 E633
59. D.S. Ludwig, N.A. Tritos, J.W. Mastaitis, R. Kulkarni, E. Kokkotou, and J. Elmquist Melanin-concentrating hormone overexpression in transgenic mice leads to obesity and insulin resistance J. Clin. Invest. 107 2001 379 386
60. D.J. Marsh, D.T. Weingarth, D.E. Novi, H.Y. Chen, M.E. Trumbauer, and A.S. Chen Melanin-concentrating hormone 1 receptor-deficient mice are lean, hyperactive, and hyperphagic and have altered metabolism Proc. Natl. Acad. Sci. USA 99 2002 3240 3245
61. C.D. Minth, H. Qiu, H. Akil, S.J. Watson, and J.E. Dixon Two precursors of melanin-concentrating hormone: DNA sequence analysis and in situ immunochemical localization Proc. Natl. Acad. Soc. USA 86 1989 4292 4296
62. M. Mori, M. Harada, Y. Terao, T. Sugo, T. Watanabe, and Y. Shimomura Cloning of a novel G protein-coupled receptor, SLT, a subtype of the melanin-concentrating hormone receptor Biochem. Biophys. Res. Commun. 283 2001 1013 1018
63. M.E. Monzon, M.M. Varas, and S.R. De Barioglio Anxiogenesis induced by nitric oxide synthase inhibition and anxiolytic effect of melanin-concentrating hormone (MCH) in rat brain Peptides 22 2001 1043 1947
64. J.F. Murray, Baker Bl, A. Levy, and C.A. Wilson The influence of gonadal steroids on Pre-pro melanin-concentrating hormone mRNA in female rats J. Neuroendocrinol. 12 2000 53 59
65. J.L. Nahon The melanin-concentrating hormone: from the peptide to the gene Crit. Rev. Neurobiol. 8 1994 221 262
66. J.L. Nahon, F. Presse, J.C. Bittencourt, P.E. Sawchenko, and W. Vale The rat melanin-concentrating hormone messenger ribonucleic acid encodes multiple putative neuropeptides coexpressed in the dorsolateral hypothalamus Endocrinology 125 1989 2056 2065
67. J.L. Nahon, F. Presse, R. Schoepfer, and W. Vale Identification of a single melanin-concentrating hormone messenger ribonucleic acid in coho salmon: structural relatedness with 7SL ribonucleic acid J. Neuroendocrinol. 3 1991 173 183
68. N. Naito, I. Kawazoe, Y. Nakai, H. Kawauchi, and T. Hirano Coexistence of immunoreactivity for melanin-concentrating hormone and α-melanocyte stimulating hormone in the hypothalamus of the rat Neurosci. Lett. 70 1986 81 85
69. P. Navarra, S. Tsagarakis, D.H. Coy, L.H. Rees, G.M. Besser, and A.B. Grossman Rat melanin concentrating hormone does not modify the release of CRH-41 from rat hypothalamus or ACTH from the anterior pituitary in vitro J. Endocrinol. 127 1990 R1 R4
70. M. Ono, C. Wada, I. Oikawa, I. Kawazoe, and H. Kawauchi Structures of two kinds of mRNA encoding the chum salmon melanin-concentrating hormone Gene 71 1988 433 438
71. N. Oshima, H. Kasukawa, R. Fijii, B.C. Wilkes, V.J. Hruby, and A.M. Castrucci Melanin-concentrating hormone (MCH) effects on teleost (Chrysiptera cyanea) melanophore J. Exp. Zool. 235 1985 175 180
72. N. Oshima, N. Nakamaru, S. Araki, and M. Sugimoto Comparative analyses of the pigment-aggregating and -dispersing actions of MCH on fish chromatophores Comp. Biochem. Physiol. C: Toxicol. Pharmacol. 129 2001 75 84
73. M. Pandolfi, M.M. Canepa, M.A. Ravaglia, M.C. Maggese, D.A. Paz, and P.G. Vissio Melanin-concentrating hormone system in the brain and skin of the cichlid fish Cichlasoma dimerus: anatomical localization, ontogeny and distribution in comparison to alpha-melanocyte-stimulating hormone-expressing cells Cell Tissue Res. 311 2003 61 69
74. P. Pissios, and E. Maratos-Flier Melanin-concentrating hormone: from fish skin to skinny mammals Trends Endocrinol. Metab. 14 2003 243 248
75. F. Presse, J.L. Nahon, W.H. Fischer, and W. Vale Structure of the human melanin concentrating hormone mRNA Mol. Endocrinol. 4 1990 632 637
76. L.E. Pritchard, A.V. Turnbull, and A. White Pro-opiomelanocortin processing in the hypothalamus: impact on melanocortin signaling and obesity J. Endocrinol. 172 2002 411 421
77. D. Qu, D.S. Ludwig, S. Gammeltoft, M. Piper, M.A. Pelleymounter, and M.J. Cullen A role for melanin-concentrating hormone in the central regulation of feeding behaviour Nature 380 1996 243 247
78. M. Rodriguez, P. Beauverger, I. Naime, H. Rique, C. Ouvry, and S. Souchaud Cloning and molecular characterization of the novel human melanin-concentrating hormone receptor MCH2 Mol. Pharmacol. 60 2001 632 639
79. M. Rossi, S.J. Choi, D. O'Shea, T. Miyoshi, M.A. Ghatei, and S.R. Bloom Melanin-concentrating hormone acutely stimulates feeding, but chronic administration has no effect on body weight Endocrinology 138 1997 351 355
80. A.W. Sailer, H. Sano, Z. Zeng, T.P. McDonald, J. Pan, and S.S. Pong Identification and characterization of a second melanin-concentrating hormone receptor MCH-2R Proc. Natl. Acad. Sci. USA 98 2001 7564 7569
81. Y. Saito, H-P. Nothacker, Z. Wang, S. Lin, F. Leslie, and O. Civelli Molecular characterization of the melanin-concentrating hormone receptor Nature 400 1999 265 269
82. Y. Saito, M. Cheng, F.M. Leslie, and O. Civelli Expression of the melanin-concentrating hormone (MCH) receptor mRNA in the rat brain J. Comp. Neurol. 435 2001 26 40
83. M.S. Sanchez, M. Barontini, I. Armando, and M.E. Celis Correlation of increased grooming behavior and motor activity with alterations in nigrostriatal and mesolimbic catecholamines after alpha-melanotropin and neuropeptide glutamine-isoleucine injection in the rat ventral tegmental area Cell Mol. Neurobiol. 21 2001 523 533
84. C.B. Saper, T.C. Chou, and J.K. Elmquist The need to feed: homeostatic and hedonic control of eating Neuron 36 2002 199 211
85. G. Skofitsch, D.M. Jacobowitz, and N. Zamir Immunohistochemical localization of a melanin concentrating hormone-like peptide in the rat brain Brain. Res. Bull. 15 1985 635 649
86. L.P. Shearman, R.E. Camacho, D. Sloan Stribling, D. Zhou, M.A. Bednarek, and D.L. Hreniuk Chronic MCH-1 receptor modulation alters appetite, body weight and adiposity in rats Eur. J. Pharmacol. 475 2003 37 47
87. M. Shimada, N.A. Tritos, B.B. Lowell, J.S. Flier, and E. Maratos-Flier Mice lacking melanin-concentrating hormone are hypophagic and lean Nature 396 1998 670 674
88. Y. Shimomura, M. Mori, T. Sugo, Y. Ishibashi, M. Abe, and T. Kurokawa Isolation and identification of melanin-concentrating hormone as the endogenous ligand of the SLC-1 receptor Biochem. Biophys. Res. Commun. 261 1999 622 626
89. A. Stricker-Krongrad, T. Dimitrov, and B. Beck Central and peripheral dysregulation of melanin-concentrating hormone in obese Zucker rats Brain Res. Mol. Brain Res. 92 2001 43 48
90. M. Suzuki, Y.K. Narnaware, B.I. Baker, and A. Levy Influence of environmental colour and diurnal phase on MCH gene expression in the trout J. Neuroendocrinol. 7 1995 319 328
91. Takahashi A, Tsuchiya K, Yamanome T, Amano M, Yasuda A, Yamori K, et al. Possible involvement of melanin-concentrating hormone in food intake in a teleost, barfin flounder. Peptides, in press.
92. Y. Takayama, C. Wada, H. Kawauchi, and M. Ono Structures of two genes coding for melanin-concentrating hormone of chum salmon Gene 80 1989 65 73
93. C.P. Tan, H. Sano, H. Iwaasa, J. Pan, A.W. Sailer, and D.L. Hreniuk Melanin-concentrating hormone receptor subtypes 1 and 2: species-specific gene expression Genomics 79 2002 785 792
94. C. Vaisse, K. Clement, B. Guy-Grand, and P. Froguel A frameshift mutation in human MC4R is associated with a dominant form of obesity Nat. Genet. 20 1998 113 114
95. M. Varas, M. Perez, O. Ramirez, and S.R. de Barioglio Melanin concentrating hormone increase hippocampal synaptic transmission in the rat Peptides 23 2002 151 155
96. M. Varas, M. Perez, M.E. Monzon, and S.R. de Barioglio Melanin-concentrating hormone, hippocampal nitric oxide levels and memory retention Peptides 23 2002 2213 2221
97. M. Verlaet, A. Adamantidis, B. Coumans, G. Chanas, W. Zorzi, and E. Heinen Human immune cells express ppMCH mRNA and functional MCHR1 receptor FEBS Lett. 527 2002 205 210
98. S. Wang, J. Behan, K. O'Neill, B. Weig, S. Fried, and T. Laz Identification and pharmacological characterization of a novel human melanin-concentrating hormone receptor, mch-r2 J. Biol. Chem. 276 2001 34664 34667