title: Effects of melanocortin-4 receptor agonists and antagonists on expression of genes related to reproduction in spotted scat, Scatophagus argus.
abstract: Melanocortin-4 receptor (Mc4r) function related to reproduction in fish has not been extensively investigated. Here, we report on gene expression changes by real-time PCR following treatment with Mc4r agonists and antagonists in the spotted scat (Scatophagus argus). Using in vitro incubated hypothalamus, the Mc4r nonselective agonist NDP-MSH ([Nle4, D-Phe7]-α-melanocyte stimulating hormone; 10-6M) and selective agonist THIQ (N-[(3R)-1, 2, 3, 4-Tetrahydroisoquinolinium-3-ylcarbonyl]- (1R)-1-(4-chlorobenzyl)-2-[4-cyclohexyl-4-(1H-1,2,4-triazol-1-ylmethyl) piperidin-1-yl]-2-oxoethylamine; 10-7M) significantly increased the expression of gnrh (Gonadotropin releasing hormone), while the Mc4r nonselective antagonist SHU9119 (Ac-Nle-[Asp-His-DPhe/DNal(2')-Arg-Trp-Lys]-NH2; 10-6M) and selective antagonist Ipsen 5i (compound 5i synthesized in Ipsen Research Laboratories; 10-6M) significantly inhibited gnrh expression after 3 h of incubation. In incubated pituitary tissue, NDP-MSH and THIQ significantly increased the expression of fshb (Follicle-stimulating hormone beta subunit) and lhb (Luteinizing hormone beta subunit), while SHU9119 and Ipsen 5i significantly decreased fshb and lhb expression after 3 h of incubation. During the in vivo experiment, THIQ (1 mg/kg bw) significantly increased gnrh expression in hypothalamic tissue, as well as the fshb and lhb expression in pituitary tissue 12 h after abdominal injection. Furthermore, Ipsen 5i (1 mg/kg bw) significantly inhibited gnrh expression in hypothalamic tissue, as well as fshb and lhb gene expression in pituitary tissue 12 h after abdominal injection. In summary, Mc4r singling appears to stimulate gnrh expression in the hypothalamus, thereby modulating the synthesis of Fsh and Lh in the pituitary. In addition, Mc4r also appears to directly regulate fshb and lhb levels in the pituitary in spotted scat. Our study suggests that Mc4r, through the hypothalamus and pituitary, participates in reproductive regulation in fish.
authors.affiliation: Key Laboratory of Marine Ecology and Aquaculture Environment of Zhanjiang, Key Laboratory of Aquaculture in South China Sea for Aquatic Economic Animal of Guangdong Higher Education Institutes, Fisheries College, Guangdong Ocean University, Zhanjiang, 524088, China.
authors.forename: Dong-Neng
authors.initials: DN
authors.lastname: Jiang
authors.affiliation: Key Laboratory of Marine Ecology and Aquaculture Environment of Zhanjiang, Key Laboratory of Aquaculture in South China Sea for Aquatic Economic Animal of Guangdong Higher Education Institutes, Fisheries College, Guangdong Ocean University, Zhanjiang, 524088, China.
authors.forename: Jian-Tao
authors.initials: JT
authors.lastname: Li
authors.affiliation: Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL, 36849, USA.
authors.forename: Ya-Xiong
authors.initials: YX
authors.lastname: Tao
authors.affiliation: Key Laboratory of Marine Ecology and Aquaculture Environment of Zhanjiang, Key Laboratory of Aquaculture in South China Sea for Aquatic Economic Animal of Guangdong Higher Education Institutes, Fisheries College, Guangdong Ocean University, Zhanjiang, 524088, China.
authors.forename: Hua-Pu
authors.initials: HP
authors.lastname: Chen
authors.affiliation: Key Laboratory of Marine Ecology and Aquaculture Environment of Zhanjiang, Key Laboratory of Aquaculture in South China Sea for Aquatic Economic Animal of Guangdong Higher Education Institutes, Fisheries College, Guangdong Ocean University, Zhanjiang, 524088, China.
authors.forename: Si-Ping
authors.initials: SP
authors.lastname: Deng
authors.affiliation: Key Laboratory of Marine Ecology and Aquaculture Environment of Zhanjiang, Key Laboratory of Aquaculture in South China Sea for Aquatic Economic Animal of Guangdong Higher Education Institutes, Fisheries College, Guangdong Ocean University, Zhanjiang, 524088, China.
authors.forename: Chun-Hua
authors.initials: CH
authors.lastname: Zhu
authors.affiliation: Key Laboratory of Marine Ecology and Aquaculture Environment of Zhanjiang, Key Laboratory of Aquaculture in South China Sea for Aquatic Economic Animal of Guangdong Higher Education Institutes, Fisheries College, Guangdong Ocean University, Zhanjiang, 524088, China. guangli211@163.com.
authors.forename: Guang-Li
authors.initials: GL
authors.lastname: Li
mesh_terms: D000818:Animals; D005260:Female; D029941:Fish Proteins / Q000235:genetics*; D037201:Follicle Stimulating Hormone, beta Subunit / Q000235:genetics; D005786:Gene Expression Regulation / Q000187:drug effects; D007987:Gonadotropin-Releasing Hormone / Q000235:genetics; D007031:Hypothalamus / Q000187:drug effects; D037101:Luteinizing Hormone, beta Subunit / Q000235:genetics; D009074:Melanocyte-Stimulating Hormones / Q000494:pharmacology; D009924:Organ Culture Techniques / Q000379:methods; D010473:Perciformes / Q000502:physiology*; D044105:Receptor, Melanocortin, Type 4 / Q000819:agonists* / Q000037:antagonists & inhibitors* / Q000235:genetics; D012098:Reproduction / Q000187:drug effects / Q000235:genetics; D044005:Tetrahydroisoquinolines / Q000494:pharmacology; D014230:Triazoles / Q000494:pharmacology; D000521:alpha-MSH / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: D029941:Fish Proteins; D037201:Follicle Stimulating Hormone, beta Subunit; D037101:Luteinizing Hormone, beta Subunit; C467221:N-(1,2,3,4-tetrahydroisoquinolinium-3-ylcarbonyl)-1-(4-chlorobenzyl)-2-(4-cyclohexyl-4-(1H-1,2,4-triazol-1-ylmethyl)piperidin-1-yl)-2-oxoethylamine; D044105:Receptor, Melanocortin, Type 4; D044005:Tetrahydroisoquinolines; D014230:Triazoles; C103272:SHU 9119; D007987:Gonadotropin-Releasing Hormone; D000521:alpha-MSH; C027756:MSH, 4-Nle-7-Phe-alpha-; D009074:Melanocyte-Stimulating Hormones
keywords: Follicle-stimulating hormone and luteinizing hormone; Gonadotropin-releasing hormone; Mc4r agonist and antagonist; Melanocortin-4 receptor; Scatophagus argus