title: Social rank-dependent expression of gonadotropin-releasing hormones and kisspeptin in the medaka brain.
abstract: Social interactions regulate the expression of several neuropeptides that have a central role in the reproductive system of mammals. Nonmammalian vertebrates also have these neuropeptides or paralogs, however, studies on the social regulation of reproductive physiology in nonmammalian species are limited. In this study, we examined whether the expression of gonadotropin-releasing hormones (GnRHs) and kisspeptin (Kiss1) is affected by social hierarchy resulting from the outcomes of male-male competition in medaka fish (Oryzias latipes). Four males were introduced to each other in an experimental tank, and classified as the most aggressive dominant or the most submissive subordinate fish, based on the frequency of their aggressive acts during a short-term competition. Dominant and subordinate males maintained their social rank during a long-term competition. Immediately after short-term competition, gonadotropin-releasing hormone-3 (GnRH3) level in the olfactory bulb was significantly higher in subordinate males than in dominant males. After long-term competition, dominant males had high level of gonadotropin-releasing hormone-1 (GnRH1) in the preoptic area, whereas subordinate males had lower Kiss1 level in the nucleus ventral tuberis. On the other hand, the levels of gonadotropin-releasing hormone-2 (GnRH2) in the nucleus lateralis valvulae and Kiss1 in the nucleus posterioris periventricularis, and plasma 11-ketotestosterone (11-KT) concentration did not differ between subordinate and dominant males after the short- and long-term competitions. These results suggest that social hierarchy regulates the expression of GnRH1, GnRH3, and Kiss1 without affecting 11-KT level in male medaka.
authors.affiliation: Department of Life Science, Faculty of Science and Technology, Kindai University, Higashiosaka, Osaka 577-8502, Japan. Electronic address: kagawa@life.kindai.ac.jp.
authors.forename: Nao
authors.initials: N
authors.lastname: Kagawa
authors.affiliation: Department of Life Science, Faculty of Science and Technology, Kindai University, Higashiosaka, Osaka 577-8502, Japan.
authors.forename: Sayuri
authors.initials: S
authors.lastname: Hirose
authors.affiliation: Department of Life Science, Faculty of Science and Technology, Kindai University, Higashiosaka, Osaka 577-8502, Japan.
authors.forename: Keiko
authors.initials: K
authors.lastname: Fujimoto
authors.affiliation: Department of Life Science, Faculty of Science and Technology, Kindai University, Higashiosaka, Osaka 577-8502, Japan.
authors.forename: Chihomi
authors.initials: C
authors.lastname: Nomura
authors.affiliation: Department of Life Science, Faculty of Science and Technology, Kindai University, Higashiosaka, Osaka 577-8502, Japan.
authors.forename: Yuuma
authors.initials: Y
authors.lastname: Fujita
authors.affiliation: Department of Life Science, Faculty of Science and Technology, Kindai University, Higashiosaka, Osaka 577-8502, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Honda
authors.affiliation: Department of Life Science, Faculty of Science and Technology, Kindai University, Higashiosaka, Osaka 577-8502, Japan.
authors.forename: Mai
authors.initials: M
authors.lastname: Komori
mesh_terms: D000374:Aggression; D000818:Animals; D001522:Behavior, Animal; D001921:Brain / Q000378:metabolism*; D007987:Gonadotropin-Releasing Hormone / Q000235:genetics* / Q000378:metabolism; D006608:Hierarchy, Social; D059648:Kisspeptins / Q000235:genetics* / Q000378:metabolism; D008297:Male; D009990:Oryzias / Q000097:blood / Q000378:metabolism*; D013739:Testosterone / Q000031:analogs & derivatives / Q000097:blood
chemical_list: D059648:Kisspeptins; D007987:Gonadotropin-Releasing Hormone; D013739:Testosterone; C003600:11-ketotestosterone
keywords: 11-Ketotestosterone; Gonadotropin-releasing hormone; Kisspeptin; Male-male competition; Medaka; Social rank