Kagawa Nao, Hirose Sayuri, Fujimoto Keiko, Nomura Chihomi, Fujita Yuuma, Honda Akira, Komori Mai
Department of Life Science, Faculty of Science and Technology, Kindai University, Higashiosaka, Osaka 577-8502, Japan.
Department of Life Science, Faculty of Science and Technology, Kindai University, Higashiosaka, Osaka 577-8502, Japan.
Gen Comp Endocrinol. 2017 Aug 1;249:48-54. doi: 10.1016/j.ygcen.2017.03.001. Epub 2017 Mar 6.
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.
社会互动调节着几种神经肽的表达，这些神经肽在哺乳动物的生殖系统中起着核心作用。非哺乳动物脊椎动物也有这些神经肽或类似物，然而，关于非哺乳动物物种生殖生理学的社会调节的研究却很有限。在本研究中，我们研究了在青鳉鱼（Oryzias latipes）中，雄性间竞争结果所导致的社会等级制度是否会影响促性腺激素释放激素（GnRHs）和亲吻素（Kiss1）的表达。将四条雄性青鳉鱼放入一个实验水箱中相互接触，并根据它们在短期竞争中攻击行为的频率，将其分为最具攻击性的优势鱼或最顺从的从属鱼。在长期竞争中，优势雄性和从属雄性保持着它们的社会等级。短期竞争结束后，从属雄性嗅球中的促性腺激素释放激素-3（GnRH3）水平显著高于优势雄性。长期竞争后，优势雄性视前区的促性腺激素释放激素-1（GnRH1）水平较高，而从属雄性腹侧结节核中的Kiss1水平较低。另一方面，在短期和长期竞争后，从属雄性和优势雄性的外侧瓣膜核中的促性腺激素释放激素-2（GnRH2）水平、室周后核中的Kiss1水平以及血浆11-酮睾酮（11-KT）浓度没有差异。这些结果表明，社会等级制度调节着雄性青鳉中GnRH1、GnRH3和Kiss1的表达，而不影响11-KT水平。
