性类固醇激素反馈调控神经内分泌系统是鱼类生殖过程的一个重要环节。然而，目前的研究多关注雄激素和雌激素的调控机理，而涉及孕酮激素的研究较少。我们近期研究明确发现，在鱼类生殖过程中发挥重要作用的孕酮类激素（17α，20β-双羟孕酮，DHP），能反馈调控斑马鱼垂体促性腺激素的表达。雌性大弹涂鱼在生殖高峰期呈现独特的半月周期产卵习性；我们的前期研究证实了褪黑素通过其位于卵泡上的受体参与了这一产卵习性的调控。然而，褪黑素虽能提高DHP的产量，但无法诱导卵子成熟，提示卵巢产生的DHP可能反馈调控促性腺激素表达，进而促进卵母细胞的成熟过程。基于上述研究基础，本项目拟以雌性大弹涂鱼为研究对象，应用活体注射、组织器官离体培养、原代细胞培养、RNA干扰、受体功能验证和转录组等技术方法，从细胞和分子水平，系统地研究孕酮类激素反馈调控促性腺激素表达的神经内分泌机理，为鱼类人工繁殖技术的完善提供科学依据。

In teleosts, the feedback regulation of gonadal steroids on reproductive neuroendocrine system is an important process of reproductive physiology. Much progress has been made in understanding the molecular mechanisms of feedback effects of androgens and estrogens, but potential effects of progestins on reproductive neuroendocrine system have received little attention. Our recent studies in zebrafish showed that 17α,20β-dihydroxy-4-pregnen-3-one (DHP), a most potent and biological relevant progestin produced in teleost, exhibited clear stimulatory effects on gonadotropins (Fshb and Lhb) expression. During reproductive peak period, the female mudskipper (Boleophthalmus pectinirostris) exhibits typical semilunar spawning rhythm (the fish stock spawns twice around the first and the last lunar quarters within a month). Our previous studies have demonstrated that melatonin and its receptors were involved in the synchronization of the semilunar spawning rhythm by acting directly on ovarian tissues to stimulate the production of DHP. However, the melatonin can not induce the oocyte maturation, which may suggest a potential feedback effects of DHP on the expression of gonadotropins which will enhance the maturation competence of oocyte. Based on these primary results, the present project aims to investigate the neuroendocrine pathway of the feedback effects of DHP on gonadotropins expression in the female mudskipper, by using intraperitoneal injection, tissue culture, primary cell culture, RNA interference, cloning and functional characterization of progesterone receptors and transcriptome analysis. The results from this study can not only further our understanding in reproductive endocrinology in teleost, but also provide useful scientific knowledge for improving the biotechnology of fish aquaculture in China.