Gonadotropin-releasing hormone (GnRH) is a key neuropeptide of the reproductive system. However, little is known about the role of GnRH in the spotted scat (Scatophagus argus). Here, three GnRH subtypes (cGnRH-II, sGnRH, and sbGnRH) were identified in the spotted scat. cGnRH-II and sGnRH were only expressed in the brains and gonads of both male and female fish, exhibiting a tissue-specific expression pattern, while sbGnRH was expressed at different transcription levels in all examined tissues. During ovarian maturation, hypothalamus-associated sbGnRH was upregulated, while the expression of sGnRH was variable and cGnRH-II first increased and then decreased. In vivo experiments showed that sbGnRH significantly promoted the expression of fsh and lh genes in a dose-dependent manner and exhibited a desensitization effect on lh expression at high concentrations. For sGnRH and cGnRH-II, only high concentrations could induce fsh and lh expression. Furthermore, treatment with highly concentrated sbGnRH peptide also induced fsh and lh expression, whereas the sGnRH and cGnRH-II peptides only induced fsh expression in vitro. 17β-Estradiol (E₂) significantly inhibited the expression of sbGnRH mRNA in a dose-dependent manner and did not impact sGnRH and cGnRH-II mRNA levels in vivo or in vitro. The inhibitory effect of E₂ on sbGnRH expression was attenuated by the estrogen receptor (ER) broad-spectrum antagonist (fulvestrant) and the ERα-specific antagonist (methyl-piperidinopyrazole), respectively, implying that the feedback regulation on sbGnRH is mediated via ERα. This study provides a theoretical basis for the reproductive endocrinology of the spotted scat by studying GnRH.

促性腺激素释放激素（GnRH）是生殖系统的关键神经肽。然而，人们对GnRH在斑点粪便（Scatophagus argus）中的作用知之甚少。在这里，在斑点猫中鉴定出三种GnRH亚型（cGnRH-II，sGnRH和sbGnRH）。cGnRH-II和sGnRH仅在雄性和雌性鱼类的大脑和性腺中表达，表现出组织特异性表达模式，而sbGnRH在所有检查的组织中以不同的转录水平表达。在卵巢成熟过程中，下丘脑相关的sbGnRH上调，而sGnRH的表达却是可变的，而cGnRH-II先升高后降低。体内实验表明，sbGnRH显着促进了fsh和lh的表达基因以剂量依赖的方式表达，并且在高浓度下对lh表达表现出脱敏作用。对于sGnRH和cGnRH-II，只有高浓度才能诱导fsh和lh表达。此外，用高度浓缩的sbGnRH肽处理也诱导了fsh和lh表达，而sGnRH和cGnRH-II肽仅在体外诱导fsh表达。17β-雌二醇（E ₂）以剂量依赖性方式显着抑制sbGnRH mRNA的表达，并且在体内或体外均不影响sGnRH和cGnRH-II mRNA的水平。E ₂的抑制作用sbGnRH的表达分别被雌激素受体（ER）广谱拮抗剂（fulvestrant）和ERα特异性拮抗剂（甲基-哌啶子基吡唑）减弱，表明sbGnRH的反馈调节是通过ERα介导的。本研究通过研究GnRH为斑点粪便的生殖内分泌学提供了理论基础。