Urotensin I (UI), a member of the corticotropin-releasing hormone family of peptides, regulates a diverse array of physiological functions, including appetite regulation, defensive behavior and stress response. In this study, firstly, the tissue-specific distribution of UI mRNA in olive flounder (Paralichthys olivaceus) was characterized and we found that UI mRNA was highly expressed in caudal neurosecretory system (CNSS) tissue. Secondly, alignment analysis found that a conserved cAMP response binding (CREB) site and a TATA element were located in the proximal promoter of UI gene. In addition, treatment of forskolin activatated cAMP-CREB pathway and induced the up-regulation of UI mRNA in cultured CNSS, suggesting the role of CREB in regulating the UI mRNA expression. Furthermore, plasma UI concentration and UI mRNA in CNSS showed obvious daily rhythm, with higher values in the daytime while lower values in the nighttime. Thirdly, using bold personality (BP) and shy personality (SP) flounder as an animal model, we found that flounder exhibited significantly higher locomotor activity in the nighttime than in the daytime (P < 0.001), and BP flounder showed significantly higher locomotor activity (P < 0.001) compared with SP flounder both in the daytime and nighttime. Analysis of feeding behavior revealed that BP flounder showed a shorter latency to feed and more attacks to prey. Furthermore, the qPCR and immunohistochemistry results showed that BP flounder expressed significantly lower level of UI mRNA and protein in CNSS tissue. Collectively, our study suggested that the UI plays an important role in locomotor activity and appetite regulation, which provides a basis for understanding the mechanism of defensive behavior and animal personality in flounder.

Urotensin I (UI) 是促肾上腺皮质激素释放激素肽家族的成员，可调节多种生理功能，包括食欲调节、防御行为和压力反应。本研究首先研究了橄榄比目鱼（Paralichthys olivaceus） UI mRNA的组织特异性分布被表征，我们发现 UI mRNA 在尾神经分泌系统 (CNSS) 组织中高度表达。其次，比对分析发现一个保守的cAMP反应结合（CREB）位点和一个TATA元件位于UI基因的近端启动子。此外，毛喉素的处理激活了 cAMP-CREB ​​通路并诱导培养的 CNSS 中 UI mRNA 的上调，表明 CREB ​​在调节 UI mRNA 表达中的作用。此外，CNSS中血浆UI浓度和UI mRNA表现出明显的昼夜节律，白天较高，夜间较低。第三，以大胆性格（BP）和害羞性格（SP）比目鱼作为动物模型，我们发现比目鱼在夜间表现出明显高于白天的运动活动（P < 0.001)，BP 比目鱼 在白天和夜间均表现出明显高于SP 比目鱼的运动活性 ( P < 0.001)。对进食行为的分析表明，BP 比目鱼表现出更短的进食潜伏期和更多的对猎物的攻击。此外，qPCR 和免疫组化结果表明，BP 比目鱼在 CNSS 组织中表达的 UI mRNA 和蛋白质水平显着降低。总的来说，我们的研究表明 UI 在运动活动和食欲调节中起着重要作用，这为理解比目鱼的防御行为和动物性格机制提供了基础。