Department of Integrative Biology, University of Guelph, Guelph, ON, Canada.
Gen Comp Endocrinol. 2011 Jan 15;170(2):365-73. doi: 10.1016/j.ygcen.2010.10.014. Epub 2010 Oct 25.
Sexually dimorphic stress responses are present in species across all vertebrate taxa and it has been suggested that these effects are mediated by circulating sex steroids. While a few species of fish have been identified as having a sexually dimorphic stress response, there is conflicting evidence as to the effects of sex steroids on the stress axis. In this study, we tested whether zebrafish exhibit a sexually dimorphic cortisol stress response and whether 17β-estradiol (E2) or 11-ketotestosterone (11KT) modulate the activity of the hypothalamic-pituitary-interrenal (HPI) axis. To accomplish this, we quantified the whole body cortisol response to a physical stressor, cortisol release in vitro, and the expression of key HPI axis regulating genes of control and E2- or 11KT-exposed zebrafish. Under control conditions no dimorphisms in the HPI axis were apparent at rest or in response to a standardized stressor. In contrast, E2-exposure blunted the cortisol response of male fish in vivo and in vitro and as well as corticotropin-releasing factor (crf) expression in the pre-optic area (POA) of the brain. While the expression of some interrenal genes was suppressed by E2-exposure, these changes occurred in both male and female zebrafish. 11KT-exposure increased whole-body cortisol of males at rest and vortex-exposed females, but had no impact on the rate of cortisol synthesis in vitro or on POA crf expression. Therefore, while we found no evidence that zebrafish exhibit a sexually dimorphic cortisol stress response, both E2 and 11KT can modulate the activity of the HPI axis in this species and do so via different mechanisms.
性二态应激反应存在于所有脊椎动物分类群的物种中，有人认为这些效应是由循环性激素介导的。虽然已经确定了一些鱼类物种具有性二态应激反应，但关于性激素对应激轴的影响存在相互矛盾的证据。在这项研究中，我们测试了斑马鱼是否表现出性二态皮质醇应激反应，以及 17β-雌二醇（E2）或 11-酮睾酮（11KT）是否调节下丘脑-垂体-肾上腺（HPI）轴的活性。为此，我们量化了全身皮质醇对物理应激源的反应、体外皮质醇释放以及控制和 E2 或 11KT 暴露的斑马鱼中关键 HPI 轴调节基因的表达。在对照条件下，HPI 轴在休息或对标准化应激源的反应中没有表现出二态性。相比之下，E2 暴露减弱了雄性鱼体内和体外的皮质醇反应以及脑前区（POA）的促肾上腺皮质释放因子（CRF）表达。虽然 E2 暴露抑制了一些肾上腺基因的表达，但这些变化发生在雄性和雌性斑马鱼中。11KT 暴露增加了休息时雄性和涡旋暴露的雌性斑马鱼的全身皮质醇，但对体外皮质醇合成率或 POA CRF 表达没有影响。因此，虽然我们没有发现斑马鱼表现出性二态皮质醇应激反应的证据，但 E2 和 11KT 都可以调节该物种 HPI 轴的活性，并且通过不同的机制。
