Best Carol, Vijayan Mathilakath M
Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada.
Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada.
Gen Comp Endocrinol. 2018 Feb 1;257:220-226. doi: 10.1016/j.ygcen.2017.07.009. Epub 2017 Jul 13.
Maternal cortisol is essential for cortisol stress axis development and de novo production of this steroid commences only after hatch in zebrafish (Danio rerio). However, very little is known about the effect of elevated cortisol levels, during the critical period of stress axis activation, on larval performance. We tested the hypothesis that elevated cortisol levels post-hatch affect behavioural performance and this is mediated by glucocorticoid receptor (GR) activation in zebrafish larvae. The behavioural response included measuring larval activity in response to alternating light and dark cycles, as well as thigmotaxis. Zebrafish larvae at 3days post-fertilization were exposed to waterborne cortisol for 24h to mimic a steroid response to an early-life stressor exposure. Also, larvae were exposed to waterborne RU-486 (a GR antagonist) either in the presence or absence of cortisol to confirm GR activation. Co-treatment with RU-486 completely abolished the upregulation of cortisol-induced 11β-hydroxysteroid dehydrogenase type 2 transcript abundance, confirming GR signalling. Cortisol-exposed larvae displayed increased locomotor activity irrespective of light condition, but showed no changes in thigmotaxis. This cortisol-mediated behavioural response was not affected by co-treatment with RU-486. Cortisol exposure also did not modify the transcript abundances of GR and mineralocorticoid receptor (MR) in zebrafish larvae. Altogether, cortisol stress axis activation post-hatch increases locomotor activity in zebrafish larvae. Our results suggest that GR signalling may not be involved in this behavioural response, leading to the proposal that cortisol action via MR signalling may influence locomotor activity in zebrafish larvae.
母体皮质醇对于皮质醇应激轴的发育至关重要，并且这种类固醇的从头合成仅在斑马鱼（Danio rerio）孵化后才开始。然而，在应激轴激活的关键时期，关于皮质醇水平升高对幼体性能的影响，我们知之甚少。我们测试了这样一个假设：孵化后皮质醇水平升高会影响行为表现，并且这是由斑马鱼幼体中的糖皮质激素受体（GR）激活介导的。行为反应包括测量幼体对明暗交替周期的活动反应以及趋触性。将受精后3天的斑马鱼幼体暴露于水中的皮质醇24小时，以模拟对早期生活应激源暴露的类固醇反应。此外，在有或没有皮质醇的情况下，将幼体暴露于水中的RU - 486（一种GR拮抗剂）以确认GR激活。与RU - 486共同处理完全消除了皮质醇诱导的2型11β - 羟类固醇脱氢酶转录本丰度的上调，证实了GR信号传导。暴露于皮质醇的幼体无论光照条件如何，运动活性都增加，但趋触性没有变化。这种皮质醇介导的行为反应不受与RU - 486共同处理的影响。皮质醇暴露也没有改变斑马鱼幼体中GR和盐皮质激素受体（MR）的转录本丰度。总之，孵化后皮质醇应激轴的激活增加了斑马鱼幼体的运动活性。我们的结果表明，GR信号传导可能不参与这种行为反应，这导致有人提出，通过MR信号传导的皮质醇作用可能会影响斑马鱼幼体的运动活性。
