Bond H, Warne J M, Balment R J
Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester M13 9PT, UK.
Gen Comp Endocrinol. 2007 Aug-Sep;153(1-3):221-7. doi: 10.1016/j.ygcen.2007.03.014. Epub 2007 May 5.
Arginine vasotocin (AVT) stimulates release of adenocorticotrophin hormone (ACTH) in trout. However, AVT's role in fish hypothalamic-pituitary-interrenal-axis (HPIA) is not fully understood. Here, we examined distribution of AVT and glucocorticoid receptor (GR) in the magnocellular preoptic nucleus (PM) and the AVT/cortisol response to acute restraint in flounder. The GR/AVT distribution in the PM was determined using double immunohistochemistry (IHC). Flounder were confined in nets, immersed in water for 30m, with plasma and tissue samples taken prior to, 3, 24 and 48h post-confinement. Plasma osmolality, Na(+), Cl(-) and cortisol were taken as indicators of HPIA activation. Plasma AVT was measured proVT mRNA expression in the PM was detected using in situ hybridisation (ISH) with a S35 labelled oligoprobe for homologous flounder proVT. Double IHC showed the presence of GR in AVT synthesising neurones of the PM. Plasma Na(+), Cl(-), osmolality and cortisol (1.0+/-0.9 to 183.6+/-3.1mM; p<0.001) increased significantly 3h post-restraint: recovering to control levels after 48h. Plasma AVT levels did not change. However, a concomitant increase in proVT mRNA expression in the magnocellular (PMm) and gigantocellular (PMg) neurones of the PM was observed (11.1+/-1.8 to 55.2+/-9.1% 24h post-restraint; p<0.001) and levels still remained significantly elevated at 48h (p<0.01). This suggests that PMm and PMg AVT neurones are associated with HPIA activation following acute restraint, including potential cortisol negative feedback. The extended elevation of hypothalamus proAVT mRNA expression following a single acute stressor affords a possible mechanism to moderate sensitivity of the HPIA to subsequent challenges.
精氨酸血管加压催产素（AVT）可刺激虹鳟鱼促肾上腺皮质激素（ACTH）的释放。然而，AVT在鱼类下丘脑-垂体-肾间轴（HPIA）中的作用尚未完全明确。在此，我们研究了牙鲆大细胞视前核（PM）中AVT和糖皮质激素受体（GR）的分布，以及牙鲆对急性束缚的AVT/皮质醇反应。采用双重免疫组织化学（IHC）法测定PM中的GR/AVT分布。将牙鲆限制在网中，浸于水中30分钟，在束缚前、束缚后3小时、24小时和48小时采集血浆和组织样本。将血浆渗透压、Na⁺、Cl⁻和皮质醇作为HPIA激活的指标。检测血浆AVT水平，并用针对牙鲆同源proVT的S35标记寡核苷酸探针通过原位杂交（ISH）检测PM中proVT mRNA的表达。双重IHC显示PM中合成AVT的神经元存在GR。束缚后3小时，血浆Na⁺、Cl⁻、渗透压和皮质醇（1.0±0.9至183.6±3.1mM；p<0.001）显著升高，48小时后恢复至对照水平。血浆AVT水平未发生变化。然而，观察到PM的大细胞（PMm）和巨细胞（PMg）神经元中proVT mRNA表达同时增加（束缚后24小时为11.1±1.8至55.2±9.1%；p<0.001），48小时时水平仍显著升高（p<0.01）。这表明PMm和PMg的AVT神经元与急性束缚后HPIA的激活有关，包括潜在的皮质醇负反馈。单次急性应激源后下丘脑proAVT mRNA表达的持续升高为调节HPIA对后续挑战的敏感性提供了一种可能的机制。
