Endocrine interaction of brain and gut that governs seawater adaptation in fishes

海洋硬骨鱼大量饮水，肠道吸收90%的海水，以应对渗透性脱水。因此，饮水和随后肠道对水的吸收对于在高渗的海洋环境中生存是必不可少的。转录组分析表明，大脑（饮水调节部位）和肠道（吸收调节部位）表达了多种激素基因，并在鳗鱼转入海水后表达上调。此外，大脑和肠道通过血流或受神经支配的神经调节饮酒和肠道吸收，从而相互作用。我们目前正在对水母中这些重要基因进行组织特异性敲低，以评估它们在海水适应中的作用。这是第一个证明大脑和肠道通过激素相互作用来适应海水的研究。

Marine teleosts drink copiously and absorb 90% of ingested seawater by the intestine to cope with osmotic dehydration. Thus, drinking and subsequent absorption of water by the intestine is essential to survive in hyperosmotic marine environment. The transcriptome analyses showed that the brain (regulatory site for drinking) and the gut (regulatory site for absorption) express several hormone genes and their expression is upregulated after transfer of eels to seawater. Furthermore, the brain and the gut interact with each other by regulating drinking and intestinal absorption through blood stream or via innervated nerves. We are currently performing tissue-specific knockdown of such important genes in medaka to evaluate their roles in seawater adaptation. This is the first study that demonstrate interactions between brain and gut via hormones for seawater adaptation.