Metamorphosis, a widespread life history strategy in metazoans, allows dispersal and use of different ecological niches through a dramatic body change from a larval stage [1, 2]. Despite its conservation and importance, the molecular mechanisms underlying its initiation and progression have been characterized in only a few animal models. In this study, through pharmacological and gene functional analyses, we identified neurotransmitters responsible for metamorphosis of the ascidian Ciona. Ciona metamorphosis converts swimming tadpole larvae into vase-like, sessile adults. Here, we show that the neurotransmitter GABA is a key regulator of metamorphosis. We found that gonadotropin-releasing hormone (GnRH) is a downstream neuropeptide of GABA. Although GABA is generally thought of as an inhibitory neurotransmitter, we found that it positively regulates secretion of GnRH through the metabotropic GABA receptor during Ciona metamorphosis. GnRH is necessary for reproductive maturation in vertebrates, and GABA is an important excitatory regulator of GnRH in the hypothalamus during puberty [3, 4]. Our findings reveal another role of the GABA-GnRH axis in the regulation of post-embryonic development in chordates.

中文翻译：

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GABA诱导的GnRH释放触发氯酸盐变态。

变态是后生动物的一种广泛的生活史策略，它允许通过从幼体阶段发生剧烈的身体变化来分散和利用不同的生态位[1、2]。尽管它具有保守性和重要性，但仅在少数动物模型中表征了其启动和发展的分子机制。在这项研究中，通过药理和基因功能分析，我们确定了负责海鞘Ciona变态的神经递质。鬣蜥变态将游泳的幼虫转变成花瓶状，无柄的成虫。在这里，我们证明神经递质GABA是变态的关键调节因子。我们发现促性腺激素释放激素（GnRH）是GABA的下游神经肽。尽管通常认为GABA是抑制性神经递质，我们发现它在Ciona变态过程中通过代谢型GABA受体正调控GnRH的分泌。GnRH是脊椎动物生殖成熟所必需的，而GABA是青春期下丘脑中GnRH的重要兴奋性调节剂[3，4]。我们的发现揭示了GABA-GnRH轴在调节卵子后胚发育中的另一个作用。