Laboratory of Regulatory Biology, Graduate School of Science and Engineering, University of Toyama Toyama, Japan.
Front Endocrinol (Lausanne). 2012 Oct 17;3:122. doi: 10.3389/fendo.2012.00122. eCollection 2012.
Gonadotropin-releasing hormone (GnRH) is an evolutionarily conserved neuropeptide with 10 amino acid residues, of which several structural variants exist. A molecular form known as GnRH2 ([His(5) Trp(7) Tyr(8)]GnRH, also known as chicken GnRH II) is widely distributed in vertebrates except for rodents, and has recently been implicated in the regulation of feeding behavior in goldfish. However, the influence of GnRH2 on feeding behavior in other fish has not yet been studied. In the present study, therefore, we investigated the role of GnRH2 in the regulation of feeding behavior in a zebrafish model, and examined its involvement in food intake after intracerebroventricular (ICV) administration. ICV injection of GnRH2 at 0.1 and 1 pmol/g body weight (BW) induced a marked decrease of food consumption in a dose-dependent manner during 30 min after feeding. Cumulative food intake was significantly decreased by ICV injection of GnRH2 at 1 pmol/g BW during the 30-min post-treatment observation period. The anorexigenic action of GnRH2 was completely blocked by treatment with the GnRH type I receptor antagonist Antide at 25 pmol/g BW. We also examined the effect of feeding condition on the expression level of the GnRH2 transcript in the hypothalamus. Levels of GnRH2 mRNA obtained from fish that had been provided excess food for 7 days were higher than those in fish that had been fed normally. These results suggest that, in zebrafish, GnRH2 acts as an anorexigenic factor, as is the case in goldfish.
促性腺激素释放激素（GnRH）是一种具有 10 个氨基酸残基的进化上保守的神经肽，存在几种结构变体。一种称为 GnRH2（[His(5) Trp(7) Tyr(8)]GnRH，也称为鸡 GnRH II）的分子形式广泛存在于脊椎动物中，但不包括啮齿动物，最近被发现与金鱼的摄食行为调节有关。然而，GnRH2 对其他鱼类摄食行为的影响尚未得到研究。因此，本研究在斑马鱼模型中研究了 GnRH2 在摄食行为调节中的作用，并检查了其在脑室内（ICV）给药后对食物摄入的影响。ICV 注射 0.1 和 1 pmol/g 体重（BW）的 GnRH2 以剂量依赖的方式在进食后 30 分钟内显著减少食物消耗。ICV 注射 1 pmol/g BW 的 GnRH2 在 30 分钟的治疗观察期间显著减少了累积食物摄入量。用 GnRH 型 I 受体拮抗剂 Antide（25 pmol/g BW）处理可完全阻断 GnRH2 的厌食作用。我们还检查了摄食条件对下丘脑 GnRH2 转录本表达水平的影响。在给予过量食物 7 天的鱼类中获得的 GnRH2 mRNA 水平高于正常喂养的鱼类。这些结果表明，在斑马鱼中，GnRH2 作为一种厌食因子发挥作用，与金鱼的情况相同。
