Mode of action and functional significance of avian gonadotropin-inhibitory hormone (GnIH): a review.
Mode of action and functional significance of avian gonadotropin-inhibitory hormone (GnIH): a review.
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DOI：
10.1002/jez.a.305
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发表时间：
2006-09
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通讯作者：
K. Tsutsui;T. Ubuka;H. Yin;T. Osugi;K. Ukena;G. Bentley;N. Ciccone;Kazuhiko Inoue;V. S. Chowdhury;P. Sharp;J. Wingfield
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作者：
K. Tsutsui;T. Ubuka;H. Yin;T. Osugi;K. Ukena;G. Bentley;N. Ciccone;Kazuhiko Inoue;V. S. Chowdhury;P. Sharp;J. Wingfield
神经肽在垂体前叶水平控制促性腺激素分泌主要是通过下丘脑十肽促性腺激素释放激素（GnRH）的刺激作用。然而，直到最近，下丘脑神经肽作用于垂体水平以负调节促性腺激素分泌，在任何脊椎动物中仍然是未知的。2000年，我们在鹌鹑的下丘脑中发现了一种新的神经肽，在垂体水平抑制促性腺激素的释放，并将其命名为促性腺激素抑制激素（GnIH）。促性腺激素抑制系统是一个有趣的概念，并为我们提供了一个前所未有的机会，从一个全新的角度研究鸟类繁殖的调节。为了阐明GnIH的作用模式，我们进一步鉴定了GnIH的受体，并表征了其在鹌鹑中的表达和结合活性。所鉴定的GnIH受体具有7个跨膜结构域，并以浓度依赖性方式特异性结合GnIH。GnIH受体在垂体和包括下丘脑在内的多个脑区均有表达。这些结果表明，GnIH直接作用于垂体通过GnIH受体抑制促性腺激素释放。GnRH也可作用于下丘脑，抑制GnRH释放。为了了解GnIH在鸟类生殖中的功能意义，我们还研究了调节GnIH表达的机制。有趣的是，褪黑激素剂量依赖性地诱导GnIH表达和褪黑激素受体（Mel（1c））在GnIH神经元中表达。因此，褪黑激素似乎通过其受体直接作用于GnIH神经元以诱导GnIH表达。这些研究表明，GnIH可能是一种重要的调节鸟类繁殖的神经肽。
Neuropeptide control of gonadotropin secretion at the level of the anterior pituitary gland is primarily through the stimulatory action of the hypothalamic decapeptide, gonadotropin-releasing hormone (GnRH). However, a hypothalamic neuropeptide acting at the level of the pituitary to negatively regulate gonadotropin secretion has, until recently, remained unknown in any vertebrate. In 2000, we discovered a novel hypothalamic neuropeptide inhibiting gonadotropin release at the level of the pituitary in quail and termed it gonadotropin-inhibitory hormone (GnIH). A gonadotropin-inhibitory system is an intriguing concept and provides us with an unprecedented opportunity to study the regulation of avian reproduction from an entirely novel standpoint. To elucidate the mode of action of GnIH, we further identified the receptor for GnIH and characterized its expression and binding activity in quail. The identified GnIH receptor possessed seven transmembrane domains and specifically bound to GnIH in a concentration-dependent manner. The expression of GnIH receptor was found in the pituitary and several brain regions including the hypothalamus. These results suggest that GnIH acts directly on the pituitary via GnIH receptor to inhibit gonadotropin release. GnIH may also act on the hypothalamus to inhibit GnRH release. To understand the functional significance of GnIH in avian reproduction, we also investigated the mechanism that regulates GnIH expression. Interestingly, melatonin induced dose-dependently GnIH expression and melatonin receptor (Mel(1c)) was expressed in GnIH neurons. Thus melatonin appears to act directly on GnIH neurons via its receptor to induce GnIH expression. Based on these studies, GnIH is likely an important neuropeptide for the regulation of avian reproduction.