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首页> 外文期刊>Frontiers in neuroendocrinology >Neuroendocrine regulation of GnRH release in induced ovulators.
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Neuroendocrine regulation of GnRH release in induced ovulators.

机译：诱导排卵中GnRH释放的神经内分泌调节。

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摘要

GnRH is the key neuropeptide controlling reproductive function in all vertebrate species. Two different neuroendocrine mechanisms have evolved among female mammals to regulate the mediobasal hypothalamic (MBH) release of GnRH leading to the preovulatory secretion of LH by the anterior pituitary gland. In females of spontaneously ovulating species, including rats, mice, guinea pigs, sheep, monkeys, and women, ovarian steroids secreted by maturing ovarian follicles induce a pulsatile pattern of GnRH release in the median eminence that, in turn, stimulates a preovulatory LH surge. In females of induced ovulating species, including rabbits, ferrets, cats, and camels, the preovulatory release of GnRH, and the resultant preovulatory LH surge, is induced by the receipt of genital somatosensory stimuli during mating. Induced ovulators generally do not show "spontaneous" steroid-induced LH surges during their reproductive cycles, suggesting that the positive feedback actions of steroid hormones on GnRH release are reduced or absent in these species. By contrast, mating-induced preovulatory surges occasionally occur in some spontaneously ovulating species. Most research in the field of GnRH neurobiology has been performed using spontaneous ovulators including rat, guinea pig, sheep, and rhesus monkey. This review summarizes the literature concerning the neuroendocrine mechanisms controlling GnRH biosynthesis and release in females of several induced ovulating species, and whenever possible it contrasts the results with those obtained for spontaneously ovulating species. It also considers the adaptive, evolutionary benefits and disadvantages of each type of ovulatory control mechanism. In females of induced ovulating species estradiol acts in the brain to induce aspects of proceptive and receptive sexual behavior. The primary mechanism involved in the preovulatory release of GnRH among induced ovulators involves the activation of midbrain and brainstem noradrenergic neurons in response to genital-somatosensory signals generated by receipt of an intromission from a male during mating. These noradrenergic neurons project to the MBH and, when activated, promote the release of GnRH from nerve terminals in the median eminence. In contrast to spontaneous ovulators, there is little evidence that endogenous opioid peptides normally inhibit MBH GnRH release among induced ovulators. Instead, the neural signals that induce a preovulatory LH surge in these species seem to be primarily excitatory. A complete understanding of the neuroendocrine control of ovulation will only be achieved in the future by comparative studies of several animal model systems in which mating-induced as well as spontaneous, hormonally stimulated activation of GnRH neurons drives the preovulatory LH surge. Copyright 2000 Academic Press.
机译：GnRH是控制所有脊椎动物物种生殖功能的关键神经肽。在雌性哺乳动物中已经进化出两种不同的神经内分泌机制来调节中下丘脑（MBH）释放的GnRH，从而导致垂体前叶LH排卵前的分泌。在自发排卵物种的雌性中，包括大鼠，小鼠，豚鼠，绵羊，猴子和妇女，由成熟卵泡分泌的卵巢类固醇会引起中位隆起的GnRH释放的脉动模式，进而刺激排卵前LH激增。 。在诱导排卵物种（包括兔子，雪貂，猫和骆驼）的雌性中，GnRH的排卵前释放以及由此产生的排卵前LH激增是由交配期间接受生殖器体感刺激引起的。诱导的排卵者通常在其生殖周期中未显示出“自发的”类固醇诱导的LH激增，表明这些物种中类固醇激素对GnRH释放的正反馈作用减少或不存在。相比之下，在某些自然排卵的物种中偶尔会发生交配引起的排卵前期激增。 GnRH神经生物学领域的大多数研究都是使用自发排卵器进行的，包括大鼠，豚鼠，绵羊和恒河猴。这篇综述总结了有关控制几种诱导排卵物种的雌性中GnRH生物合成和释放的神经内分泌机制的文献，并尽可能将其结果与自发排卵物种的结果进行了对比。它还考虑了每种排卵控制机制的适应性，进化优势和劣势。在雌性诱导排卵物种中，雌二醇在大脑中发挥作用，从而诱发性行为和性行为。诱导的排卵者在排卵前释放GnRH的主要机制涉及中性和脑干去甲肾上腺素能神经元的激活，该过程是由于在交配期间收到雄性的生殖器体感信号而产生的。这些去甲肾上腺素能神经元投射到MBH，并在激活时促进GnRH从正中隆起的神经末梢释放。与自发排卵相比，几乎没有证据表明内源性阿片肽通常会抑制诱导排卵中的MBH GnRH释放。相反，在这些物种中引起排卵前LH激增的神经信号似乎主要是兴奋性的。未来只有通过几种动物模型系统的比较研究才能完全了解排卵的神经内分泌控制，在该模型中，交配诱导的以及自发的，激素刺激的GnRH神经元激活会驱动排卵前LH激增。版权所有2000学术出版社。

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