Physiology of Hypothalamic Neurosteroidal Progesterone

描述(申请人提供)：神经类固醇，在大脑中合成的类固醇，与从应激、抑郁、焦虑到认知的一系列功能有关。黄体酮是一种神经类固醇，它是一种与生殖调节有关的经典性激素。虽然中枢神经系统具有合成孕酮的能力，但到目前为止，似乎只有来自卵巢和肾上腺的外周孕酮才能调节生殖。我们的初步研究表明，雌激素诱导的下丘脑孕酮合成足以启动排卵和交配所需的生殖事件。去卵巢和去肾上腺(OVX/ADX)大鼠的雌激素刺激增加了下丘脑孕酮水平。在这些动物中，雌激素诱导了前凸行为和孕激素依赖的前向行为。类似地，雌激素刺激OVX/ADX大鼠导致黄体生成素(LH)激增。在这些大鼠中，阻断3β-羟基类固醇脱氢酶(3β-HSD)--一种将孕烯醇酮转化为孕酮的酶--可以阻止黄体生成素激增。雌激素刺激培养的星形胶质细胞合成孕酮，提示胶质细胞可能介导雌激素正反馈。这些数据表明，在没有外周类固醇生成组织的情况下，雌激素可以通过刺激神经类固醇孕酮的合成来诱导孕酮依赖事件。我们建议检验这一假设：雌激素刺激下丘脑孕酮的合成，从而激活调节黄体生成素峰值和性行为的回路。建议进行三个实验：首先，使用完整和OVX/ADX大鼠模型，我们将直接测试雌激素诱导的促黄体生成素激增是否依赖于下丘脑神经类固醇孕酮的增加。其次，我们建议在体外和体内确定雌激素是否增加合成孕酮所需的类固醇生成酶(P450侧链裂解和3β-HSD)的表达和/或活性。第三，使用相同的完整和OVX/ADX大鼠模型，我们将确定雌激素诱导的下丘脑孕酮是否足以促进性行为。这些研究将证明神经类固醇孕酮的生理学，并为中枢神经系统中雌激素正反馈的机制提供重要的新信息。

DESCRIPTION (provided by applicant): Neurosteroids, steroids synthesized in the brain, have been implicated in functions ranging from stress, depression, anxiety, to cognition. One neurosteroid is progesterone, a classic sex hormone involved in the regulation of reproduction. Although the CNS has the capacity to synthesize progesterone, to date it has appeared that only peripheral progesterone, from the ovaries and adrenals, regulates reproduction. Our preliminary studies have demonstrated that estrogen-induced hypothalamic progesterone synthesis is sufficient to initiate reproductive events necessary for ovulation and copulation. Estrogen stimulation of ovariectomized and adrenalectomized (ovx/adx) rats increased hypothalamic progesterone levels. In such animals, estrogen induced lordosis behavior and progesterone dependent proceptive behavior. Similarly, estrogen stimulation of ovx/adx rats induced a luteinizing hormone (LH) surge. In these rats, blocking 3beta-hydroxysteroid dehydrogenase (3beta-HSD), the enzyme that converts pregnenolone to progesterone, prevented the LH surge. Estrogen stimulates astrocytes in culture to synthesize progesterone, suggesting that glial cells may mediate estrogen-positive feedback. These data indicate that, absent the peripheral steroidogenic tissues, estrogen can induce progesterone dependent events by stimulating the synthesis of neurosteroidal progesterone. We propose to test the hypothesis: estrogen stimulates synthesis of hypothalamic progesterone that activates circuits regulating the LH surge and sexual behavior. Three experiments are proposed: First, using intact and ovx/adx rat models we will directly test whether the estrogen-induced LH surge is dependent on increased hypothalamic neurosteroidal progesterone. Second, we propose to determine whether estrogen increases the expression and/or activity of steroidogenic enzymes (P450 side chain cleavage and 3beta-HSD) needed to synthesize progesterone, in vitro and in vivo. Third, using the same intact and ovx/adx rat models, we will determine whether estrogen-induced hypothalamic progesterone is sufficient to facilitate sexual behavior. These studies will demonstrate the physiology of neurosteroidal progesterone and provide important new information about the mechanism of estrogen-positive feedback in the CNS.