ESTROGEN INFLUENCES ON NEUROENDOCRINE AGING

雌激素对神经内分泌衰老的影响

• 批准号: 6299415
• 负责人: ANDREA C GORE
• 金额: $ 32.12万
• 依托单位: MOUNT SINAI SCHOOL OF MEDICINE OF CUNY
• 依托单位国家: 美国
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-04-01 至 2001-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6299415
• 关键词: Macaca mulatta; NMDA receptors; RNase protection assay; age difference; animal old age; estrogens; female; gene expression; glutamates; gonadotropin releasing factor; high performance liquid chromatography; hormone regulation /control mechanism; hormone therapy; hypothalamus; immunocytochemistry; laboratory rat; menopause; messenger RNA; neurons; neuroregulation; ovariectomy; perfusion; radioimmunoassay; receptor expression; reproductive development; western blottings

Reproductive aging is characterized by changes in estrogen levels; however, the brain itself is subject to age-related changes, some of which may be consequences of altered estrogen levels, and others which may be estrogen-independent. Therefore, the present proposal will examine the interactions of estrogen with hypothalamic neurons in the brain during reproductive senescence. Studies will focus on estrogen regulation of gonadotropin-releasing hormone (GnRH) neurons, the key cells regulating the reproductive axis, as well as the mediation of estrogen's effects on GnRH neurons by glutamatergic neurons, acting via the NMDA receptor. In order to better characterize effects of estrogen and hypothalamic aging, as well as their interactions, studies will be performed in the experimental model of ovariectomy (OVX), with or without estrogen replacement, as well as the natural model of ovarian- intact animals, at different stages of reproductive function and endogenous estrogen levels. Specific Aims 1 and 2 will investigate mechanisms for estrogen's effects on hypothalamic function during aging in young, middle-aged (MA) and old Sprague-Dawley OVX rats, given long-term or short-term estrogen or vehicle replacement (Aim 1) or in ovarian-intact young, MA and old rats during the estrous cycle (Aim 2). For Aim 2, animals are utilized on pro-estrus the day of the pre-ovulatory GnRH/LH surge, with high estrogen levels, or on diestrus I, a day of low estrogen levels. Acyclic rats will be utilized on persistent estrus (high estrogen) or persistent estrus (high estrogen) or persistent diestrus (low estrogen). In both of these aims, effects of estrogen on GnRH and NMDA receptor subunit mRNAs and proteins will be quantitated by RNase protection assay and Western blots, respectively. The localization of NMDA receptor subunits on GnRH neurons, and their regulation by estrogen and aging, will be determined. The responsiveness of the GnRH neurosecretory system to administration of an NMDA receptor agonist will also be assessed. Specific Aims 3 and 4 will investigate the physiological changes in estrogen regulation of hypothalamic neurons, using the rhesus monkey, with its 28 day menstrual cycle, as an experimental model. Aim 3 will examine changes in hypothalamic GnRH and glutamate release and the regulation of GnRH release by NMDA receptor activation in OVX young and old monkeys, with or without long-term or short-term estrogen replacement. Aim 4 will make similar measurements in ovarian-intact young and old rhesus monkeys across the natural menstrual cycle during periods of high estrogen (late follicular phase) or low estrogen (late luteal phase); comparisons will be made with amenorrheic aged monkeys. Experiments are anticipated to provide insight into the neurobiological effects of an estrogen deficiency at menopause.

生殖衰老的特点是雌激素水平的变化；然而，大脑本身会发生与年龄相关的变化，其中一些可能是雌激素水平改变的结果，而另一些则可能与雌激素无关。因此，本提案将研究生殖衰老过程中雌激素与大脑下丘脑神经元的相互作用。研究重点是雌激素对促性腺激素释放激素 (GnRH) 神经元（调节生殖轴的关键细胞）的调节，以及谷氨酸能神经元通过 NMDA 受体介导雌激素对 GnRH 神经元的影响。为了更好地表征雌激素和下丘脑衰老的影响及其相互作用，将在有或没有雌激素替代的卵巢切除术（OVX）实验模型以及卵巢完整动物的自然模型中进行研究，不同阶段的生殖功能和内源性雌激素水平。具体目标 1 和 2 将研究在给予长期或短期雌激素或媒介物替代（目标 1）或发情周期期间卵巢完整的幼鼠、MA 和老年大鼠（目标 2）。对于目标 2，动物在发情前（排卵前 GnRH/LH 激增当天）使用，雌激素水平较高，或在动情间期 I（雌激素水平较低的一天）使用。无周期大鼠将用于持续发情（高雌激素）或持续发情（高雌激素）或持续发情间期（低雌激素）。在这两个目标中，雌激素对 GnRH 和 NMDA 受体亚基 mRNA 和蛋白质的影响将分别通过 RNase 保护测定和蛋白质印迹进行定量。 NMDA 受体亚基在 GnRH 神经元上的定位及其受雌激素和衰老的调节将被确定。还将评估 GnRH 神经分泌系统对 NMDA 受体激动剂给药的反应性。具体目标3和4将使用具有28天月经周期的恒河猴作为实验模型，研究雌激素调节下丘脑神经元的生理变化。目标 3 将检查 OVX 幼猴和老年猴中下丘脑 GnRH 和谷氨酸释放的变化以及 NMDA 受体激活对 GnRH 释放的调节，无论有或没有长期或短期雌激素替代。目标 4 将在高雌激素（卵泡期晚期）或低雌激素（黄体期晚期）期间的自然月经周期中，对卵巢完整的年轻和年老恒河猴进行类似的测量；将与闭经的老年猴子进行比较。预计实验将深入了解绝经期雌激素缺乏的神经生物学影响。