ESTROGEN INFLUENCES ON NEUROENDOCRINE AGING

雌激素对神经内分泌衰老的影响

• 批准号: 6098857
• 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: 1999
• 资助国家: 美国
• 起止时间: 1999-04-21 至 2000-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6098857
• 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.

生殖衰老的特征是雌激素水平的变化。但是，大脑本身会受到与年龄相关的变化的约束，其中一些可能是雌激素水平改变的后果，而另一些可能是与雌激素无关的结果。因此，本提案将检查雌激素在生殖衰老过程中与大脑中下丘脑神经元的相互作用。研究将侧重于促性腺激素释放激素（GNRH）神经元的雌激素调节，调节生殖轴的关键细胞，以及通过NMDA受体作用的谷氨酸能神经元对雌激素对GNRH神经元的影响的介导。为了更好地表征雌激素和下丘脑衰老及其相互作用的影响，在卵巢切除术（OVX）的实验模型中，将进行研究，并在卵巢完整动物的自然模型中，以及在生殖功能和内生雌激素水平的不同阶段。具体目的1和2将研究年轻，中年（MA）和旧的Sprague-Dawley OVX大鼠衰老期间雌激素对下丘脑功能的影响的机制，鉴于长期或短期的雌激素或车辆替代（AIM 1）或卵巢直觉的年轻人，MA和老鼠在ESTROUS周期期间（AIM 2）。对于AIM 2，在卵巢前GNRH/LH激增的那天，动物被用于促进，具有较高的雌激素水平，或Diestrus I（雌激素水平低的一天）。无环大鼠将用于持续的雌激素（高雌激素）或持续性雌激素（高雌激素）或持续性二肠（低雌激素）。在这两个目的中，雌激素对GnRH和NMDA受体亚基mRNA和蛋白质的影响分别通过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对雌激素和衰老的调节。 GNRH神经分泌系统对施用NMDA受体激动剂的响应能力也将得到评估。具体目的3和4将研究下丘脑神经元的雌激素调节的生理变化，使用恒河猴作为实验模型，其月经周期为28天。 AIM 3将检查下丘脑GNRH和谷氨酸释放的变化，以及在OVX年轻猴子中，NMDA受体激活对GnRH释放的调节，具有长期或短期雌激素的替代。 AIM 4将在高雌激素（晚期卵泡期）或低雌激素（Luteal阶段晚期）的时期内在自然月经周期中进行类似的测量。比较将与闭经的老化猴子进行。预计实验可以洞悉更年期雌激素缺乏的神经生物学作用。