Neuroendocrine Regulation on Age-related Changes of Reproductive Function

本研究的目的是分析与年龄相关的生殖功能改变的机制，特别是神经内分泌功能。主要研究成果总结如下：1.研究成果。免疫细胞化学和放射免疫分析结果显示，LHRH神经元在雄性大鼠比雌性大鼠更早开始功能。结论：1.在维持成年雌性大鼠LHRH和LH周期性释放的过程中，视交叉上核在保持前传入或后传入不变的情况下可以正常发挥作用。在生长激素(GH)脉冲性释放方面，老年大鼠GH脉冲峰和垂体GH含量均降低。同时发现肝细胞膜GH结合部位增多，血浆生长抑素-C水平降低。还研究了下丘脑-神经垂体系统的增龄性变化。研究发现，随着年龄的增长，加压素神经元的可塑性降低。这一发现为研究其他神经内分泌系统中与年龄相关的变化提供了一种方法。卵泡刺激素(FSH)受体在睾丸中的亲和力最初较低，但在分娩前亲和力增加到成年水平。在小鼠中，睾丸FSH受体的浓度增加到青春期，与大鼠相似。然而，在小鼠中，由于FSH受体的下调，FSH受体在青春期后减少。电子显微镜放射自显影和动力学研究表明，FSH-FSH受体复合体的内化对于下调很重要。本项目的代表性报告列在下一页。

The purpose of the present study is to analyze the mechanism of age-relate changes of reproductive function, with special reference to neuroendocrine function. The important findings are summarized as follows.1. The results of immonocytochemistry and radioimmonoassay revealed that LHRH neurons start functioning earlier in male rats than females. For the maintenance of cyclic release of LHRH and LH in adult female rats, the suprachiasmatic nucleus could normally play a role, if either the anterior or posterior afferents was left intact.2. As concerns the pulsatile release of growth hormone (GH), old rats showed a decrease in pulse peak and pituitary content of GH. Simultaneously, the increase in the number of GH binding sites in hepatic membrane fraction and the decrease in plasma level of somatomedin-C were found.3. Age-related changes in the hypothalamic-neurohypophyseal system was also studied. It was found that vasopressin neuronal plasticity was decreased as age advances. This finding affords an approach to age-related changes in other neuroendocrine system.4. Follicle-stimulating hormone (FSH) receptor in the testes was low in affinity at first but before parturition the affinity increased to the adult level. In the mouse, the concentration of testicular FSH receptors increased until puberty similar to that in the rat. However, in the mouse fsh receptors decreased after puberty due to downregulation of FSH receptors. The electron microscopic autoradiography and kinetic study revealed that internalization of FSH-FSH receptor complex is important for the downregulation.Representative reports for the present project are listed in the next page.