Central nervous system regions involved in the estrogen-induced afternoon prolactin surge. II. Implantation studies.
Central nervous system regions involved in the estrogen-induced afternoon prolactin surge. II. Implantation studies.
复制标题
中枢神经系统区域参与雌激素引起的下午催乳素激增。
作者：
J. Pan;R. Gala
正常骑行雌性大鼠在发情前期下午血浆催乳素水平明显升高。在发情第1天摘除卵巢完全消除PRL峰，注射100微克长效雌激素聚雌二醇磷酸不仅维持峰高，而且放大和延长了峰高。在内侧视前区(MPO)，但不在大脑皮层(CC)，双侧植入含雌二醇(E_2)的插管[用胆固醇(C)稀释1：4]，也保持了这种激增。在长期去卵巢的大鼠，双侧杏仁皮质内侧核(CMA)或下丘脑腹内侧核植入1：5、1：10、1：20和1：200的E_2管，或单纯植入第三脑室均未能在12天后引起PRL峰。与植入C的对照组相比，类似的单一植入垂体前叶(AP)的大鼠血浆催乳素(PRL)水平升高，但没有明显的峰值。在1700h和1900h，MPO内只有双侧注入E_2引起血浆PRL显著升高，而在MPO内注入较高浓度的E_2(1：4)和较短的采样间隔，可在第2-4天诱导出显著的下午PRL峰值。然而，雌二醇的全身效应，如阴道角化和子宫重量增大，也是明显的。在其他大脑区域进行类似的植入也有相同的结果。进一步将E2与C的稀释度从1：10增加到1：200可消除E2植入的全身效应，而PRL峰的诱导能力仍然存在。似乎最高稀释的E2植入物(1：150和1：200)具有最高的PRL反应和持续最多的天数。在不同脑区(1：100和1：200)使用高度稀释的E2植入，MPO和下丘脑腹内侧是最敏感的区域，其他区域，包括视交叉上核、CMA、AP和CC则无效。综上所述，在脑内植入高度稀释的E_2似乎能有效地抑制下午的催乳素释放；CMA、视交叉上核、AP和CC不是诱导PRL释放的雌激素反馈部位，而MPO是在被检查的诱导下午PRL激增的脑区中雌激素作用最敏感的区域。
In the intact cycling female rat, there is a surge of plasma PRL during the afternoon of proestrus. Ovariectomy on diestrous day 1 eliminated the PRL surge completely, and injection of 100 micrograms polyestradiol phosphate, a long-acting estrogen, not only maintained the surge, but amplified and prolonged it. Bilateral implantation of an estradiol (E2)-containing cannula [diluted 1:4 with cholesterol (C)] in the medial preoptic area (MPO), but not in the cerebral cortex (CC), also maintained the surge. In long term ovariectomized rats, bilateral implantation of E2-containing cannulae (1:5, 1:10, 1:20, and 1:200) in the corticomedial amygdala (CMA) or ventromedial nucleus of the hypothalamus or a singular implantation in the third ventricle failed to induce a PRL surge 12 days later. Similar singular implantation in the anterior pituitary (AP) increased the basal levels of plasma PRL compared to those in C-implanted controls, but no surge was evident. Only bilateral implantation of E2 in the MPO induced a small but significant rise of plasma PRL at 1700 and 1900 h. Using higher concentration implants with a higher E2 concentration (1:4) in the MPO and sampling at shorter intervals, significant afternoon PRL surges were induced on days 2-4. However, systemic effects of E2, i.e. vaginal cornification and uterine weight enlargement, were also evident. Similar implants in other brain regions had the same results. Further increasing the E2 to C dilution from 1:10 to 1:200 eliminated the systemic effect of E2 implants, while the PRL surge-inducing ability persisted. It appears that the highest diluted E2 implants (1:150 and 1:200) gave the highest PRL response and persisted for the greatest number of days. Using the highly diluted E2 implants (1:100 and 1:200) in various brain regions, the MPO and the ventromedial hypothalamus were the most sensitive areas in inducing the PRL surge; the other areas studied, including suprachiasmatic nuclei, CMA, AP, and CC were ineffective. In conclusion, highly diluted E2 implants in the brain appear to be effective in obtaining a specific effect on the afternoon PRL surge; the CMA, suprachiasmatic nuclei, AP, and CC are not estrogen feedback sites for the induction of PRL release, and the MPO was the most sensitive area of the estrogen action in the brain regions examined for the induction of the afternoon PRL surge.