Studies on PMSG-Induced Persistent Estrus in Rats -The Primary factors responsible for This phenomenon, Its Characteristics and Restoration to the Normal Cycle-

我们以前报道过，在发情周期的特定时期给药PMSG可以使许多大鼠无限期地持续发情。在本研究中，部分澄清了造成这一现象的主要因素，其特点和通过各种处理恢复到正常周期。在给药后4天，每天测定血清促性腺激素、催乳素和性类固醇浓度。从第1天到第3天，与对照组相比，PMSG处理大鼠的LH浓度显著增加。然而，在整个实验期间，他们的卵泡刺激素水平仍然很低。由于这种激素的作用，在第2天和第3天，血清睾酮和雌二醇水平显著升高。持续发情期间，黄体生成素水平低于对照组，卵泡刺激素水平高于对照组。黄体生成素和卵泡刺激素分泌延迟作为负反馈反应在大鼠卵巢切除术后。在这些大鼠中，由于雌二醇植入而产生的LH分泌是低正反馈反应。注射HCG和黄体酮诱导排卵，然后恢复周期。然而，当它们与雄性大鼠配对一周后，没有排卵。刺激子宫颈不能恢复正常的月经周期。综上所述，我们得出以下结论：1)PMSG引起的激素失衡抑制了促黄体生成素的激增，使发情无限期延长或持续；2)在持续发情期间，低的负反馈和正反馈反应表明黄体生成素和卵泡刺激素水平异常，存在与交配有关的中枢神经系统功能障碍；3)通过适当的治疗可以恢复正常的发情周期。

We previously reported that estrus can be made to continue indefinitely in many rats by administration of PMSG at a specified period during its cycle. In the present study, partial clarification was made of the primary factors responsible for this phenomenon, its characteristics and restoration to the normal cycle by various treatments.Serum concentrations of gonadotropins and prolactin and sex steroids were measured on each of the 4 following days after PMSG administration. LH concentration was found to have significantly increased from day 1 to day 3 in PMSG treated rats compared with the control. Their FSH levels, however, remained low throughout the experimental period. The serum levels of testosterone and estradiol increased greatly on days 2 and 3 as a result of this hormone. During the persistent estrus, the LH level was lower and FSH higher than in the control. LH and FSH secretions were delayed as a negative feedback response in rats following ovariectomy. In these rats, the secretion of LH due to estradiol implantation was noted as a low positive feedback response. HCG and progeterone injections induced ovulation and then the restoration of the cycle. However, no ovulation occurred when they were paired with male rats for a week. The normal cycle was not recovered by stimulation of the uterine cervix.Based on the results obtained, the following conclusions were drawn: 1)hormone imbalance due to PMSG administration inhibits LH surge for ovulation and prolongs or causes estrus to continue indefinitely; 2) during persistent estrus, low negative and positive feedback response is indicative of abnormal levels of LH and FSH and there is dysfunction of the central nervous system in relation to mating and 3) and the regular estrous cycle can be restored through appropriate treatment.