Brown T J, Blaustein J D
Brain Res. 1985 Dec 9;358(1-2):180-90. doi: 10.1016/0006-8993(85)90962-x.
The hypothesis that the termination of sexual receptivity (heat) in female guinea pigs results from loss of progestin receptors from hypothalamic cell nuclei was tested. First, we attempted to find an optimal dose of progesterone that would result in a prolonged period of sexual receptivity. Ovariectomized guinea pigs were implanted with 10% estradiol capsules. Forty hours later, each received one of several sized progesterone capsules before being tested hourly for lordosis. Surprisingly, none of the progesterone doses resulted in delayed heat termination. In order to determine whether elevated levels of estradiol and progesterone maintain elevated levels of nuclear progestin receptors despite the lack of effect on heat duration, animals were treated as described above except that only one size progesterone capsule (3.0 cm) or an empty capsule was implanted. Despite elevated serum progesterone concentrations, nuclear progestin receptor levels decreased gradually and approached control levels at about the same time as heat termination had occurred in similarly-treated animals. Cytosol progestin receptor levels decreased following progesterone treatment and remained lowered at all times measured. In order to further investigate the relationship between blood progesterone concentrations and retention of nuclear progestin receptors we decreased blood progesterone concentrations by removing progesterone capsules 2 h following insertion. Nuclear progestin receptor levels declined gradually concurrent with a decline in serum progesterone levels in animals exposed to progesterone capsules for only 2 h. In animals exposed to capsules continuously, nuclear progestin receptor levels again decreased but at a slightly slower rate. In order to test the effect of progesterone capsule removal on female sexual behavior, ovariectomized guinea pigs were treated as described and tested hourly for lordosis. Fewer animals in the group exposed to progesterone capsules for 2 h became sexually receptive as compared to animals continuously-exposed to progesterone capsules. Of those animals that did respond, heat termination had occurred by the same time that nuclear progestin receptor levels had returned to control levels in similarly-treated animals. These experiments support the hypothesis that heat termination results from the loss of progestin receptors from hypothalamic cell nuclei. In addition, they demonstrate that circulating progesterone levels play a role in regulating nuclear progestin receptor retention.
对雌性豚鼠性接受能力（发情）的终止是由于下丘脑细胞核中孕激素受体丧失这一假说进行了验证。首先，我们试图找到一个能使性接受能力延长的最佳孕酮剂量。对卵巢切除的豚鼠植入10%的雌二醇胶囊。40小时后，每只豚鼠接受几种不同大小的孕酮胶囊中的一种，然后每小时检测一次其脊柱前凸情况。令人惊讶的是，没有一个孕酮剂量能导致发情终止延迟。为了确定尽管对发情持续时间没有影响，但雌二醇和孕酮水平升高是否能维持细胞核孕激素受体水平升高，动物的处理方式如上所述，只是只植入一种大小的孕酮胶囊（3.0厘米）或一个空胶囊。尽管血清孕酮浓度升高，但细胞核孕激素受体水平逐渐下降，并在与同样处理的动物发情终止大致相同的时间接近对照水平。孕酮处理后细胞质孕激素受体水平下降，并在所有测量时间内一直保持较低水平。为了进一步研究血液中孕酮浓度与细胞核孕激素受体保留之间的关系，我们在插入孕酮胶囊2小时后取出胶囊以降低血液中孕酮浓度。在仅暴露于孕酮胶囊2小时的动物中，细胞核孕激素受体水平随着血清孕酮水平的下降而逐渐下降。在持续暴露于胶囊的动物中，细胞核孕激素受体水平再次下降，但速度稍慢。为了测试取出孕酮胶囊对雌性性行为的影响，对卵巢切除的豚鼠进行上述处理，并每小时检测一次其脊柱前凸情况。与持续暴露于孕酮胶囊的动物相比，暴露于孕酮胶囊2小时的组中出现性接受能力的动物较少。在那些有反应的动物中，发情终止发生的时间与同样处理的动物中细胞核孕激素受体水平恢复到对照水平的时间相同。这些实验支持了发情终止是由于下丘脑细胞核中孕激素受体丧失这一假说。此外，它们还表明循环孕酮水平在调节细胞核孕激素受体保留方面发挥作用。
