de Greef W J, Schenck P E, Vreeburg J T, van der Vaart P D, Baum M J
J Endocrinol. 1981 Apr;89(1):13-23. doi: 10.1677/joe.0.0890013.
Daily administration of oestradiol benzoate, beginning 10 days after mating, stimulates lordosis behaviour in deciduomata-bearing pseudopregnant rats, but not in pregnant rats. The inhibition of this behaviour during pregnancy was not prevented by reducing the number of conceptuses to two, by removing the fetuses while leaving the placentas in utero, or by removing the ovaries and administering progesterone to prevent abortion. Removal of the uterus or fetuses and placentas on day 12, however, led to high levels of lordosis behaviour. Thus, it is likely that the placenta produces a factor which inhibits the behavioural responsiveness to oestrogen. Plasma levels of progesterone, androsterone and dihydrotestosterone were higher during the second half of pregnancy than in the second half of pseudopregnancy prolonged by uterine decidualization. The possible involvement of these steroids in the inhibition of lordosis behaviour was investigated by increasing their levels in deciduomata-bearing pseudopregnant rats and determining the effect on oestrogen-induced lordosis behavior. Little suppression of this behaviour was seen when the pseudopregnant rats were treated with progesterone or androsterone whereas treatment with dihydrotestosterone resulted in a significant inhibition of lordosis behavior. However, the dose of dihydrotestosterone required to do so resulted in high, non-physiological plasma levels of this steroid. No inhibition of lordosis behaviour was observed when dihydrotestosterone levels were approximately threefold those normally present in pregnant rats. It is concluded that none of these three steroids is primarily responsible for the suppression of lordosis behaviour during pregnancy.
从交配后10天开始每日注射苯甲酸雌二醇，可刺激怀有蜕膜的假孕大鼠出现脊柱前凸行为，但对怀孕大鼠则无此作用。通过将孕体数量减少至两个、在子宫内保留胎盘而取出胎儿或摘除卵巢并给予孕酮以防止流产等方法，均不能阻止怀孕期这种行为的抑制。然而，在第12天切除子宫或胎儿及胎盘，会导致脊柱前凸行为水平升高。因此，胎盘很可能产生一种抑制对雌激素行为反应性的因子。怀孕后半期血浆孕酮、雄酮和双氢睾酮水平高于因子宫蜕膜化而延长的假孕后半期。通过提高怀有蜕膜的假孕大鼠体内这些类固醇的水平并确定其对雌激素诱导的脊柱前凸行为的影响，研究了这些类固醇在抑制脊柱前凸行为中可能的作用。当用孕酮或雄酮处理假孕大鼠时，几乎未见这种行为受到抑制，而用双氢睾酮处理则导致脊柱前凸行为受到显著抑制。然而，产生这种作用所需的双氢睾酮剂量导致该类固醇血浆水平升高至非生理水平。当双氢睾酮水平约为正常怀孕大鼠体内水平的三倍时，未观察到脊柱前凸行为受到抑制。结论是，这三种类固醇均不是怀孕期脊柱前凸行为抑制的主要原因。
