Role of catechol estrogens in activation of lordosis in female rats and guinea pigs.

In a variety of experiments, we tested the effectiveness of the 2-hydroxylated estrogen in facilitating sexual receptivity. A single injection of 2-hydroxy-estradiol-17beta (2-OHE2) to ovariectomized rats or 2-hydroxy-estrone (2-OHE1) to ovariectomized guinea pigs was ineffective in priming animals for facilitation of sexual receptivity even when a subsequent injection of progesterone was administered. The only facilitatory effect of catechol estrogens on lordosis that was demonstrated in this study occurred when 2-OHE2 was injected in combination with E2 and a subsequent injection of progesterone was given to rats. These results suggest a cooperatively between catechol estrogen and E2, but they also indicate that catechol estrogens, by themselves, do not play a crucial role in mediating sexual receptivity in rodents.