Abstract
In vivo experiments, a single administration of progesterone or prednisone induced ovulation and larger dosages of them reduced significantly the ovulatory response. Moreover, ovulation induced by them was facilitated by the simultaeneous addition of either HCG or PMS which was subthreshold amounts to induce ovulation by itself.
Estradiol could not induce ovulation by itself.
In vitro experiments, progesterone, prednisone, testosterone and newly formed synthetic progestogens had potent ovulatory capacity. In addition, estradiol blocked significantly pituitary-induced ovulation, but this inhibition was readily removed if progesterone were added to the pituitary-estrogen combinations.
It is proposed that amphibian ovulation is induced by the direct action of steroids on the ovary without the mediation of the hypothalamic-pituitary axis.
