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Discussions 



(stria temiinaiis) has occurred? With regard to the first question we have obtained 

 some recent data which would further tend to support the hypothesis that the anterior 

 hypothalamic area is the site of the deleterious androgen action. 



The biphasic action of progesterone in first facilitating and then inhibiting the 

 discharge of gonadotropin in the rat is well recognized. Everett {Endocrinology 43, 

 389, 1948) has demonstrated that administration of progesterone to a normal cyclic 



Fig. 7. Effects of spaced injections of progesterone on vaginal cycle of androgen-sterilized, 



persistent-estrous rat. Abbreviations used in this and Fig. 8: I, Proestrus; III, Estrus; 



L, Laparotomy; CL, Corpora lutea; A, Autopsy. Solid bars indicate persistent vaginal 



comification ; blank spaces represent days of diestrus. 



rat on the last day of diestrus will advance ovulation one day. Spaced injections of 

 progesterone when administered to the spontaneous persistent-estrous rat (DBN 

 strain) will likewise induce ovulation (Everett, J. W., Endocrinology 32, 285, 1943). 

 We have attempted also to ovulate the androgen-sterilized rat by either spaced or 

 daily injections of progesterone. Following the procedure described by Everett (1943) 

 for the induction of ovulation in the spontaneous persistent-estrous rat, single "inter- 

 rupting" dosages of 2.0 mg of progesterone were administered to each of 4 groups 

 of 8 adult sterile rats. This injection generally resulted in a 3-day period of diestrus 

 followed by one day of proestrus at which time a second "ovulatory" dose of proges- 

 terone was administered. Laparotomy was ordinarily performed 48 hr after the second 

 injection, at which time the ovaries were examined for the presence of corpora lutea. 

 Regardless of the dosage used, ovulation did not occur (Fig. 7). These results were 

 confirmed at autopsy by histological examination of all ovaries. In a second series of 

 experiments a single "interrupting" dose of 2.0 mg of progesterone was adminis- 

 tered to each of 4 groups of 8 animals. Following this single injection, daily sub- 

 cutaneous injections of either 0.25, 0.5, 1.0, or 2.0 mg were given to one or the other 

 of the four groups for a 3-to 4-\veek period. Twenty-four to 48 hr after the last injec- 

 tion, the animals were sacrificed and the ovaries examined for the presence of corpora 

 lutea. The effects of such treatment on the vaginal cycles are summarized in Fig. 8. 

 Although the vaginal cycles could be restored with the lower dosages, ovulation did 

 not occur in any of the groups studied. 



These results suggest that progesterone does not facilitate ovulation by a direct 

 action on the adenohypophysis. As demonstrated previously, the pituitary of the 



