Estrogen- and progesterone-induced uterine motility of anestrous goats.

Uterine motility was studied in the anestrous goats after a series of estradiol injections was given and after estradiol-plus-progesterone treatment was administered. Estradiol (0.1 mg/kg) given alone by intramuscular route every 6 hours for 4 continuous days produced only a moderate increase in the uterine contractions during treatment, but significantly higher amplitude and frequency of contractions occurred at 2 days after treatment was stopped. The same doses of estradiol administered for a 24-hour period and followed by 4 injections of progesterone (1.0 mg/kg) given intramuscularly once a day produced a moderate response during treatment, but depressed the amplitude and the frequency of contractions after the treatment was stopped. The results indicate that the tissues primed with estrogen produced a stimulatory effect after their estrogen contents diminished. Progesterone, likewise, produced inhibition after a decrease in the progesterone contents of the uterine tissue.