Abstract
Summary
Ovulation was advanced 24 hr by a single injection sc of estradiol benzoate (EB) at 10:00 am on the first day of diestrus in 4-day cyclic rats. Phenobarbital prevented this EB-induced ovulation if given at 1:30 pm on the second day of diestrus, but not when given at 5:30 pm. However, pseu-dopregnancy occurred in all animals receiving EB. When animals treated with EB were exposed to fertile males on the second day of diestrus, over 80% mated but normal pregnancy did not ensue. Normal pregnancy of EB-treated rats occurred only after the termination of pseudopregnancy subsequent to EB-induced ovulation. These results suggest that EB injection initiates the ovulating hormone release and results in the advancement of ovulation.
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