The luteolytic and abortifacient potential of an estrogen-bromergocryptine regimen in the baboon.

Administration of 1 mg of estradiol benzoate (E2B) daily to normally cycling baboons on days 6, 7 and 8 after ovulation significantly shortens the luteal phase to 13.8 +/- 0.3 days (n = 5) from 16.0 +/- 0.6 days (n = 8) in vehicle-treated controls, and causes an early decline in plasma progesterone concentration. When 1 mg/kg bromergocryptine (CB-154) was administered twice daily in combination with the E2B treatment, there was an earlier depression of plasma progesterone and a further shortening of the luteal phase to 12.3 +/- 0.5 days (n = 4). In five pregnant baboons, the E2B/CB-154 treatment initiated on postconception day 20 produced a substantial depression of plasma progesterone, followed by a posttreatment rebound to control values, without apparent effect on the pregnancy. In both cycling and pregnant baboons, this dose of CB-154 produced a significant and sustained reduction in plasma prolactin levels.