Possible mode of action of prostaglandins: V - differential effects of prostaglandin F2α before and after the establishment of placental physiology in pregnant rats

Prostaglandin F₂α (PGF₂α) at a dose level of 2.00 mg/kg body weight could cause complete resorption of the implanted blastocysts when injected either on day 10 or day 11 of pregnancy in rats. The same injection apparently failed to induce abortion or resorption in rats having functional placentae on day 12 or day 13 of pregnancy. It was moreover observed that a concomitant exogenous administration of either prolactin or progesterone alongwith PGF₂α could successfully reverse the abortifacient property of PGF₂α and keep the status of the ovaries, embryos, placentae etc. identical to that obtained in the control. It was suggested from the experimental evidences that the abortifacient effects of PGF₂α in the rat might possibly be mediated through the pituitary or hypothalamo-pituitary complex.