Effect of the timing of perphenazine administration on pregnancy in the rat

Perphenazine in doses of 10--50 mg kg-1 day-1 given at the early stages of pregnancy delayed nidation up to day 8 of pregnancy. Once nidation had occurred the length of the rest of the gestation period was normal. Doses of up to 20 mg perphenazine kg-1 day-1, injected on days 1--7, prolonged gestation but the mothers and young were apparently normal; lower doses were effective only when treatment commenced soon after copulation. The delay in implantation of the ovum caused by perphenazine was corrected and and implantation was brought about immediately, by injection of 0.1 microgram oestradiol together with perphenazine. It is suggested that perphenazine delays and prevents implantation in rats by counteracting oestrogen release from the ovaries.