ABSTRACT
One mg of ergocornine methanesulphate was injected into pseudopregnant rats; the time at which the vaginal smear became pro-oestrous was noted. Pro-oestrus appeared two days after the injection of ergocornine, independent of whether the drug was administered on days L1, L2, L3, L4 or L5 (L1 = first day of leucocytic vaginal smear). Injection of 5 mg/d progesterone delayed, but did not usually prevent, the onset of pro-oestrus. Pro-oestrus appeared 3 days after the last injection of progesterone. These results show that ergocornine induces the appearance of oestrus by effecting progesterone withdrawal rather than by direct activation of folliculotrophins.
