Involvement of the vomeronasal organ and prolactin in pheromonal induction of delayed implantation in mice.

Pregnancy block caused by exposure of mated female mice to a strange male was significantly reduced by bilateral destruction of the vomeronasal organ. Treatment of newly mated females with alpha-bromocriptine also produced pregnancy block. Pregnancy block also occurred in mated females exposed to strange male odours, but the blastocysts which had failed to implant were still present in the uterus and were viable for up to 15 days after mating. Implantation was induced in such mice by administration of exogenous progesterone and oestradiol.