Impairment of eggs implantation by exposure to alien male during early stages of pregnancy can be completely prevented by blockade of the dopaminergic neurons of the central nervous system (CNS) or by increase of the prolactin (Prl) level in pregnant female mice. Stimulation of serotoninergic neurons delayed the pheromonal effect. Blockade of serotoninergic neurons or treatment by ergocriptine on the 2nd and 3rd day of pregnancy inhibited eggs implantation. These results indicate that Prl release in female mice during the time of implantation is under dopaminergic and serotoninergic control, but pheromonal effect is transmitted by dopaminergic system.