Imprinting of a Nonpheromonal Cue and Its Protective Effect on Alien Male-Induced Implantation Failure in Mice.

Bruce effect or alien male-induced implantation failure is a well-studied phenomenon in mice. The presence of stud male during exposure to an alien male protects the female from implantation failure. The pheromones of the stud male are imprinted in the female at the time of mating and act as a luteotrophic agent. We tested whether a nonpheromonal cue exposed to the female during pericopulatory sensitive period could protect pregnancy in newly inseminated females exposed to alien males. Virgin females were allowed to mate in the presence of a cotton ball smeared with groundnut oil as a nonpheromonal cue. When these females were exposed to alien males in the presence of groundnut oil, the majority of the females retained their pregnancy. We evidenced that a nonpheromonal cue could possibly protect the female from alien male-induced implantation failure. The majority of the females exposed to the nonpheromonal cue during the pre-or postcopulatory interactions with the males, exhibited higher rate of pregnancy failure on reexposure to the same cue at the time of exposure to alien males. The protective effect of the nonpheromonal cue is observed only when the female is exposed to it during the pericopulatory sensitive period.