Mouse pregnancy blocking pheromones

Male mouse urine applied directly to the external nares of the female produces pregnancy block (Dominic, 1964). In mice, the vomeronasal mediates this block (Bellringer etal., 1980). The pregnancy-block pheromone of the male may be a product of androgen metabolism, and not one of androgen-dependent... 

When a newly impregnated female mouse is confined with a strange male, that is a male which has an odor different from that of her mate, implantation failure and a rapid return to estrus is observed. This pregnancy-blocking is not observed if the female is exposed to a castrated male, but treatment of the male with testosterone restores his production of pregnancy-blocking pheromone (342). 

Marchlewsbca-Koj (330) fractionated male mouse urine and found that the pregnancy-blocking pheromone is a peptide or a substance bound with the peptide fraction. 

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