Intense arousal of novel male mice in proximity to previously inseminated females: Inactivation of males via chlorpromazine does not diminish the capacity to disrupt pregnancy

In the course of investigating early pregnancy disruptions by novel males, intense behavioral interactions and chemical emissions were observed among males housed in proximity to inseminated females. These interactions were evident despite wire-mesh separations between males and females. Experiments were designed to examine whether such arousal plays a role in pregnancy disruption. During the first 5 days of pregnancy, inseminated CF-1 strain female mice were either left undisturbed or exposed to novel outbred males. Physical separations between males did not diminish the frequency of pregnancy disruption. Subsequently, we investigated whether heavy sedation of novel males via chronic chlorpromazine administration would diminish the capacity to disrupt pregnancy. Pregnancy was disrupted to the same degree in females exposed to drug-treated males and those exposed to alert competing males given vehicle injections. These data show an unprecedented degree of arousal and pheromonal emission among competing males but suggest that these factors are not critical for the capacity to disrupt pregnancy.