Repeated Non-Contact Exposure to Pups Inhibits Infanticidal and Facilitates Paternal Behavior in Virgin Adult Male Mice (C57bl6)

Abstract

Pup-naïve virgin adult male mice are mainly infanticidal when exposed to pups for the first time. The processes underlying pup-directed aggression and the transition toward parental care are poorly understood. Social isolation has been shown to inhibit infanticidal behavior in some strain of mice. However, it is unclear if highly infanticidal male CB57BL6 mice can sensitize after repeated exposures to pups. The aim of this study was to determine whether repeated non-contact exposure to pups, with or without movement restriction and social isolation, can inhibit infanticidal behavior in male mice. We also investigated whether pup-directed aggression was associated with male-male aggression in a resident-intruder test. We found that repeated non-contact exposure to pups, in socially isolated males or in males with movement restraint, significantly reduced the incidence of aggression towards pups and increased the incidence of parental behavior. Social isolation or movement restraint alone had no significant effect. Finally, the frequency of pup-directed aggression was not associated with the levels of male-male aggression. This study shows that the experience of being exposed to newborns without contact with them can inhibit the highly driven impulsive-like attacking behavior towards pups and facilitate parental behavior. Our results suggest that aggressive behavior towards pups can be blocked in naïve male mice and that this behavior differs from male-male aggression.

Keywords: infanticide, movement restraint, social isolation, male sensitization, paternal behavior