Abstract
Background Aggression is an evolutionarily conserved, adaptive component of social behavior. Studies in male mice illustrate that aggression is influenced by numerous factors including the degree to which an individual finds aggression rewarding and will work for access to attack and subordinate mice. While such studies have expanded our understanding of the molecular and circuit mechanisms of male aggression very little is known about female aggression, owed in part to limited availability of valid mouse models in females.
Methods Here we use an ethologically relevant model of male vs. female aggression by pair housing adult male and female outbred CFW mice with opposite sex cage mates. We assess reactive (defensive) aggression in the resident intruder (RI) test and appetitive (rewarding) aggression in the aggression conditioned place preference (CPP) and operant self-administration (SA) tests.
Results Our results show dramatic sex differences in both qualitative and quantitative aspects of reactive vs. appetitive aggression. Males exhibit more wrestling and less investigative behavior during RI, find aggression rewarding and will work for access to a subordinate to attack. Females exhibit more bites, alternate between aggressive behaviors and investigative behaviors more readily during RI, however, they do not find aggression to be rewarding or reinforcing.
Conclusions These results establish sex differences in aggression in mice, providing an important resource for the field to better understand the circuit and molecular mechanisms of aggression in both sexes.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
Funding and Disclosure: The authors declare that they do not have any conflicts of interest (financial or otherwise) related to the text of the paper. The research was supported R01MH127820 (SJR), R01MH114882 (SJR), R01MH104559 (SJR), R01 MH120514 (SJR), R01 MH120637 (SJR), R00DA045662 (SAG), P30DA048736 (SAG), NARSAD Young Investigator Award 27082 (SAG), and F31MH125587-01 (NLG). Some figures created with BioRender.com.