title: Impairment of interstrain social recognition during territorial aggressive behavior in oxytocin receptor-null mice.
abstract: In humans, oxytocin has been shown to be involved in in-group cooperative behaviors and out-group aggression. Studies have also demonstrated that oxytocin plays a pivotal role in social recognition. However, no empirical research has investigated the effect of oxytocin on in-group and out-group aggressiveness. We employed a resident-intruder paradigm to assess the ability of resident male mice to discriminate intruder male strain differences. We found that resident male mice exhibited higher frequencies of attack bites against intruders of different strains than against intruders of their own strain. Subsequently, we examined whether the interstrain recognition was regulated by the oxytocin system using oxytocin receptor (OTR)-null mice. OTR wild-type or heterozygous residents displayed higher aggression toward intruders of a strain different from their own (C57BL/6J). On the other hand, OTR-null residents exhibited greater aggression toward intruders of the same strain compared to OTR wild-type or heterozygous residents, and aggression levels were not different compared to those exhibited toward other strains. Our findings demonstrated that the oxytocin system contributes to interstrain social recognition in territorial aggression in male mice, implying that one function of oxytocin is to promote an in-group "tend-and-defend" response, such as in-group favoritism, which could be evolutionarily conserved in mammals.
authors.affiliation: Companion Animal Research, School of Veterinary Medicine, Azabu University, Sagamihara 252-5201, Japan.
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Hattori
authors.affiliation: Companion Animal Research, School of Veterinary Medicine, Azabu University, Sagamihara 252-5201, Japan.
authors.forename: Kouta
authors.initials: K
authors.lastname: Kanno
authors.affiliation: Companion Animal Research, School of Veterinary Medicine, Azabu University, Sagamihara 252-5201, Japan.
authors.forename: Miho
authors.initials: M
authors.lastname: Nagasawa
authors.affiliation: Department of Molecular and Cell Biology, Graduate School of Agricultural Science, Tohoku University, Miyagi 981-8555, Japan.
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Nishimori
authors.affiliation: Companion Animal Research, School of Veterinary Medicine, Azabu University, Sagamihara 252-5201, Japan. Electronic address: mogik@azabu-u.ac.jp.
authors.forename: Kazutaka
authors.initials: K
authors.lastname: Mogi
authors.affiliation: Companion Animal Research, School of Veterinary Medicine, Azabu University, Sagamihara 252-5201, Japan.
authors.forename: Takefumi
authors.initials: T
authors.lastname: Kikusui
mesh_terms: D000374:Aggression / Q000502:physiology*; D000818:Animals; D001522:Behavior, Animal; D001921:Brain / Q000502:physiology* / Q000503:physiopathology*; D008297:Male; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D010121:Oxytocin / Q000378:metabolism; D018045:Receptors, Oxytocin / Q000378:metabolism*; D012919:Social Behavior; D013037:Spatial Behavior
chemical_list: C576074:OXTR protein, mouse; D018045:Receptors, Oxytocin; D010121:Oxytocin
keywords: Aggressive behavior; Interstrain recognition; Oxytocin; Oxytocin receptor