REDUCED AGGRESSIVE-BEHAVIOR IN MICE WITH TARGETED DISRUPTION OF THE OXYTOCIN GENE

Oxytocin (OT) has been reported to mediate aggressive and affiliative behaviours in several species. The behavioural role of OT has been est ablished with physiological manipulations that potentially affected bl ood pressure, which may have indirectly affected the behaviours under study. To provide converging evidence of the physiological role of OT in aggressive behavior, wild type (WT), heterozygous (OT-/+), and homo zygous (OT-/-) mutant mice were tested in two aggression paradigms. In general, there was no significant difference in aggressiveness betwee n WT and OT-/+ mice. However, there were significant reductions in the duration of aggressive behaviors among OT-/- animals, especially in a gonistic encounters within neutral arenas. The OT-/- mice did not exhi bit any sensorimotor deficits or display any altered general anxiety l evels that may have accounted for the observed reduction in aggressive behavior, These data indicate that aggression is mediated in part by OT in mice and that increased aggressiveness is not an obligatory phen otypic result of targeted genetic disruption of any gene.