Female oxytocin gene‐knockout mice, in a semi‐natural environment, display exaggerated aggressive behavior

Abstract

Compared to results from a generation of neuropharmacological work, the phenotype of mice lacking the oxytocin (OT) peptide gene was remarkably normal. An important component of the current experiments was to assay OT-knockout (OTKO) and wild-type (WT) littermate control mice living under controlled stressful conditions designed to mimic more closely the environment for which the mouse genome evolved. Furthermore, our experimental group was comprised of an all-female population, in contrast to previous studies which have focused on all-male populations. Our data indicated that aggressive behaviors initiated by OTKO during a food deprivation feeding challenge were considerably more intense and diverse than aggressive behaviors initiated by WT. From the measures of continuous social interaction in the intruder paradigm, it emerged that OTKO mice were more offensively aggressive (attacking rumps and tails) than WT. In a test of parental behaviors, OTKO mice were 100% infanticidal while WT were 16% infanticidal and 50% maternal. Finally, 'alpha females' (always OTKO) were identified in each experiment. They were the most aggressive, the first to feed and the most dominant at nesting behaviors. Semi-natural environments are excellent testing environments for elucidating behavioral differences between transgenic mice and their WT littermates which may not be ordinarily discernible. Future studies of mouse group behavior should include examining female groupings in addition to the more usual all-male groups.

Intergenerational effects of cocaine on maternal aggressive behavior and brain oxytocin in rat dams

“…Several reports suggest that altered oxytocin activity could affect MA through stressresponse systems (Ferris et al 1992;Lubin et al 2003;Bosch et al 2005;Ragnauth et al 2005). Studies linking rearing to oxytocin system and stress response development (Francis et al 1999;Pedersen and Boccia 2000;Meaney 2001) may be particularly relevant to our findings in the FGDs.…”

Pervasive social deficits, but normal parturition, in oxytocin receptor-deficient mice

“…Seminatural environment-housed Oxt Ϫ/Ϫ females from Oxt ϩ/Ϫ dams showed high levels of aggression and infanticidal behaviors, unlike cage-housed Oxt Ϫ/Ϫ females from Oxt ϩ/Ϫ dams (28). These results indicate that postnatal environment also affects the behavior via the OXT͞OXTR system.…”

“…This contradiction might be caused by differences in the targeting construct used, which resulted in the elimination of the majority of the Neurophysin but not the OXT coding region of the Oxt gene, or in the testing paradigm used (9,27). In the study reporting decreased duration of aggressive attack, the tests were performed in a neutral arena, although in our study and in those of others reporting increased aggression (16,28), a resident intruder paradigm was used. Therefore, the changes in aggression due to disruption of the OXT system may be context-dependent.…”

Reduced ultrasonic vocalizations in vasopressin 1b knockout mice

“…Targeted gene mutations in mice provide model systems to evaluate the role of a specific neuropeptide or its receptor in a social behavior. Oxytocin knockout mice revealed the role of oxytocin in mediating social recognition, social memory, aggression, maternal behaviors, and ultrasonic vocalizations by pups separated from the nest [5,10,29,39,42,57]. Vasopressin receptor subtype V1a (Avpr1a) knockout mice displayed impaired social recognition and low anxiety-like behaviors [4,5,12], and reduced responses to social olfactory cues [51].…”