Behavioural consequences of repeated social defeat in the mouse: preliminary evaluation of a potential animal model of depression

The behavioural consequences of repeated social defeat, coupled with the stress of continuously living opposite a dominant animal, were assessed in male NMRI mice. The method adopted here differed from the previously published techniques in that the physical element of the social defeat procedure was reduced to a minimum. The subordinate animals consistently weighed less than control animals, and displayed a reduced number of visits to the partition compared to the dominant animals, which has previously been used as a marker of social behaviour. The subordinate animals did not show any differences in the amount of ethanol solution consumed compared to controls, and did not display an increase in immobility time measured in the forced swimming test. The subordinate animals did, however, display anxiogenic-like behaviour as indicated by an increased aversion of the light section of the black/white test box, which was partially reversed by chronic treatment (3 weeks; 20 mg/kg/day) with the antidepressant, citalopram. Decreased exploration by the subordinate animals in the black/white test bore was also observed, which was reversed by chronic citalopram treatment. It is suggested that, whilst the model requires further validation, it mag be a useful approach for the study of antidepressant compounds. (C) 1999 Lippincott Williams & Wilkins.