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 st ress of continuously living opposite a dominant animal, were assessed in ma le NMRI mice. The method adopted here differed from the previously publishe d techniques in that the physical element of the social defeat procedure wa s reduced to a minimum. The subordinate animals consistently weighed less t han control animals, and displayed a reduced number of visits to the partit ion compared to the dominant animals, which has previously been used as a m arker of social behaviour. The subordinate animals did not show any differe nces in the amount of ethanol solution consumed compared to controls, and d id not display an increase in immobility time measured in the forced swimmi ng test. The subordinate animals did, however, display anxiogenic-like beha viour as indicated by an increased aversion of the light section of the bla ck/white test box, which was partially reversed by chronic treatment (3 wee ks; 20 mg/kg/day) with the antidepressant, citalopram. Decreased exploratio n 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 & W ilkins.