Defeat followed by individual housing results in long-term impaired reward- and cognition-related behaviours in rats

In contrast to the well-documented acute effects on behavioural sensitivity, chronic effects that persist for weeks or even months after the cessation of the stressor received relatively little attention. This study aimed at the long-term effects of a severe stressor, i.e. social defeat followed by individual housing. Defeated and subsequently individually housed animals displayed impaired social memory, decreased social interaction and diminished anticipation for a sucrose solution for up until a period of 3 months after defeat. Remarkably, social housing counteracted the defeat-induced effects. The impaired capability to anticipate for a reward was discussed in relation to anhedonia, an important symptom of human depression. Moreover, the disturbed memory, the chronic nature of the effects, and the therapeutic effects of social housing, suggest that the defeat model may serve as a potential model for human psychopathology. (C) 2000 Elsevier Science B.V. All rights reserved.