Modeling fighting deprivation effect in mouse repeated aggression paradigm.

Male mice with a long positive fighting history develop behavioral psychopathology, which includes abnormal aggression, hostility, hyperactivity, stereotypic reactions and other behavioral phenotypes. We also found that the "winners" (mice that had each won 20 daily encounters in succession) develop an enhanced level of aggression after a no-fight period, compared to their respective levels of aggressive behavior before the fighting deprivation. Natural hedonic stimuli (such as access to females or sweet water), supplied to the winners during this no-fight period, appear to play a minor role in triggering this phenomenon. Therefore, it appears that fighting deprivation per se stimulates an elevated aggression in male mice, which also display aberrant behaviors formed under repeated experience of aggression accompanied by victories. This behavioral approach may be useful for modeling the effect of fighting deprivation in mouse paradigms based on repeated aggression.