EFFECTS OF A SHORT-PERIOD OF ISOLATION IN ADULTHOOD ON THE AGGRESSIVE-BEHAVIOR OF DOMINANT AND SUBORDINATE MALE-MICE

Male ddY mice were used to investigate the effect of a short period of isolation in adulthood on aggressive behavior. The relationship betwe en the dominance status previous to isolation and the effect of isolat ion was investigated. The mice were kept in isolation for 3 weeks from 9 weeks of age, during which intruder tests were conducted once a wee k. They then went through an encounter test, in which the mice encount ered dominant or subordinate mice in a neutral space. The number of th e formerly-dominant isolated mice that attacked the intruder mice decr eased at first and then increased. The latency to attack also lengthen ed at first and then shortened. Seven former-dominants continued to sh ow aggression throughout the experiment. The number of the formerly-su bordinate isolated mice that attacked the intruder mice increased line arly. But 3 former-subordinates did not show aggression through the en tire experiment. After 3 weeks isolation, the number of mice that show ed aggression and the amount of aggression did not differ between the former-dominants and subordinates. Isolation housing was concluded to differentially affect the dominant and subordinate mice during the 3 w eeks of isolation. It was also concluded to differentially affect the mice of absolute dominance and relative dominance differentially. The aggressive behavior of the isolated mice appears to occur independentl y of site.