The effect of social isolation on the aggressive and defensive behavior in mice

Abstract

Objective To study the influence of social isolation(SI) on the aggressive and defensive ability in mice. Methods The Kunming mice of postnatal 21 days were divided into the control group, SI groups (2, 4 and 8 weeks) and gregarious group by randomized block design and ten animals in each group. SI groups were isolated for 2, 4 and 8 weeks respectively, and the gregarious group would be returned to the normal socialized housing condition for 2 weeks after isolation, meanwhile the same aged mice were selected as the relative controls. All animals were measured the aggressive ability by carrying resident intruder tests. Results After 2 weeks social isolation, the social investigation increased with weak aggressive ability significantly (attack latency: SI (433.7±174.4)s, control (28.7±15.4)s), and defensive ability enhanced. The social behavior in the SI 4 weeks became less, while the aggressive ability increased significantly (attack times: SI(7.4±4.3), control(0.5±0.9)) and the defensive ability reduced. Both the social behavior and the aggressive ability increased significantly(attack times: SI(20.0±16.9), control(2.3±7.3)) and the defensive ability reduced in the SI 8 weeks.Compared to the control groups, both social behavior and defensive ability reduced in gregarious group, but aggressive ability enhanced, which suggest resocialization did not ameliorate the abnormity of social behavior as well as aggressive and defensive ability. Conclusion Social isolation in different degree induces changes of the aggressive and defensive ability of experimental animals and resocialization can't improve abnormal aggressive ability induced by social isolation. Key words: Social isolation; Mice; Aggressive behavior; Defensive behavior