title: Social isolation-induced aggression potentiates anxiety and depressive-like behavior in male mice subjected to unpredictable chronic mild stress.
abstract: BACKGROUND
  Accumulating epidemiological evidence shows that life event stressors are major vulnerability factors for psychiatric diseases such as major depression. It is also well known that social isolation in male mice results in aggressive behavior. However, it is not known how social isolation-induced aggression affects anxiety and depressive-like behavior in isolated male mice subjected to unpredictable chronic mild stress (CMS), an animal model of depression.
  
  
  RESULTS
  C57/B6 male mice were divided into 3 groups; non-stressed controls, in Group I; isolated mice subjected to the CMS protocol in Group II and aggression by physical contact in socially isolated mice subjected to the CMS protocol in Group III. In the sucrose intake test, ingestion of a 1% sucrose solution by mice in Groups II and III was significantly lower than in Group I. Furthermore, intake of this solution in Group III mice was significantly lower than in Group II mice. In the open field test, mice in Group III, showed reduced locomotor activity and reduced entry and retention time in the central zone, compared to Groups I and II mice. Moreover, the distances moved in 1 hour by Group III mice did not differ between night and morning. In the light/black box test, Groups II and III animals spent significantly less time in the light box compared to Group I animals. In the tail suspension test (TST) and forced swimming test (FST), the immobility times of Group II and Group III mice were significantly longer than in Group I mice. In addition, immobility times in the FST were significantly longer in Group III than in Group II mice.
  
  
  CONCLUSIONS
  These findings show that social isolation-induced aggression could potentiate anxiety and depressive-like behaviors in isolated male mice subjected to CMS.
authors.affiliation: Department of Psychiatry, First Affiliated Hospital of Medical College of Xi'an Jiaotong University, Xian, China.
authors.forename: Xian-cang
authors.initials: XC
authors.lastname: Ma
authors.forename: Dong
authors.initials: D
authors.lastname: Jiang
authors.forename: Wen-hui
authors.initials: WH
authors.lastname: Jiang
authors.forename: Fen
authors.initials: F
authors.lastname: Wang
authors.forename: Min
authors.initials: M
authors.lastname: Jia
authors.forename: Jin
authors.initials: J
authors.lastname: Wu
authors.forename: Kenji
authors.initials: K
authors.lastname: Hashimoto
authors.forename: Yong-hui
authors.initials: YH
authors.lastname: Dang
authors.forename: Cheng-ge
authors.initials: CG
authors.lastname: Gao
mesh_terms: D000818:Animals; D001007:Anxiety / Q000209:etiology*; D003863:Depression / Q000209:etiology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D012934:Social Isolation; D013312:Stress, Physiological