Original Article

Exp Neurobiol 2012; 21(1): 16-22

Published online March 31, 2012

© The Korean Society for Brain and Neural Sciences

Repeated Short-term (2h×14d) Emotional Stress Induces Lasting Depression-like Behavior in Mice

Kyoung-Shim Kim1, Hye-Joo Kwon2,3, In-Sun Baek4 and Pyung-Lim Han2,3,4*

1Laboratory Animal Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon 305-860, 2Brain Disease Research Institute, 3Department of Brain and Cognitive Sciences, 4Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Korea

Correspondence to: *To whom correspondence should be addressed.
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Chronic behavioral stress is a risk factor for depression. To understand chronic stress effects and the mechanism underlying stress-induced emotional changes, various animals model have been developed. We recently reported that mice treated with restraints for 2 h daily for 14 consecutive days (2h-14d or 2h×14d) show lasting depression-like behavior. Restraint provokes emotional stress in the body, but the nature of stress induced by restraints is presumably more complex than emotional stress. So a question remains unsolved whether a similar procedure with "emotional" stress is sufficient to cause depression-like behavior. To address this, we examined whether "emotional" constraints in mice treated for 2h×14d by enforcing them to individually stand on a small stepping platform placed in a water bucket with a quarter full of water, and the stress evoked by this procedure was termed "water-bucket stress". The water-bucket stress activated the hypothalamus-pituitary-adrenal gland (HPA) system in a manner similar to restraint as evidenced by elevation of serum glucocorticoids. After the 2h×14d water-bucket stress, mice showed behavioral changes that were attributed to depression-like behavior, which was stably detected >3 weeks after last water-bucket stress endorsement. Administration of the anti-depressant, imipramine, for 20 days from time after the last emotional constraint completely reversed the stress-induced depression-like behavior. These results suggest that emotional stress evokes for 2h×14d in mice stably induces depression-like behavior in mice, as does the 2h×14d restraint.

Keywords: emotional stress, anxiety, depression, behavior