Unpredictable chronic mild stress not chronic restraint... : NeuroReport (original) (raw)

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Unpredictable chronic mild stress not chronic restraint stress induces depressive behaviours in mice

Zhu, Shenghuaa; Shi, Ruoyangb; Wang, Junhuic,d; Wang, Jun-Fenga; Li, Xin-Minc

Departments of aPharmacology and Therapeutics

bHuman Anatomy and Cell Science, Faculty of Medicine, University of Manitoba, Winnipeg, Manitoba

cDepartment of Psychiatry, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada

dMental Health Center, Shantou University, Shantou, Guangdong, China

Correspondence to Xin-Min Li, MD, PhD, Department of Psychiatry, 1E7.31 Walter C. Mackenzie Health Sciences Centre, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada T6G 2B7 Tel: +1 780 4076503; fax: +1 780 4076804; e-mail: [email protected]

Received June 10, 2014

Accepted July 9, 2014

Abstract

The chronic stress model was developed on the basis of the stress–diathesis hypothesis of depression. However, these behavioural responses associated with different stress paradigms are quite complex. This study examined the effects of two chronic stress regimens on anxiety-like and depressive behaviours. C57BL/6 mice were subjected to unpredictable chronic mild stress or to chronic restraint stress for 4 weeks. Subsequently, both anxiety-like behaviours (open field, elevated plus maze and novelty suppressed feeding) and depression-like behaviours (tail suspension, forced swim and sucrose preference) were evaluated. Both chronic stress models generated anxiety-like behaviours, whereas only unpredictable chronic mild stress could induce depressive behaviours such as increased immobility and decreased sucrose consumption. These results of the present study provide additional evidence on how chronic stress affects behavioural responses and point to the importance of the validity of animal models of chronic stress in studying depression.