A standardized protocol for repeated social defeat stress in mice

Abstract

A major impediment to novel drug development has been the paucity of animal models that accurately reflect symptoms of affective disorders. In animal models, prolonged social stress has proven to be useful in understanding the molecular mechanisms underlying affective-like disorders. When considering experimental approaches for studying depression, social defeat stress, in particular, has been shown to have excellent etiological, predictive, discriminative and face validity. Described here is a protocol whereby C57BL/6J mice that are repeatedly subjected to bouts of social defeat by a larger and aggressive CD-1 mouse results in the development of a clear depressive-like syndrome, characterized by enduring deficits in social interactions. Specifically, the protocol consists of three important stages, beginning with the selection of aggressive CD-1 mice, followed by agonistic social confrontations between the CD-1 and C57BL/6J mice, and concluding with the confirmation of social avoidance in subordinate C57BL/6J mice. The automated detection of social avoidance allows a marked increase in throughput, reproducibility and quantitative analysis. This protocol is highly adaptable, but in its most common form it requires 3–4 weeks for completion.

Chronic psychosocial stress in mice leads to changes in brain functional connectivity and metabolite levels comparable to human depression

“…Control mice remained in littermate pairs, the standard condition in our laboratory, and were handled and weighed daily. The CPS protocol is modified from the standard CSD protocol (Golden et al, 2011) in terms of: timing the attacks and limiting maximum attack-time per mouse per day to 60 s (versus 10 min) and trimming the incisor teeth of CD-1 mice to prevent bite wounding (versus no teeth trimming and regular bite wounding). These modifications were combined with an increase in the duration of the stressor to 15 days (versus 10 days), thereby increasing comparability to other chronic rodent stressors such as chronic unpredictable mild stress (Willner, 1997).…”

“…In mice, chronic social stressors combined with behavioural tests have identified changes in emotional, motivational and cognitive states that are relevant to human psychopathologies. For example, chronic social defeat (CSD) (Golden et al, 2011) leads to social avoidance and decreased interest in gustatory reward (Covington et al, 2009;Krishnan et al, 2007). In vivo electrophysiology has provided evidence for altered PFC -amygdala coherence in terms of neuronal firing in CSD mice (Kumar et al, 2014).…”

“…These CPS effects are obtained without dividing mice into susceptible versus resilient sub-groups based on their subsequent passive avoidance of the aggressor mouse strain, the method used in the common CSD protocol (Golden et al, 2011). That is, we use an "inclusive" experimental design, as used extensively with other stressors e.g.…”

Mouse social stress induces increased fear conditioning, helplessness and fatigue to physical challenge together with markers of altered immune and dopamine function

“…Stressed CSD mice display submissive behaviour but this fails to deter/control attacks by the dominant mice (Kudryavtseva et al, 1991). Bite wounds are common in the standard CSD protocol (Golden et al, 2011), somewhat impacting on its aetiological validity as an emotional psychosocial stressor. Readout tests of CSD effects have focussed on passive avoidance of the 5 aggressor mouse strain in a social proximity test (Krishnan et al, 2007;Savignac et al, 2011b); that is, on increased emotional reactivity to the specific learned uncontrollable social stimulus (Russo et al, 2012).…”

“…The proinflammatory cytokines of tumor necrosis factor (TNF) and interleukin-6 (IL-6) are increased in a majority of depression patients relative to matched controls (Dowlati et al, 2010;Maes, 2010). To render CSD aetiologically valid with respect to stress induced inflammation it was essential to introduce refinements to prevent the bite wounding that is frequent in the standard CSD protocol (Golden et al, 2011). The peripheral immune-inflammation markers of plasma TNF and IL-6 levels and spleen mass were measured.…”