Fig. 2.

Schematic overview of commonly used animal models of depression and tests of depression- and anxiety-like behavior. a Chronic social defeat stress (CSDS) [17, 86] is useful in modeling differential susceptibility. Many people remain resilient to depression in the face of stress. After CSDS, susceptible mice exhibit a depression-like phenotype characterized by reduced social interaction (also reduced sucrose preference, increased immobility in a forced swim test, circadian, and metabolic changes) whereas resilient mice continue to seek out social interaction and, unlike susceptible mice, are similar to non-stressed controls on a range of depression-relevant metrics, although, like susceptible mice, they show increased anxiety indicated by reduced center exploration in an open field. b Learned helplessness is another commonly used model of depression. After experiencing repeated inescapable footshock, susceptible animals fail to escape from signaled shocks when given the opportunity, but some animals will escape, demonstrating resilience. Chronic mild stress or chronic variable stress (c) refer to a number of protocols in which mice or rats are repeatedly exposed to a single stressor or a variety of stressors over days or weeks. Stressors may include a wide range of manipulations such as tail suspension, restraint, footshock, noise and bright light. d Susceptibility is assessed by increases in depression- and anxiety-like behavior. Depression-like behavior is typically assessed by tests such as forced swim, tail suspension, sucrose preference, or open field. Anxiety-like behavior is also assessed in an open field or elevated plus maze test. See Table 3 for a complete description of paradigms and tests