Abstract
BackgroundChronic social defeat stress induces depression and anxiety-like behaviors in rodents and also responsible for differentiating defeated animals into stress susceptible and resilient groups. The present study investigated the effects of social defeat stress on a variety of behavioral parameters like social behavior, spatial learning and memory and anxiety like behaviors. Additionally, the levels of various dopaminergic markers, including the long and short form of the D2 receptor, and total and phosphorylated dopamine and cyclic adenosine 3′,5′-monophosphate regulated phosphoprotein-32, and proteins involved in intracellular trafficking were assessed in several key brain regions in young adult mice.MethodsMouse model of chronic social defeat was established by resident-intruder paradigm, and to evaluate the effect of chronic social defeat, mice were subjected to behavioral tests like spontaneous locomotor activity, elevated plus maze (EPM), social interaction and Morris water maze tests.ResultsMice were divided into susceptible and unsusceptible groups after 10 days of social defeat stress. The susceptible group exhibited greater decreases in time spent in the open and closed arms compared to the control group on the EPM. In the social interaction test, the susceptible group showed greater increases in submissive and neutral behaviors and greater decreases in social behaviors relative to baseline compared to the control group. Furthermore, increased expression of D2L, D2S, Rab4, and G protein-coupled receptor associated sorting protein-1 was observed in the amygdala of the susceptible group compared to the control group.ConclusionThese findings suggest that social defeat stress induce anxiety-like and altered social interacting behaviors, and changes in dopaminergic markers and intracellular trafficking-related proteins.
Highlights
Chronic social defeat stress induces depression and anxiety-like behaviors in rodents and responsi‐ ble for differentiating defeated animals into stress susceptible and resilient groups
To date, no studies have investigated the effects of social defeat stress on D2 long form (D2L) or D2 short form (D2S) except for one study from our research group [21], which found increased expression of D2S and D2L in the prefrontal cortex (PFC) of susceptible mice compared to controls
The present study aimed to investigate the effects of chronic social defeat on a variety of behavioral parameters, including the social interaction, elevated plus maze (EPM), and Morris water maze (MWM) tests, and the levels of dopaminergic markers (D2L, D2S, and total and p-DARPP-32) and proteins involved in intracellular trafficking in several brain regions of mice known to be affected in stress-related disorders such as anxiety and depressive disorders [31], and schizophrenia [32]
Summary
Chronic social defeat stress induces depression and anxiety-like behaviors in rodents and responsi‐ ble for differentiating defeated animals into stress susceptible and resilient groups. To date, no studies have investigated the effects of social defeat stress on D2L or D2S except for one study from our research group [21], which found increased expression of D2S and D2L in the prefrontal cortex (PFC) of susceptible mice compared to controls. Our research group reported significant increases in the expression of total DARPP-32 and phosphorylated DARPP-32 (p-DARPP-32) in the PFC and amygdala (AMY) of defeated mice [26]. Those studies did not separate defeated mice into susceptible and unsusceptible groups, which is important for exploring the mechanisms that underlie the susceptibility to stress
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