Abstract
Voluntary exercise has been reported to have a therapeutic effect on many psychiatric disorders and social stress is known to impair social interaction. However, whether voluntary exercise could reverse deficits in social behaviors induced by chronic social defeat stress (CSDS) and the underlying mechanism remain unclear. The present study shows CSDS impaired social preference and induced social interaction deficiency in susceptible mice. Voluntary wheel running (VWR) reversed these effects. In addition, CSDS decreased the levels of tyrosine hydroxylase in the ventral tegmental area and the D2 receptor (D2R) in the nucleus accumbens (NAc) shell. These changes can be recovered by VWR. Furthermore, the recovery effect of VWR on deficits in social behaviors in CSDS mice was blocked by the microinjection of D2R antagonist raclopride into the NAc shell. Thus, these results suggest that the mechanism underlying CSDS-induced social interaction disorder might be caused by an alteration of the dopamine system. VWR may be a novel means to treat CSDS-induced deficits in social behaviors via modifying the dopamine system.
Highlights
Social interaction disorders such as social avoidance and lack of desire for social interaction are common symptoms of psychiatric disorders (Miyoshi and Morimura, 2010; Rosa et al, 2018)
D2 receptor (D2R) levels in the nucleus accumbens (NAc) shell of mice in the SD group (p < 0.01) were significantly lower compared to the NC group, and Voluntary wheel running (VWR) up-regulated Chronic social defeat stress (CSDS)-induced decrease in D2R expression in the NAc shell (p < 0.01) (Figure 4). These results suggest that D2R in the NAc shell might be involved in NC, control group; SD, chronic social defeat stress; SD + VWR, SD + voluntary wheel running
The results of the present study agree with these previous findings. These results show that VWR reversed the decrease of both Tyrosine hydroxylase (TH) positive neurons and TH expression in the ventral tegmental area (VTA) induced by CSDS, the reversing effect of VWR on the decrease of TH positive neurons in the VTA is more significant than the reversing effect on the decrease of TH expression in the VTA
Summary
Social interaction disorders such as social avoidance and lack of desire for social interaction are common symptoms of psychiatric disorders (Miyoshi and Morimura, 2010; Rosa et al, 2018). Chronic social defeat stress (CSDS) is widely used for research on the social stress in animal models (Krishnan et al, 2007; Rosa et al, 2018). Previous reports showed that CSDS can reduce the tendency to interact with other individuals in susceptible mice, and symptoms include social avoidance and decreased social sniffing (Jin et al, 2015; Huang et al, 2016). This effect can last at least 3 weeks after the last day of CSDS (Krishnan et al, 2007; Razzoli et al, 2011).
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