Effects of chronic social defeat stress on behavior and choline acetyltransferase, 78-kDa glucose-regulated protein, and CCAAT/enhancer-binding protein (C/EBP) homologous protein in adult mice

RATIONALE

Social defeat stress induces physiological and behavioral symptoms, including anxiety, anhedonia, immune deficits, and altered expression of key brain genes.

OBJECTIVES

The present study investigated the effects of social defeat stress on the behaviors and expressions of Chat, Grp78, and chop in the brains of adult mice.

METHODS

Adult mice were divided into susceptible and unsusceptible groups after 10 days of social defeat stress. In experiment 1, behavioral tests were conducted, and brains were processed for Western blotting at day 27 after stress. In experiment 2, social avoidance tests were conducted, and brains were processed for Western blotting at day 12 after stress.

RESULTS

The results indicate decreased and increased locomotion and anxiety behavior in all defeated mice. Decrease in social interaction, increased immobility, and impaired memory performance were only observed in susceptible mice. A decrease in the Chat level at days 12 and 27 was noted in the prefrontal cortex (PFC), amygdala (Amyg), and dorsal hippocampus (HIP) in defeated mice. The expression levels of Grp78 and chop measured on days 12 and 27 were significantly greater in the Amyg of susceptible mice. In the PFC and HIP, defeated mice displayed different patterns in the levels of Grp78 and chop expressions measured on days 12 and 27.

CONCLUSIONS

The present study demonstrated that chronic social defeat stress in mice produces stress-related behaviors. Different response patterns were noted for Grp78 and chop expression among the groups in terms of brain regions and time-course effects.

Therapeutic potential of Gastrodia elata Blume for the treatment of Alzheimer's disease

Several studies have demonstrated that the Chinese herb Gastrodia elata Blume can protect against amyloid beta-peptide (Aβ)-induced cell death. To investigate the possible therapeutic effects of Gastrodia elata Blume on Alzheimer's disease, we established a rat model of Alzheimer's disease by injecting Aβ25-35 into bilateral hippocampi. These rats were intragastrically administered 500 or 1 000 mg/kg Gastrodia elata Blume per day for 52 consecutive days. Morris water maze tests showed that Gastrodia elata Blume treatment significantly improved the spatial memory of Alzheimer's disease rats. Congo red staining revealed that Gastrodia elata Blume significantly reduced the number of amyloid deposits in the hippocampus of these rats. Western blot analysis showed that choline acetyltransferase expression in the medial septum and hippocampus was significantly increased by the treatment of Gastrodia elata Blume, while Ellman method showed significant decrease in the activity of acetylcholinesterase in all three regions (prefrontal cortex, medial septum and hippocampus). These findings suggest that long-term administration of Gastrodia elata Blume has therapeutic potential for Alzheimer's disease.

Effects of chronic mild stress in female bax inhibitor-1-gene knockout mice

OBJECTIVE

The anti-apoptotic protein Bax inhibitor-1 (BI-1) is a regulator of apoptosis linked to endoplasmic reticulum (ER) stress, and BI-1(-/-) mice exhibit increased sensitivity to tissue damage. The purpose of this study was to investigate the role of BI-1 in the pathogenesis of chronic mild stress (CMS)-induced depression-like behaviors in BI-1(-/-) mice.

METHODS

We delivered CMS for 2 or 6 weeks in BI-1-knockout and wild-type mice. Control groups of BI-1-knockout and wild-type mice were left undisturbed. The measured parameters were sucrose consumption at weeks 1, 2, 3, 4, 5, and 6, spontaneous locomotion, and a forced swimming test (FST) at weeks 2 and 6.

RESULTS

Significant decreases in sucrose consumption and increases in immobility time in the FST were observed in both stress groups compared with the non-stress groups. Interestingly, at week 2, but not at week 6, BI-1(-/-)-stress mice showed less sucrose intake and greater immobility time than did BI-1(+/+)-stress mice.

CONCLUSION

These results suggest that BI-1 may play role in protecting against the depressogenic effects of CMS in the short term, but not in the long term. Further study is required to deepen understanding of the role of BI-1 in protecting against depression.