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.