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, sponta-neous 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 shor