Altered theta oscillations in basolateral amygdala and ventral hippocampus related to social defeat.

Background: Depression is a prevalent mental disorder, and prolonged exposure to social defeat is a major contributing factor in the onset of depression. Repeated social defeat stress (RSDS) is a commonly used animal model for depression, significantly impacting on the pathogenesis of depression-related to social disorders. The basolateral amygdala (BLA) and the ventral hippocampus (vHPC) are critical brain regions involved in RSDS-induced social behavioral disorders, but the specific neural oscillations occurring in these regions following social defeat remain unclear.

Methods: Using simultaneous multi-electrode recordings, we captured local field potentials (LFPs) from BLA and vHPC while the stressed mice underwent a social interaction test. Power spectral analysis and Amplitude transform entropy were respectively applied to assess social defeat-induced alterations in neural oscillatory activity and directional inter-regional communication.

Results: Our study demonstrated that repeated social defeat induces social avoidance and depression-like behaviors. Notably, the power spectral analysis within the BLA and vHPC revealed statistically differences in the theta band (4-12 Hz) between control and RSDS groups, particularly during the With CD1 phase in the 0-3 s stage, when mice entered the social interaction zone, compared to the - 3 -0 s stage prior to enter the zone. Moreover, machine learning analysis successfully classified control and RSDS groups based on neural oscillatory activity in the BLA and vHPC. Finally, ketamine treatment was found to reduce social avoidance and depressive-like behaviors, as well as enhance theta oscillation in the BLA and vHPC.

Conclusion: These results suggest that social defeat alters theta oscillations in the BLA and vHPC, highlighting potential therapeutic avenues for addressing depression-related social dysfunction.