2.6 Chronic social defeat stress
The social defeat stress model of depression was performed according to our previously reported methods(X. Jiang, Lin, Cheng, & Wang, 2020). Adult male C57BL/6J mice were the subjects, and CD1 retired breeders were the aggressors. Each C57BL/6J mice was exposed to a different aggressive CD1 mice each day for 10 minutes over a total of 14 days. After the 10 minutes of contact, the defeated C57BL/6J mice were separated from the CD1 aggressors for the next 24 hours by plastic dividers containing holes, where they were exposed to chronic defeat stress in the form of threaten. Undefeated control mice were handled daily. Twenty-four hours after the last stress, defeated C57BL/6J mice were subjected to the social interaction test and sorted into either susceptible or unsusceptible phenotype based on interaction scores. All the CSDS-unsusceptible mice were removed. Then the CSDS-susceptible mice were housed individually and received daily injections of tested drugs or vehicle for another 14 days. After that, various behavioral tests were performed.