Involvement of opioid system in antidepressant-like effect of the cannabinoid CB1 receptor inverse agonist AM-251 after physical stress in mice

Summary Cannabinoid inverse agonists possess antidepressant‐like properties, but the mechanism of this action is unknown. Numerous studies have reported the interaction between opioid and cannabinoid pathways. In this study, acute foot‐shock stress was used in mice to investigate the involvement of the opioid pathway in the antidepressant‐like effect of the cannabinoid CB1 receptor inverse agonist AM‐251. Stress was induced by intermittent foot‐shock stimulation for 30 min. Then, using the forced swimming test (FST) and tail suspension test (TST), the immobility time was measured. Results show that the immobility time was significantly prolonged in animals subjected to foot‐shock stress, compared with non‐stressed controls (P