The antidepressant action of cannabis as well as the interaction between antidepressants and the endocannabinoid system has been reported. This study was conducted to assess the antidepressantlike activity of Δ 9 -THC and other cannabinoids. Cannabinoids were initially evaluated in the mouse tetrad assay to determine doses that do not induce hypothermia or catalepsy. The automated mouse forced swim (FST) and tail suspension (TST) tests were used to determine antidepressant action. At doses lacking hypothermic and cataleptic effects (1.25, 2.5, and 5 mg/kg, i.p.), both Δ 9 -THC and Δ 8 -THC showed a U-shaped dose response with only Δ 9 -THC showing significant...
