Functional effects of synthetic cannabinoids versus Δ ⁹ -THC in mice on body temperature, nociceptive threshold, anxiety, cognition, locomotor/exploratory parameters and depression

Synthetic cannabinoids are psychoactive substances designed to mimic the euphorigenic effects of the natural cannabis. Novel unregulated compounds appear once older compounds become illegal. It has been previously reported that synthetic cannabinoids are different than Δ ⁹ -tetrahydrocannabinol (Δ ⁹ -THC) as they have chemical structures unrelated to Δ ⁹ -THC, different metabolism and, often, greater toxicity. This study aimed to investigate the effects of three novel synthetic cannabinoids and pure Δ ⁹ -THC on body temperature, nociceptive threshold, anxiety, memory function, locomotor and exploratory parameters, and depression. We performed a battery of behavioural and motor tests starting 50 minutes post i.p. injection of each drug to adult ICR mice. The synthetic cannabinoids that were used are AB-FUBINACA, AB-CHMINACA and PB-22. All synthetic cannabinoids and Δ ⁹ -THC caused hypothermia, but only Δ ⁹ -THC induced a clear antinociceptive effect. All synthetic cannabinoids and Δ ⁹ -THC caused decreased anxiety levels, spatial memory deficits and decreased exploratory behaviour as measured in the elevated plus maze, Y-maze and staircase paradigm, respectively. However, all synthetic cannabinoids but not Δ ⁹ -THC demonstrated decreased locomotor activity in the staircase test. Moreover, only AB-FUBINACA and Δ ⁹ -THC affected the gait balance and grip strength of the mice as was assessed by the latency time to fall from a rod. In the forced swimming test, PB-22 caused elevated depression-like behaviour while AB-FUBINACA induced a reversed effect. These results suggest varied effects among different synthetic cannabinoids and Δ ⁹ -THC. Further studies are needed to characterize the overall effects and differences between these synthetic cannabinoids and Δ ⁹ -THC.