Effects of synthetic cannabinoids on electroencephalogram power spectra in rats

Several synthetic cannabinoids have recently been distributed as psychoactive adulterants in many herbal products on the illegal drug market around the world. However, there is little information on pharmacology and toxicology of such compounds. Although Δ9-tetrahydrocannabinol (Δ9-THC), a psychoactive cannabinoid of marijuana, was reported to affect electroencephalograms (EEG) of rats, the effects of synthetic cannabinoids are unknown. We examined the pharmacological activities of three synthetic cannabinoids; cannabicyclohexanol (CCH), CP-47,497 and JWH-018; by analyzing EEG power spectra and locomotor activity after intraperitoneal administration to rats and compared them with those of Δ9-THC. The three compounds significantly increased the EEG power in the frequency range of 5.0–6.0 Hz for the first 3 h, while Δ9-THC decreased the power spectra in the wide range of 7.0–20.0 Hz during the first hour. These results indicate that the effect of the three compounds on EEG is different from that of Δ9-THC. Additionally, CCH, CP-47,497 and JWH-018 significantly decreased the locomotor activity for 11.5 h, 11 h and 4.5 h, respectively, after administration which was longer than that of Δ9-THC (3.5 h). Furthermore, all three compounds significantly reduced the total amounts of locomotor activity during a 3-h, 6-h and 12-h period after injection, whereas no statistical difference was observed for the Δ9-THC injection. Among the three compounds, CCH and CP-47,497 exerted a longer duration of the change in the EEG power spectra and suppression of the locomotor activity than JWH-018.