The psychoactive plant cannabinoid, Δ 9- tetrahydrocannabinol, is antagonized by Δ 8- and Δ 9-tetrahydrocannabivarin in mice in vivo

Abstract

Background and purpose: To follow up in vitro evidence that Δ 9-tetrahydrocannabivarin extracted from cannabis (eΔ 9-THCV) is a CB 1 receptor antagonist by establishing whether synthetic Δ 9-tetrahydrocannabivarin (O-4394) and Δ 8-tetrahydrocannabivarin (O-4395) behave as CB 1 antagonists in vivo. Experimental approach: O-4394 and O-4395 were compared with eΔ 9-THCV as displacers of [ 3]-CP55940 from specific CB 1 binding sites on mouse brain membranes and as antagonists of CP55940 in [ 35S]GTPγS binding assays performed with mouse brain membranes and of R-(+)-WIN55212 in mouse isolated vasa deferentia. Their ability to antagonize in vivo effects of 3 or 10 mg kg -1 (i.v.) Δ 9-tetrahydrocannabinol in mice was then investigated. Key results: O-4394 and O-4395 exhibited similar potencies to eΔ 9-THCV as displacers of [ 3]-CP55940 (K i=46.6 and 64.4 nM, respectively) and as antagonists of CP55940 in the [ 35S]GTPγS binding assay (apparent K B=82.1 and 125.9 nM, respectively) and R-(+)-WIN55212 in the vas deferens (apparent K B=4.8 and 3.9 nM respectively). At i.v. doses of 0.1, 0.3, 1.0 and/or 3 mg kg -1 O-4394 and O-4395 attenuated Δ 9- tetrahydrocannabinol-induced anti-nociception (tail-flick test) and hypothermia (rectal temperature). O-4395 but not O-4394 also antagonized Δ 9-tetrahydrocannabinol-induced ring immobility. By themselves, O-4395 and O-4394 induced ring immobility at 3 or 10 mg kg -1 (i.v.) and antinociception at doses above 10 mg kg -1 (i.v.). O-4395 also induced hypothermia at 3 mg kg -1 (i.v.) and above. Conclusions and implications: O-4394 and O-4395 exhibit similar in vitro potencies to eΔ 9-THCV as CB 1 receptor ligands and as antagonists of cannabinoid receptor agonists and can antagonize Δ 9- tetrahydrocannabinol in vivo. © 2007 Nature Publishing Group All rights reserved.