Background and purpose: Cannabinoids (CBs) are known to be vasoactive and to regulate tissue inflammation. The present study examined the in vivo vasomotor effects of the CB 2 receptor agonists JWH015 and JWH133 in rat knee joints. The effect of acute and chronic joint inflammation on CB 2 receptor-mediated responses was also tested. Experimental approach: Blood flow was assessed in rat knee joints by laser Doppler imaging both before and following topical administration of CB 2 receptor agonists. Vasoactivity was measured in normal, acute kaolin/carrageenan inflamed and Freund's complete adjuvant chronically inflamed knees. Key results: In normal animals, JWH015 and JWH133 caused a concentration-dependent increase in synovial blood flow which in the case of JWH133 was blocked by the selective CB 2 receptor antagonist AM630 as well as the transient receptor potential vanilloid-1 (TRPV1) antagonist SB366791. The vasodilator effect of JWH133 was significantly attenuated in both acute and chronically inflamed knees. Given alone, AM630 had no effect on joint blood flow. Conclusion and implications:In normal joints, the cannabinomimetic JWH133 causes hyperaemia via a CB 2 and TRPV1 receptor mechanism. During acute and chronic inflammation, however, this vasodilatatory response is significantly attenuated.

Because UDCA is used in treating certain clinical disorders, these results provide a rationale for human clinical trials using this and related drugs for treatment of Duchenne and related muscular dystrophies.