Background & Objective: ‎Cannabinoids have a dose-related antinociceptive effect in animals and humans through Cannabinoid receptors (CB1,CB2). Several ‎studies have suggested that CB2 receptors are not expressed in the CNS but others suggest that there are a few, although significant, receptors in that area. To date no studies have been done on the antinociceptive effect of central administration of a CB2 agonist. In this study the central and peripheral analgesic effect of JWH133 (a CB2 agonist) was examined.‎
Materials & Methods: Male mice were used in this study. The antinociceptive effects of intracerebroventricular (i.c.v.) administration of JWH133 ‎using formalin test was studied in stereotaxed mice after one week of ‎surgery and the insertion of a stainless steel cannula in the left cerebroventricle. To study peripheral effects of JWH133, the drug was administered intraperitoneally (i.p.).
Results: The i.c.v injection of JWH133 had no effect but i.p. injection of the drug had analgesic effects.
Conclusion: The present results may suggest that there are no any effective analgesic CB2 receptors in the CNS.