Antinociceptive Effect of Peripheral and Intracerebroventricular Administration of JWH۱۳۳ in Mice.

Background & Objective: ‎Cannabinoids have a dose-related antinociceptive effect in animals and humans through Cannabinoid receptors (CB۱,CB۲). Several ‎studies have suggested that CB۲ 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 CB۲ agonist. In this study the central and peripheral analgesic effect of JWH۱۳۳ (a CB۲ agonist) was examined.‎ Materials & Methods: Male mice were used in this study. The antinociceptive effects of intracerebroventricular (i.c.v.) administration of JWH۱۳۳ ‎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 JWH۱۳۳, the drug was administered intraperitoneally (i.p.). Results: The i.c.v injection of JWH۱۳۳ 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 CB۲ receptors in the CNS.