RESUMO
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. 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.]. The i.c.v injection of JWH133 had no effect but i.p. injection of the drug had analgesic effects. The present results may suggest that there are no any effective analgesic CB2 receptors in the CNS