Influence of phenylmethylsulfonyl fluoride on anandamide brain levels and pharmacological effects

The endogenous cannabinoid anandamide produces cannabimimetic effects simil ar to those produced by Delta(9)-tetrahydrocannabinol (Delta(9)-THC), but h as a much shorter duration of action due to its rapid metabolism to arachid onic acid and polar metabolites via action of fatty acid amide hydrolase (F AAH). Our earlier observations that anandamide's effects persisted after br ain levels of anandamide itself had substantially dropped prompted us to ex amine the influence of the irreversible amidase inhibitor, phenylmethyl sul fonyl fluoride (PMSF), on the brain levels and pharmacological effects of a nandamide. As shown previously, pretreatment with PMSF resulted in a leftwa rd shift of the anandamide dose effect curves for antinociception and hypot hermia in male mice. Brain and plasma levels of anandamide, arachidonic aci d and polar metabolites peaked at 1 min after i.v. injection with H-3-anand amide and remained high at 5 min post-injection, with levels falling sharpl y thereafter. Pretreatment with PMSF (30 mg/kg, i.p.) Drier to an injection of 1 or 10 mg/kg H-3-anandamide resulted 5 min later in enhanced brain lev els of anandamide compared to those obtained with H-3-anandamide plus vehic le injection. Levels of arachidonic acid and polar metabolites in brain wer e not significantly increased. The clear correspondence between brain level s of anandamide following pretreatment with PMSF and pharmacological activi ty suggests that this parent compound is responsible for the antinociceptio n and hypothermia that occurred 5 min after injection. These results furthe r suggest that metabolite contribution to anandamide's effects, if any, wou ld occur primarily at later times. (C) 2000 Elsevier Science Inc. All right s reserved.