SEROTONIN AND OPIATE INVOLVEMENT IN THE ANTINOCICEPTIVE EFFECT OF ACETYLSALICYLIC-ACID

Acetylsalicylic acid (ASA), 400 mg/kg i.p., displayed antinociceptive activity in both the hot-plate and the formalin test, ASA significantl y increased brain serotonin (5-HT) content and reduced the number of 5 -HT2 receptors in cortical brain membranes 30 min after drug administr ation, Pretreatment with naloxone abolished the antinociceptive activi ty of both ASA and morphine in the hot-plate and formalin tests and pr evented the increase in cerebral 5-HT concentration and the reduction in 5-HT2 receptors in cortical membranes induced by ASA, The serum sal icylate concentrations were not affected by pretreatment with naloxone , These data indicate a central antinociceptive activity of ASA and su ggest that ASA may exert its antinociceptive action through serotonerg ic and opiatergic pathways.