EFFECT OF ACETYLSALICYLIC-ACID ON FORMALIN TEST AND ON SEROTONIN SYSTEM IN THE RAT-BRAIN

1. Acetylsalicylic acid (ASA; 400 mg/kg, IP) increased serotonin (5-HT ) content in rat brain but did not modify the number or the affinity o f 5-HT1A receptors in the pens and the cerebral cortex, whereas the nu mber of cortical 5-HT2 receptors decreased significantly. 2. Pretreatm ent with parachlorophenylaline (100 mg/kg/day for 4 days) depleted 5-H T brain content but modified neither the serum levels of salicylates n or the 5-HT2 cortical receptor characteristics, and it abolished the a ntinociceptive effect of ASA, 400 mg/kg, in the first phase of the for malin test. 3. These data support the involvement of the central serot onergic system in the antinociceptive activity of ASA. (C) 1998 Elsevi er Science Inc.