Central antinociceptive activity of acetylsalicylic acid is modulated by brain serotonin receptor subtypes

Male Wistar rats were treated with ondansetron (1 and 2 mg/kg s.c.), ketanserin (0.2, 1 and 5 mg/kg s.c.) or NAN-190 (1, 3 and 5 mg/kg i.p.) 15 min before acetylsalicylic acid (ASA, 400 mg/kg i.p.), and 30 min thereafter the pain threshold was evaluated. The antinociceptive activity of ASA in the hot-plate test was variously affected by ondansetron, ketanserin and NAN-190: at the highest dose (2 mg/kg s.c.) ondansetron abolished it while ketanserin (5 mg/kg s.c.) significantly reduced it, and NAN-190 (1-5 mg/kg) did not significantly modify the effect of ASA. Binding experiments indicate that both ondansetron and ketanserin completely prevented the decrease in the maximum number of 5-HT2 receptors (B-max) provoked by ASA. These data indicate that the central antinociceptive activity of ASA is modulated in a different manner by serotonin receptor antagonists, and that 5-HT2 and 5-HT3 receptors may exert a pivotal role in nociception, alone or in association. Copyright