Lack of activity of azapropazone in the hot-plate test and in 5-HT1A and 5-HT2 receptor subtypes in rat brain membranes

This study aimed to investigate the antinociceptive activity of azapropazone (AZA), a weak prostaglandin synthesis inhibitor using the hot-plate test, and its ability to modify the serotonin-binding capacity in rat brain membranes. it revealed that AZA had no antinociceptive effect in the hot-plate test at the doses of 400 and 600 mg/kg when orally administered (p.o.), and at 400, 500 and 600 mg/kg after intraperitoneal injection (i.p.). At the dose of 600 mg/kg i.p. the drug failed to modify the number and the affinity of 5-HT1A and 5-HT2 receptors in rat brain membranes. in accordance with our previous findings on a positive correlation between NSAIDs antinociception in this experimental model and changes in 5-HT receptor characteristics, these results suggest an association between the lack of AZA-mediated antinociception in the hot-plate test and the drug's inability to modify the characteristics of 5-HT1A and 5-HT2 receptor binding sites in rat brain membranes.