Comparison of the effect of irindalone, a novel serotonin 5-HT2 antagonist and ketanserin on mechanical responses of rat thoracic aorta.

The relaxant effect of irindalone [+)-(1R, 3.S)-1-[2-[4-[3-(p-fluorophenyl)-1-indanyl]-1-piperazinyl] ethyl]2-imidazolidinone) and ketanserin was studies on active tension in isolated rat thoracic aorta. Irindalone and ketanserin caused a concentration-related inhibition of serotonin-induced contractions and shifted the serotonin curve to the right. Irindalone was more potent in inhibiting the serotonin-induced contractions and ketanserin was. The slopes of the Schild plots for the two substances were slightly, but not significantly, different from each other. This indicates that irindalone had a more pronounced serotonin antagonistic effect than ketanserin.