Influence of captopril on the vasopressor effect of serotonin in pithed rats

In pithed rats intravenous administration of serotonin (5.0, 10.0, 20.0, 30.0 and 50.0 micrograms/kg) produced a dose-dependent increase in blood pressure. The pressor response to serotonin was significantly reduced by captopril (1.0, 5.0 and 50.0 mg/kg) in a dose-dependent manner. Captopril did not attenuate the response of the isolated tail artery to serotonin (5-HT) and did not amplify the dilator effect of serotonin in pithed rats pretreated with ketanserin (1.0 mg/kg). These data suggest that the action of captopril does not depend on its influence on serotoninergic receptors in blood vessels.