Peripheral serotonin2 receptor blockade does not inhibit 5-hydroxytryptophan-induced aldosterone stimulation.

To assess the effects of serotonin receptor blockade on 5-hydroxytryptophan (5HTP)-induced aldosterone secretion, we studied six normal men using the serotonin antagonists ketanserin and methysergide. The subjects were studied on three separate occasions, and pretreatment with dexamethasone was given before each study. On two occasions, the pretreatment period also included administration of a serotonin antagonist, either ketanserin (120 mg/day) or methysergide (6 mg/day). On the day of study, the subjects were given a single oral 200-mg dose of 5HTP. Plasma levels of aldosterone increased significantly after 5HTP treatment compared to basal levels during each stage of the study. No significant difference in response in the three studies was found. We conclude that peripheral blockade of serotonin2 receptors does not abolish 5HTP-induced aldosterone stimulation, and that this stimulation is most likely mediated by central pathways.