EFFECTS OF RITANSERIN, A NOVEL SEROTONIN-S-2 RECEPTOR ANTAGONIST, ON THE SECRETION OF PITUITARY-HORMONES IN NORMAL HUMANS

The availability of a new potent and selective serotonin-S-2 antagonis t, ritanserin (RIT), encouraged us to further investigate the effect o f serotonin on the basal secretion of anterior pituitary hormones in n ormal humans. Administered in a single 30-mg dose to group 1 consistin g of 10 normal women, RIT failed to affect the baseline LH, FSH, GH or TSH levels. In group 2 consisting of 20 normal subjects (ten males an d ten females), the same dose of RIT decreased in parallel both ACTH a nd cortisol levels but only at 180 min. Group 3 consisting of 8 normal men was studied on three separate occasions seven days apart: each su bject received graded doses of 10 mg, 20 mg and 30 mg RIT. The mean ba seline PRL concentration at 180 min as well as the net integrated area under the hormone curve (nAUC) decreased only after the highest dose, while the baseline cortisol concentrations at 180 min as well as the corresponding nAUC values displayed a clear dose-dependent response. T he findings indicated the seretonin-S-2 receptors to be only partially involved in the basal secretion of ACTH in normal humans.