Ritanserin, a serotonin-s₂ receptor antagonist, does not prevent 5-hydroxytryptophan-induced β-ep, β-lph and cortisol secretion

Ritanserin, a new serotonin antagonist selective upon S₂ receptor subclass is available. Thus, in order to better define the positive control of serotoninergic pathway on proopiomelanocortin (POMC)-related peptide release, a group of 7 healthy male volunteers has been submitted to a 5-hydroxytryptophane (5-OH-TP) test (200 mg p.o.) before and after 4days Ritanserin pretreatment. Plasma β-endorphin (β-EP), p-lipotropin (β-LPH) and cortisol levels were measured hourly for 4 h after each 5-OH-TP loading. Hormonal levels were measured by specific RIAs on extracted (cortisol) and chromatographed (β-EP and β-LPH) plasma samples. Basal plasma concentrations of the three hormones were unchanged by Ritanserin pretreatment. Similarly, the integrated areas of β-LPH, β-EP and cortisol release in response to 5-OH-TP remained unaffected by the receptor blockade. These data confirm that serotonin-acting drugs are able to stimulate POMC-related peptide release and indicatethat such interaction is not mediated through S2 receptor subclass.