Ritanserin, a Serotonin-S2 Receptor Antagonist, Does Not Prevent 5-Hydroxytryptophan-Induced β-EP, β-LPH and Cortisol Secretion

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Abstract
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 4 days Ritanserin pretreatment. Plasma β-endorphin (β-EP), β-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 indicate that such interaction is not mediated through S2 receptor subclass.