CAN A SEROTONIN TYPE-3 (5-HT3) RECEPTOR ANTAGONIST REDUCE EXPERIMENTALLY-INDUCED ITCH

Background: Serotonin type 3 (5-HT3) receptor antagonists have been re ported to be a novel therapeutic principle for the treatment of choles tatic and uremic pruritus. Objective: To determine the antipruritic ef fect of a 5-HT3 receptor antagonist (tropisetron) on histamine and ser otonin-induced itch under experimental conditions in comparison to nat ive skin and after pretreatment with an orally applied antihistamine ( cetirizine). Methods: Histamine and serotonin were iontophoretically a pplied in 10 healthy volunteers, Wheals and flares were planimetricall y evaluated, Itching and burning sensations were entered oil a scale o ver 24 min, The examination also comprised alloknesis, elicitation of perifocal itch sensation by usually non-itching (e.g. mechanical) stim uli. Results: Tropisetron did not have any significant influence on hi stamine-induced reactions but could significantly reduce serotonin-ind uced flares, Cetirizine led to a significant reduction of all histamin e-induced parameters and abolished serotonin-induced wheals. Conclusio ns: Serotonin has an own pruritic potency and does not only act over h istamine containing mast cells. The antipruritic effect of tropisetron reported in cholestatic and uremic pruritus could not be verified in healthy persons under experimental conditions.