Can a serotonin type 3 (5-HT3) receptor antagonist reduce experimentally-induced itch?

Abstract.

Background: Serotonin type 3 (5-HT3) receptor antagonists have been reported to be a novel therapeutic principle for the treatment of cholestatic and uremic pruritus.¶Objective: To determine the antipruritic effect of a 5-HT3 receptor antagonist (tropisetron) on histamine and serotonin-induced itch under experimental conditions in comparison to native skin and after pretreatment with an orally applied antihistamine (cetirizine).¶Methods: Histamine and serotonin were iontophoretically applied in 10 healthy volunteers. Wheals and flares were planimetrically evaluated. Itching and burning sensations were entered on a scale over 24 min. The examination also comprised alloknesis, elicitation of perifocal itch sensation by usually non-itching (e.g. mechanical) stimuli.¶Results: Tropisetron did not have any significant influence on histamine-induced reactions but could significantly reduce serotonin-induced flares. Cetirizine led to a significant reduction of all histamine-induced parameters and abolished serotonin-induced wheals.¶Conclusions: Serotonin has an own pruritic potency and does not only act over histamine containing mast cells. The antipruritic effect of tropisetron reported in cholestatic and uremic pruritus could not be verified in healthy persons under experimental conditions.