This study investigated endogenous mediators involved in mosquito allergyassociated itching in mice. An intradermal injection of an extract of mosquito salivary gland elicited marked scratching in sensitized mice. The 5-lipoxygenase inhibitor zileuton (100 mg / kg), the 5-lipoxygenase activating peptide inhibitor MK-886 (10 mg / kg), and the glucocorticoid betamethasone 17-valerate (3 mg / kg) inhibited the scratching. The scratching was not affected by the cyclooxygenase inhibitors

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... and ketoprofen, the TP prostanoid receptor antagonist SQ-29548, the leukotriene B 4 antagonist ONO-4057, the cysteinyl leukotriene antagonist pranlucast, the leukotriene D 4 antagonist MK-571, the platelet-activating factor antagonist CV-3988, the nitric oxide synthase inhibitor N G -nitro-L-arginine methyl ester, the H 2 histamine-receptor antagonist cimetidine, the H 1 histamine-receptor antagonist terfenadine plus cimetidine, and cypoheptadine that blocks the 5-HT 1/ 2 serotonin receptors. Zileuton (100 mg / kg) inhibited the increased activity of the cutaneous nerve branch induced by an intradermal injection of the extract, suggesting the peripheral action. Zileuton and MK-886 (10 and 100 µM) did not affect high K + -induced increase in intracellular Ca 2+ concentration in cultured dorsal root ganglion neurons. The results suggest that 5-lipoxygenase metabolite(s) other than leukotriene B 4 and cysteinyl leukotrienes are involved in mosquito allergy-associated itching.