PAF- and histamine-receptor antagonists lessen allergen-induced hearing impairment in guinea pigs

We have demonstrated degranulation of mast cells in the endolymphatic sac as well as an increase in audiological threshold shift in the experimental animal models following antigen provocation. Mast cells, however, release such chemical mediators as histamine, platelet activating factor (PAF), and leukotriene due to an antigen-antibody reaction on the cell surface. The aim of this study was to clarify the major chemical mediators responsible for hearing impairment in the animal models following antigen provocation. Guinea pigs were actively sensitized with DNP-Ascaris and provoked with an injection of DNP-BSA. A significant audiological threshold shift was observed at 1, 10, 24, and 72 h following challenge with allergen. The peak shift was at 10 h; all changes were reversed after 7 days. This threshold shift was abolished by prior injection of either a histamine- or PAF-receptor antagonist to allergen, but not of a leukotriene-receptor antagonist. Results suggest that histamine and PAF are involved in the hearing impairment induced by allergen exposure in the guinea pig.