Type 1 Allergy-Induced Endolymphatic Hydrops and the Suppressive Effect of H1-Receptor Antagonist (Olopatadine Hydrochloride)

Objective To investigate whether endolymphatic hydrops (EH) is experimentally induced by type 1 (or immediate) hypersensitivity allergic reaction and to investigate the inhibitory action of a histamine H-1-receptor antagonist (olopatadine hydrochloride [OLO-Hy]) on allergic EH induced by systemic immune challenge with 2,4-dinitrophenylated-Ascaris (DNP-As). Methods The experimental animals were actively sensitized with DNP-As twice at a 4-week interval and were provoked by an injection of DNP-BSA including DNP-As 1 week after the second sensitization. The OLO-Hy (+) group received oral administration of OLO-Hy (30 mg/kg) 1 hour before the provocation, whereas the OLO-Hy (-) group received distilled water. The temporal bones in all animals were light microscopically examined to assess the degree of EH quantitatively and the expression of degranulated mast cells in the endolymphatic sac. Results Endolymphatic hydrops was observed 1, 6, 12, and 24 hours after the last sensitization in the OLO-Hy (-) group but was not observed in the OLO-Hy (+) group. Quantitative analysis of the increase ratios (IRs) of the cross-sectional area of the scala media revealed that the IRs of the OLO-Hy (-) group were significantly greater compared with those of the control group (p < 0.001). There was also a significant difference in the IRs between the OLO-Hy (-) and OLO-Hy (+) groups (p < 0.001). Conclusion The systemic sensitization with DNP-As produced allergy-induced experimental EH by type 1 hypersensitivity allergic reaction, and the development of this EH was prevented by histamine H-1-receptor antagonists.