Comparison of cedar pollen-induced allergic rhinitis in passively and actively sensitized guinea pigs

We have developed an allergic rhinitis model in guinea pigs using Japanese cedar pollen as antigen. In the present study, we examined whether provocat ion by pollen induces similar magnitudes of rhinitis Symptoms in passively and actively sensitized guinea pigs. One group of animals was actively sens itized by intranasal application of pollen extract, and another was passive ly sensitized by intraperitoneal injection with anti-pollen serum. Actively and passively sensitized groups were then challenged by repeated and a sin gle pollen inhalation, respectively. In both groups, sneeze was induced imm ediately after the challenge. The actively sensitized animals developed not only early but also late nasal blockage, whereas the passively sensitized animals showed only early nasal blockage. In both groups, an HI antagonist, mepyramine, inhibited the occurrence of sneezing but did not inhibit nasal blockage. Nasal hyperresponsiveness to intranasal instillation of leukotri ene D-4 was obvious only in the actively sensitized animals. We thus conclu de that although early nasal blockage is induced by a single antigen-antibo dy reaction, repetitive anaphylactic reaction is required for occurrence of late nasal blockage and hyperresponsiveness to stimuli. Furthermore, hista mine plays a central role in induction of sneezing but not in nasal blockag e, irrespective of whether animals are actively or passively sensitized.