| Summary: | ABSTRACT: Whether a state of nasal hyperresponsiveness influences antigen-induced biphasic nasal blockage and sneezing were examined using a guinea pig model of allergic rhinitis. Sensitized animals were challenged with an antigen, Japanese cedar pollen, once every week. Before the 13th challenge, the animals were randomly divided into 2 groups, and then the 13th challenge was performed (Groups A-0 and B-0). The 14th challenge was done on day 2 (Group A-2) and on day 7 (Group B-7) after the 13th challenge, on which nasal hyperresponsiveness was present and absent, respectively. Biphasic nasal blockage and sneezing after the challenge in Group A-2 were more severe than those in Group A-0, while those of Group B-7 were almost the same as those of Group B-0. An anti-histaminic, mepyramine, inhibited sneezing but not the biphasic nasal blockage in Group B-7. A cysteinyl leukotriene (CysLT) antagonist, pranlukast, suppressed the late nasal blockage but not the early blockage and sneezing in Group B-7. In contrast, in Group A-2, mepyramine significantly attenuated not only sneezing but also the early nasal blockage. Pranlukast significantly inhibited both nasal blockage and sneezing in Group A-2. In conclusion, nasal hyperresponsiveness aggravated the antigen-induced nasal responses, to which histamine and CysLTs considerably contributed.
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