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The effects of antigen and histamine on the changes of nasal passage patency in 112 guinea pigs with or without allergic rhinitis were evaluated by acoustic rhinometry. The percent change of volume from the nostril to 2 cm into the nasal cavity showed significant reduction of 31.10 +/- 4.11% at 10 minutes and 31.10 +/- 4.11% at 30 minutes after antigen challenge in sensitized guinea pigs. The pretreatment with ketotifen, an H1-histamine receptor antagonist as well as mast cell stabilizing drug, blocked dose-dependently the effects of antigen on those changes in volume. Furthermore, instillation of 10(4) micrograms/mL histamine reduced significantly nasal passage patency to 33.77 +/- 4.63% at 10 minutes and 42.76 +/- 3.32% at 30 minutes after challenge compared with that before challenge and ketotifen inhibited the effects of histamine, which indicated that histamine is an important mediator of allergic upper airway responses in guinea pigs. These results show that acoustic rhinometry is a useful technique to assess the nasal blockade in allergic guinea pigs.

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