by histamine  . The H1 receptor consists of an active and inactive conformation coexisting in equilibrium. As an inverse agonist, the drug stabilizes the inactive conformation of the H1 receptor, causing a shift in the equilibrium toward the inactive
Figure 2. Nasal congestion ameliorated by fexofenadine. Data were expressed as “MCA Change” (post-challenge MCA/pre-challenge MCA) %. Data represent the mean ± standard deviation (SD). Open bar: vehicle administration (n = 4), solid bar: fexofenadine administration (n = 4), p < 0.05.
state. Therefore, frequent and prophylactic use of fexofenadine effectively blocks active H1 receptor-mediated signaling. In the present study, even a single dose of fexofenadine demonstrated amelioration of nasal congestion. Higher doses and repeated administration of fexofenadine are expected to diminish nasal congestion to greater extent.
In conclusion, an acoustic rhinometry technique for the quantitative assessment of nasal congestion was successfully applied for the first time in an allergic model of cynomolgus macaques sensitized with Japanese cedar pollen. Using this technique and model, the ameliorative effect of an antihistamine drug, fexofenadine, was evaluated on nasal obstructionin the early phase response of allergic rhinitis.
We are grateful to Mr. Ryoji Kato (Yushin Precision Equipment Co., Ltd.) and Mr. Toshihito Akashi (Department of Medical Equipment, Finggal Link Co., Ltd.) for generous assistance on rhinometry. We also thank the staff at Intelligence and Technology Lab. Inc. for their excellent animal handling and supporting the experiment.
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