The Phosphodiesterase 4 Inhibitor Prevents Antigen-induced Biphasic Nasal Obstruction in Brown Norway Rats

ABSTRACT Background Nasal obstruction is considered the most serious problem for patients with allergic rhinitis. We have previously established a model of nasal obstruction in guinea pigs. In the present study, we tried to establish an allergic model of nasal obstruction using Brown Norway (BN) rats to evaluate the effects of phosphodiesterase (PDE) 4 inhibitors in this model. Methods The volume of the nasal cavity was measured with an acoustic rhinometer. Decrease in the volume of the nasal cavity was taken as nasal obstruction. BN rats were actively sensitized with ovalbumin conjugated with aluminium hydroxide. Intranasal antigen instillation induced biphasic nasal obstruction in sensitized BN rats. Results Early and late phase responses (EPR and LPR) were observed peaking at 0.5 and 6 hours after the antigen challenge, respectively. Chlorpheniramine did not inhibit EPR or LPR at 10 mg/kg, although the dose was sufficient for the compound to exert its anti-histamine activity. Prednisolone inhibited both responses at 30 mg/kg. Rolipram and CDP-840, PDE4 inhibitors, inhibited both responses at 100 mg/kg. KF19514, a PDE1/4 dual inhibitor, inhibited EPR at 0.1 mg/kg or more and inhibited LPR at 10 mg/kg. Conclusions The present study provides a simple model of allergic biphasic nasal obstruction in BN rats, and also suggests that the PDE4 inhibitor may alleviate nasal obstruction in patients with allergic rhinitis.