Changes in Nasal Resistance and Nasal Geometry Using Pressure and Acoustic Rhinometry in a Feline Model of Nasal Congestion

This is the first report describing the use and pharmacological characterization of nasal patency by both pressure rhinometry and acoustic rhinometry (AcR) in an experimental cat model of nasal congestion. In pressure rhinometry studies, aerosolized compound 48/80 (0.1–3.0%), a mast cell liberator, increased nasal airway resistance (NAR) 1.2 ± 0.6, 5.8 ± 0.5, 8.6 ± 1.1 and 7.9 ± 1.5 cmH₂O·L/minute, respectively. Increases in NAR produced by compound 48/80 were associated with a 395% increase in histamine concentration found in the nasal lavage fluid. Pretreatment with the α-adrenoreceptor agonist, phenylpropanolamine (PPA; 0.1–3.0 mg/kg, i.v.), and the NO synthetase inhibitor, N^G-nitro-L-arginine (L-NAME; 10 mg/kg, i.v.) attenuated the increases in NAR produced by compound 48/80. The histamine H₁ antagonist chlorpheniramine (1.0 mg/kg, i.v.) and the H₂ antagonist, ranitidine (1.0 mg/kg, i.v.) had no decongestant activity. Also without decongestant activity were the muscarinic antagonist atropine, the cyclooxygenase inhibitor indomethacin, and the 5-HT blocker methysergide. Aerosolized histamine (0.1–1.0%) also produced a dose dependent increase in NAR. In studies using acoustic rhinometry (AcR), intranasal application of compound 48/80 (0.1–1.0%) elicited pronounced decreases in nasal cavity volumes and minimum cross-sectional area (A_min). Pretreatment with PPA (3 mg/kg, i.v. or 10 mg/kg, p.o.) attenuated the decreases in nasal volume and A_min. The effects of topical intranasal histamine (0.1–1.0%) on nasal geometry were similar to compound 48/80. We conclude that the cat is a useful model for evaluating the pharmacological actions of potential nasal decongestants. Furthermore, we also conclude that AcR is a useful method for noninvasive assessment of nasal patency in a preclinical setting.