Alpha-2c-Adrenergic Receptors Contribute to Basal Nasal Patency in the Anesthetized Cat

Background: Nasal congestion is the most troublesome symptom associated with a variety of upper airway diseases, including allergic rhinitis and the common cold. A better understanding of the mechanisms that regulate nasal cavity caliber may engender the development of novel treatment strategies. It is well accepted that α-adrenergic (both α 1 and α 2 ) mechanisms play a fundamental role in the control and maintenance of basal nasal patency. JP-1302 is a selective α 2c -subtype antagonist that has been recently described in the scientific literature. Thus, we sought to examine the potential effects of this new pharmacological tool on basal nasal patency. Methods: Using acoustic rhinometry, we studied the activity of the selective α 2c -antagonist JP-1302 on nasal cavity volumes in an anesthetized cat. Cumulative concentrations of JP-1302 were applied directly into the right nasal cavity. Changes in the nasal cavity geometry of the drug-treated naris relative to the untreated left nasal cavity were determined. In separate studies, the nonselective α 2 -antagonist yohimbine and the nonselective α 1 -antagonist prazosin were run as comparators. Systolic blood pressure was measured at the hind leg, using an ultrasonic Doppler flow detector. Results: JP-1302 (0.03, 0.1, 0.3 and 1.0%) administered by the intranasal route decreased nasal cavity volumes from baseline values by 17, 25, 40 and 40%, respectively. Yohimbine (0.03, 0.1, 0.3 and 1.0%) decreased volumes by 19, 36, 46 and 53%, and topical administration of the nonselective α 1 -antagonist prazosin (0.001, 0.003, 0.01, 0.03 and 0.1%) decreased volumes by 6, 47, 56, 64 and 71%, respectively. JP-1302, yohimbine and prazosin, at the dose level tested, did not alter the blood pressure. Conclusions: The present set of experiments indicates that both α 1 - and α 2 -adrenergic receptors are involved in the maintenance of basal nasal patency in the cat. Moreover, α 2c -receptors may play a significant role in the sympathetic control of upper airway function.