Effects of lung inflation on nasal airway resistance in the anesthetized rat

Abstract

Nasal airway resistance was assessed in halothane-anesthetized rats by measuring the transnasal pressure at constant airflow through both nasal cavities. Low inflation pressure (2.5-5 cm H2O) decreased nasal airway resistance, whereas higher inflation pressures (10-20 cm H2O) caused a biphasic response: an initial increase in resistance followed by decrease in resistance. The nasal responses to all levels of inflation where completely abolished by hexamethonium, guanethidine, or bretylium pretreatment or cervical sympathectomy and greatly lessened by cervical vagotomy or phenoxybenzamine pretreatment. Atropine and propranolol pretreatments had no effect on the responses. The findings indicate that the nasal airway resistance is related to the level of inflation through pulmonary reflexes with afferents along the vagi and efferents via the α-adrenergic nervous system.