THE ROLE OF NITRIC-OXIDE IN THE NEURAL CONTROL OF NASAL FLUID PRODUCTION

The production of nasal fluids serves an important role in the protect ion of the upper respiratory system, but can also be a troublesome sym ptom of rhinitis. The chief sources of nasal fluids are serous and muc ous glandular secretion, epithelial goblet cell exocytosis, and exudat ion from submucosal blood vessels. This study was designed to investig ate the role of nitric oxide in neurogenically mediated nasal vascular exudation and mucus secretion. A rat model of the naso-nasal reflex w as developed in which one nasal cavity was challenged with histamine w hile albumin and mucin production were measured in the continuously pe rfused contralateral side. Histamine challenge was associated with a s ignificant rise in contralateral albumin and mucin content. Perfusion with a nitric oxide synthase inhibitor (L-NAME) in the nasal cavity co ntralateral to nasal challenge was found to block albumin leakage, but not mucin secretion, on that side. The inhibition of vascular exudati on was overcome by the addition of L-arginine, the natural substrate o f nitric oxide synthase, to the perfusate. Treatment of the ipsilatera l nasal cavity with L-NAME did not significantly alter the contralater al response. A high correlation was observed between albumin and mucin concentration in the perfusate. These findings indicate that NO is a mediator of the effector arm of the naso-nasal reflex that increases v ascular permeability, but is not involved in the sensory nerve afferen t pathway or in reflex mucin release. Further elucidation of the role of NO in nasal physiology may lead to novel pharmacotherapeutic approa ches to the treatment of allergic and nonallergic rhinitis.