The Role of Nitric Oxide in the Neural Control of Nasal Fluid Production

Abstract

The production of nasal fluids serves an important role in the protection of the upper respiratory system, but can also be a troublesome symptom of rhinitis. The chief sources of nasal fluids are serous and mucous glandular secretion, epithelial goblet cell exocytosis, and exudation from submucosal blood vessels. This study was designed to investigate the role of nitric oxide in neurogenically mediated nasal vascular exudation and mucus secretion. A rat model of the naso-nasal reflex was developed in which one nasal cavity was challenged with histamine while albumin and mucin production were measured in the continuously perfused contralateral side. Histamine challenge was associated with a significant rise in contralateral albumin and mucin content. Perfusion with a nitric oxide synthase inhibitor (L-NAME) in the nasal cavity contralateral to nasal challenge was found to block albumin leakage, but not mucin secretion, on that side. The inhibition of vascular exudation was overcome by the addition of L-arginine, the natural substrate of nitric oxide synthase, to the perfusate. Treatment of the ipsilateral nasal cavity with L-NAME did not significantly alter the contralateral 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 vascular permeability, but is not involved in the sensory nerve afferent pathway or in reflex mucin release. Further elucidation of the role of NO in nasal physiology may lead to novel pharmacotherapeutic approaches to the treatment of allergic and nonallergic rhinitis.