Sensory, parasympathetic, and sympathetic neural influences in the nasal mucosa.

Neural mechanisms contribute to many nasal symptoms and syndromes. Sensory nerve stimulation by irritants, mast cell products, and inflammatory mediators leads to sneezing and other systemic reflexes. Parasympathetic reflexes and sensory axon responses combine to increase nasal blood flow, fill venous sinusoids (which thickens the mucosa and reduces nasal patency), induce plasma extravasation, and stimulate glandular secretion of mucous and serous cell products. These putative roles for nerves and neuropeptides in pathologic events open new therapeutic avenues. Anticholinergic agents, peptide neurotransmitter agonists and antagonists, drugs to reduce or modulate sensory or parasympathetic nerve function, potent topically applied glucocorticosteroids, and agents to inactivate inflammatory, secretory, or vascular cells may be of use. Ablation of sensory nerves by topical application of the chili pepper neurotoxin capsaicin has been successful in reducing the symptoms of refractory vasomotor rhinitis.