Vasoactive intestinal polypeptide nerves in human upper respiratory tract.

Immunoreactive vasoactive intestinal polypeptide (VIP), a recently recognized neuropeptide with a possible transmitter function has been demonstrated in nerves of the human upper respiratory tract. VIP nerves predominate in the inferior turbinate of the nose and in the tracheal wall. They are distributed in the subepithelial connective tissue, around blood vessels and seromucous glands. Scattered VIP nerves are observed also in the tracheal smooth muscle. VIP immunoreactive nerve cell bodies are found only in the tracheal wall, suggesting a local origin of the VIP nerves in this organ. Available information indicates that the VIP-containing nerves constitute a separate component of the autonomic nervous system in addition to the adrenergic and cholinergic ones.