Occurrence and distribution of VIP nerves in the nasal mucosa and tracheobronchial wall.

Nerves displaying vasoactive intestinal peptide (VIP) immunoreactivity were detected in the upper respiratory tract of guinea pigs, rabbits and cats. VIP nerves were numerous in the cat, less numerous in the rabbit and rare in the guinea pig. In the nasal mucosa, fine varicose VIP nerves were found to surround nasal glands and small blood vessels. In the tracheobronchial wall VIP nerves were observed around seromucous glands, blood vessels and smooth muscle. Ganglia located in the walls of the trachea and main bronchi contained clusters of VIP immunoreactive nerve cell bodies, conceivably representing the origin of the VIP fibres found in this region.