Innervation of airway smooth muscle: fine structure.

Abstract

Nerve fibers of various origins run within the musculature of the trachea and bronchi. Their sources are varied and not well characterized. The main source of afferent fibers to trachea and bronchi is the vagus nerves (with nerve cell bodies in the nodose ganglion); whether there are also some afferent fibers from dorsal root ganglia remains to be proven. The vagal (afferent) fibers represent the largest nerve supply to the bronchial and tracheal muscles of the mouse, as judged from the extent of the loss of intramuscular nerve endings after vagotomy (46). The majority of efferent fibers originate from cell bodies in the tracheal and bronchial ganglia (see chapter by R. Coburn in this volume) (and possibly in some other of the many ganglia associated with mediastinal organs). These neurones are mainly driven by vagal nerve fibers and are part of the parasympathetic outflow; they include excitatory and inhibitory neurones. Axons projecting from these ganglion cells to the tracheal muscle of the ferret have been traced after intracellular injection of horseradish peroxidase (31).