PULMONARY NEUROEPITHELIAL BODIES ARE INNERVATED BY VAGAL AFFERENT NERVES - AN INVESTIGATION WITH IN-VIVO ANTEROGRADE DIL TRACING AND CONFOCAL MICROSCOPY

The pulmonary airway and alveolar epithelia contain distinctly innerva ted clusters of basally granulated cells: the neuroepithelial bodies. In the past, morphological criteria and the results of selective vagot omy have led to the interpretation that their innervation is sensory. Consequently, they are regarded as receptor organs. As a further test of this hypothesis, the present investigation set out to label vagal s ensory nerve fibres to the lungs by anterograde neural tracing, and to establish the relationship between these fibres and the neuroepitheli al bodies. A fluorescent neural tracer was injected unilaterally into the left or right nodose ganglion of adult rats. After suitable surviv al times, thick frozen sections of lung tissue were studied with laser scan confocal microscopy. Sensory nerve fibres were seen to run in th e airway walls and occasionally penetrated the epithelium, where they formed complex terminals. The resulting intraepithelial sensory end or gans showed a close morphological resemblance to the neuroepithelial b odies. Subsequently, electron microscopic investigation of such identi fied structures revealed the typical ultrastructural characteristics o f neuroepithelial bodies: corpuscular cells containing dense cored sec retory vesicles and contacted by mitochondria-rich nerve endings. We c onclude that anterograde tracing of sensory nerves from the nodose gan glion confirms the receptor nature of the pulmonary neuroepithelial bo dies, which may correspond to a subpopulation of the irritant and C-fi bre receptors.