PULMONARY INTRAEPITHELIAL VAGAL NODOSE AFFERENT NERVE-TERMINALS ARE CONFINED TO NEUROEPITHELIAL BODIES - AN ANTEROGRADE TRACING AND CONFOCAL MICROSCOPY STUDY IN ADULT RATS

Our present understanding of the morphology of neuroepithelial bodies (NEBs) in mammalian lungs is comprehensive. Several hypotheses have be en put forward regarding their function but none has been proven concl usively. Microscopic data on the innervation that appears to affect th e reaction of NEBs to stimuli have given rise to conflicting interpret ations. The aim of this study has been to check the validity of the hy pothesis that pulmonary NEBs receive an extensive vagal sensory innerv ation. The fluorescent neuronal tracer DiI was injected into the vagal sensory nodose ganglion and NEBs were visualized in tote by using imm unocytochemistry and confocal microscopy on 100-mu m-thick frozen sect ions of the lungs of adult rats. The most striking finding was the ext ensive intraepithelial terminal arborizations of DiI-labelled vagal af ferents in intrapulmonary airways, apparently always co-appearing with calcitonin gene-related peptide (CGRP)-immunoreactive NEBs. Not all N EBs received a traced nerve fibre. Intrapulmonary CGRP-containing nerv e fibres, including those innervating NEBs, always appeared to belong to a nerve fibre population different from the DiI-traced fibres and h ence did not arise from the nodose ganglion. Therefore, at least some of the pulmonary NEBs in adult rats are supplied with sensory nerve fi bres that originate from the vagal nodose ganglion and form beaded ram ifications between the NEB tells, thus providing support for the hypot hesis of a receptor function for NEBs.