Phylogenetic aspects of the neuroepithelial bodies

Neuroepithelial bodies (NEB) are small groups of cells bound together by desmosomes and which form part of the epithelium lining the bronchopulmonary ducts. The cells have an irregular, columnar shape often with laterally placed microvilli and unspecialized cytoplasmic protrusions into the intercellular spaces. Their most distinctive cytoplasmic feature is the numerous dense cored vesicles (DCV) located towards the basal region of each cell. A variety of peptides and the monoamine serotonin are distributed within these DCV. Evidence has been shown for the occurrence of more than one type of DCV for the co-existence of various peptides and serotonin in the same DCV and for morphological and functional variations in cells forming a NEB. In some animals the apical pole is in direct contact with the lumen of the duct, whereas in others the NEB is isolated from the lumen by either ciliated epithelial or Clara-like cells. When the apical pole contacts the lumen, the surface of each cell bears microvilli and occasionally a single cilium. The NEB of eutherian mammals are sensitive to a number of experimental procedures including hypoxia, hypercapnia and vagal stimulation. Experimental lesions above and below the nodose ganglion have shown that the major part of the innervation is afferent with collateral branches off the afferent forming efferent, cholinergic endings. A small efferent input is also derived directly from the central nervous system. These studies suggest that a minor component of the efferent innervation is derived contralaterally or from intrapulmonary ganglia. Other forms of innervation identified by transmission electron microscopy in some mammals and lower vertebrates include cholinergic reciprocal synapses, adrenergic and peptidergic nerve junctions.(ABSTRACT TRUNCATED AT 250 WORDS)