Intrapulmonary neuro-epithelial bodies in newborn rabbits

Abstract

Neonatal rabbit neuro-epithelial bodies (NEB) were investigated under various experimental conditions with light microscopy, microspectrography, morphometry and electron microscopy. (1) Hypoxia causes a decreased amine fluorescence intensity and an increased secretory exocytosis of dense core vesicles (DCV). Otherwise the NEB appear structurally normal. (2) Hypercapnia also produces a decreased fluorescence and an increased exocytosis; ultrastructurally, however, the dense core of DCV fragmentizes. (3) Hyperoxia does not appear to affect significantly either fluorescence or exocytosis. (4) The uptake of biogenic amines such as 5-HTP and L-DOPA was demonstrated by fluorometry and electron microscopy. (5) Reserpine, on the other hand, provokes an amine depletion with a decrease of the NEB fluorescence and an ultrastructural palor of the DCV. (6) Intratracheally administered nicotine is accompanied by a decreased fluorescence and a distinct exocytosis of fragmented DCV. The reaction of NEB to hypoxia and hypercapnia suggests that these corpuscles could be intrapulmonary chemoreceptors (in addition to the classically known central and peripheral chemoreceptors), inducing a reflex reaction through the liberation of DCV at the corpuscular sensible nerve endings and via the CNS. In addition, they may subserve a local intrapulmonary effect by modulating directly the hypoxic and hypercapnic pulmonary vasoconstriction and thus the V/Q ratio.