CNS innervation of vagal preganglionic neurons controlling peripheral airways: a transneuronal labeling study using pseudorabies virus

The CNS cell groups that project to vagal preganglionic neurons which inner vate the most distal part of the airways were identified by the viral retro grade transneuronal labeling method. Pseudorabies virus (PRV) was injected into the lung parenchyma of C8 spinal rats and after 5 days survival, brain tissue sections from these animals were processed for immunohistochemical detection of PRV. Retrogradely labeled parasympathetic preganglionic cells (first-order neurons) were seen mainly in the ventral medulla oblongata: th e compact portion of the nucleus ambiguus and the area ventral to it. Occas ionally, a few labeled cells were seen within the rostral part of the dorsa l vagal nucleus. This labeling pattern correlated well with the retrograde cell body labeling seen following cholera toxin beta-subunit (CT-b) injecti ons in the lung parenchyma. PRV transneuronally labeled neurons (second-ord er and/or presumed third-order neurons) were found throughout the CNS with the characteristic labeling in the brainstem. Labeled neurons were identifi ed along and just beneath the ventral medullary surface, and in nearby area s: the parapyramidal, retrotrapezoid, gigantocellular and lateral paragigan tocellular reticular nuclei, as well as the caudal raphe nuclei (raphe pall idus, obscurus, and magnus). Several nucleus tractus solitarius (nTS) regio ns contained labeled cells including the commissural, medial, and ventrolat eral nTS subnuclei. The A5 cell group and a small number of locus coeruleus neurons were also labeled. PRV-infected neurons were present in the Kollik er-Fuse and Barrington's nuclei. In the mesencephalon, neurons within the v entral periventricular gray matter were labeled. Labeling was present in th e dorsal, lateral and paraventricular hypothalamic nuclei, and within the a mygdaloid complex. In summary, the parasympathetic preganglionic neurons th at innervate the peripheral airways are controlled by networks of lower bra instem and suprapontine neurons that lie in the same regions known to be in volved in central regulation of autonomic functions. (C) 1999 Published by Elsevier Science B.V. All rights reserved.