CNS INNERVATION OF AIRWAY-RELATED PARASYMPATHETIC PREGANGLIONIC NEURONS - A TRANSNEURONAL LABELING STUDY USING PSEUDORABIES VIRUS

The CNS cell groups that innervate the tracheal parasympathetic pregan glionic neurons were identified by the viral retrograde transneuronal labeling method. Pseudorabies virus (PRV) was injected into the trache al wall of C8 spinal rats and after 4 days survival, brain tissue sect ions from these animals were processed for immunohistochemical detecti on of PRV. Retrogradely labeled parasympathetic preganglionic neurons were seen in three sites in the medulla: the compact portion of the nu cleus ambiguus, the area ventral to the nucleus ambiguus, and the rost ralmost portion of the medial nucleus tractus solitarius (NTS); this l abeling pattern correlated well with the retrograde cell body labeling seen following cholera toxin beta-subunit injections in the tracheal wall. PRV transneuronally labeled neurons were found throughout the CN S with the most abundant labeling concentrated in the ventral medulla oblongata. Labeled neurons were identified along the ventral medullary surface, and in nearby areas including the parapyramidal, retrotrapez oid, gigantocellular and lateral paragigantocellular reticular nuclei as well as the caudal raphe nuclei (raphe pallidus, obscurus, and magn us). Serotonin (5-HT) neurons of the caudal raphe complex (B1-B3 cell groups) and ventromedial medulla were labeled as well as a few Cl adre nergic neurons. The A5 cell group was the major noradrenergic area lab eled although a small number of locus coeruleus neurons were also labe led. Several NTS regions contained labeled cells including the commiss ural, intermediate, medial, central, ventral, and ventrolateral subnuc lei. PRV infected neurons were present in the Kolliker-Fuse and Barrin gton's nuclei. In the rostral mesencephalon, the precommissural nucleu s of the dorsal periventricular gray matter was labeled. Labeling was present in the dorsal, lateral and paraventricular hypothalamic nuclei . In summary, the airway parasympathetic preganglionic neurons are inn ervated predominantly by a network of lower brainstem neurons that lie in the same regions known to be involved in respiratory and cardiovas cular regulation. These findings are discussed in relationship to some of the potential CNS mechanisms that may be operative in airway disor ders as well as potentially involved in certain fatal respiratory cond itions such as Ondine's curse and sudden infant death syndrome (SIDS).