Phenotypic traits of the hypothalamic PVN cells innervating airway-related vagal preganglionic neurons

The paraventricular nucleus of the hypothalamus (PVN) integrates multiple inputs via projections from arginine vasopressin (AVP)- and oxytocin (OXT)-containing neurons to the brain stem and spinal cord as well as regulates respiratory and cardiovascular stress-related responses, which also affect airway function. In the present study, we used immunocytochemistry and the retrograde transneuronal tracer, Bartha strain of pseudorabies virus expressing green fluorescent protein (PRV-GFP), to localize AVP- and OXT-producing neurons that project to airway-related vagal preganglionic neurons (AVPNs) innervating intrapulmonary airways. PRV-GFP was microinjected into the upper right lung lobe, and after 4 days survival, hypothalamic tissue sections were processed for co-expression of PRV-GFP and AVP or PRV-GFP and OXT. In addition, in a separate group of five rats, Phaseolus vulgaris leucoagglutinin (PHAL), an anterograde tracer, was injected unilaterally into the PVN and cholera toxin beta subunit was microinjected into the tracheal wall. Analysis of five successfully infected animals showed that 14% of PRV-GFP labeled neurons express AVP traits and 18% of transneuronally-labeled neurons contain OXT. Furthermore, the identified AVPNs innervating extrathoracic trachea receive axon terminals of the PVN neurons. The results indicate that AVP- and OXT-producing PVN cells, via direct projections to the AVPNs, could modulate cholinergic outflow to the airways, as a part of overall changes in response to stress.