Structural survey of airway sensory receptors in the rabbit using confocal microscopy

Information on the morphology of airway receptors is limited. The present study surveys rabbit airway receptors using immunohistochemical and fluorescent labeling to identify their structure with confocal microscopy. Various receptor types were observed to have multiple branches where a parent axon fed several structures. Receptors were located in different layers of the airway, i.e., smooth muscle, lamina propria (submucosa) and the epithelium. Smooth muscle and submucosal receptors were innervated by thick myelinated fibers, while epithelial receptors were supplied by thin-diameter axons. Structures of smooth muscle receptors and some submucosal receptors covered a relatively large area, while epithelial receptors were less extended. In addition, intrapulmonary ganglia were also labeled. Some were closely associated with the axons of smooth muscle receptors.