Mapping the innervation of the bronchial tree in fetal and postnatal pig lung using antibodies to PGP 9.5 and SV2.

The extent of the innervation in the adventitial surface of the airway wall is demonstrated by mapping all the nerves and ganglia of the first trimester fetal and postnatal (4-wk-old) pig lung. We used antibodies to two pan-neuronal nerve markers-Protein Gene Product (PGP) 9.5, a nonspecific marker for all nerves, and synaptic vesicle protein 2 (SV2), a marker of synaptic vesicle membranes-to obtain detailed maps of the innervation of the airways. The airway smooth muscle has been stained concurrently with an antibody to alpha-actin. To obtain an overview of the passage of nerves down the bronchial tree, whole mounts of the bronchial tree have been imaged using confocal microscopy. Several conclusions can be drawn from our work: (1) Nerves branch from the main nerve trunks to form an extensive plexus covering the surface of the smooth muscle in fetal pigs but penetrate through the smooth muscle and are more organized in postnatal airways. In general, two main nerve trunks per airway were observed. (2) The antibody to PGP 9.5 in the fetal lung revealed in many ganglia and nerve trunks, the latter exhibiting cell profiles. In the postnatal lung, cell bodies were restricted to ganglia in the central airways. (3) The antibody to SV2, in general, showed varicose staining of the fine nerve fibers at both ages.