Structural organization of the enteric nervous system in the cattle esophagus revealed by wholemount immunohistochemistry.

In ruminants the motility patterns of the esophageal tube are characterized by physiological regurgitations including both anterograde and retrograde peristaltic movements. These complex motor functions require an elaborated enteric nervous system (ENS) for the generation of the underlying intrinsic reflex circuits. The structural organization of the esophageal ENS was studied in fetuses of cattle (n=6) by means of wholemount preparations obtained from different segments of the esophagus. Demonstration of nerve cells, ganglia and nerve fibers strands (NFS) was achieved by immunohistochemistry using the general neuronal marker protein gene product (PGP) 9.5. The myenteric plexus represented the most prominent nerve network composed of differently shaped ganglia and interconnecting NFS. Frequenitly the myenteric ganglia were arranged in two separate layers interweaving with the adjacent muscle coat. From the cervical towards the thoracic segment of the esophagus the density and size of myenteric ganglia increased and the NFS exhibited thicker diameters. The submucosal and mucosal plexus consisted of NFS ramifying throughout the tela submucosa and the lamina propria mucosae. The networks showed no evidence of ganglia nor single nerve cells. The findings illustrate that intrinsic esophageal nerve cells are confined to the myenteric plexus. Since the esophageal tube has no secretory functions, secreto-motor neurons are not required in the submucosal and mucosal plexus layers. The structural organization of the intramural nerve networks--in particular the specific arrangement of the myenteric plexus--reflects the substantial contribution of the esophageal ENS to the coordination and mediation of esophageal motility in ruminants.