Innervation of the chicken esophagus wall: Localization and distribution of the acetylcholinesterase-positive nervous elements and ultrastructure

We have studied the distribution pattern of the acetylcholinesterase-positive innervation of the four-week-old chicken esophagus. We localized the different innervation plexuses and their inter-connections on sections of tissue samples. Later, we observed the three-dimensional structure of the plexuses by means of histochemical methods on whole-mount preparations, after delaminating the esophagus wall. We also studied the components of the nervous plexuses by optic microscopy on semi-thin cuts stained with toluidin blue, and studied their ultrastructure by transmission electron microscopy. In the myenteric plexus we observed compact ganglions between both muscle layers, as well as intra and inter-fascicular neuronal cell bodies in the circular muscle layer. Nervous trunks and fibers distribute along the connective tissue among the muscular bundles. The submucous plexus was found to be less abundant in nervous elements titan the myenteric plexus, and its ganglions were smaller. In the lamina propria abundant AChE+ fibers, which innervate the glands at their base, and in the surroundings of the tubules up to the epithelium were seen. On whole-mount preparations we describe that the ganglions of the myenteric plexus are larger and form a denser network than in the submucous plexus. TEM revealed varicosities with cholinergic, adrenergic, peptidergic and mixed vesicles.