Prenatal development of the myenteric plexus in cat stomach.

The prenatal development of the myenteric (Auerbach) plexus in cat stomach has been studied light- and electronmicroscopically. Neuroblasts and axon bundles of the myenteric plexus are found in the gastric wall of the smallest embryos studied (10-15 mm) even before its layers are formed. The plexus elements are not separated from the mesenchyme with a basal membrane. In the larger embryos (40-55 mm) the myenteric plexus is already between two muscle layers. The ganglia are shaped and contain more neuroblasts. A small part of the nerve cells are advanced in their maturation--primary and secondary dendrites are emanated and they are slightly AChE-positive. The maturation of the nerve perikarya is intense during prenatal life. In 95-115 mm long embryos the differentiation of a considerable part of the nerve cells is advanced and it is possible to distinguish some ultrastructural types of myenteric neurones. The number of AChE-positive neuroblasts is increased and there are more dendritic profiles in the neuropile.