Distribution of nitric oxide synthase-immunoreactive neurons in the submucosal plexus of the porcine small intestine.

This study analyses the occurrence of NOS-immunoreactive neurons in the enteric nervous system of the porcine small intestine, and particularly their distribution pattern in the ganglia of the two submucosal plexuses, the external submucosal plexus and the internal submucosal plexus. Numerous NOS-immunoreactive nerve cell bodies were found in the external submucosal plexus, as well as in the myenteric plexus. In 1 cm2 of the surface of the submucosal whole-mount preparation, we counted 186 NOS-immunoreactive nerve cell bodies in the external submucosal plexus, which is about 27% of the total number of nerve cells in that plexus. As against this, we found only very few NOS-immunoreactive nerve cells in the internal submucosal plexus. In the external submucosal plexus, these cells are often located together, forming aggregates within the ganglia. NOS-immunoreactive nerve cells are of different sizes and shapes. Some of them have a multidendritic uniaxonal appearance. NOS-immunoreactive nerve fibres can be observed in all three ganglionic networks, surrounding NOS-immunoreactive as well as nonimmunoreactive nerve cell bodies and forming varicosities in close proximity to the nerve cell bodies.