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 th e enteric nervous system of the porcine small intestine, and particula rly their distribution pattern in the ganglia of the two submucosal pl exuses, the external submucosal plexus and the internal submucosal ple xus. Numerous NOS-immunoreactive nerve cell bodies were found in the e xternal submucosal plexus, as well as in the myenteric plexus. In 1 cm 2 of the surface of the submucosal whole-mount preparation, we counted 186 NOS-immunoreactive nerve cell bodies in the external submucosal p lexus, which is about 27 % of the total number of nerve cells in that plexus. As against this, we found only very few NOS-immunoreactive ner ve cells in the internal submucosal plexus. In the external submucosal plexus, these cells are often located together, forming aggregates wi thin the ganglia. NOS-immunoreactive nerve cells are of different size s and shapes. Some of them have a multidendritic uniaxonal appearance. NOS-immunoreactive nerve fibres can be observed in all three ganglion ic networks, surrounding NOS-immunoreactive as well as nonimmunoreacti ve nerve cell bodies and forming varicosities in close proximity to th e nerve cell bodies.