CHARACTERIZATION OF NEURONS WITH NITRIC-OXIDE SYNTHASE IMMUNOREACTIVITY THAT PROJECT TO PREVERTEBRAL GANGLIA

Retrograde dye tracing was combined with immunohistochemistry to deter mine the distributions of nitric oxide synthase (NOS) immunoreactive n erve cells that project to prevertebral ganglia from the gastrointesti nal tract and spinal cord of the guinea pig. An antiserum was raised a gainst the neuronal form of NOS by selecting an amino-acid sequence sp ecific to this form as immunogen. The antiserum recognised a single ba nd at 150 kDa on Western blots of rat brain extract. Enteric nerve cel ls that were labelled by Fast Blue injected into the coeliac ganglion were not NOS immunoreactive in the small intestine, whereas 40-70% wer e reactive in the large intestine. Retrograde dye injected into the in ferior mesenteric ganglion labels cells in the colon and rectum; 60-70 % were immunoreactive for NOS. The NOS-immunoreactive nerve fibres ari sing in the intestine appear to end selectively around somatostatin-im munoreactive nerve cells in the coeliac and inferior mesenteric gangli a. Preganglionic nerve cell bodies in the intermediolateral column and dorsal commissural nucleus from T12 to L2 were labelled from the infe rior mesenteric ganglion. Nearly 70% of neurons at each level were NOS immunoreactive. Thus, two sources of NOS terminals in prevertebral ga nglia have been identified, intestinofugal neurons of the large, but n ot the small intestine, and sympathetic preganglionic neurons.