Locations and chemistries of sympathetic nerve cells that project to the gastrointestinal tract and spleen.

Retrograde tracing was used to determine the locations of sympathetic nerve cells whose axons project to the stomach, small intestine, caecum, proximal colon, distal colon and spleen of the guinea-pig. Projections from prevertebral ganglia were organotopically arranged within and between ganglia. The cranially located coeliac ganglion provided the major input to proximal gut regions; the distal gut received more caudal input, from superior and inferior mesenteric and the hypogastric nerve ganglia. Nevertheless, minor proportions of the innervation of some target organs arose from other than the closest ganglion and the caecum had input from each of the coeliac, superior mesenteric and inferior mesenteric ganglia. Topography within a ganglion was best defined in the coeliac, in which nerve cells whose axons projected to the spleen, stomach and duodenum were preferentially laterally located, whereas most of those projecting to the proximal colon were medial. Fewer neurons projected from paravertebral--compared with prevertebral--ganglia to abdominal viscera. Projections to the stomach came from all thoracic chain ganglia, those to the duodenum and spleen from lower thoracic ganglia and those to the large intestine from lumbar chain ganglia. It is suggested that the previously reported chemical topography of nerve cells in sympathetic ganglia might be secondary to their organotopic organization.