Segmental organization of sympathetic preganglionic neurons of the splanchnic nerve as revealed by retrograde transport of horseradish peroxidase.

Spinal nerves were transected at selected thoracic levels on the left side and the central cut end of the left major splanchnic nerve was exposed to horseradish peroxidase (HRP) in order to study the preganglionic sympathetic organization in the spinal cord of the cat. In three animals, a total of 4235 HRP labeled neurons were observed (uncorrected counts) in five regions: intermediolateral nucleus (IML) (82.8%), lateral funiculus (LF) (14.7%), intercalatus nucleus (IC) (2.1%), central autonomic (CA) (0.3%) and the anterior horn (AH) (0.1%). The neuronal distribution indicates that sympathetic preganglionic neurons in the thoracic spinal cord are segmentally organized.