Cytoarchitecture and dendroarchitecture of sympathoadrenal preganglionic neurons in rats--a study with CB-HRP

The cytoarchitecture and dendroarchitecture of sympathoadrenal preganglionic neurons (SAPN) that innervate the adrenal medulla have been studied in adult rats. Retrograde transport of choleragen subunit B horseradish peroxidase conjugate (CB-HRP) injected into the left adrenal medulla resulted in the labelling of SAPN in the ipsilateral intermediate zone from T1 to L1 segments. Four subnuclei of SAPN were distinguished and located in ILP, ILF, IC and ICPe of the spinal cord respectively. The dendritic trees of neurons in ILP exhibited dendritic patterns with extension oriented longitudinally and mediolaterally. The present findings provide detailed descriptions of the somatic structure and accompanying dendritic trees of SAPN. The observation also include anatomical evidence that two systems of circuits may exist in regulating the activities of SAPN; one is the classic core circuits system which mainly received the inputs from fibers in parallel direction with longitudinal dendrites in ILP and the other is the paralateral circuits system which chiefly received the inputs from fibers in perpendicular direction with radial dendrites in white matter.