A correlative quantitative study comparing the nerve fibers in the cervical sympathetic trunk and the locus of the somata from which they originate in the rat.

Correlative quantitative analyses were performed on the rat comparing the number of fibers in the cervical sympathetic trunk (CST) and the horseradish peroxidase (HRP)-labeled neurons in the superior cervical sympathetic ganglion (SCG), stellate ganglion, as well as in the spinal cord. The total number of nerve fibers in the left CST was 4180 +/- 169 (mean +/- S.E.M.) among which 92 +/- 3 (mean +/- S.E.M.) were myelinated. The diameter of unmyelinated fibers was 0.68 +/- 0.22 (mean +/- S.D.) microns and showed single-peaked distribution. After the application of HRP to the proximal cut end of the CST, labeled neurons were found in the stellate ganglion as well as in the ipsilateral spinal cord from C7 to T4 segments. The total number of HRP-labeled neurons in the spinal cord was 1334 +/- 45 (mean +/- S.E.M.) with the range between 844 and 1808. Ninety-nine percent of labeled neurons were located in the intermediolateral column and in the lateral funiculus while 1% were in the intercalated region and central autonomic area. Labeled neurons were encountered only sporadically in the dorsal root ganglia (DRG) from C8 to T3 level. After the application of HRP to the distal cut end of the CST, about 200 labeled neurons were observed in the caudal part of the SCG. The present results were discussed with special reference to the organization of the CST of the rat.