The distribution of the sympathetic preganglionic neurons projecting onto the stellate ganglion of the guinea pig. A horseradish peroxidase study.

After injection of horseradish peroxidase (HRP) into the stellate ganglion (SG) of the guinea pig, labelled cells were found in the C8-T11 spinal cord segments. The HRP-positive neurons were located in the nucleus intermedio-lateralis pars principalis and funicularis (ILp and ILf) and in the nucleus intercalatus proprius and pars paraependymalis (ICp and ICpe). The ICp and ICpe neurons represented approximately one-fourth of the total number of labelled cells. The ILp and ILf neurons were mainly located in the T2 and T3 segments whereas the ICp and ICpe neurons occurred mainly in the T4 to T6 segments where the ICpe cell group formed a continuous cell column dorsal to the central canal. The possible correlation between the segmental distribution and peripheral sympathetic effects was discussed.