The location and characteristics of sympathetic preganglionic neurones in the lower thoracic spinal cord of dog and cat.

The retrograde transport of horseradish peroxidase from a white ramus communicans has been used to define the precise segmental location of sympathetic preganglionic cell bodies in the spinal cord of the cat and dog. All labelled cells were found ipsilaterally and were confined to the spinal cord segment from which the ramus originated. Most lay in the intermediolateral cell column and the immediately adjacent white matter, though others were scattered in more medial areas of the grey matter. We suggest that the observed distribution of sympathetic preganglionic neurones, the orientation of their processes and the paths taken by their axons are a direct result of cell migration during the embryological development of the spinal cord.