Projections from the dorsal column nuclei and the spinal cord to the red nucleus in cat.

The projections of the red nucleus (RN) from the dorsal column nuclei (DCN) and the spinal cord have been investigated in cats with the degeneration method. After electrolytic DCN lesions and unilateral cordotomies including the lateral and ventral funiculi, the degeneration was studied in Fink-Heimer stained sections. Contralateral to a DCN lesion terminal degeneration was found along the whole rostrocaudal extent of the red nucleus. In most portions the degeneration was scattered, but dense zones were present, too. Terminal fibers were present in both magnocellular and parvocellular parts. After a gracile lesion the degenerating fibers were restricted to the ventral part of the RN, while the terminal patterns did not differ significantly after cuneate and large DCN lesions. The spinal fibers were found ipsilateral to the cordotomy. Like the DCN fibers, the spinal fibers were present along the whole rostrocaudal extent of the RN and in both magno- and parvocellular zones. Their distribution in the transverse plane was similar, as well. However, the present material was not sufficient to show subtle differences between the DCN and spinal projections, nor to show a possible somatotopical organization of the spinal projection.