HORSERADISH-PEROXIDASE STUDY OF PRIMARY AFFERENT-PROJECTIONS TO THE MEDULLARY CUNEATE NUCLEUS IN THE RAT

HRP was used to label first order afferent cells of the dorsal root ganglia which synapse at the cuneate nucleus. The results show that it is a population of predominantly large cells that project monosynaptically to the medullary cuneate nucleus and thus support anatomical and physiological studies showing that directly projecting axons to the dorsal column nuclei are larger, faster and conduct information from a select class of sensitive cutaneous mechanoreceptors. The finding, that approximately 20% of DRG neurons can be labeled from the dorsal column nuclei, is consistent with previous estimates of dorsal root fiber projections in the dorsal column based on Marchi degeneration. © 1979.