Somatotopic organization of the cuneate nucleus in the rat: transganglionic labelling with WGA-HRP.

A novel somatotopic map of primary cutaneous afferents projecting to the cuneate nucleus in the rat was determined by transganglionic transport of wheat-germ agglutinin conjugated to horseradish peroxidase and free horseradish peroxidase. Intracutaneous injections of tracer into different limited regions of the forelimb resulted in discrete areas of label for each injection site, with little or no overlap into other projection areas. The map of cutaneous projections onto the cuneate nucleus revealed by our anatomical tracing provided much more detail than any previous study in the rat, and demonstrated some significant differences from earlier maps based on electrophysiological recordings.