Afferent projections from forelimb muscles to the external and main cuneate nuclei in the cat. A study with transganglionic transport of horseradish peroxidase.

Muscular and cutaneous afferents from distal forelimb distributed to the cuneate and external cuneate nuclei have been demonstrated in cat with the method of transganglionic transport of horseradish peroxidase. Injections of the same tracer were also done in ganglia C7 to T6 to demonstrate the afferents to these two nuclei. It is concluded that only muscle afferents terminate in the external cuneate nucleus. Afferents from paw and forearm occupy sequential territories in the medial part of the nucleus, which are only partly exclusive. Afferents from individual flexor muscles of forearm occupy distinct sites but their distributions overlap with those of forearm extensor muscles. In the external cuneate nucleus, the distributions of afferents from individual muscles constitute integral parts of a segmental representation. In the cuneate nucleus, cutaneous afferents are located dorsally and terminate over cells of the "clusters". Muscle afferents are distributed in ventral regions and are topographically arranged. They terminate over "reticular" regions.