Arborizations of single corticofugal axons in the feline cuneate nucleus stained by iontophoretic injection of horseradish peroxidase.

Terminal aborizations and synaptic boutons of cortical afferents to the cuneate nucleus were examined by light and electromicroscopy following intra-axonal staining with HRP. Two populations of afferents are described: (1) direct corticocuneate fibers, and (2) fibers destined for the spinal cord which issue collateral branches to the cuneate nucleus. Corticocuneate terminals primarily contact fine dendrites located in the ventral parts of the nucleus. These results are discussed in relation to previous anatomical findings and to new concepts of cuneate nucleus organization.