Identification of phrenic afferents to the external cuneate nucleus: a fluorescent double-labeling study in the cat

In the cat, C5-C6 dorsal root ganglion cells related to phrenic afferents projecting directly to the ipsilateral external cuneate nucleus (ECN) were submitted to a double-labeling procedure using anterogradely transported Fast Blue and retrogradely transported Nuclear yellow. These afferents, certainly related to muscle spindles and/or Golgi tendon organs, are very few and terminate preferentially in the intermediate and rostral parts of the ECN. Our results confirm previous electrophysiological and histological studies on the participation of phrenic afferents to the spino-cuneo-cerebellar pathway ascending through the dorsal columns.