Projections of cervical nerves to the rat medulla

The central course of dorsal root ganglia (DRG) fibers from C1, C2 and C3, and particularly, their brainstem terminations were studied in rats using anterograde transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP). WGA-HRP was injected into the exposed DRG, and after 3 days the animals were sacrificed and sections of spinal cord and brainstem were processed with tetramethylbenzidine and examined for anterograde transport. Labeled fiber terminals were identified in the dorsal horn and the central cervical nucleus in the spinal cord, and in the intermediate nucleus, cuneate nucleus, external cuneate nucleus and the caudal portion of the nucleus of the solitary tract (NTS) in the brainstem. The projection of primary sensory fibers to the visceral NTS is suggestive of a functional relationship between upper cervical and vagal nerve afferents. The potential association of these nerves with clinical problems of headache and other cephalgias is of interest.