Evidence for spinal origin of neurons synapsing with dorsal root ganglion cells of the cat.

Dorsal root ganglia (C3) of the cats have been examined with the electron microscope after dorsal and ventral rhizotomies and horseradish peroxidase injection into the ventral horn of the spinal cord (C3). Axo-somatic synapses were found in the dorsal root ganglia and, moreover, they showed early signs of anterograde terminal degeneration after a 48 h survival period. On the other hand, several synapses were anterogradely labeled with horseradish peroxidase. The present study strongly suggests, therefore, that axons from spinal neurons pass through the dorsal and/or ventral root and their terminals make synaptic contact with dorsal root ganglion cells.