Tracing of afferent pathways from the femoral-saphenous vein to the dorsal root ganglia using transport of horseradish peroxidase

The retrograde transport of horseradish peroxidase (HRP) was used to trace afferents from the femoral-saphenous vein to the dorsal root ganglia in the cat. Afferents arising along the entire length of the vein projected to very localized spinal levels; 63% of the labeled cells counted were located in the L 6 dorsal root ganglion, 37% were located in the L 5 ganglion and less than 1% were located at other levels. Most of the cell bodies labeled by the application of HRP to the femoral-saphenous vein were small in size (diameter < 35 μm). However, some large cell bodies (diameter > 50 μm) were also noted. It was estimated that over two-thirds of the femoral-saphenous venous afferents were C fibers; at least 15% were estimated to be A fibers. The largest venous afferents were predicted to conduct action potentials at approximately 60 m/s.