Sensory innervation of the rat hind paw: morphometric comparison between sural and saphenous nerves.

Abstract

Previous studies on dermatome mappings of the rat hind paws investigated the C‐fibers distribution and then assumed that the A‐fibers distributions resemble that of the C‐fibers. We investigated the morphometry of fascicles and myelinated fibers (A‐fibers) in the sural and saphenous nerves in young rats. Six 30‐day‐old female Wistar rats had their right and left sural and saphenous nerves prepared for light microscopy and morphometry. Comparisons were made between segments (proximal vs distal) and sides (left vs right) for the same nerves and between nerves (sural vs saphenous) from the same side and differences were considered if p<0.05. Both the sural and saphenous nerves are longitudinally symmetrical on both sides. Both nerves also exhibited lateral symmetry. Also, no significant differences were found between nerves. Myelinated fibers and respective axons diameter, as the G ratio histograms are unimodal in both nerves, regardless of segments or sides. This indicates that the nerves investigated did not reach fully development in animals aged 30 days. The similar number of myelinated fibers, associated with their similar size in both sural and saphenous nerves suggests that the innervation territory for both nerves is equally distributed at the foot. This information is useful for studies of sensory neuropathies, in particular, studies of nerve regeneration.