Expansion of spinal cord primary sensory afferent projection following combined sciatic nerve resection and saphenous nerve crush: a horseradish peroxidase study in the adult rat

Transganglionic transport of horseradish peroxidase was used to study the potential for collateral sprouting of saphenous nerve afferent fibers in the lumbar dorsal horn of the adult rat following (1) combined unilateral saphenous nerve crush and ipsilateral sciatic nerve resection, (2) unilateral saphenous nerve crush, and (3) unilateral sciatic nerve resection. The saphenous nerve on the nonlesioned contralateral side served as control. Eight weeks after the lesion(s) the animals were subjected to bilateral application of horseradish peroxidase to the saphenous nerves. The distribution of the ensuing labeling in the superficial dorsal horn was subsequently mapped. Combined saphenous nerve crush and sciatic nerve resection resulted in expansion of the saphenous nerve projection area in the dorsal horn when compared to the nonlesioned control side (mean = 13%, P less than 0.05). No expansion of the saphenous nerve projection was found following isolated saphenous nerve crush or sciatic nerve resection, respectively (P greater than 0.05). The findings indicate that in the adult rat, central processes of primary sensory neurons which are regenerating their peripheral processes can extend collateral sprouts into adjacent projection areas in the superficial dorsal horn subjected to previous deafferentation by peripheral nerve resection.