Lack of topographical specificity in peripheral nerve regeneration in rats

In a previous study we found that sensory regeneration was neurotropically selective regardless of the end organ, but motor regeneration was not, whic h made us doubt the existence of topographic specificity. The purpose of th e present study was to confirm the existence of topographic specificity in rats. The proximal stump of either the peroneal or tibial nerve was inserte d into the proximal limb of a silicone Y-chamber. Both distal stumps of per oneal and tibial nerve were inserted into the distal Limbs. The gap between the stumps was set at either 4 mm (n = 8, on each subgroup) or 8 mm (n = 8 , on each subgroup). Six weeks later the number of regenerated axons in the distal two limbs were counted and compared. The number of regenerated axon s towards the distal tibial nerve side was significantly larger in every mo del. Regenerated axons from the proximal peroneal stump did not preferentia lly choose the distal peroneal stump. The existence of topographic specific ity is unlikely.