Allodynia induced by regenerating axons is not positively correlated with degree of autotomy in the rat.

We studied in the rat whether the incidence of autotomy correlated positively with severity of tactile allodynia induced by regenerating axons. Before transection and surgical repair of the sciatic nerve, the status of sensory function was studied by stimulating mechanically the central part of the plantar paw with von Frey-hairs. Thereby we determined the threshold to evoke the hindpaw withdrawal reflex. One and 2 months after the nerve transection and repair, the thresholds of the traumatized paws were lower than the pre-trauma thresholds. The contralateral paw withdrawal thresholds did not change during the follow-up time. The results indicated that regenerating axons may cause tactile allodynia and that the severity of this allodynia does not correlate positively with the incidence of autotomy. We found no contralateral allodynia after nerve transection and repair.