Axon resealing following transection takes longer in central axone than inperipheral axons: Implications for axonal regeneration

Injury to axons in the CNS leads to little regenerative repair and loss of function, Conversely, injury to axons in the PNS results in vigorous regrow th of severed axons, usually with restoration of function, This difference is generally attributed to a CNS environment that either cannot support or actively inhibits regeneration and/or a failure of CNS neurons to survive a xotomy. One of the earliest responses of neurons to axotomy is the resealin g of cut axons, A delay in resealing could affect a neuron's ability to sur vive axotomy and to regenerate a new axon. In the present experiments, usin g a dye exclusion technique, we demonstrate that following transection of a peripheral sensory nerve, axons reseal within 8-10 h, whereas following op tic nerve transection complete resealing does not occur for more than 20 h, These results show that resealing of cut axons in a CNS environment is sig nificantly delayed compared with axons in the PNS and suggest that this cou ld contribute to the failure of CNS neurons to regenerate following injury. (C) 2000 Academic Press.