Journal of Neuroscience, Vol 4, 1736-1744, Copyright © 1984 by Society for Neuroscience
A conditioning lesion of the peripheral axons of dorsal root ganglion cells accelerates regeneration of only their peripheral axons
MM Oblinger and RJ Lasek
Axotomy of the peripheral axon of dorsal root ganglion (DRG) cells is known
to result in chromatolysis and changes in protein synthesis in DRG cells.
We investigated whether a stimulus produced by peripheral branch axotomy
would affect the regenerative properties of both the central and peripheral
axon of the DRG cell equally. To examine this question, a conditioning
crush lesion was made distally on the sciatic nerve 2 weeks prior to a
testing lesion of either the dorsal root or peripheral branch axon near the
DRG. Fast axonal transport of radioactive proteins was used to assess
regeneration of DRG axons. In the adult rat, leading peripheral branch
axons normally regenerate at a rate of 4.4 mm/day. If a conditioning lesion
of the sciatic nerve is made 2 weeks before the test lesion, the rate of
peripheral branch axonal regeneration increases by 25% to 5.5 mm/day. This
effect is not limited to the fastest growing axons in the nerve since a
population of more slowly growing axons also exhibits accelerated outgrowth
in response to a prior peripheral axotomy. In contrast to this, the fastest
growing central branch axons of DRG cells, which normally regenerate at a
rate of 2.5 mm/day, are not significantly affected by a prior peripheral
axotomy. A population of more slowly growing axons in the dorsal root also
does not exhibit accelerated outgrowth in response to a peripheral
conditioning lesion. The results of these experiments indicate that changes
in the DRG neuron's metabolism induced by prior axotomy of its peripheral
axon do not affect the regenerative properties of both axons equally. This
raises the possibility that accelerated axonal outgrowth in only one axonal
branch results from a differentially regulated supply of proteins to the
two axons by the DRG cell body.