Expression of c‐Jun as a response to dorsal root and peripheral nerve section in damaged and adjacent intact primary sensory neurons in the rat

R Jenkins, SB McMahon, AB Bond… - European Journal of …, 1993 - Wiley Online Library
R Jenkins, SB McMahon, AB Bond, SP Hunt
European Journal of Neuroscience, 1993Wiley Online Library
It was previously shown that the immediate early gene, c‐jun, was highly expressed over
long periods, in both peripheral sensory and motor neurons following axon damage or block
of axoplasmic transport. Here we have examined the question of whether the expression of c‐
Jun protein is related to axon injury per se or to the process of axon growth. We have
examined dorsal root ganglion (DRG) cells subjected to different manipulations which are
associated with varying degrees of regrowth, as follows:(i) after peripheral nerve section …
Abstract
It was previously shown that the immediate early gene, c‐jun, was highly expressed over long periods, in both peripheral sensory and motor neurons following axon damage or block of axoplasmic transport. Here we have examined the question of whether the expression of c‐Jun protein is related to axon injury per se or to the process of axon growth. We have examined dorsal root ganglion (DRG) cells subjected to different manipulations which are associated with varying degrees of regrowth, as follows: (i) after peripheral nerve section, where it appears that all damaged neurons make some regenerative effort. 1 – 24 days after sciatic nerve section and ligation most cells in L4/L5 DRG were c‐Jun‐positive; (ii) after section of the central processes of the DRG cells, which then showed a slow and limited regrowth of their axons towards, but not into, the spinal cord. This resulted in a variable, but significant, expression of c‐Jun in a small number of DRG cells; (iii) in intact sensory neurons that were offered the opportunity to sprout into adjacent denervated peripheral tissue. The sciatic nerve was ligated and the response of cells in the L3 ganglia (many of which project to the saphenous nerve) was measured. A small but significant number of cells were c‐Jun‐positive; (iv) in intact sensory neurons that were offered the opportunity to sprout centrally into partialy denervated neuropil of the spinal cord. We examined neurons in the L3 DRG after rhizotomy of the adjacent L4/L5 dorsal roots. Previous work suggests that sensory neurons show at best a very limited growth under these conditions. No significant increase was seen in c‐Jun expression in these cases. These results suggest that c‐Jun expression is closely correlated with growth and regeneration, and not simply a consequence of neuronal injury.
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