Expression of NGF receptor and GAP‐43 mRNA in DRG neurons during collateral sprouting and regeneration of dorsal cutaneous nerves

Publisher Website
Google Scholar
Abstract
The collateral sprouting of intact sensory axons and the regenertion of damaged ones differ in a number of respects. Regeneration is triggered by axotomy-induced damage, probably involves the loss of a peripheral signal, and appears to occur independently of NGF, while collateral sprouting is evoked and sustained by an increase in a target-driven signal, namely NGF. New findings strengthen the distinction between these two phenomena. Nerve growth factor receptor (NGFR) mRNA is increased in undamaged DRG neurons whose axons are sprouting into denervated skin. This response is related to an increased availablity of target-derived NGF, a proposal supported by a number of findings including increased NGF mRNA in the denervated target. In contrast, we observed little or no change in the NGFR mRNA levels in regenerating neurons, consistent with the observations that NGF does not play a role in this process. However, increases in neuronal GAP-43 mRNA are found during both regeneration and collateral sprouting, a result in keeping with the proposal that GAP-43 is primarily associated with nerve growth, and the observation that GAP-43 expression is not especially influenced by NGF. 1994 John Wiley & Sons, Inc.