Journal of Neuroscience, Vol 10, 926-934, Copyright © 1990 by Society for Neuroscience
Correlation between GAP43 and nerve growth factor receptors in rat sensory neurons
VM Verge, W Tetzlaff, PM Richardson and MA Bisby
Division of Neurosurgery, Montreal General Hospital, Canada.
In mature rat sensory neurons, expression of the gene for the growth-
associated protein, GAP43, was studied by in situ hybridization with a cDNA
probe. Among neurons in normal lumbar dorsal root ganglia, labeling for
GAP43 mRNA was heterogeneous, approximately one-half of the neurons being
densely labeled. To characterize the latter population, individual neurons
were examined in adjacent sections processed either for GAP43 hybridization
or NGF-receptor radioautography. Virtually all neurons with high-affinity
NGF binding sites had high basal levels of GAP43 mRNA and most
GAP43-positive neurons bore NGF receptors. Another NGF-responsive
population, sympathetic neurons in the superior cervical ganglion, also had
high basal concentrations of GAP43 mRNA. Further co-localization studies in
dorsal root ganglia were performed with immunohistochemistry for
somatostatin and enzyme histochemistry for acid phosphatase. The latter 2
groups of sensory neurons have been previously shown to lack high- affinity
receptors and were here shown to have low basal concentrations of GAP43
mRNA. From this and earlier studies, it can be assumed that substance
P-immunoreactive neurons and strongly positive CGRP neurons synthesize
GAP43 at high basal rate. One week following peripheral nerve transection,
almost all neurons had high concentrations of GAP43 mRNA without
correlation with NGF binding. Intrathecal infusion of NGF after the sciatic
nerve was cut did not strongly influence this post- traumatic elevation in
GAP mRNA. In normal dorsal root ganglia, neurons that have high-affinity
NGF binding sites and are therefore potentially responsive to NGF also have
high basal rates of synthesis of GAP43.(ABSTRACT TRUNCATED AT 250 WORDS)
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