Volume 16, Number 9,
Issue of May 1, 1996
pp. 2901-2911
Copyright ©1996 Society for Neuroscience
Differential Expression of the p75 Nerve Growth Factor Receptor
in Glia and Neurons of the Rat Dorsal Root Ganglia after Peripheral
Nerve Transection
Received Dec. 12, 1995; revised Feb. 7, 1996; accepted Feb. 12, 1996.
Xin-Fu Zhou1,
Robert
A. Rush1, and
Elspeth M. McLachlan2
1 Department of Physiology and Centre of Neuroscience,
Flinders University of South Australia, Bedford Park 5042, Australia,
and 2 Princes of Wales Medical Research Institute,
Randwick, NSW 2031, Australia
Sympathetic nerve terminals on blood vessels within the dorsal root
ganglia sprout after sciatic nerve lesions in the rat. The mechanism
underlying this phenomenon is not clear, but might be predicted to
involve nerve growth factor or its homologs because these factors are
known to trigger collateral sprouting of undamaged sympathetic
noradrenergic terminals. We have found that sciatic nerve lesions lead
to a decreased expression of neuronal p75, the low-affinity receptor
for the neurotrophins, but an increased expression of glial p75 in
ipsilateral dorsal root ganglia. Intriguingly, the increased expression
of p75 was found primarily in association with glia surrounding
large-diameter neurons, which are those associated with the
noradrenergic sprouts. A smaller but significant glial response was
also found in contralateral ganglia. The glial response in ipsilateral
ganglia could be mimicked by ventral, but not dorsal, root transection.
The dorsal root lesion-induced glial responses in contralateral ganglia
were greater than those induced by ventral root or sciatic nerve
lesions. Combined lesions of dorsal root and either ventral root or
sciatic nerve did not prevent the glial responses of ipsilateral
ganglia, suggesting that a peripheral signal is involved.
Colocalization studies indicate that tyrosine
hydroxylase-immunoreactive nerve sprouts were associated with
p75-immunoreactive glial cells. Thus, increased glial synthesis of p75
might provide an explanation for the abnormal growth of sympathetic
fibers in dorsal root ganglia after peripheral nerve injury.
Key words:
satellite cells;
glial fibrillary acidic protein;
sympathetic;
nerve injury;
glia;
sprouting;
tyrosine hydroxylase