Ha. Lekan et al., LOSS OF DORSAL-ROOT GANGLION-CELLS CONCOMITANT WITH DORSAL-ROOT AXON SPROUTING FOLLOWING SEGMENTAL NERVE LESIONS, Neuroscience, 81(2), 1997, pp. 527-534
Tight ligation of the fifth and sixth lumbar segmental nerves in the r
at provides a model of neuropathic pain. We used this model to assess
the changes in primary afferent input to the dorsal hem in neuropathic
pain syndromes. Dorsal roots and ganglia were examined for up to 32 w
eeks following segmental nerve ligation. Stereologic and morphometric
techniques revealed a notable decrease in the numbers of dorsal root g
anglion cells and unmyelinated dorsal root axons by six weeks post-inj
ury. By 32 weeks following segmental nerve ligations, the numbers of d
orsal root ganglion cells have dropped to 50% of pre-ligation levels w
hile the numbers of dorsal root axons have increased to normal levels
predominantly due to sprouting of myelinated fibres. These findings in
dicate that although there is a great loss of dorsal root ganglion cel
ls, there is dramatic sprouting of myelinated fibres and possibly some
sprouting of unmyelinated fibres in the dorsal roots. Additionally, a
difference in the responses of unmyelinated and myelinated fibres to
this peripheral nerve injury is revealed. These changes in dorsal root
ganglion cells and their central axons may underlie certain aspects o
f abnormal pain syndromes because of changes in the types and quantity
of input the dorsal horn receives. (C) 1997 IBRO. Published by Elsevi
er Science Ltd.