C. Molander et al., SOMATOTOPIC REDISTRIBUTION OF C-FOS EXPRESSING NEURONS IN THE SUPERFICIAL DORSAL HORN AFTER PERIPHERAL-NERVE INJURY, Neuroscience, 84(1), 1998, pp. 241-253
The functional somatotopic reorganization of the lumbar spinal cord do
rsal horn after nerve injury was studied in the rat by mapping the sti
mulus-evoked distribution of neurons expressing proto-oncogene c-fos.
In three different nerve injury paradigms, the saphenous nerve was ele
ctrically stimulated at C-fibre strength at survival times ranging fro
m 40 h to more than six months: 1) Saphenous nerve stimulation from th
ree weeks onwards after ipsilateral sciatic nerve transection resulted
in an increase in the number of Fos-immunoreactive neurons within the
dorsal horn saphenous territory in laminae I-II, and an expansion of
the saphenous territory into the denervated sciatic territory until 24
weeks postinjury. 2) Saphenous nerve stimulation from five days onwar
ds after ipsilateral sciatic nerve section combined with saphenous ner
ve crush resulted in an increase in the number of Fos-immunoreactive n
eurons within the dorsal horn saphenous nerve territory, and an expans
ion of the saphenous nerve territory into the denervated sciatic nerve
territory. 3) Stimulation of the crushed nerve (without previous adja
cent nerve section) at five days, but not al eight months resulted in
a temporary increase in the number of Fos-immunoreactive neurons withi
n the territory of the injured nerve, and no change in area at either
survival time. The results indicate that nerve injury results in an in
creased capacity of afferents in an adjacent uninjured, or regeneratin
g nerve, to excite neurons both in its own and in the territory of the
permanently injured nerve in the dorsal horn. The onset and duration
of the increased postsynaptic excitability and expansion depends on th
e types of nerve injuries involved. These findings indicate the comple
xity of the central changes that follows in nerve injuries that contai
n a mixture of uninjured, regenerating and permanently destroyed affer
ents. (C) 1998 IBRO. Published by Elsevier Science Ltd.