Ks. Chung et al., NEONATAL SCIATIC-NERVE LESION TRIGGERS THE SPROUTING OF FIBERS IN THECONTRALATERAL VENTRAL ROOT OF THE RAT, Brain research, 632(1-2), 1993, pp. 80-85
We explored the possibility that unilateral neurectomy of the sciatic
nerve of the rat at the neonatal stage triggers sprouting of afferent
fibers in the contralateral ventral root. 3 months after neonatal scia
tic neurectomy, the numbers of both myelinated and unmyelinated fibers
in the L5 and L3 ventral roots were counted on electron micrographic
montages. Age-matched littermates were used as unoperated controls. To
identify regenerating axons, electron microscopic immunohistochemistr
y was done on the ventral roots using antibody against growth-associat
ed phosphoprotein (GAP-43). Neonatal sciatic neurectomy resulted in: (
1) about a three-fold increase in the number of unmyelinated fibers in
the contralateral L5 ventral root as compared with the unoperated con
trol; (2) about a 25-fold increase in the number of unmyelinated fiber
s in the ipsilateral L5 ventral root as compared with the control; (3)
similar to 25% of the unmyelinated fibers in the contralateral L5 ven
tral root expressing GAP-43; and (4) no significant change in the numb
er of unmyelinated fibers in the L3 ventral root of either side as com
pared with the control. The data suggest that a neonatal sciatic neure
ctomy of the rat triggers sprouting of unmyelinated afferent fibers in
the ventral root of the contralateral as well as the ipsilateral side
. The sprouting is restricted, however, to spinal segments which recei
ve inputs from the sciatic nerve.