K. Chung et al., SPROUTING SYMPATHETIC FIBERS FORM SYNAPTIC VARICOSITIES IN THE DORSAL-ROOT GANGLION OF THE RAT WITH NEUROPATHIC INJURY, Brain research, 751(2), 1997, pp. 275-280
Peripheral nerve injury in a rat model (spinal nerve ligation) of neur
opathic pain triggers sprouting of sympathetic fibers in the dorsal ro
ot ganglion (DRG). This sympathetic sprouting has been suggested as an
important underlying mechanism for pain behaviors, To investigate the
possibility of functional interaction between sprouted sympathetic fi
bers and sensory neurons, the present study examined the fine morpholo
gy and structural relationship between sympathetic fibers and the DRG
neurons by electron microscopy. Sympathetic postganglionic fibers, as
identified by electron microscopic immunostaining for tyrosine hydroxy
lase (TH), were all unmyelinated fibers and some of them ended as grow
th cones. In addition, many vesicle-containing axonal enlargements (we
will refer these as synaptic varicosities) were found in the intersti
tial space around DRG neurons, and some were enclosed within the satel
lite cell capsule which surrounded the DRG soma. The presence of sympa
thetic synaptic varicosities near or in apposition with either the DRG
somata or their processes provides a structural basis for possible in
teractions between sensory neurons and sympathetic fibers in the DRG o
f neuropathic rats. (C) 1997 Elsevier Science B.V.