Sympathetic sprouting in sensory ganglia depends on the number of injured neurons

We examined whether the extent of sympathetic sprouting in the dorsal root ganglion was a function of the number of injured nerve fibers. We compared two groups of rats. One group was subjected to unilateral superior and infe rior caudal trunk transections; at the level between the S-1 and S-2 spinal nerves (S-1 group) and the other group was subjected to unilateral superio r caudal trunk transection at the same level (S group). Immunohistochemical staining with tyrosine hydroxylase (TH) antibody of the S-1 DRG revealed t hat the degree of TH-immunoreactive fibers was more extensive in the S-1 gr oup than in the S group. However, there was no difference in the severity o f neuropathic pain behaviors between the two groups.' These results suggest that the extent of sympathetic sprouting in the DRG following peripheral n erve injury is proportionally related to the amount of injured nerve fibers , but not related to the degree of neuropathic pain behaviors. (C) 2001 Lip pincott Williams & Wilkins.