ABNORMALITIES OF SYMPATHETIC INNERVATION IN THE AREA OF AN INJURED PERIPHERAL-NERVE IN A RAT MODEL OF NEUROPATHIC PAIN

Using the rat model that we have developed, a potential underlying mec hanism for sympathetically maintained neuropathic pain (SMP) was explo red. In rats showing neuropathic pain behaviors after a tight ligation of the L, spinal nerve, putative sympathetic postganglionic fibers we re examined in the injured spinal nerve and the dorsal root ganglion ( DRG), using immunohistochemical staining with antibody against tyrosin e hydroxylase (TH). In the neuropathic rats, there was an increase in the number of TH-immunolabeled fibers in the spinal nerve, and some DR G cells were surrounded by the labeled fibers. These abnormalities of sympathetic postganglionic innervation of the injured spinal nerve or the DRG may be a part of the mechanisms underlying the development of SMP.