SIGNS OF NEUROPATHIC PAIN DEPEND ON SIGNALS FROM INJURED NERVE-FIBERSIN A RAT MODEL

The present study was undertaken to determine the role of injured fibe rs in the development of neuropathic pain using our earlier establishe d rat model. Our model was produced by placing tight ligatures to the L5 or both the L5 and L6 spinal nerves on one side in the rat. These r ats showed long-lasting behavioral signs of mechanical allodynia and h eat hyperalgesia. Using the uniqueness of our model, 3 specific questi ons are being asked concerning the initiation and maintenance of behav ioral signs for neuropathic pain, The results of behavioral tests perf ormed after various surgical manipulations suggest that: (1) periphera l nerve injury itself is the critical factor for the development of be havioral signs of neuropathic pain; (2) signs of neuropathic pain appe ar only when injury occurs at a part of the peripheral nerve distal to the dorsal root ganglion; and (3) signals (either electrical or chemi cal) entering the spinal cord from the injured fibers or the dorsal ro ot ganglion cells play a critical role for both initiation and mainten ance of the neuropathic pain state.