Abstract

A new animal model is proposed of neuropathic pain in rats. In this model, damage to the tibial and sural nerves produces behavioral and electrophysiological signs of profound pain. In the experiment, under pentobarbital anesthesia, male Sprague-Dawley rats were subjected to surgical injuries to the tibial and sural nerves by tightly ligating and then sectioning out 10mm-long part of each nerve. The rats showed apparent signs of spontaneous pain. They also showed mechanical allodynia in responding to von Frey filament stimulation and cold allodynia to aceton treatment when these treatments were given to the paws of the injured side. The neuronal responses in the L4 or L5 spinal cord were further recorded with sympathetic manipulations, intravenous injection of phentolamine, an alpha-antagonist, or electrical stimulation of the preganglionic nerve fibers in order to determine whether the neuropathic pain in this model is a sympathetically maintained (SMP) or sympathetically independent pain (SIP). Neither manipulation resulted in any significant change in the neuronal response, which suggests that the sympathetic nervous system is not involved in the development of neuropathic pain in this model. In conclusion the new animal model has been consistant in producing neuropathic behaviors and seems useful for the investigation of sympathetically independent pain.