The effect of conduction block on the spinal release of immunoreactive-neuropeptide Y (ir-NPY) in the neuropathic rat

Peripheral nerve injury may result in significant changes in neuropeptide p roduction and the development of neuropathic pain behaviour. Rats with a ch ronic constriction injury of one sciatic nerve were used to study the spina l release of immunoreactive neuropeptide Y (ir-NPY), using the antibody-coa ted microprobe technique. Previous work has shown an increase in NPY synthe sis by large to medium-sized primary afferent neurones, as well as a new ar ea of ir-NPY release in the deep dorsal horn on the side of nerve injury, w hen compared to uninjured rats. The stimulus for spontaneous ir-NPY release was unclear, but may have been due to ectopic neuronal discharges developi ng after nerve injury. This study used local anaesthetic to block all elect rical input from the injured nerve. No change was found in the new zone of spontaneous release of ir-NPY in the deep dorsal horn ipsilateral to nerve injury. It appears therefore, that ir-NPY is released from the central term ination of primary afferent neurones, without regulation from neuronal acti vity in the primary afferent neurones themselves. (C) 2001 International As sociation for the Study of Pain. Published by Elsevier Science B.V. All rig hts reserved.