Axonal accumulation of hyperpolarization-activated cyclic nucleotide-gated cation channels contributes to mechanical allodynia after peripheral nerve injury in rat.

Abstract	Peripheral nerve injury causes neuropathic pain including mechanical allodynia and thermal hyperalgesia due to central and peripheral sensitization. Spontaneous ectopic discharges derived from dorsal root ganglion (DRG) neurons and from the sites of injury are a key factor in the initiation of this sensitization. Numerous studies have focused primarily on DRG neurons; however, the injured axons themselves likely play an equally important role. Previous studies of neuropathic pain rats with spinal nerve ligation (SNL) showed that the hyperpolarization-activated cyclic nucleotide-gated cation (HCN) channel in DRG neuronal bodies is important for the development of neuropathic pain. Here, we investigate the role of the axonal HCN channel in neuropathic pain rats. Using the chronic constriction injury (CCI) model, we found abundant axonal accumulation of HCN channel protein at the injured sites accompanied by a slight decrease in DRG neuronal bodies. The function of these accumulated channels was verified by local application of ZD7288, a specific HCN blocker, which significantly suppressed the ectopic discharges from injured nerve fibers with no effect on impulse conduction. Moreover, mechanical allodynia, but not thermal hyperalgesia, was relieved significantly by ZD7288. These results suggest that axonal HCN channel accumulation plays an important role in ectopic discharges from injured spinal nerves and contributes to the development of mechanical allodynia in neuropathic pain rats.
Authors	Yu-Qiu Jiang, Guo-Gang Xing, Sheng-Lan Wang, Hui-Yin Tu, Ye-Nan Chi, Jie Li, Feng-Yu Liu, Ji-Sheng Han, You Wan
Journal	Pain (Pain) Vol. 137 Issue 3 Pg. 495-506 (Jul 31 2008) ISSN: 1872-6623 [Electronic] United States
PMID	18179873 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
Chemical References	Cyclic Nucleotide-Gated Cation Channels
Topics	Animals Axons (metabolism) Cyclic Nucleotide-Gated Cation Channels (metabolism) Ganglia, Spinal (physiopathology) Hyperalgesia (physiopathology) Ion Channel Gating Male Membrane Potentials Peripheral Nerve Injuries Peripheral Nerves (physiopathology) Posterior Horn Cells (metabolism) Rats Rats, Sprague-Dawley Touch

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