title: Electroacupuncture improves thermal and mechanical sensitivities in a rat model of postherpetic neuralgia.
abstract: BACKGROUND
  Electroacupuncture (EA) is effective in relieving pain in patients with postherpetic neuralgia (PHN). However, the mechanism underlying the therapeutic effect of EA in PHN is still unclear. Systemic injection of resiniferatoxin (RTX), an ultrapotent analog of TRPV1 agonist, in adult rats can reproduce the clinical symptoms of PHN by ablating TRPV1-expressing sensory neurons. In this study, we determined the beneficial effect of EA and the potential mechanisms in this rat model of PHN.
  
  
  METHODS
  PHN was induced in rats by a single injection of RTX. Thermal hyperalgesia was tested with a radiant heat stimulus, and mechanical allodynia was quantified with von Frey filaments. TRPV1 receptors were shown by using immunofluorescence labeling. The ultrastructural changes of the sciatic nerve were assessed by electron microscopic examination. The sprouting of myelinated primary afferent terminals into the spinal dorsal horn was mapped by using the transganglionic tracer cholera toxin B-subunit (CTB).
  
  
  RESULTS
  RTX injection diminished thermal sensitivity and gradually induced tactile allodynia within 3 weeks. EA applied to GB30 and GB34 at 2 and 15 Hz, but not 100 Hz, significantly increased the thermal sensitivity 4 weeks after treatment and decreased the tactile allodynia 2 weeks after treatment in RTX-treated rats. EA treatment at 2 and 15 Hz recovered the loss of TRPV1-positive dorsal root ganglion neurons and their central terminals of afferent fibers in the spinal superficial dorsal horn of RTX-treated rats. Moreover, EA significantly reduced the loss of unmyelinated fibers and the damage of the myelinated nerve fibers of RTX-treated rats. Furthermore, EA at 2 and 15 Hz inhibited the sprouting of myelinated primary afferent terminals into the spinal lamina II of RTX-treated rats.
  
  
  CONCLUSIONS
  EA treatment improves thermal perception by recovering TRPV1-positive sensory neurons and nerve terminals damaged by RTX. EA Also reduces RTX-induced tactile allodynia by attenuating the damage of myelinated afferent nerves and their abnormal sprouting into the spinal lamina II. Our study provides new information about the mechanisms of the therapeutic actions of EA in the treatment of PHN.
authors.affiliation: Department of Neurobiology, School of Basic Medicine, Tongji Medical College of Huazhong University of Science and Technology, 13 Hangkong Road, Wuhan, 430030, PR China.
authors.forename: Cai-hua
authors.initials: CH
authors.lastname: Wu
authors.forename: Zheng-tao
authors.initials: ZT
authors.lastname: Lv
authors.forename: Yin
authors.initials: Y
authors.lastname: Zhao
authors.forename: Yan
authors.initials: Y
authors.lastname: Gao
authors.forename: Jia-qing
authors.initials: JQ
authors.lastname: Li
authors.forename: Fang
authors.initials: F
authors.lastname: Gao
authors.forename: Xian-fang
authors.initials: XF
authors.lastname: Meng
authors.forename: Bo
authors.initials: B
authors.lastname: Tian
authors.forename: Jing
authors.initials: J
authors.lastname: Shi
authors.forename: Hui-lin
authors.initials: HL
authors.lastname: Pan
authors.forename: Man
authors.initials: M
authors.lastname: Li
mesh_terms: D000818:Animals; D002772:Cholera Toxin / Q000378:metabolism; D004195:Disease Models, Animal; D004224:Diterpenes; D015671:Electroacupuncture; D005727:Ganglia, Spinal / Q000378:metabolism / Q000473:pathology; D006930:Hyperalgesia / Q000473:pathology* / Q000628:therapy*; D008297:Male; D009186:Myelin Sheath / Q000378:metabolism; D051474:Neuralgia, Postherpetic / Q000473:pathology* / Q000628:therapy*; D009475:Neurons, Afferent / Q000378:metabolism / Q000473:pathology; D020671:Posterior Horn Cells / Q000378:metabolism / Q000473:pathology; D021122:Protein Subunits / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012584:Sciatic Nerve / Q000473:pathology / Q000648:ultrastructure; D050916:TRPV Cation Channels / Q000378:metabolism; D013696:Temperature; D013997:Time Factors
chemical_list: D004224:Diterpenes; D021122:Protein Subunits; D050916:TRPV Cation Channels; C494484:TRPV1 receptor; D002772:Cholera Toxin; C024353:resiniferatoxin
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