title: Involvement of NGF in the rat model of persistent muscle pain associated with taut band.
abstract: Myofascial pain syndrome (MPS) is an important clinical condition characterized by chronic muscle pain and a myofascial trigger point (MTrP) located in a taut band (TB). However, its pathogenic mechanism is still unclear. We developed an animal model relevant to conditions of MPS, and analyzed the mechanism of the muscle pain in this model. We applied eccentric contraction (EC) to a rat's gastrocnemius muscle (GM) for 2 weeks, and examined the mechanical withdrawal thresholds, histological changes, and expressions and contents of nerve growth factor (NGF). The mechanical withdrawal threshold decreased significantly at the next day of first EC and continued up to 9 days after EC. TBs were palpable at 3 to 8 days after initiation of EC. In EC animals, necrotic and regenerating muscle cells were found significantly more than in control animals. In EC animals, NGF expressions in regenerating muscle cells and NGF contents of GM were significantly higher than control animals. Administration of NGF receptor (TrkA) inhibitor K252a showed significant suppression of mechanical hyperalgesia in EC animals. Repeated EC induced persistent mechanical muscle hyperalgesia associated with TB. NGF expressed in regenerating muscle cells may have an important role in persistent mechanical muscle hyperalgesia which might be relevant to pathogenesis of MPS.
  
  
  CONCLUSIONS
  The present study shows that NGF expressed in regenerating muscle cells is involved in persistent muscular mechanical hyperalgesia. NGF-TrkA signaling in primary muscle afferent neurons may be one of the most important and promising targets for MPS.
authors: Department of Functional Anatomy and Neuroscience, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan.
authors: Koei
authors: K
authors: Hayashi
authors: Noriyuki
authors: N
authors: Ozaki
authors: Kenji
authors: K
authors: Kawakita
authors: Kazunori
authors: K
authors: Itoh
authors: Kazue
authors: K
authors: Mizumura
authors: Koichi
authors: K
authors: Furukawa
authors: Masaya
authors: M
authors: Yasui
authors: Kiyomi
authors: K
authors: Hori
authors: Shuang-Qin
authors: SQ
authors: Yi
authors: Takeshi
authors: T
authors: Yamaguchi
authors: Yasuo
authors: Y
authors: Sugiura
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D002227:Carbazoles / Q000494:pharmacology; D004195:Disease Models, Animal; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D006930:Hyperalgesia / Q000188:drug therapy / Q000503:physiopathology*; D026121:Indole Alkaloids / Q000494:pharmacology; D008297:Male; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D059352:Musculoskeletal Pain / Q000473:pathology / Q000503:physiopathology*; D020932:Nerve Growth Factor / Q000378:metabolism*; D010147:Pain Measurement; D017288:Pain Threshold / Q000187:drug effects / Q000502:physiology*; D011312:Pressure / Q000009:adverse effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors; D061028:Trigger Points / Q000503:physiopathology*
chemical_list: D002227:Carbazoles; D004791:Enzyme Inhibitors; D026121:Indole Alkaloids; D020932:Nerve Growth Factor; C049985:staurosporine aglycone