title: Sensory innervation of rat contracture shoulder model.
abstract: BACKGROUND
  To date, few studies have investigated the cause of pain experienced by patients with frozen shoulder. The purposes of this study were to establish a rat contracture model and clarify the innervation pattern of the glenohumeral (GH) joint and subacromial bursa (SAB) using immunohistochemistry in the dorsal root ganglion (DRG) neurons.
  
  
  METHODS
  The rat contracture models were made by tying the animal's humerus and scapula with No. 2-0 FiberWire (Arthrex, Naples, FL, USA). Contracture was confirmed on x-ray images taken 8 weeks after the operation. Subsequently, two kinds of neurotracers, Fluoro-Gold (FG) (Fluorochrome, Denver, CO, USA) and 1,1'-dioctadecyl-3,3,3',3'-tetramethyl-indocarbocyanine perchlorate (DiI) (Molecular Probes, Eugene, OR, USA), were used to detect the GH joints and SAB separately. FG tracers were injected into GH joints, and DiI tracers were injected into the SAB. At 7 days after injection, DRGs were harvested between C1 and T1. Immunohistochemistry by use of calcitonin gene-related peptide (CGRP) was performed. CGRP is thought to be one of the causes of pain sensation in joint disease. We evaluated the percentages of FG-labeled CGRP-immunoreactive (CGRP-ir) neurons in the total number of FG-labeled neurons and of DiI-labeled CGRP-ir neurons in the total number of DiI-labeled neurons.
  
  
  RESULTS
  Abduction and total arc of the rotation were statistically significantly decreased in the contracture group. Furthermore, the percentage of CGRP-ir DRG neurons was significantly higher in the contracture group in both the GH joint and SAB.
  
  
  CONCLUSIONS
  These results show that pain sensation in rat shoulder contracture may be induced by the up-regulation of CGRP expression in DRG neurons.
authors.affiliation: Department of Orthopedic Surgery, Chiba University Graduate School of Medicine, Chiba, Japan. nobunobu1215@yahoo.co.jp
authors.forename: Nobuyasu
authors.initials: N
authors.lastname: Ochiai
authors.forename: Seiji
authors.initials: S
authors.lastname: Ohtori
authors.forename: Tomonori
authors.initials: T
authors.lastname: Kenmoku
authors.forename: Hironori
authors.initials: H
authors.lastname: Yamazaki
authors.forename: Satoko
authors.initials: S
authors.lastname: Ochiai
authors.forename: Takashi
authors.initials: T
authors.lastname: Saisu
authors.forename: Keisuke
authors.initials: K
authors.lastname: Matsuki
authors.forename: Kazuhisa
authors.initials: K
authors.lastname: Takahashi
mesh_terms: D000818:Animals; D018771:Arthralgia / Q000503:physiopathology*; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism*; D003286:Contracture / Q000503:physiopathology*; D004195:Disease Models, Animal; D005727:Ganglia, Spinal / Q000378:metabolism*; D008297:Male; D016059:Range of Motion, Articular; D051381:Rats; D017207:Rats, Sprague-Dawley; D012785:Shoulder Joint / Q000294:innervation*; D015854:Up-Regulation
chemical_list: D015740:Calcitonin Gene-Related Peptide