title: Inflammatory pain-related traits of sensory DRG neurons innervating the hip joints.
abstract: BACKGROUND
  Hip pain is transmitted to the dorsal horn of the spinal cord via the dorsal root ganglion (DRG), which contains two types of neurons with differential sensitivity to neurotrophic factors. If either type predominantly innervates the hip joint, it may represent a good target for hip joint pain treatment.
  
  
  METHODS
  Inflammation was induced in the left hip joint of rats (n = 10) by using complete Freund's adjuvant. Fluoro-Gold (FG) was applied to the hip joint after 7 days, and T12-L6 DRGs were double-stained for calcitonin gene-related peptide (CGRP) and isolection-IB4 1 week later.
  
  
  RESULTS
  FG-labeled neurons in the control group were distributed throughout the left DRG from T13 to L5, primarily in L2 to L4, and CGRP-positive neurons were significantly more frequent than IB4-binding neurons. In the inflammatory group, FG-labeled neurons were similarly distributed, primarily at L3 and L4, and CGRP-positive neurons were significantly more frequent than IB4-binding neurons. The percentage of CGRP-positive neurons was significantly greater in the inflammatory group (P < 0.05).
  
  
  CONCLUSIONS
  Most small neurons innervating the hip joint express CGRP. Furthermore, hip joint inflammation caused an increase in CGRP-positive neurons, but not in IB4-binding neurons. Our results suggest that CGRP-expressing nerve growth factor-dependent neurons are primarily responsible for hip joint pain and may represent therapeutic targets.
authors.affiliation: Department of Orthopedic Surgery, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba 260-8670, Japan. Electronic address: oirakanag7620@yahoo.co.jp.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Nakajima
authors.affiliation: Department of Orthopedic Surgery, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba 260-8670, Japan.
authors.forename: Seiji
authors.initials: S
authors.lastname: Ohtori
authors.affiliation: Department of Orthopedic Surgery, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba 260-8670, Japan.
authors.forename: Junichi
authors.initials: J
authors.lastname: Nakamura
authors.affiliation: Department of Orthopedic Surgery, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba 260-8670, Japan.
authors.forename: Takane
authors.initials: T
authors.lastname: Suzuki
authors.affiliation: Department of Orthopedic Surgery, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba 260-8670, Japan.
authors.forename: Yasuchika
authors.initials: Y
authors.lastname: Aoki
authors.affiliation: Department of Orthopedic Surgery, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba 260-8670, Japan.
authors.forename: Atsuya
authors.initials: A
authors.lastname: Watanabe
authors.affiliation: Department of Orthopedic Surgery, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba 260-8670, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Takazawa
authors.affiliation: Department of Orthopedic Surgery, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba 260-8670, Japan.
authors.forename: Kazuhisa
authors.initials: K
authors.lastname: Takahashi
mesh_terms: D000818:Animals; D018771:Arthralgia / Q000188:drug therapy / Q000473:pathology / Q000503:physiopathology*; D001168:Arthritis / Q000188:drug therapy / Q000473:pathology* / Q000503:physiopathology; D001707:Biopsy, Needle; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism*; D004195:Disease Models, Animal; D005727:Ganglia, Spinal / Q000473:pathology / Q000503:physiopathology; D006621:Hip Joint / Q000294:innervation* / Q000473:pathology; D007150:Immunohistochemistry; D008297:Male; D009475:Neurons, Afferent; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012016:Reference Values; D012680:Sensitivity and Specificity
chemical_list: D015740:Calcitonin Gene-Related Peptide