title: Effect of applying p75NTR saporin to a punctured intervertebral disc on calcitonin gene-related peptide expression in rat dorsal root ganglion neurons.
abstract: BACKGROUND
  Recent studies have revealed that the low-affinity nerve growth factor receptor, p75 neurotrophin receptor (p75NTR), is important in inflammatory pain. Moreover, p75NTR immunoreactive sensory nerve and dorsal root ganglion (DRG) neurons have been found to innervate lumbar intervertebral discs. The purpose of the current study was to investigate the effect of p75NTR saporin, a toxin used to destroy p75NTR, on calcitonin gene-related peptide (CGRP), an inflammatory neuropeptide associated with pain, in DRG neurons innervating punctured intervertebral discs in rats.
  
  
  METHODS
  The neurotracer fluorogold (FG) was applied to the surfaces of L5/6 discs to label their innervating DRG neurons (n = 30). Of 30 rats, 10 were in a nonpunctured disc sham surgery control group (nonpuncture group), and the other 20 were in experimental groups in which intervertebral discs were punctured with a 23-gauge needle. p75NTR saporin was applied to the discs of 10 rats (puncture + p75NTR saporin group) and the other 10 received the same volume of saline (puncture + saline group). At 14 days after surgery, DRGs from L1 to L6 were harvested, sectioned, and immunostained for CGRP, and the proportions of CGRP-immunoreactive DRG neurons was evaluated.
  
  
  RESULTS
  Of the FG-labeled neurons innervating the L5/6 disc, the proportion of CGRP-immunoreactive neurons was 32% +/- 6% (mean +/- SE) in the nonpuncture group, 47.2% +/- 8% in the puncture + saline group, and 34.6% +/- 9% in the puncture + p75NTR saporin group. The proportion of CGRP-immunoreactive neurons was significantly greater in the puncture + saline group compared with the nonpuncture and puncture + p75NTR saporin groups (P < 0.01).
  
  
  CONCLUSIONS
  Half of the DRG neurons innervating the discs were positive for CGRP in the puncture + saline group. CGRP is important for mediating inflammatory and nerve-injured pain and may be important in discogenic pain. However, p75NTR saporin suppressed CGRP expression in DRG neurons. Therefore, p75NTR may be an important receptor for mediating discogenic pain via CGRP expression.
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medicine, Chiba University, Chuo-ku, Chiba, Japan.
authors.forename: Ai
authors.initials: A
authors.lastname: Sugiura
authors.forename: Seiji
authors.initials: S
authors.lastname: Ohtori
authors.forename: Masaomi
authors.initials: M
authors.lastname: Yamashita
authors.forename: Kazuyo
authors.initials: K
authors.lastname: Yamauchi
authors.forename: Gen
authors.initials: G
authors.lastname: Inoue
authors.forename: Munetaka
authors.initials: M
authors.lastname: Suzuki
authors.forename: Masaki
authors.initials: M
authors.lastname: Norimoto
authors.forename: Sumihisa
authors.initials: S
authors.lastname: Orita
authors.forename: Yawara
authors.initials: Y
authors.lastname: Eguchi
authors.forename: Kazuki
authors.initials: K
authors.lastname: Kuniyoshi
authors.forename: Nobuyasu
authors.initials: N
authors.lastname: Ochiai
authors.forename: Shunji
authors.initials: S
authors.lastname: Kishida
authors.forename: Masashi
authors.initials: M
authors.lastname: Takaso
authors.forename: Yasuchika
authors.initials: Y
authors.lastname: Aoki
authors.forename: Tetsuhiro
authors.initials: T
authors.lastname: Ishikawa
authors.forename: Gen
authors.initials: G
authors.lastname: Arai
authors.forename: Masayuki
authors.initials: M
authors.lastname: Miyagi
authors.forename: Hiroto
authors.initials: H
authors.lastname: Kamoda
authors.forename: Junichi
authors.initials: J
authors.lastname: Nakamura
authors.forename: Kazuhisa
authors.initials: K
authors.lastname: Takahashi
mesh_terms: D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism*; D005727:Ganglia, Spinal / Q000378:metabolism*; D007403:Intervertebral Disc / Q000293:injuries*; D008159:Lumbar Vertebrae / Q000294:innervation*; D008297:Male; D009419:Nerve Tissue Proteins; D051381:Rats; D017207:Rats, Sprague-Dawley; D017978:Receptors, Growth Factor; D017475:Receptors, Nerve Growth Factor / Q000502:physiology*; D054789:Ribosome Inactivating Proteins, Type 1; D000076985:Saporins; D013266:Stilbamidines
chemical_list: C049774:2-hydroxy-4,4'-diamidinostilbene, methanesulfonate salt; D009419:Nerve Tissue Proteins; D017978:Receptors, Growth Factor; D017475:Receptors, Nerve Growth Factor; D054789:Ribosome Inactivating Proteins, Type 1; D013266:Stilbamidines; C068313:Ngfr protein, rat; D000076985:Saporins; D015740:Calcitonin Gene-Related Peptide