title: Sensory innervation of the lateral portion of the lumbar intervertebral disc in rats.
abstract: BACKGROUND
  An annular tear extending to the outer one-third of the annulus is thought to be one of the causes of low back pain. However, some patients have bilateral low back symptoms, even if the annular tear is localized in the lateral disc. Because nociceptive information from the lateral disc is transmitted by the dorsal root ganglion (DRG) neurons innervating the lateral disc, we investigated the distribution of the DRG neurons innervating the lateral portion of the disc.
  
  
  OBJECTIVE
  To clarify the distribution and pathway of the DRG neurons innervating the lateral portion of the L5-L6 disc in rats.
  
  
  METHODS
  Using the retrograde tracing method, we studied the innervation pattern of the lateral portion of the L5-L6 intervertebral disc in rats.
  
  
  METHODS
  The retrograde transport of Fluoro-Gold (F-G; Fluorochrome, Denver, CO) was used in 22 rats. Subjects included a nontreated group (n=16) and a sympathectomized group (n=6). Seven days after the application of F-G crystals to the left lateral portion of the L5-L6 disc, bilateral T12-L6 DRGs were observed by fluorescent microscopy.
  
  
  RESULTS
  In the nontreated group, of all the F-G-labeled neurons, 93.1% were present in the left DRGs and 6.9% were in the right DRGs. The number of labeled neurons was largest in the left L2 DRGs. In the sympathectomized group, the numbers of labeled neurons in the T13, L1 and L2 DRGs were significantly lower than the numbers in the nontreated group.
  
  
  CONCLUSIONS
  Results of this study indicate that DRG neurons innervating the lateral portion of the disc are distributed mainly in the ipsilateral side but also in the contralateral side. The DRG neurons in T13, L1 and L2 innervate the lateral portion of the L5-L6 disc through the paravertebral sympathetic trunks.
authors.affiliation: Department of Orthopedic Surgery, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-Ku, Chiba City 260-8670, Japan. yasuaoki@h6.dion.ne.jp
authors.forename: Yasuchika
authors.initials: Y
authors.lastname: Aoki
authors.forename: Yuzuru
authors.initials: Y
authors.lastname: Takahashi
authors.forename: Kazuhisa
authors.initials: K
authors.lastname: Takahashi
authors.forename: Tanemichi
authors.initials: T
authors.lastname: Chiba
authors.forename: Masahiro
authors.initials: M
authors.lastname: Kurokawa
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Ozawa
authors.forename: Hideshige
authors.initials: H
authors.lastname: Moriya
mesh_terms: D000818:Animals; D005456:Fluorescent Dyes / Q000008:administration & dosage / Q000378:metabolism; D005727:Ganglia, Spinal / Q000033:anatomy & histology* / Q000378:metabolism / Q000601:surgery; D007403:Intervertebral Disc / Q000294:innervation*; D008159:Lumbar Vertebrae / Q000294:innervation*; D008297:Male; D008856:Microscopy, Fluorescence; D009412:Nerve Fibers / Q000378:metabolism; D009475:Neurons, Afferent / Q000166:cytology* / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013266:Stilbamidines / Q000008:administration & dosage / Q000378:metabolism; D013562:Sympathectomy
chemical_list: C049774:2-hydroxy-4,4'-diamidinostilbene, methanesulfonate salt; D005456:Fluorescent Dyes; D013266:Stilbamidines