title: [The Expression of Substance P in Sensory Neurons and Nerve Fibers Associated with "Sanyinjiao" (SP 6) Region in the Rat].
abstract: OBJECTIVE
  To explore the innervation and biochemical characteristics associated with acupoint "Sanyinjiao" (SP 6) in the rat by using neural tracing and immunofluorescence techniques.
  
  
  METHODS
  Five male SD rats were used in the present study. Alexa Fluor 488 conjugated cholera toxin subunit B (AF 488-CTB, 5 L, 1%) was injected into the site superior to the prominence of the medial malleolus, a corresponding site to acupoint SP 6 in the human body. After 3 surviving days, the rat's local tissue of SP 6 region, spinal cord and dorsal root ganglia (DRGs) at lumbar (L) segments (L 1 - S 1) were dissected following perfusion with 4% paraformaldehyde, cut into sections (20 μm for DRG and SP 6, and 40 μm for spinal cord) and observed under light microscope. In addition, substance P (SP) immunoreaction in the spinal cord, DRG and SP 6 region tissues was examined with immunofluorescence.
  
  
  RESULTS
  All the labeling of AF 488-CTB appeared on the ipsilateral side of the injection. The labeled sensory and motor neurons distributed in L 3 - L 6 DRGs and spinal ventral horns with high concentration in the L 4 and L 5 segments. In addition, SP-positive neural labeling was found in small sensory neurons in DRG, axonal terminals in lamina I - II of spinal dorsal horns, and free nerve fibers in local subcutaneous tissues. Additionally, 24. 1 % of AF 488-CTB labeled sensory neurons simultaneously presented a SP-positive expression.
  
  
  CONCLUSIONS
  These findings reveal that the sensory and motor neurons associated with acupoint SP 6 distribute in L 3- L 6 DRGs and spinal ventral horns of rats, concentrating in the L 4 and L 5 segments, and 24.1% sensory neurons show SP-positive, suggesting a possible involvement of the primary SP-positive sensory neurons in the transmission of acupuncture stimulation signals.
authors.forename: Kun
authors.initials: K
authors.lastname: Zhang
authors.forename: Dong-sheng
authors.initials: DS
authors.lastname: Xu
authors.forename: Jing-jing
authors.initials: JJ
authors.lastname: Cui
authors.forename: Zhi-yun
authors.initials: ZY
authors.lastname: Zhang
authors.forename: Xiang-hong
authors.initials: XH
authors.lastname: Jing
authors.forename: Wan-zhu
authors.initials: WZ
authors.lastname: Bai
mesh_terms: D015669:Acupuncture Points; D000818:Animals; D006801:Humans; D009412:Nerve Fibers / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011984:Sensory Receptor Cells / Q000378:metabolism*; D013116:Spinal Cord / Q000378:metabolism; D013373:Substance P / Q000235:genetics* / Q000378:metabolism
chemical_list: D013373:Substance P