title: Substance P and beta-endorphin mediate electro-acupuncture induced analgesia in mouse cancer pain model.
abstract: BACKGROUND
  Opioid analgesics are generally used to combat the pain associated with cancerous conditions. These agents not only inhibit respiratory function and cause constipation, but also induce other significant side effects such as addiction and tolerance, all of which further contribute to a reduced quality of life for cancer patients. Thus, in the present study, the effects of electro-acupuncture treatment (EA) on mechanical allodynia were examined in a cancer pain mouse model.
  
  
  METHODS
  In order to produce a neuropathic cancer pain model, S-180 sarcoma cells were inoculated around the sciatic nerve of left legs of Balb/c mice. Magnetic Resonance Imaging (MRI) scanning confirmed the mass of S-180 cancer cells embedded around the sciatic nerve. Mechanical allodynia was most consistently induced in the mouse sarcoma cell line S-180 (2 x 10(6)sarcoma cells)-treated group compared to all the other groups studied. EA stimulation (2 Hz) was administered daily to ST36 (Zusanli) of S-180 bearing mice for 30 min for 9 days after S-180 inoculation.
  
  
  RESULTS
  EA treatment significantly prolonged paw withdrawal latency from 5 days after inoculation. It also shortened the cumulative lifting duration from 7 days after inoculation, compared to the tumor control. Also, the overexpression of pain peptide substance P in the dorsal horn of the spinal cord was significantly decreased in the EA-treated group compared to the tumor control on Day 9 post inoculation. Furthermore, EA treatment effectively increased the concentration of beta-endorphin in blood and brain samples of the mice to a greater extent than that of the tumor control as well as the normal group. The concentration of beta-endorphin for EA treatment group increased by 51.457% in the blood and 12.6% in the brain respectively, compared to the tumor control group.
  
  
  CONCLUSIONS
  The findings of this study suggest that a S-180 cancer pain model is useful as a consistent and short time animal model. It also indicated that EA treatment could be used as an alternative therapeutic method for cancer pain due to a consequent decrease in substance P and increase in beta-endorphin levels.
authors.affiliation: College of Oriental Medicine, Kyung-Hee University, Seoul 130-701, South Korea. strong79@khu.ac.kr
authors.forename: Hyo-Jeong
authors.initials: HJ
authors.lastname: Lee
authors.forename: Jae-Ho
authors.initials: JH
authors.lastname: Lee
authors.forename: Eun-Ok
authors.initials: EO
authors.lastname: Lee
authors.forename: Hyo-Jung
authors.initials: HJ
authors.lastname: Lee
authors.forename: Kwan-Hyun
authors.initials: KH
authors.lastname: Kim
authors.forename: Sun-Hyung
authors.initials: SH
authors.lastname: Kim
authors.forename: Keun-Sung
authors.initials: KS
authors.lastname: Lee
authors.forename: Hee-Jae
authors.initials: HJ
authors.lastname: Jung
authors.forename: Sung-Hoon
authors.initials: SH
authors.lastname: Kim
mesh_terms: D015667:Acupuncture Analgesia; D000818:Animals; D045744:Cell Line, Tumor; D004195:Disease Models, Animal; D015671:Electroacupuncture; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D018377:Neurotransmitter Agents / Q000378:metabolism; D017288:Pain Threshold; D012510:Sarcoma 180 / Q000628:therapy*; D012584:Sciatic Nerve / Q000502:physiology; D013373:Substance P / Q000378:metabolism*; D001615:beta-Endorphin / Q000378:metabolism*
chemical_list: D018377:Neurotransmitter Agents; D013373:Substance P; D001615:beta-Endorphin