title: Acupuncture at distant myofascial trigger spots enhances endogenous opioids in rabbits: a possible mechanism for managing myofascial pain.
abstract: OBJECTIVE
  Acupuncture applied at myofascial trigger points (MTrPs) of distant anatomical regions, to reduce pain in a patient's area of primary complaint, is one strategy that is available to manage myofascial pain. However, the endogenous opioid-mediated analgesic mechanism of distant acupuncture associated with pain control is still unclear. This aims of this study were to evaluate the changes in enkephalin and β-endorphin in serum, spinal cord, dorsal root ganglion (DRG) and muscle induced by acupuncture at distant myofascial trigger spots (MTrSs, similar to human MTrPs) in rabbits, to explore its underlying remote analgesic mechanism.
  
  
  METHODS
  Acupuncture at MTrSs of a distant muscle (gastrocnemius) was performed either for one session or five daily sessions in rabbits. The levels of enkephalin and β-endorphin in proximal muscle (biceps femoris), serum, DRGs and spinal cords (L5-S2) were then determined by immunoassay immediately and 5 days after treatment.
  
  
  RESULTS
  Immediately after treatment, acupuncture comprising both one dose and five doses significantly enhanced spinal enkephalin expression and serum β-endorphin levels (p<0.05). However, only five-dose acupuncture significantly enhanced the β-endorphin levels in the biceps femoris and DRGs (p<0.05), while 1-dose acupuncture did not (p>0.05). Furthermore, 5 days after treatment, significantly increased levels of spinal enkephalin and serum β-endorphin persisted in animals that received 5-dose acupuncture (p<0.05).
  
  
  CONCLUSIONS
  This study demonstrates that interactions within the endogenous opioid system may be involved in the remote effects of acupuncture treatment and could be a potential analgesic mechanism underlying MTrP pain management.
authors.affiliation: Department of Physical Therapy, Graduate Institute of Rehabilitation Science, China Medical University, Taichung, Taiwan.
authors.forename: Yueh-Ling
authors.initials: YL
authors.lastname: Hsieh
authors.affiliation: Taiwan Myopain Society, Taichung, Taiwan.
authors.forename: Chang-Zern
authors.initials: CZ
authors.lastname: Hong
authors.affiliation: Department of Physical Medicine and Rehabilitation, Da-Chien Hospital, Miao-Li, Taiwan.
authors.forename: Szu-Yu
authors.initials: SY
authors.lastname: Liu
authors.affiliation: School of Chinese Medicine, College of Chinese Medicine, China Medical University, Taichung, Taiwan Department of Physical Medicine and Rehabilitation, China Medical University Hospital, Taichung, Taiwan.
authors.forename: Li-Wei
authors.initials: LW
authors.lastname: Chou
authors.affiliation: Department of Physical Medicine and Rehabilitation, Cheng Ching General Hospital, Taichung, Taiwan.
authors.forename: Chen-Chia
authors.initials: CC
authors.lastname: Yang
mesh_terms: D015669:Acupuncture Points; D015670:Acupuncture Therapy; D000818:Animals; D004745:Enkephalins / Q000097:blood / Q000134:cerebrospinal fluid / Q000378:metabolism*; D005157:Facial Pain / Q000628:therapy*; D005727:Ganglia, Spinal / Q000378:metabolism; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism; D059408:Pain Management; D011817:Rabbits; D061028:Trigger Points; D001615:beta-Endorphin / Q000097:blood / Q000134:cerebrospinal fluid / Q000378:metabolism*
chemical_list: D004745:Enkephalins; D001615:beta-Endorphin
keywords: ACUPUNCTURE; MYOFASCIAL PAIN; PAIN RESEARCH