title: Electroacupuncture analgesia with different frequencies is mediated via different opioid pathways in acute visceral hyperalgesia rats.
abstract: OBJECTIVE
  To investigate the efficacy of electroacupuncture (EA) alleviation of acute visceral hyperalgesia, the frequency dependence of this efficacy, and the difference in endogenous opioid pathways as underlying mechanism explaining the frequency dependence.
  
  
  METHODS
  A visceral hyperalgesia model was established by colorectal instillation of 2% acetic acid (AA) in adult rats. EA treatment at 2Hz, 100Hz, 2/100Hz and sham EA were performed at two bilateral acupoints, ST-36 and ST-37, in the hind-limbs. Naloxone (NLX, 2mg/kg) was administered intraperitoneally 5min before the application of EA. The visceral sensation was quantified by scores of abdominal withdrawal reflex (AWR) and values of rectus abdominis electromyograms (EMGs) in response to colorectal distension (CRD).
  
  
  RESULTS
  Acute visceral hyperalgesia was produced by instillation of AA. The hyperalgesia reached the peak at 2h, and maintained steadily for >6h. EA treatment at 2Hz, 100Hz and 2/100Hz attenuated the acute hyperalgesia, and the attenuation lasted for 2.5h, 2h and 3h, respectively. Sham EA produced no such effect. The analgesic potencies of EA treatment at 2Hz, 100Hz and 2/100Hz were completely blocked, almost not affected, and partially blocked by NLX. In the latter two frequencies, the analgesic durations were shortened to 1.5h and 2h, respectively.
  
  
  CONCLUSIONS
  EA can alleviate acute visceral hyperalgesia. Effective EA analgesia at different frequencies are potentially mediated via different endogenous opioid pathways.
authors.affiliation: Laboratory of Neuronal Network and Systems Biology, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China.
authors.forename: Debo
authors.initials: D
authors.lastname: Qi
authors.affiliation: Laboratory of Neuronal Network and Systems Biology, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China.
authors.forename: Shuqin
authors.initials: S
authors.lastname: Wu
authors.affiliation: Laboratory of Neuronal Network and Systems Biology, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China.
authors.forename: Yuhua
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Laboratory of Neuronal Network and Systems Biology, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China. Electronic address: wmli9110@fudan.edu.cn.
authors.forename: Weimin
authors.initials: W
authors.lastname: Li
mesh_terms: D000701:Analgesics, Opioid / Q000627:therapeutic use*; D000818:Animals; D015671:Electroacupuncture; D006930:Hyperalgesia / Q000188:drug therapy* / Q000378:metabolism; D008297:Male; D009270:Naloxone / Q000627:therapeutic use*; D009292:Narcotic Antagonists / Q000627:therapeutic use*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D000701:Analgesics, Opioid; D009292:Narcotic Antagonists; D009270:Naloxone
keywords: Acute visceral hyperalgesia; Electroacupuncture; Naloxone; Opioid pathways; Rats