title: 100-Hz Electroacupuncture but not 2-Hz Electroacupuncture is Preemptive Against Postincision Pain in Rats.
abstract: Preemptive analgesia involves introducing an analgesic before noxious stimulation. Electroacupuncture (EA) activates descending mechanisms that modulate nociceptive inputs into the spinal dorsal horn. This study evaluated whether preoperative EA is more effective than postoperative EA in reducing incision pain in rats. The nociceptive threshold to mechanical stimulation was utilized to examine the effects of an intraperitoneal injection of saline (0.1 mL/kg) or naloxone (1 mg/kg) on antinociception induced by a 20-minute period of 2-Hz or 100-Hz EA applied to the Zusanli (ST36) and Sanyinjiao (SP6) acupoints before surgical incision, or 10 minutes after or 100 minutes after surgical incision of the hind paw. The extent of mechanical hyperalgesia after the incision was significantly attenuated by the application of 100-Hz EA preoperatively, but not by its application at 10 minutes or 100 minutes postoperatively. By contrast, 2-Hz EA was effective against postoperative hyperalgesia when applied 10 minutes or 100 minutes after surgery but not when it was applied preoperatively. Only the effect of 2-Hz EA applied 10 minutes after surgery was sensitive to naloxone. The present study showed for the first time that 100-Hz EA, but not 2-Hz EA, exerts a nonopioidergic preemptive effect against postincision pain in rats.
authors.affiliation: Department of Physiotherapy, College of Nursing of the Federal University of Alfenas-UNIFAL, Alfenas, Brazil.
authors.forename: Marcelo Lourenço
authors.initials: ML
authors.lastname: Silva
authors.affiliation: Department of Physiotherapy, College of Nursing of the Federal University of Alfenas-UNIFAL, Alfenas, Brazil.
authors.forename: Josie Resende Torres
authors.initials: JR
authors.lastname: Silva
authors.affiliation: Department of Pharmacology, Ribeirão Preto Medical School-University of São Paulo, Ribeirão Preto, Brazil. Electronic address: wadprado@fmrp.usp.br.
authors.forename: Wiliam Alves
authors.initials: WA
authors.lastname: Prado
mesh_terms: D015669:Acupuncture Points; D000818:Animals; D015671:Electroacupuncture / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D008297:Male; D009270:Naloxone / Q000008:administration & dosage; D009292:Narcotic Antagonists / Q000008:administration & dosage; D010147:Pain Measurement; D010149:Postoperative Pain / Q000188:drug therapy / Q000628:therapy*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D009292:Narcotic Antagonists; D009270:Naloxone
keywords: electroacupuncture; incision pain; naloxone; preemptive analgesia