title: A minimal stress model for the assessment of electroacupuncture analgesia in rats under halothane.
abstract: The use of anesthetics in acupuncture analgesia is controversial. We evaluate a steady-state light anesthesia model to test whether minimal stress manipulation and reliable measurement of analgesia could be simultaneously achieved during electroacupuncture (EA) in animals. A series of experiments were performed. Firstly, EA compliance and tail-flick latencies (TFL) were compared in rats under 0.1%, 0.3%, 0.5%, 0.7%, or 1.1% halothane for 120min. Under 0.5% halothane, TFL were then measured in groups receiving EA at intensity of 3, 10 or 20 volt (V), 1 or 2mg/kg morphine, 20V EA plus naloxone, or control. Subsequently, the effect of EA on formalin-induced hyperalgesia was tested and c-fos expression in the spinal dorsal horn was analyzed. Rats exhibited profound irritable behaviors and highly variable TFL under 0.1% or 0.3% halothane, as well as a time-dependent increase of TFL under 0.7% or 1.1% halothane. TFL remained constant at 0.5% halothane, and needle insertion and electrical stimulation were well tolerated. Under 0.5% halothane, EA increased TFL and suppressed formalin-induced hyperalgesia in an intensity-dependent and naloxone-reversible manner. EA of 20V prolonged TFL by 74%, suppressed formalin-induced hyperalgesia by 32.6% and decreased c-fos expression by 29.7% at the superficial and deep dorsal horn with statistically significant difference. In conclusion, 0.5% halothane provides a steady-state anesthetic level which enables the humane application of EA stimulus with the least interference on analgesic assessment. This condition serves as a minimal stress EA model in animals devoid of stress-induced analgesia while maintaining physiological and biochemical response in the experiment.
authors.affiliation: Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei, Taiwan.
authors.forename: Yeong-Ray
authors.initials: YR
authors.lastname: Wen
authors.forename: Geng-Chang
authors.initials: GC
authors.lastname: Yeh
authors.forename: Bai-Chuang
authors.initials: BC
authors.lastname: Shyu
authors.forename: Qing-Dong
authors.initials: QD
authors.lastname: Ling
authors.forename: Kuo-Ching
authors.initials: KC
authors.lastname: Wang
authors.forename: Ta-Liang
authors.initials: TL
authors.lastname: Chen
authors.forename: Wei-Zen
authors.initials: WZ
authors.lastname: Sun
mesh_terms: D015667:Acupuncture Analgesia / Q000379:methods*; D018685:Anesthetics, Inhalation / Q000494:pharmacology; D000818:Animals; D004195:Disease Models, Animal; D015671:Electroacupuncture; D006221:Halothane / Q000494:pharmacology; D006930:Hyperalgesia / Q000628:therapy; D008297:Male; D009474:Neurons / Q000378:metabolism; D010147:Pain Measurement; D017288:Pain Threshold; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011930:Reaction Time / Q000502:physiology; D013312:Stress, Physiological / Q000517:prevention & control*; D013623:Tail
chemical_list: D018685:Anesthetics, Inhalation; D016760:Proto-Oncogene Proteins c-fos; D006221:Halothane