title: Comparison of electroacupuncture and morphine-mediated analgesic patterns in a plantar incision-induced pain model.
abstract: Electroacupuncture (EA) is a complementary therapy to improve morphine analgesia for postoperative pain, but underlying mechanism is not well-known. Herein, we investigated EA-induced analgesic effect in a plantar incision (PI) model in male Sprague-Dawley rats. PI was performed at the left hind paw. EA of 4 Hz and high intensity or sham needling was conducted at right ST36 prior to PI and repeated for another 2 days. Behavioral responses to mechanical and thermal stimuli, spinal phospho-ERK, and Fos expression were all analyzed. In additional groups, naloxone and morphine were administered to elucidate involvement of opioid receptors and for comparison with EA. EA pretreatment significantly reduced post-PI tactile allodynia for over 1 day; repeated treatments maintained analgesic effect. Intraperitoneal naloxone could reverse EA analgesia. Low-dose subcutaneous morphine (1 mg/kg) had stronger inhibitory effect on PI-induced allodynia than EA for 1 h. However, analgesic tolerance appeared after repeated morphine injections. Both EA and morphine could equally inhibit PI-induced p-ERK and Fos inductions. We conclude that though EA and morphine attenuate postincision pain through opioid receptor activations, daily EA treatments result in analgesic accumulation whereas daily morphine injections develop analgesic tolerance. Discrepant pathways and mechanisms underlying two analgesic means may account for the results.
authors.affiliation: Graduate Institute of Clinical Medicine, College of Medicine, China Medical University, Taichung, Taiwan.
authors.forename: Yen-Jing
authors.identifier: 0000-0002-6164-5502
authors.initials: YJ
authors.lastname: Zeng
authors.affiliation: Department of Anesthesiology, School of Medicine, China Medical University, Taichung, Taiwan.
authors.forename: Shih-Ying
authors.initials: SY
authors.lastname: Tsai
authors.affiliation: Department of Anesthesiology, School of Medicine, China Medical University, Taichung, Taiwan ; Department of Anesthesiology, China Medical University Hospital, No. 2, Yuh-Der Road, North District, Taichung 40447, Taiwan.
authors.forename: Kuen-Bao
authors.initials: KB
authors.lastname: Chen
authors.affiliation: Graduate Institute of Acupuncture Science, College of Chinese Medicine, China Medical University, Taichung, Taiwan ; Department of Acupuncture, China Medical University Hospital, Taipei Branch, Taipei, Taiwan ; Acupuncture Research Center, China Medical University, Taichung 40447, Taiwan.
authors.forename: Sheng-Feng
authors.initials: SF
authors.lastname: Hsu
authors.affiliation: Department of Pediatrics, School of Medicine, Taipei Medical University, Taipei, Taiwan ; Guang Li Biomedicine, Inc., Xizhi, New Taipei City, Taiwan.
authors.forename: Julia Yi-Ru
authors.initials: JY
authors.lastname: Chen
authors.affiliation: Department of Anesthesiology, School of Medicine, China Medical University, Taichung, Taiwan ; Department of Anesthesiology, China Medical University Hospital, No. 2, Yuh-Der Road, North District, Taichung 40447, Taiwan ; Graduate Institute of Acupuncture Science, College of Chinese Medicine, China Medical University, Taichung, Taiwan ; Pain Management and Research Center, China Medical University Hospital, Taichung 40447, Taiwan ; Department of Anesthesiology, Shin-Kong Memorial Hospital, Taipei, Taiwan ; Research Center for Chinese Medicine and Acupuncture, China Medical University, Taichung 40447, Taiwan.
authors.forename: Yeong-Ray
authors.identifier: 0000-0003-2023-6523
authors.initials: YR
authors.lastname: Wen