Biophysical Basis for Meridian and Acupoint Functions

7/25/2019 Biophysical Basis for Meridian and Acupoint Functions

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Biophysical Basis for Meridian

and Acupoint Functions

Guest Editors: Guanghong Ding, Ying Xia, Wolfgang Schwarz, and Di Zhang

Evidence-Based Complementary and Alternative Medicine


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Biophysical Basis for Meridian and

Acupoint Functions


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Biophysical Basis for Meridian and

Acupoint Functions

Guest Editors: Guanghong Ding, Ying Xia, Wolfgang Schwarz,

and Di Zhang


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Copyright Hindawi Publishing Corporation. All rights reserved.

Tis is a special issue published in Evidence-Based Complementary and Alternative Medicine. All articles are open access articlesdistributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in anymedium, provided the original work is properly cited.


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Editorial Board

M. A. Abdulla, MalaysiaJon Adams, AustraliaZuraini Ahmad, MalaysiaU. P. Albuquerque, BrazilGianni Allais, Italyerje Alraek, NorwaySouliman Amrani, MoroccoAkshay Anand, IndiaShrikant Anant, USAManuel Arroyo-Morales, SpainSyed B. Asdaq, Saudi ArabiaSeddigheh Asgary, IranHyunsu Bae, Republic of KoreaLijun Bai, ChinaSandip K. Bandyopadhyay, IndiaSarang Bani, IndiaVassya Bankova, BulgariaWinfried Banzer, GermanyVernon A. Barnes, USASamra Bashir, Pakistan

Jairo Kenupp Bastos, BrazilSujit Basu, USADavid Baxter, New ZealandAndre-Michael Beer, GermanyAlvin J. Beitz, USAYong Chool Boo, Republic of KoreaFrancesca Borrelli, ItalyGloria Brusotti, ItalyIshfaq A. Bukhari, PakistanArndt Bussing, GermanyRainer W. Bussmann, USARaffaele Capasso, ItalyOpher Caspi, IsraelHan Chae, KoreaShun-Wan Chan, Hong KongIl-Moo Chang, Republic of KoreaRajnish Chaturvedi, IndiaChun ao Che, USAzeng-Ji Chen, aiwanKevin Chen, USAJian-Guo Chen, ChinaHubiao Chen, Hong KongYunfei Chen, ChinaJuei-ang Cheng, aiwanEvan Paul Cherniack, USA

Jen-Hwey Chiu, aiwanW. Chi-shing Cho, Hong KongJae Youl Cho, KoreaSeung-Hun Cho, Republic of KoreaChee Yan Choo, MalaysiaLi-Fang Chou, aiwanRyowon Choue, Republic of KoreaShuang-En Chuang, aiwanJ.-H. Chung, Republic of KoreaEdwin L. Cooper, USAGregory D. Cramer, USAMeng Cui, ChinaRoberto N. Cuman, BrazilVincenzo De Feo, ItalyR. De la Puerta Vazquez, SpainMartin Descarreaux, USAAlexandra Deters, GermanySiva S. Durairajan, Hong KongMohamed Eddouks, MoroccoTomas Efferth, Germany

obias Esch, USASaeed Esmaeili-Mahani, IranNianping Feng, ChinaYibin Feng, Hong KongJosue Fernandez-Carnero, SpainJuliano Ferreira, BrazilFabio Firenzuoli, ItalyPeter Fisher, UKW. F. Fong, Hong KongJoel J. Gagnier, CanadaSiew Hua Gan, MalaysiaJian-Li Gao, ChinaGabino Garrido, ChileM. N. Ghayur, PakistanAnwarul Hassan Gilani, PakistanMichael Goldstein, USAMahabir P. Gupta, PanamaSvein Haavik, NorwayAbid Hamid, IndiaN. Hanazaki, BrazilK. B. Harikumar, IndiaCory S. Harris, CanadaTierry Hennebelle, FranceSeung-Heon Hong, KoreaMarkus Horneber, Germany

Ching-Liang Hsieh, aiwanJing Hu, ChinaSheng-eng Huang, aiwanBenny an Kwong Huat, SingaporeRoman Huber, GermanyAngelo Antonio Izzo, ItalySuresh Jadhav, IndiaKanokwan Jarukamjorn, TailandYong Jiang, ChinaZheng L. Jiang, ChinaStefanie Joos, GermanySirajudeen K. N. S., MalaysiaZ. Kain, USAOsamu Kanauchi, JapanDae Gill Kang, Republic of KoreaWenyi Kang, ChinaShao-Hsuan Kao, aiwanKrishna Kaphle, NepalKenji Kawakita, JapanJong Yeol Kim, Republic of Korea

Youn Chul Kim, Republic of KoreaCheorl-Ho Kim, Republic of KoreaYoshiyuki Kimura, JapanJoshua K. Ko, Chinaoshiaki Kogure, JapanJian Kong, USANandakumar Krishnadas, IndiaYiu Wa Kwan, Hong KongKuang Chi Lai, aiwanChing Lan, aiwanAlfred Langler, GermanyLixing Lao, Hong KongClara Bik-San Lau, Hong KongJang-Hern Lee, Republic of KoreaMyeong Soo Lee, Republic of Koreaat leang Lee, SingaporeChristian Lehmann, CanadaMarco Leonti, ItalyLawrence Leung, CanadaKwok Nam Leung, Hong KongPing-Chung Leung, Hong KongChunGuang Li, AustraliaXiu-Min Li, USAPing Li, ChinaShao Li, China


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Man Li, ChinaMin Li, ChinaYong Hong Liao, ChinaSabina Lim, KoreaBi-Fong Lin, aiwanWen Chuan Lin, ChinaChristopher G. Lis, USAGerhard Litscher, AustriaI-Min Liu, aiwanKe Liu, ChinaYijun Liu, USACun-Zhi Liu, ChinaGaofeng Liu, ChinaGail B. Mahady, USAJuraj Majtan, SlovakiaSubhash C. Mandal, IndiaJeanine L. Marnewick, South AfricaVirginia S. Martino, ArgentinaJames H. McAuley, AustraliaKarin Meissner, GermanyAndreas Michalsen, GermanyDavid Mischoulon, USASyam Mohan, Saudi Arabia

J. Molnar, HungaryValerio Monteiro-Neto, BrazilHyung-In Moon, Republic of KoreaAlbert Moraska, USAMark Moss, UKYoshiharu Motoo, JapanFrauke Musial, GermanyMinKyun Na, Republic of KoreaRichard L. Nahin, USAVitaly Napadow, USAF. R. F. Nascimento, BrazilS. Nayak, rinidad And obagoRoland Ndip Ndip, South AfricaIsabella Neri, Italy. B. Nguelefack, CameroonMartin Offenbaecher, GermanyKi-Wan Oh, Republic of KoreaYoshiji Ohta, JapanOlumayokun A. Olajide, UKTomas Ostermann, GermanyStacey A. Page, Canadaai-Long Pan, aiwanBhushan Patwardhan, India

Berit Smestad Paulsen, NorwayAndrea Pieroni, ItalyRichard Pietras, USAWaris Qidwai, PakistanXianqin Qu, AustraliaCassandra L. Quave, USARoja Rahimi, IranKhalid Rahman, UKCheppail Ramachandran, USAGamal Ramadan, EgyptKe Ren, USAMan Hee Rhee, Republic of KoreaMee-Ra Rhyu, Republic of KoreaJose Luis Ros, SpainPaolo Roberti di Sarsina, ItalyBashar Saad, Palestinian AuthoritySumaira Sahreen, PakistanOmar Said, IsraelLuis A. Salazar-Olivo, MexicoMohd. Zaki Salleh, MalaysiaAndreas Sandner-Kiesling, AustriaAdair Santos, BrazilG. Schmeda-Hirschmann, Chile

Andrew Scholey, AustraliaVeronique Seidel, UKSenthamil R. Selvan, USAuhinadri Sen, IndiaHongcai Shang, ChinaRonald Sherman, USAKaren J. Sherman, USAKuniyoshi Shimizu, JapanKan Shimpo, JapanByung-Cheul Shin, KoreaYukihiro Shoyama, JapanChang-Gue Son, KoreaRachid Soulimani, FranceDidier Stien, FranceShan-Yu Su, aiwanMohd Roslan Sulaiman, MalaysiaVenil N. Sumantran, IndiaJohn R. S. abuti, Ugandaoku akahashi, USARabih alhouk, LebanonWen-Fu ang, ChinaYuping ang, ChinaLay Kek eh, Malaysia

Mayank Takur, GermanyMenaka C. Tounaojam, IndiaMei ian, ChinaEvelin iralongo, AustraliaStephanie jen-A-Looi, USAMichaTl omczyk, PolandYao ong, Hong KongKarl Wah-Keung sim, Hong KongVolkan ugcu, urkeyYew-Min zeng, aiwanDawn M. Upchurch, USAMaryna Van de Venter, South AfricaSandy van Vuuren, South AfricaAlfredo Vannacci, ItalyMani Vasudevan, MalaysiaCarlo Ventura, ItalyWagner Vilegas, BrazilPradeep Visen, CanadaAristo Vojdani, USAShu-Ming Wang, USAChong-Zhi Wang, USAChenchen Wang, USAY. Wang, USA

Kenji Watanabe, JapanJintanaporn Wattanathorn, TailandJenny M. Wilkinson, AustraliaDarren R. Williams, Republic of KoreaHaruki Yamada, JapanNobuo Yamaguchi, JapanJunqing Yang, ChinaYong-Qing Yang, ChinaEun Jin Yang, Republic of KoreaLing Yang, ChinaXiufen Yang, ChinaKen Yasukawa, JapanMin Ye, ChinaM. Yoon, Republic of KoreaJie Yu, ChinaZunjian Zhang, ChinaHong Q. Zhang, Hong KongWei-Bo Zhang, ChinaJin-Lan Zhang, ChinaBoli Zhang, ChinaRuixin Zhang, USAHong Zhang, ChinaHaibo Zhu, China


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Contents

Effect of Electroacupuncture on Rat Ischemic Brain Injury: Importance of Stimulation Duration,Fei Zhou, Jingchun Guo, Jieshi Cheng, Gencheng Wu, and Ying XiaVolume , Article ID , pages

Understanding Central Mechanisms of Acupuncture Analgesia Using Dynamic Quantitative Sensory

esting: A Review, Jiang-i Kong, Rosa N. Schnyer, Kevin A. Johnson, and Sean MackeyVolume , Article ID , pages

Electroacupuncture and Brain Protection against Cerebral Ischemia: Specic Effects of Acupoints ,Fei Zhou, Jingchun Guo, Jieshi Cheng, Gencheng Wu, Jian Sun, and Ying XiaVolume , Article ID , pages

From Acupuncture to Interaction between -Opioid Receptors and Na+ Channels: A Potential Pathway

to Inhibit Epileptic Hyperexcitability, Dongman Chao, Xueyong Shen, and Ying XiaVolume , Article ID , pages

Electroacupuncture-Induced Attenuation of Experimental Epilepsy: A Comparative Evaluation of

Acupoints and Stimulation Parameters, Xuezhi Kang, Xueyong Shen, and Ying XiaVolume , Article ID , pages

Effects of Electroacupuncture at Auricular Concha Region on the Depressive Status of Unpredictable

Chronic Mild Stress Rat Models, Ru-Peng Liu, Ji-Liang Fang, Pei-Jing Rong, Yufeng Zhao, Hong Meng,Hui Ben, Liang Li, Zhan-Xia Huang, Xia Li, Ying-Ge Ma, and Bing ZhuVolume , Article ID , pages

An Acupuncture Research Protocol Developed from Historical Writings by Mathematical Reections: A

Rational Individualized Acupoint Selection Method for Immediate Pain Relief, Sven Schroeder,Gesa Meyer-Hamme, Jianwei Zhang, Susanne Epplee, Tomas Friedemann, and Weiguo HuVolume , Article ID , pages

Te Neural Pathway of Reex Regulation of Electroacupuncture at Orofacial Acupoints on Gastric

Functions in Rats, Jianhua Liu, Wenbin Fu, Wei Yi, Zhenhua Xu, and Nenggui XuVolume , Article ID , pages

Biophysical Characteristics of Meridians and Acupoints: A Systematic Review, Juan Li, Qing Wang,Huiling Liang, Haoxu Dong, Yan Li, Ernest Hung Yu Ng, and Xiaoke WuVolume , Article ID , pages

ranscutaneous Auricular Vagus Nerve Stimulation Protects Endotoxemic Rat from

Lipopolysaccharide-Induced Inammation, Yu Xue Zhao, Wei He, Xiang Hong Jing, Jun Ling Liu, Pei JingRong, Hui Ben, Kun Liu, and Bing ZhuVolume , Article ID , pages

Inhibition of Activity of GABA ransporter GA by-Opioid Receptor, Lu Pu, Nanjie Xu, Peng Xia,Quanbao Gu, Shuanglai Ren, Tomas Fucke, Gang Pei, and Wolfgang SchwarzVolume , Article ID , pages

Electrical Potential of Acupuncture Points: Use of a Noncontact Scanning Kelvin Probe , Brian J. Gow,Justine L. Cheng, Iain D. Baikie, rjan G. Martinsen, Min Zhao, Stephanie Smith, and Andrew C. AhnVolume , Article ID , pages


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Interstitial Fluid Flow: Te Mechanical Environment of Cells and Foundation of Meridians , Wei Yao,Yabei Li, and Guanghong DingVolume , Article ID , pages

Research on Nonlinear Feature of Electrical Resistance of Acupuncture Points , Jianzi Wei, Huijuan Mao,Yu Zhou, Lina Wang, Sheng Liu, and Xueyong ShenVolume , Article ID , pages

Stimulation of RPV by Green Laser Light, Quanbao Gu, Lina Wang, Fang Huang,and Wolfgang SchwarzVolume , Article ID , pages

Terapeutic Effects of Acupuncture through Enhancement of Functional Angiogenesis and

Granulogenesis in Rat Wound Healing, Sang In Park, Yun-Young Sunwoo, Yu Jin Jung, Woo Chul Chang,Moon-Seo Park, Young-An Chung, Lee-So Maeng, Young-Min Han, Hak Soo Shin, Jisoo Lee,and Sang-Hoon LeeVolume , Article ID , pages

Auricular Acupuncture and Vagal Regulation, Wei He, Xiaoyu Wang, Hong Shi, Hongyan Shang, Liang Li,Xianghong Jing, and Bing ZhuVolume , Article ID , pages

Hemodynamic Changes in the Brachial Artery Induced by Acupuncture Stimulation on the LowerLimbs: A Single-Blind Randomized Controlled rial, Masashi Watanabe, Shin akayama, Atsushi Hirano,

akashi Seki, and Nobuo YaegashiVolume , Article ID , pages

Investigation of Acupuncture Sensation Patterns under Sensory Deprivation Using a Geographic

Information System, Florian Beissner and Irene MarzolffVolume , Article ID , pages

Effects of Moxibustion Stimulation on the Intensity of Infrared Radiation of ianshu (S) Acupoints

in Rats with Ulcerative Colitis, Xiaomei Wang, Shuang Zhou, Wei Yao, Hua Wan, Huangan Wu, Luyi Wu,Huirong Liu, Xuegui Hua, and Peifeng ShiVolume , Article ID , pages

Observation of Pain-Sensitive Points along the Meridians in Patients with Gastric Ulcer or Gastritis ,

Hui Ben, Liang Li, Pei-Jing Rong, Zhi-Gao Jin, Jian-Liang Zhang, Yan-Hua Li, and Xia LiVolume , Article ID , pages

In Adjuvant-Induced Arthritic Rats, Acupuncture Analgesic Effects Are Histamine Dependent:

Potential Reasons for Acupoint Preference in Clinical Practice, Meng Huang, Di Zhang, Zhe-yan Sa,Ying-yuan Xie, Chen-li Gu, and Guang-hong DingVolume , Article ID , pages

A Review of Acupoint Specicity Research in China: Status Quo and Prospects, Ling Zhao, Ji Chen,Cun-Zhi Liu, Ying Li, Ding-Jun Cai, Yong ang, Jie Yang, and Fan-Rong LiangVolume , Article ID , pages


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Effects of Electroacupuncture of Different Frequencies on the Release Prole of Endogenous Opioid

Peptides in the Central Nerve System of Goats, Li-Li Cheng, Ming-Xing Ding, Cheng Xiong,Min-Yan Zhou, Zheng-Ying Qiu, and Qiong WangVolume , Article ID , pages

Patch Clamp: A Powerful echnique for Studying the Mechanism of Acupuncture, D. ZhangVolume , Article ID , pages

Systems Biology of Meridians, Acupoints, and Chinese Herbs in Disease , Li-Ling Lin, Ya-Hui Wang,Chi-Yu Lai, Chan-Lao Chau, Guan-Chin Su, Chun-Yi Yang, Shu-Ying Lou, Szu-Kai Chen, Kuan-Hao Hsu,Yen-Ling Lai, Wei-Ming Wu, Jian-Long Huang, Chih-Hsin Liao, and Hsueh-Fen Juan

Volume , Article ID , pages

NMDA Receptor-Dependent Synaptic Activity in Dorsal Motor Nucleus of Vagus Mediates the

Enhancement of Gastric Motility by Stimulating S, Xinyan Gao, Yongfa Qiao, Baohui Jia,Xianghong Jing, Bin Cheng, Lei Wen, Qiwen an, Yi Zhou, Bing Zhu, and Haifa QiaoVolume , Article ID , pages

Evaluation of the Effect of Laser Acupuncture and Cupping with Ryodoraku and Visual Analog Scale on

Low Back Pain, Mu-Lien Lin, Hung-Chien Wu, Ya-Hui Hsieh, Chuan-sung Su, Yong-Sheng Shih,Chii-Wann Lin, and Jih-Huah WuVolume , Article ID , pages

Acupuncture Alleviates Colorectal Hypersensitivity and Correlates with the Regulatory Mechanism of

rpV and p-ERK, Shao-Jun Wang, Hao-Yan Yang, and Guo-Shuang XuVolume , Article ID , pages

Are Primo Vessels (PVs) on the Surface of Gastrointestine Involved in Regulation of Gastric Motility

Induced by Stimulating Acupoints S or CV?, Xiaoyu Wang, Hong Shi, Hongyan Shang,Yangshuai Su, Juanjuan Xin, Wei He, Xianghong Jing, and Bing ZhuVolume , Article ID , pages

Measurements of Location-Dependent Nitric Oxide Levels on Skin Surface in relation to AcupuncturePoint, Yejin Ha, Misun Kim, Jiseon Nah, Minah Suh, and Youngmi LeeVolume , Article ID , pages

Evaluate Laser Needle Effect on Blood Perfusion Signals of Contralateral Hegu Acupoint with Wavelet

Analysis, Guangjun Wang, Yuying ian, Shuyong Jia, Gerhard Litscher, and Weibo ZhangVolume , Article ID , pages


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Hindawi Publishing CorporationEvidence-Based Complementary and Alternative MedicineVolume , Article ID ,pageshttp://dx.doi.org/.//

Research ArticleEffect of Electroacupuncture on Rat Ischemic Brain Injury:Importance of Stimulation Duration

Fei Zhou,1,2 Jingchun Guo,3 Jieshi Cheng,3 Gencheng Wu,3 and Ying Xia4,5

Shanghai Research Center or Acupuncture and Meridians, Shanghai , China Gongli Hospital, Pudong New District, Shanghai , China Shanghai Medical College o Fudan University, Shanghai , China Te University o exas Medical School at Houston, Houston, X , USA Yale University School o Medicine, New Haven, C , USA

Correspondence should be addressed to Ying Xia; [email protected]

Received August ; Revised November ; Accepted December

Academic Editor: Di Zhang

Copyright Fei Zhou et al. Tis is an open access article distributed under the Creative Commons Attribution License, whichpermits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

We explored the optimal duration o electroacupuncture (EA) stimulation or protecting the brain against ischemic injury. Teexperiments were carried out in rats exposed to right middle cerebral artery occlusion (MCAO) or min ollowed by -hrreperusion. EA was delivered to Shuigou (Du ) and Baihui (Du ) acupoints with sparse-dense wave (/ Hz) at . mA

or , , , and min, respectively. Te results showed that min EA, starting at minutes afer the onset o MCAO(EA duringMCAO) or minutes afer reperusion (EA afer MCAO), signicantly reduced ischemic inarct volume, attenuated neurologicaldecits, and decreased death rate with a larger reduction o the ischemic inarction in the ormer group. Also in the group o EAduring MCAO, this protective benet was positively proportional to the increase in the period o stimulation, that is, increasedprotection in response to EA rom - to -min stimulation. In all groups, EA induced a signicant increase in cerebral bloodow and promoted blood ow recovery afer reperusion, and both blood ow volume and blood cell velocity returned to thepreischemia level in a short period o time. Surprisingly, EA or min did not show reduction in the neurological decits orthe inarct volume and instead demonstrated an increase in death rate in this group. Although EA or min still increased theblood ow during MCAO, it led to a worsening o perusion afer reperusion compared to the group subjected only to ischemia.Te neuroprotection induced by an optimal period ( min) o EA was completely blocked by Naltrindole, a-opioid receptor(DOR) antagonist ( mg/kg, i.v.). Tese ndings suggest that earlier EA stimulation leads to better outcomes, andthat EA-inducedneuroprotection against ischemia depends on an optimal EA-duration via multiple pathways includingDOR signaling, while over-length stimulation exacerbates the ischemic injury.

1. Introduction

Ischemic/hypoxic brain injury, such as stroke, leads to seriousand complex pathophysiological changes affecting multiplelevels o the brain, and sports a high global mortality rateas the leading cause o neurological disability []. Inspite o extensive research conducted in the past severaldecades, limited therapeutic options are available againstischemic/hypoxic brain injury till date. Te vast physical,emotional,and nancial tollsthat stroke inicts upon patientsand their amilies imposes a daunting and continuous chal-lenge to the medical community []. Previous studies at

our laboratory and at those o others have shown that elec-troacupuncture (EA), at appropriate acupoints with suitablestimulation parameters, signicantly attenuates neurologicaldecits, inarct volume and mortality in animal modelsexposed to ischemic insults [], which may potentiallyshed a new light on developing a better modality or ischemicbrain injury. Indeed, there is substantial clinical evidencedemonstrating benecial effects o acupuncture on strokepatients [].

Because o inadequate control, poor methodologicalquality and small samples seen in previous studies, theefficacy o acupuncture on hypoxic/ischemic injury is still


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unproven in clinical settings. In act, major controversies existwith regards to the effectiveness o acupuncture in strokepatients []. Tese may, at least partially, be attributedto the varied approaches adopted in different studies, andsince acupuncture induces complex changes at multiple levelsin the central nervous system, the outcomes also differ

with varying acupunctural methods []. Tereore, itis extremely important to dene what optimal parametersare required or acupuncture treatment in ischemic/hypoxicbrain injury.

owards this goal, our serial studies have establishedthat EA treatment or acute stroke in experimental animalsis critically dependent upon specic acupoints along withstimulation currents o specic intensities and requencies[, ]. Since the timing and duration o medical treat-ment has a huge impact on patients with acute stroke [],we conducted this work to address two undamental issues,that is, () when should EA be applied to induce optimalprotection, during or afer ischemia?, and () what durationo EA application is optimal to induce maximal benecialeffect on the ischemic brain?

2. Materials and Methods

.. Animals. Adult male Sprague-Dawley rats (g)were used or the experiments. All animals were purchasedwith permission rom the Experimental Animal Center orthe Shanghai Chinese Academy o Science. Te animals werehoused at an ambient temperature o 24 1C and wereprovided with ree access to ood and water. All surgicalprocedures were approved by the Animals Care and UseCommittees o Fudan University Shanghai Medical College,

Shanghai, China, and were perormed under anesthesia(chlorate hydrate, mg/kg, i.p.).

.. Cerebral Blood Flow Monitoring. Te cerebral bloodow was measured using laser-Doppler perusion monitor(LDPM, PeriFlux, Perimed, Sweden). Te major stepso the procedure were as ollows: rst, a small hole wasdrilled in the right parietal bone at a point . mm posteriorto the bregma and mm lateral to the sagittal suture, aspreviously described [, , ]. Te supercial micro-vesselso cerebral pia mater were accessed using a laser Dopplerprobe (. mm diameter) inserted into the hole at a deptho mm and xed to the skull bone. Te probe was used

to measure the blood perusion to the cortex to recordthe cerebral blood ow. Continuous monitoring o cerebralblood ow was perormed beginning minutes prior tothe induction o cerebral ischemia until at least minutesafer reperusion. As per the manuacturers guidelines, themeasured change in perusion values was dependent onthe number o blood cells present and their velocity in thearea illuminated by the tip o the probe. Te changes inthe cerebral blood ow o a localized area, recorded as ameasure o the dynamic changes in Perusion Units (PU),concentration o the moving blood cells (CMBC), and the

velocity o blood cells (Velocity), were constantly monitoredin real-time using LDPM. PU is an index o cerebral blood

ow and is expressed as the product o the number o movingblood cells and their relative velocities.

.. Method or Inducing Cerebral Ischemia. We ollowed themethods described by Longa et al. [] that are also detailedin our previous publications [, ] or creating a ocal

cerebral ischemia model by middle cerebral artery occlusion(MCAO). Animals were taken under anesthesia to surgicallyexpose their right common carotid, external carotid andinternal carotid arteries. Afer ligation o the distal endo the right external carotid artery, it was incised and a monolament nylon suture ( mm length, . mmdiameter with a . mm diameter round tip, MONOSOF,SN-G, USA) was introduced to the right external carotidartery and urther into the right internal carotid artery or mm up till the origin o the right middle cerebral artery.Te blood ow to the right middle cerebral artery was thenoccluded at this level.

We constantly monitored the blood ow in all animals to

ensure that a uniorm cerebral ischemia level was maintainedacross all groups in a standard ashion. Te blood owwas controlled by adjusting the suture in the artery or theinduction o ischemia. Te ischemic rats that showed a stabledrop o% in PU compared to the baseline level (beoreMCAO), that is, reaching a level o% o the baseline PU,were used or urther experimentation. Te PU was kept at alow level with minor uctuations during the entire ischemicperiod without any signicant change except during EAapplication. Afer the occlusion, reperusion o the ischemicarea was allowed by withdrawing the suture rom the rightexternal carotid artery. Cortical blood ow changes weremonitored in all animals beginning minutes prior to the

induction o cerebral ischemia until at least minutes aferreperusion. Tis duration was inclusive o the entire lengtho MCAO and o EA as well.

Body temperature was maintained at .C .Cthroughout the surgical procedures till the animal recoveredrom anesthesia. Afer the reperusion, the animals werehoused or hours at an ambient temperature o C.Te same surgical procedures were perormed on the animalsin the sham-operation group, excluding MCAO.

.. Electroacupuncture Methods. WHO standards were ol-lowed or the name and localization o acupoints [, ].Shuigou (Du ) and Baihui (Du ) are acupoints

located on the head and ace. Shuigou (Du ) is located at apoint on the midline o the upper lip /rds rom the mouthto the nose. Baihui (Du ) is located ata pointon themidlineo the head, approximately midway on the line connecting theapices o both auricles.

o obtain optimal EA effect that induces maximum pro-tection against cerebral ischemia, we applied EA at Shuigou(Du ) and Baihui (Du ) with / Hz sparse-denserequency at a constant intensity o .mA in all EAgroups, beginning at min afer the onset o MCAO or minafer MCAO. Te selection o the acupoints and stimulationparameters was based on the results o our serial studies inthe past [,].


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In determination o effects o different EA periods oncerebral ischemia, EA was applied using varying lasting-durations,that is, beginning at min afer the onset o MCAOand continued up to minutes, minutes, minutes, and minutes, respectively. Five different groups were studiedin the present study with the numbers in each group ranging

rom to : MCAO only (Ischemia, = 45), MCAO plusEA or min (EA- min, = 18), MCAO plus EA or min(EA- min, = 16), MCAO plus EA or min (EA- min, = 30), and MCAO plus EA or min (EA- min, = 30).

EA was delivered through stainless steel liorm needles( mm in length and . mm in diameter, Suzhou MedicalApparatus Limit Co., China) by an EA apparatus (ModelG--II, Shanghai Medical Instruments High-ech Co.,China). Te needle on Du is inserted mm deep, verticalto the plane o the skin. At Du , the needle is insertedobliquely and to a depth o mm [, , , , ]. Teintensity and requency o the output waves with a negative-going pulse on the posterior border (pulse width =.ms. ms; component o direct current=Zero) were monitoredon a general oscillograph (Model XJA, Shanghai XinJianInstrument and Equipment Co., China).

.. -Opioid Receptors Blockade. Te rats were randomlyassigned to one o the our experimental groups: () Ischemiaalone ( = 7); () Ischemia + EA at Shuigou (DU ) andBaihui (DU ) ( = 8); () Ischemia + Naltrindole ( = 8),in which rats were administered Naltrindole ( mg/kg i.v.) min beore the onset o MCAO; and () Ischemia + EA +Naltrindole ( = 1 0), in which the animals were treatedwith both EA and Naltrindole. EA was started min aferischemia and continued to min afer ischemia in this seto experiments.

.. Mortality and Neurological Decits Monitoring. Someischemic rats died between and hrs afer reperusion.Te death rates were reported or this period based on thenumber o dead rats and thetotal number o the rats allocatedto the given group. A myriad o actors could be implicatedas the cause o death, as or example hemorrhage. However,investigating the precise cause o death was not our aim inthis work.

Assessments on neurological decits were made on ani-mals in all groups. Te rats that died within h afer

MCAO were excluded. Assessments were made h aferreperusion just beore the sampling o brain tissue was done.Te assessments on neurological decits were blinded, thatis, the person evaluating and scoring the neurological decitsbased on pre-set criteria had no prior knowledge on thegroups and treatments. Te degree o neurological decitswas graded rom grades [,]. Te criteria were set asollows: Grade normal, symmetrical movement withoutany abnormal sign; Grade incomplete stretch o the lefanterior limb when the tail was lifed up; Grade dodderycrawl along with the signs o Grade ; Grade kept the lefanterior limb close to the breast when the tail was lifed up;Gradelef turn when crawling; Grade lef anteriorclaw

pushed backward along with the signs o Grade ; Grade repeated rotational motion with an immotile posterior leflimb; and Grade lef recumbent position because o bodysupporting incapability.

.. Cerebral Inarct Measurement. Afer the assessment o

neurological decits, animals were sacriced under anesthe-sia and samples o brain were taken. Te brain slices wereprepared as . mm sections ( = ) and were incu-bated in a solution o triphenyltetrazolium chloride (C, g/L) or minutes at C beore being transerred intoparaormaldehyde solution ( g/L) or xing the inarctedarea. Te inarct region appeared white or pale while thenormal tissue appeared red [, ]. Pictures were takeno the brain slices with a digital camera and the volume oinarct was analyzed using a computer-assisted image systemwith AC-U sofware (Nikon). Relative inarct ratio wascalculated using the ollowing equation [, , ]: ( lef hemisphere area (non-ischemic side) non-inarct area

o whole brain slices)/( lef hemisphere areas) %.Tis equation excludes the actors that could result in aninaccurate calculation o the inarct volume (such as edema).

.. Data Analysis. Te cerebral blood ow was calculatedrom PU, CMBC, and velocity measurements. All individualmeasurements were compared to the baseline values, beoreMCAO (control level), in each animal. Te grouped valueswere compared between different groups. An average gradeo neurological decits per group was used to make compar-isons between groups. Cerebral inarct volume was expressedas a percent raction o the entire cerebral volume.

All data is presented as mean SD and subjected to

statistical analysis. Te rate o death was compared using theChi-square test. All other data was subjected to Analysis o

variance (ANOVA), t-test, Rank-Sum test, and/or Chi-squaretest. Te changes were considered to be signicant i the

value was less than ..

3. Results

.. Different Effects Induced by EA Starting afer the Onseto MCAO versus Post-MCAO. In the group o Ischemia( = 4 5), with hr MCAO and hr reperusion, about% (/) o the rats died within hours afer the onseto reperusion. At hours o reperusion, the living rats

displayed serious neurological decits (Grade 6.0 0.5, =37). C staining showed that the volume o cerebral inarctwas about one third o the whole brain (32.8% 3.7%, = 16)(able, Figure(a)). Te inarct areas were mainly localizedin the rontoparietal lobes o the cortex and striatum in theright hemisphere (ischemic side, Figure(a)).

EA starting at min afer the onset o MCAO induceda marked protection against cerebral ischemia, leading to asignicant reduction o inarct volume, neurological decits,and death rate (able , Figures (b)(d)). EA starting at min afer MCAOinduced a similar outcome in the ischemicrats (reer to Figure). However, it seemed that EA induceda larger reduction o the inarct volume in the ormer than


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: EA period-dependent protection against ischemic injury.

Groups Neurological decit Inarct volume Death rate

Ischemia .. ( ) ( = 37) 32.8% 3.7% ( = 16) % ( out o )

EA- min .. ( ) ( = 16) 25.6% 5.3% ( = 12) % ( out o )

EA- min .. ( ) ( = 15) 15.4% 4.2% ( = 12) % ( out o )

EA- min .. ( ) ( = 28)

4.9% 1.2% ( = 12)

% ( out o )

EA- min .. () ( = 12) 34.3% 2.4% ( = 12) % ( out o )

< 0.05versus Ischemia. < 0.01versus Ischemia. < 0.01versus EA- min. Note that EA signicantly reduced the inarct volume, neurological

decit, and death rate and this protective effect became better and better when the length o EA increased rom to minutes. However, EA or mins didnot improve the neurological decit and inarct volume and even increased the death rate.

(a) Ischemia (MCAO- min)

(b) Ischemia + EA-min (c) Ischemia + EA- min (d) Ischemia + EA- min (e) Ischemia + EA-min

F : EA-induced changes in cerebral inarct size in a time-dependent manner. Te brain slices were subjected to C staining andthe ischemic inarct volume was quantied by a computerized image system. Te slices on therighto each column show the backside othelefslices. Note that the inarct region (pale-white portion) was mainly located in the striatum and the rontoparietal cortex in the righthemisphere. Te MCAO-induced inarction (a) was signicantly reduced by EA at Du and Du acupoints or min (b), min (c), and

min (d). In contrast, EA or min (e) enabled no protection against the cerebral inarction.

the later group. EA afer the onset o MCAO reduced theinarct volume by% (able and Figure ), while EA aferMCAO, by% (reer to Figure ). Tese results suggest thatearly institution o EA stimulation induces better protectionagainst cerebral ischemic injury.

.. Increased EA Protection with Increased Periods o theStimulation rom to mins. In the group o MCAO plusEA or min (EA- min, = 18), except or rats that diedat and hours afer the onset o reperusion (%, /,

< 0.01versus Ischemia), the degree o average neurologicaldecits in the living ischemic rats was slightly improved(Grade5.0 0.5, = 16, < 0.05 versus Ischemia). Teinarct volume was slightly reduced (25.6%+ 5.3%, = 12, < 0.05versus Ischemia) (able and Figure(b)). In thegroup o MCAOplusEA or min (EA- min, = 16), onlyone rat died at hours afer the onset o reperusion (%,/, < 0.01versus Ischemia), with a greater improvementin average neurological decits (Grade 3.0 0.5, = 15, < 0.01versus Ischemia) along with a signicant reductionin inarct volume (15.4% 4.2%, = 12, < 0.01 versusIschemia) (able and Figure(c)). In the group o MCAOplus EA or min (EA- min, = 30), the neurological

decits were greatly attenuated (Grade 1.0 0.5, = 28, < 0.01versus Ischemia) and a signicant decrease in deathrate (%, /, < 0.01 versus Ischemia) was noted. Teinarct volume was reduced by % (4.9% 1.2%, = 12, < 0.01 versus Ischemia) (able and Figure (d)). Incomparison to the groups o EA or min and EA or min,EA or min induced more benecial effects in all aspectsincluding neurological decits, ischemic inarct and deathrate (able , Figures (b)(d)). Tese results suggest that theEA protection is dependent on an appropriate EA duration.

.. Exacerbation o Ischemic Injury by Over-Length Stimula-tion o EA. We investigated to see i the EA protection wouldbe urther enhanced by a longer duration o EA stimulation.Tereore, we assigned a ew rats to a new group with MCAOplus EA or minutes (EA- min, = 30). o our surprise,EA or min signicantly increased the mortality in thisgroup o ischemic rats. More than hal o the animals in thisgroup (%, /) died within . to hours afer the onseto reperusion. All o the dying rats maniested symptomssuch as convulsions, tumbling, piloerection, and perspiration(wet eathers) and other abnormalities. When compared theIschemia group, the death rate increased by olds (%,


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out o , < 0.01versus Ischemia) in this group. Althoughthe remaining living rats survived or hours afer thereperusion, they suffered rom severe neurological decits(Grade ) and were even worse than the group with onlyIschemia (Grade6.0 + 0.5with range o , < 0.05). Interms o the inarct volume, EA or min did not reduce the

inarct volume at all (34.3% 2.4%, = 12, > 0.05versusIschemia). (able, Figure(e)). Tese results suggest thatan increased duration o EA stimulation application urtherexacerbates the ischemic insult, instead o conerring anyprotection.

.. EA-Induced Increase in Cerebral Blood Flow duringMCAO. Using a Laser-Doppler Perusion Monitor, we con-tinuously monitored the real time changes in cerebral bloodow in all the groups beginning at min prior to MCAOtill min afer the onset o reperusion (suture withdrawal),and compared differences in the cerebral blood ow at thepre-MCAO level, during MCAO with/without EA, and early

stages o reperusion between various groups (Figures,,,and).

Consistent with our previous studies [, ], afer theinsertion o a nylon suture into the right middle cerebralartery, the blood perusion (PU) to the monitored corteximmediately decreased by% (i.e., reaching the level at% o the pre-MCAO level). During the entire period oMCAO, the local blood ow was maintained at this low levelwith a minor uctuation. CMBC dropped by% o thebase-value (i.e., reaching a level at % o the pre-MCAOlevel) with a slight deceleration o blood cell velocity (reducedby% o the pre-MCAO level). Tese changes indicatedthat MCAO induced a greater reduction in the blood volume

as compared to the velocity o blood cells (Figures (a)and).

In all the EA groups, EA induced an instant and signi-icant increase in the blood ow o the ischemic brain. Teblood ow changed isochronously with the current impulsein response to EA stimulation (Figures(b)(e)and ).EA induced an increase in PU to % o the control ( 0.05

versus Ischemia + EA) (Figure ). Tese results indicatethat -opioid receptor plays a very important role in the

EA-induced protection against ischemic injury.

4. Discussion

Tisis therst studyto systematically dene optimal durationo EA stimulation to inducebenecial effectsagainst ischemicinarction, neurological decits and mortality. Our resultsshow that EA given or minutes signicantly reducesischemic inarct volume and decreases neurological decitsand mortality rate. On the other hand, EA given or mindid not show reduction in the neurological decits or theinarct volume, and rather demonstrated an increase in deathrate in this group. However, all groups showed an increase


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F : Representative trace recordings o the blood ow in the rats with or without EA. Blood Perusion (PU), Concentration o MovingBlood Cells (CMBC),and Velocity o Blood Cells (Velocity) were measured in the ischemic rats by a Laser DopplerPerusion Monitor system.(a) Effect o MCAO- min on CBF during ischemia and afer reperusion in Ischemia group. (b) Effect o EA or min at acupoints o DuandDu on CBF. (c) Effect o EAor min on CBF. (d) Effect o EAor min onCBF. (e) Effect o EAor min on CBF. Notethat thePU and CMBC decreased immediately afer MCAO and the blood ow was maintained at a low level with small uctuations duringthe entireperiod o MCAO with a slight decrease in the velocity. Afer the onset o reperusion, PU and CMBC increased with a urther decrease in thevelocity. EA induced an isochronous increase in PU and CMBC with a decrease in velocity during MCAO. Afer reperusion, PU, CMBC,and velocity all increased rapidly and reached the baseline values within min afer reperusion onset in groups o EA or min. EA or min, however, induced a greater decrease in PU, CMBC, and velocity than the changes observed in the Ischemia group afer reperusion.


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< 0.01, Ischemia+EA versus Ischemiagroup during MCAO; % afer reperusion in all EA groupsincluding EA- min.

EA treatment although the underlying mechanism remainsunknown.

Te act that over-length o EA stimulation increasesthe blood ow under MCAO, but does not lead to anyprotection against ischemic injury strongly suggests thatoptimal EA stimulation induces a multi-level regulation inthe brain via a complex mechanism. A single actor, suchas, an increase in the blood ow under ischemic conditions,may not be enough to induce protection against ischemia.Appropriate stimulation is extremely important or maximal

mobilization o various survival signals and activation oprotective pathways in the ischemic brain.

One o these pathways could involve DOR-mediatedsurvival signaling. We have previously demonstrated thatDOR is important in inducing neuroprotection [,]. DORactivation attenuates hypoxic, ischemic, or excitatory injuryin the neurons and the brain [, , ]. Evidence showsthat both manual acupuncture and EA enhance the activityo the endogenous opioid system, including DOR, in thebrain [,]. Tereore, the DOR-mediated protection


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F : Effect o Naltrindole on EA-induced protection againstischemic inarct size. Quantitative volumes o the ischemic inarctwere determinedbasedon thepercentage othe whole brain volume.Note that the ischemia-induced inarct was reduced by the EAstimulation (

< 0.05versus ischemia group), which was almostcompletely reversed afer treatment with Naltrindole (N, mg/kg,i.v.) (

< 0.05versus Ischemia+EA+Naltrindole).

might play a very important role in the EA-induced pro-tection against ischemic injury. Indeed, we rst reportedthat microinjection o a DOR antagonist, Naltrindole, intothe cerebral ventricle attenuated the EA-induced cerebralprotection against ischemic inarction, suggesting DORsinvolvement in the EA-induced protection against brainischemia []. Furthermore, our studies and those o otherssuggest that EA signicantly increases the density o DOR inthe ischemic cortex and that DOR signaling could mediatethe EA induced neuroprotection against ischemic injury [,, ]. In the present study, we observed that intravenousinjection o Naltrindole almost completely blocked the EA-induced neuroprotection against ischemic injury. All o these

observations consistently avor the critical role o DOR inEA-induced neuroprotection against cerebral ischemia. Onthe other hand, EA can activate additional neurotransmittersystems such as neurotrophic actors in the brain that enableurther protection under ischemic conditions [].

Tus, EA targets multiple mechanisms to achieve a pro-tective effect against ischemic insults, including an increasein the cerebral blood ow under ischemia, an improvedrecovery o the blood ow afer reperusion, upregulation othe DOR pathway, and other survival signals. An optimalduration o EA stimulation can combine and direct all othese protective pathways against ischemic stress, while anover-stimulation o EA, despite increasing the blood ow

during MCAO, can set this balance o combined protectionoff.

Moreover, our present results show that EA applicationduring MCAO induces a stronger protection than EA aferMCAO, suggesting that an early institution o EA treatmentis required to achieve better neuroprotection against ischemic

injury. Tis is similar to the goals o tPA treatment in termso the importance o the therapeutic window [, ]. Anearly mobilization o protective power may prevent neuronsrom initiating the process o apoptosis/necrosis in the brain.ime is brain, which is also true in the case o EA treatmentor ischemic brain injury.

In summary, our results suggest early EA treatment withoptimal stimulation parameters or an appropriate period iscritical to achieve a therapeutic effect or neuroprotectionagainst ischemic insult. Te previous controversies in the lit-erature on EA treatment or stroke can be partially attributedto the differences in conditions o the patients andEA param-eters. Further in-depth investigations into the optimal EAparameters and its underlying mechanisms can help improveclinical outcomes o patients with ischemic/hypoxic injury inthe brain.

Acknowledgments

Tis work was supported by NSFC (, ),NBRP (CB; CB), SCSM(DZ), NIH (A- and HD-), andVivian L. Smith Neurologic Foundation.

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Hindawi Publishing CorporationEvidence-Based Complementary and Alternative MedicineVolume , Article ID ,pageshttp://dx.doi.org/.//

Review ArticleUnderstanding Central Mechanisms of Acupuncture

Analgesia Using Dynamic Quantitative Sensory Testing:A Review

Jiang-Ti Kong,1 Rosa N. Schnyer,2 Kevin A. Johnson,1 and Sean Mackey1

Stanford Systems Neuroscience & Pain Laboratory, Department of Anesthesiology, Division of Pain Medicine,School of Medicine, Stanford University, Arastradero Road, Suite , Palo Alto, CA , USA

School of Nursing, Te University of exas at Austin, Austin, X , USA

Correspondence should be addressed to Jiang-i Kong; [email protected]

Received November ; Revised March ; Accepted March

Academic Editor: Di Zhang

Copyright Jiang-i Kong et al. Tis is an open access article distributed under the Creative Commons Attribution License,which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

We discuss the emerging translational tools or the study o acupuncture analgesia with a ocus on psychophysical methods. Tegap between animal mechanistic studies and human clinical trials o acupuncture analgesia calls or effective translational tools thatbridge neurophysiological data with meaningul clinical outcomes. emporal summation (S) and conditioned pain modulation(CPM) are two promising tools yet to be widely utilized. Tese psychophysical measures capture the state o the ascending

acilitation and the descending inhibition o nociceptive transmission, respectively. We review the basic concepts and currentmethodologies underlying these measures in clinical pain research, and illustrate their application to research on acupunctureanalgesia. Finally, we highlight the strengths and limitations o these research methods and make recommendations on uturedirections. Te appropriate addition o S and CPM to our current research armamentarium will acilitate our efforts to elucidatethe central analgesic mechanisms o acupuncture in clinical populations.

1. Overview of Research onAcupuncture Analgesia

Te treatment o chronic pain is the most well-known clinicalapplication o acupuncture in the west [, ]. Acupuncture

originated in China more than years ago and has gainedpopularity in America since the landmark NIH ConsensusConerence in []. Despite broad use, there continuesto be ambiguity regarding the efficacy and mechanisms oacupuncture as an analgesic modality. Discrepancies betweenthe results o basic science experiments and clinical trialso acupuncture underscore the controversy surrounding itstherapeutic value. Te purpose o this review is to outlineemerging translational clinical research methods or assess-ing the central mechanisms o acupuncture analgesia inhumans. We begin by summarizing our current understand-ing o the analgesic mechanisms o acupuncture based onanimal and human clinical studies.

.. Animal Studies. Animal studies have identied manypotential biochemical and neuroanatomical substrates oacupuncture analgesia. Wang et al. [,], Zhao [], and Han[, ] have published excellent comprehensive reviews othese studies. From a biochemical standpoint, it appears that

acupuncture may alter the metabolism o substrates involvedin both the ascending acilitory pathways (N-methyl-D-aspartate receptors [], substance P [], and interleukin-[]) and the descending inhibitory pain pathways (endoge-nous opioids [], serotonin [], and norepinephrine []).From a neuroanatomical standpoint, several central nervoussystem structures are reported to mediate acupuncture anal-gesia, including the periaqueductal gray, the nucleus raphemagnus, the locus ceruleus, the arcuate nucleus, the amyg-dala, andthe nucleus accumbens [, ]. It is importantto notethe link between the biochemical and anatomical substrates.For example, low-requency electroacupuncture triggers therelease o enkephalins and endorphins in the periaqueductal


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gray, the arcuate nucleus, and the caudate nucleus []. Tesestructures then send projections to the spinal dorsal horn viathe dorsal lateral uniculi []. Increases in serotonin releaseat the nucleus raphe magnus and norepinephrine release inthe locus ceruleus are also crucial to analgesia induced byelectroacupuncture [].

In addition to the classic neurotransmitters and anatomi-cal pathways involved in centralpain processing, other mech-anisms also contribute to acupuncture analgesia [], includ-ing the hypothalamus-pituitary-adrenal axis (regulatingperipheral inammatory response to pain) [], the auto-nomic nervous system (regulating local circulation) [,],and the glial system [] (contributing to inammationaround spinal and cerebral neural pathways).

.. Human Studies. Although animal studies can provideinsight into acupunctures mechanism o action, establishingthe efficacy o acupuncture or treating chronic pain inhumans is challenging, owing to the variability o studymethods and outcomes []. However, an increasing body orobust and rigorous evidence indicates that acupuncture maybe an effective intervention or the management o chronicpain []. Researchers rom the Acupuncture rialistsCollaboration, a group, which was established to synthesizedata rom high-quality randomized trials on acupuncture orchronic pain, recently published a meta-analysis o clinicaltrials involving , patients []. Te analysis showed thatacupuncture consistently yielded greater pain reduction ascompared with controls in back and neck pain, arthritis, andheadaches. When sham acupuncture was used as the control,the differences were modest but remained statistically signi-cant. Larger differences were seen when standard care (whichtypically included oral medications and regular physician andphysical therapy visits) was used as the control [].

Tese results indicate that both specic (i.e., site oneedling and stimulation techniques) and nonspecic (i.e.,context effects, expectations, etc.) components can contributeto acupunctures therapeutic effect in treating chronic pain.Understanding the possible mechanisms o these effects inchronic pain remains crucial in elucidating the potentialtherapeutic value o acupuncture in chronic pain.

.. Need for ranslational Studies Bridging MechanismsObserved in Animals to Clinical Populations. Animal studies

are o limited benet in ully modeling the human experienceo acupuncture ando chronic pain, andthe research methodsused in clinical trials provide only a limited understandingo acupunctures mechanism o action in humans. Tis gapbetween animal mechanistic studies and human clinicaltrials remains one o the greatest challenges in acupunctureresearch today. Te white paper published by the Society oAcupuncture Research (SAR) acknowledged this challengeand proposed goals or uture studies []. One o the keyrecommendations was the development o biomarkers thatcan provide meaningul correlations between physiologicaleffects measured in animal studies and patient-reportedoutcomes in clinical trials.

o this end, we discuss the emerging translationalresearch methods or assessing the central mechanisms oaction o acupuncture analgesia in humans. As background,we rst review the basic mechanisms o the central nervoussystem involved in nociception and human pain perception.Next, we ocus the review on two research approaches that

likely will emerge as valuable tools or understanding painprocessing in acupuncture: temporal summation and condi-tioned pain modulation. We describe the physiologic mech-anism, methodology, and applications o these methods inpain research. Ten, we examine the current application otemporal summation and conditioned pain modulation toacupuncture research and make recommendations on uturedirections.

2. Nociceptive Pathways andNeural Processing

..Nociceptive Pathways.Fivemajor components are involvedin the perception o pain: () the primary peripheral noci-ceptors; () the spinal secondary neurons; () the relayneurons (such as those in the thalamus); () cortical andsubcortical networks responsible or sensory, emotional, andcognitive integration o pain (e.g., theprimary sensorycortex,insula, prerontal cortex, and anterior cingulate cortex); ()the descending modulatory neurons that originate in subcor-tical structures (e.g., the periaqueductal grey and locusceruleus) and project back to the spinal dorsal horn neuronsor descending pain processing [].

.. Central Nociceptive Processing. Modulation o nocicep-

tive signals occurs beyond the peripheral nociceptors in thecentral nervous system. Tis modulation includes processesat the spinal cord and at subcortical and cortical brainstructures (components , , , and rom above).

First, much o the central nociceptive processing occursin the spinal dorsal horn [, ]. At least two types ospinal secondary neurons are ound in the dorsal horn: thenociceptive-specic (NS) neurons and wide dynamic range(WDR) neurons. Te WDR neurons are capable o windup,wherein repetitive noxious stimulation with requenciesabove . Hz (the natural requency o the WDR neurons)leads to amplication in output o the WDR neurons [].Such increased wind-up is implicated in a variety o chronic

pain conditions [,,].Te output o the spinal secondary neurons is dependent

on ascending input rom the peripheral nociceptors, and itis also modulated by spinal interneurons and descendingprojections rom supraspinal centers. Te dynamic balance othese three sources o inuence determines the nal outputrom the spinal secondary neurons, which project upwardto the relay centers and ultimately to the cerebral cortexor pain perception. Tis complex interaction o ascendingand descending inuence on the spinal transmission opain, commonly reerred to as the gate control theory, wasoriginally discovered by Melzack and Wall [] and has sincebeen validated by many [,].


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: Overview o S and CPM.

S CPM

Experimental construct Repeats o brie noxious stimuli A test stimulus measured beore and afer a

conditioning stimulus

ypical magnitudes in healthysubjects

in a visual analog scale (VAS) [] % reduction in pain rating []

Underlying CNS physiology Windup: increased spinal WDR output due to

repetitive C-ber stimulation at>.HzDNIC: global reduction o WDR sensitivity due toa single, heterotopic, noxious stimulation

Pain-processing pathwaysinvolved

Ascending acilitation o nociceptive input Descending inhibition o nociceptive input

Augmenting actorsAdvanced age [], emale sex [,], paincatastrophizing [], anxiety, ear o pain,and location (trunk> extremities) []

Reducing actors

Advanced age [,,], emale sex (mixedresults [,,]), pain catastrophizing [,],poor sleep [,], depression [], and opioiduse []

Second, equally important site o central pain processingoccurs in the brain via the complex interaction betweenthe cortex and subcortical nuclei [, ]. Te brain isconsidered crucial or translating nociceptive signals into theconscious perception o pain. Nociceptive signals are relayedrom the thalamus to primary and secondary somatosensoryregions, and subsequent brain regions are linked to visceralsensation (i.e., insula), emotion (i.e., limbic system), atten-tion (i.e., anterior cingulate), and cognition (i.e., prerontalcortex). Te brain also exerts descending modulation onnociceptive processing via subcortical structures such asthe periaqueductal gray (PAG), the rostroventral medulla(RVM), the hypothalamus, the parabrachial nucleus, and the

nucleus tractus solitarius. Complex reciprocal interactionsexist between the subcortical and cortical centers o painprocessing. Eventually, the descending bers travel in thedorsal lateral uniculus to reach secondary and inter neuronsin the spinal dorsal horn [].

3. Dynamic Quantitative Sensory Testing

Quantitative sensory testing (QS), also known as psy-chophysical testing, reers to tests o sensory perceptionduring the administration o stimuli with predeterminedphysical properties and ollowing specic protocols [].Tese tests are generally sae and noninvasive or use in

human studies, and neuroscience research links these teststo biological underpinnings. Backonja, Arendt-Nielsen, andPau [] have published in-depth reviews o quantitativesensory testing.

QS can be subdivided into static QS and dynamic QS[,]. Static QS typically reers to the measurement othe threshold that primarily reects states o the peripheralnervous system. Conversely, dynamic QS involves agitationo the pain-perceiving system in a way that exposes a certainmechanism o pain processing beyondthe peripheral nervoussystem. wo extensively studied dynamic paradigms aretemporal summation (S) and conditioned pain modula-tion (CPM), which represent the ascending acilitatory and

descending inhibitory aspects o central pain processing,respectively [].able summarizes the basic concept andcharacteristics o S and CPM.

.. emporal Summation. emporal summation (S) reersto the increased perception o pain in response to repetitivenoxious stimuli deliveredat requencies above . Hz [, ].It is ofen called windup pain, or temporal summation osecond pain.

... Animal Studies and Molecular Mechanisms. emporalsummation is the behavioral correlate o windup o spinalwide dynamic range (WDR) neurons at the dorsal horn[, ]. In animal studies, researchers made single-berrecordings rom the periphery C bers and their destinedsecondary neurons in the spinal dorsal horn. With successiveC-ber activations (by either noxious heat or noxious elec-trical stimulation) at requencies over . pulses per second,WDR neurons displayed increased requency and amplitudeo discharges []. Tese physiologic changes were correlatedto behavioral experiments in humans under the same exactstimulation paradigm: they rated the pain with increasingintensity []. Tus, S QSis thought to represent ascendingspinal windup o pain processing.

... Increase of S in Chronic Pain and Risk Factors. S iselevated in a wide variety o pain syndromes, ranging romthose that cause idiopathic total body pain (e.g., bromyalgia[]) to those considered driven entirely by peripheral actors(e.g., knee arthritis []). Increasing evidence suggests thatabnormally augmented S is at least partially responsible orthe development o these chronic pain conditions []. Fur-thermore, researchers have identied important risk actors(able ) that increase S, including older age [], emalesex [, ], psychological actors (anxiety [], ear [],and catastrophizing []), and location o test (the backexhibits higher S than the upper or lower extremities []).


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: Common methods used to generate and compute S.

ype o stimulus Experimental paradigms Variables used to quantiy S

Heat pulses heat pulses (.. s each) delivered at.. Hz either via a continuous contact thermode[] or intermittent contact probe []

S magnitude: the difference in pain ratingsbetween rst and last, or rst and most painulpulse, slope o the rst ew pulses, or themagnitude o th pulse [,]

Electrical stimulation A single stimulus o a train o ve -ms pulses at

Hz, repeated times at or Hz [,]

Electrical pain threshold (EP-): intensity atwhich the subject begins to eel pain at the th orth pulse [,], or nociceptive withdrawalreex threshold (NWR-), the intensity at whichlimb exion occurs [] in response to theelectrical stimulation

Pin prick stimuli o or mN are delivered, and painratings or all ten stimuli averaged versus that o asingle stimulus are obtained []

Windup ratio: pain o train o pricks deliveredat Hz over pain o a single prick []

Pressure en -s pressure stimuli delivered by an algometer

with s between pulses [,]S magnitude: difference in pain rating betweenthe rst and th stimuli [,]

... Methodology for Measurement. Although S is likelya powerul tool or pain research, the lack o a single,standardized, broadly accepted protocol remains a challengewhen interpreting previous work and planning uture studies.A variety o noxious stimuli can be used to generate S,including heat, pin pricks, and electrical stimulation [].Although there is no consensus on the quantication o S[], brie repetitions o identical noxious stimuli aretypically given, and the research participant is ofen asked torate the changing pain sensation afer one or several o thestimuli.able outlines examples o several commonly usedexperimental protocols to generate and compute S.

For heat paradigms, the difference in the pain scorebetween the rst and most painul pulse, the slope o painincrease, or even the raw pain score rom the fh pulse can beused to calculate the magnitude o S [,,]. When pinpricks are used as the noxious stimuli, the German ResearchNetwork on Neuropathic Pain [] recommends a standardprotocol where either or mN pin tips are applied as asingle stimulus and as a series o stimuli given at Hz. Teparticipant is asked to give a single pain rating or the singlestimulus andthen an average rating orthe stimuli repeatedat Hz. Te ratio o average pain rating o the consecutivestimuli to the rating o the single stimulus is dened as S or,alternatively, as the windup ratio.

... emporal Summation in Acupuncture Studies. Teapplication o S to acupuncture research in humans islimited despite the act that the results o several animalstudies indicate that acupuncture produces strong, centralmodulatory effects and that S reects the state o centralpain acilitation. Currently, only two clinical studies havebeen perormed involving S in acupuncture.

In the rst study, Zheng et al. [] randomized healthy volunteers to blindly receiving minutes o elec-troacupuncture, manual acupuncture, and nonpenetratingsham acupuncture in one leg. Te S threshold or trainso electrical stimulation was assessed beore, immediatelyafer, and hours afer the treatments on the ipsilateral leg,

contralateral leg, and contralateral arm. Te results demon-strated that electroacupuncture increased the S threshold(i.e., reduced S) in the ipsilateral and contralateral leg up to hours afer the treatment. In contrast,manual acupunctureproduced no signicant change in the S threshold, althoughit showed a trend o increase as compared with shamacupuncture. Te increase in S threshold was the greatestin the ipsilateral leg, ollowed by the contralateral leg; theleast change was seen in the contralateral arm, suggestingsegmental specicity o the acupuncture interventions.Tis isoneo the very ew studies demonstrating that different ormso needle manipulation produced differences in human painperception linked to a mechanism o central pain processing.Finally, this study demonstrated peripheral inuences oacupuncture, as electroacupuncture augmented not only theS threshold but also the pain detection threshold to single-pulse electrical stimulation.

In the second study, by obbackx et al. [], patientswith chronic neck pain due to whiplash injury underwentone session o manual acupuncture ( minutes) and onesession o relaxation therapy (length not specied) in randomorder with a -week between-session washout period. Teprimary outcomes assessed were pressure pain sensitivityto an analogue algometer and S scores to consecutiveapplications o pressure stimuli using the same algometer ata pressure above the pain threshold. Te study ound thatacupuncture caused a greater reduction o the pressure pain

threshold as compared with relaxation therapy but producedno change in the S scores. Te authors concluded thatin patients with chronic pain, acupuncture does not affectcentral pain processing.

Te inconsistency in the methods used as well as thelimited results rom these two studies underscore the need oruture studies to help urther elucidate the role o acupunc-ture in central pain processing in human subjects. Speci-cally, both Zheng andobbackxdemonstrated that afer a sin-gle session, manual acupuncture did not result in a signicantchange in S. However, Zheng was able to demonstrate a sig-nicant decrease in S afer electroacupuncture (obbackxonly studied manual acupuncture). Tese results suggest that


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electroacupuncture mayexert a stronger inuence on S thanmanual acupuncture. Future studies should be conductedto compare electroacupuncture with manual acupuncture inlarger cohorts o patients with chronic pain.

Itis alsoimportant to note that these studies involved onlyone acupuncture session. In acupuncture practice, a single

session is rarely considered sufficient to produce clinicallysignicant effects or the treatmento chronic pain.Tereore,when translating the results o studies o animal modelsand healthy human subjects to the clinical pain population,multiple acupuncture sessions with treatment requency o atleast once a week should be considered.

We also recommend perorming quantitative sensorytesting at multiple anatomical sites adjacent to and at adistance rom the site treated or pain. Zheng et al. demon-strated a stronger effect o acupuncture in homotopic versusheterotopic sites, while obbackx collected data only on thearm, distal to the neck where the pain and the majority o theneedling were located.

Last but not least, there is a need to distinguish theperipheral and central components o acupuncture analgesia.Specically, Zheng demonstrated increase in the thresholdto both temporal summation and to single-pulse protocols,suggesting acupunctures involvement in both central andperipheral nociceptive modulation. Te authors urther sug-gest that a mechanism independent o NMDA blockade, suchas peripheral opioid receptor activation [], may play a role.o test this hypothesis, selective blockade o NMDA and-opioid receptors should be used. Furthermore, additionalbiomarkers o central (e.g., secondary hyperalgesia to cap-saicin []) and peripheral pain processing (pressureand heatpain threshold []) may also be used to prole the painmodulatory mechanisms o acupuncture.

.. Conditioned Pain Modulation. Conditioned pain modu-lation (CPM) reers to the phenomenon whereby a noxiousstimulus at one body part results in reduced pain perceptionto another noxious stimulus at a distant, heterotopic bodypart [, ]. Te rst stimulus is reerred to as the con-ditioning stimulus; the second stimulus, whose pain ratingdecreases afer the application o the conditioning stimulus,is reerred to as the test stimulus []. CPM has been shownto be a separate phenomenon rom cognitive distraction [,]. A variety o other terms have also been used to describeCPM, such as pain inhibiting pain, heterotopic noxious

conditioning stimulation, and counterirritation [, ].CPM was also reerred to as diffuse noxious inhibitorycontrol (DNIC). However, international experts have agreedto distinguish DNIC, a neurophysiologic process, rom CPM,a behavioral correlate o this process (see below) [].

... Animal Studies and Molecular Mechanisms. CPM isthe behavioral correlate to diffuse noxious inhibitory control(DNIC) [], an inhibitory mechanism involving the spinal-bulbo-spinal loop in animal neurophysiological studies [].In , Le Bars et al. discovered that when noxious stimuli(A-- or C-ber-mediated) are applied anywhere outsidethe excitatory receptive eld o a spinal or trigeminal

WDR neuron, the response to any noxious input withinits receptive eld is prooundly inhibited [,]. Le Barsgroup subsequently ound that DNIC is mediated by thesubnucleus reticularis dorsalis (SRD) in the caudal medulla[], which receives noxious input via pathways in the ventrallateral quadrant o the spinal cord [], and sends global

inhibitory signals to WDR neurons rom all spinal levels viathe dorsolateral uniculi []. Finally, the strong correlationbetween the signal reduction in the WDR neurons and thepain reduction in a CPM paradigm, in both extent andtime course, supports the notion that CPM is the behavioralcorrelate o DNIC [].

... Decrease of CPM in Chronic Pain and Risk Factors. LikeS, CPM is altered in many chronic pain conditions, such asbromyalgia [], tension-type headache [], irritable bowelsyndrome [], and arthritis o the hip []. Rather than anincrease as with S, a decrease in CPM is seen. As showninable , the risk actors or decreased CPM are similar to

those or increased S. Tese include older age [,,],emale sex [, , ], and psychological actors such ascatastrophizing [,]. However, the relationship betweenemale sex and decreased CPM is less straight orward assome studies showed clear increase in CPM associated withemale sex, while others did not nd such association [, ,]. Large variations in methodology may partially contributeto this discrepancy [,]. Furthermore, chronic opioid use[], depressed mood [], and poor sleep also decrease CPM[,].

... Measurement Methodology. Tere is no single, standardprotocol or measuring CPM. able summarizes the keycomponents in generating CPM and demonstrates exampleso their variability. Pud et al. [] published an excellentreview o CPM methods. In short, a test stimulus is measuredbeore the application o the conditioningstimulusto obtain abaseline and is measured again during or afer the applicationo the conditioning stimulus to quantiy the magnitude oCPM relative to the baseline. Te noxious test and condition-ing stimuli are typically administered at anatomically distinctlocations.

Te most common conditioning stimulus is a cold waterbath applied to the contralateral hand. However, other con-ditioning stimuli have been used, including isotonic salineinjections and heat pain. It is the general consensus that the

conditioning stimulus must be noxious in order to triggerCPM[, ]. Once the noxious threshold hasbeen exceeded,the intensity o the conditioning stimulus may not matter,according to reports by Granot et al. [] and Nir et al. [].Te duration o the conditioning stimulus is usually between seconds and minutes or the cold water bath [].

In contrast to the conditioning stimulus, there is a largevariation in the choice o test stimulus. Pain recordings oa standard stimulus or pain thresholds rom any type ostimulation (electrical, chemical, heat, pressure, etc.) can beused []. Te magnitude o CPM is measured by the changerom baseline in the test stimulus to afer the conditioningstimulus is applied. Te CPM effect appears to peak during


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: Examples o varied parameters in generating CPM.

Parameter Examples

Conditioning stimulus Cold water bath (C) [], heat (thermode or water bath) [], hypertonic

saline injection [], and inated blood pressure cuff []

esting stimulus Pain detection thresholds [], rating o a predetermined single pain stimulus [],

and S protocols []

When to measure test stimulusagain

Varies widely: rom during the conditioning stimulus [] up to min afer theconditioning stimulus []

Location o stimulus Large variation in the relative distance between the testing and conditioning stimuli:

or example, upper body to upper body [] versus upper body to lower body []

Computation Relative or absolute changes in threshold measures or ratings o predetermined pain

stimulus []

the application o the conditioning stimulus and ades rapidlyrom to minutes afer the conditioning stimulus ceases[, , , ]. One report indicates that the approxi-mate median magnitude o CPM represents about a %decrease in pain rating, regardless o the test stimulus used

[]. Tere is some indication that CPM is stronger whenthe test and conditioning stimuli are applied at a greateranatomical distance rom the CPM stimulus site (e.g., CPM isstronger or the hand-to-contralateral leg than or the hand-to-contralateral hand) [,].

In summary, the best means o capturing robust CPM isto use a strong, noxious conditioning stimulus (such as coldimmersion o the contralateral distal extremity) and measurethe change in the test stimulus during the latter part othe conditioning stimulus. As with S, signicant variationsexist in the methodologies used to generate and computeCPM, making it difficult to make comparisons across studiesand subjects. Future efforts should ocus on identiying a

standardized, broadly accepted protocol or CPM.

... CPM in Acupuncture Studies. Similar to S, the useo CPM to study acupuncture analgesia is limited. Tereare only two direct studies on acupuncture analgesia andCPM/DNIC, both o which ocused on the question owhether acupuncture analgesia is equivalent to CPM/DNIC.o date,no onehas studied how acupuncture stimulation maymodulate the extent o DNIC.

Te rst acupuncture-DNIC study was carried out byBingetal.[]. Output rom WDRneurons in the trigeminal

nucleus o rodents was measured using the patch-clamptechnique. Te conditioning stimuli consisted o manualacupuncture applied to Zusanli (a classic acupuncture point)and to an adjacent nonacupuncture point, both located onthe right hind limb, and a standard noxious stimulusimmersion o the lef hind limb in a C hot water bath.All three stimuli resulted in a similar degree o inhibition inthe ring o the trigeminal WDR neurons (.% and .%).Furthermore, the inhibition resulting rom all three stimulidemonstrated a similar time course or decay and a similarresponse to naloxone, which reversed the inhibition by about%. Te authors concluded that acupuncture maneuverstrigger the neural mechanisms involved in DNIC.

Te second acupuncture-DNIC (CPM) study was done inhealthy human volunteers using a crossover design []. Itdirectly compared the effects o acupuncture, sham acupunc-ture, and a .C cold water bath (as a conditioning stimulusin the upper extremity). Te test stimulus was the pressure

pain threshold at the second toe. Te verum acupunctureinvolved the penetration o Hegu (a classic acupuncturepoint) with a needle without manipulation, and retainingthe needle or minutes. Te sham acupuncture involvedthe tapping and placement o a nonpenetrating Streitbergerdevice [] at Hegu or minutes. Te results showedthat the cold bath resulted in much stronger increase inthe pressure pain threshold as compared with verum andsham acupuncture. Furthermore, there was no statisticallysignicant difference between the verum and sham. Teauthors concluded that acupuncture as perormed in this trialexerted a small analgesic effect notdifferent rom placebo andthat the analgesic effect was unlike CPM.

It is difficult to compare these studies because o severalreasons. First, the test and conditioning stimuli differedsignicantly between the two studies. Second, as the authorso the second paper mentioned, their acupuncture needlingwas only minimally painul (pain score about . . out oa -point scale). Because prior studies have shown that CPMwill only work when the conditioning stimulus is beyondthe noxious threshold, it is not surprising that acupuncturedid not trigger CPM in these studies. Tird, Deqi, a uniquecomposite o sensations (such as deep ache and tinglingsensation) considered essential or clinical efficacy accordingto traditional Chinese medicine [], was not elicited in thesecond study. In real clinical practice, the acupuncturist aims

to achieve Deqi, retains the needles in the body or between and minutes, and ofen uses more than one needle [].Tereore, the treatment perormed in the second study doesnot represent typical clinical practice. Future studies shouldocus on adapting CPM or the clinical study o acupunctureanalgesia using acupuncture methods that are consistent withclinical practice.

Last but not least, the duration o CPM/DNIC is short-lived. Directly comparing acupuncture with CPM will nothelp understand the clinically relevant long-term analgesia byacupuncture. Because DNIC/CPM is considered to play a rolein mediating pain perception in chronic pain conditions [,, ], it would be more relevant to study how acupuncture


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inuences CPM rather than simply to treat acupuncture as aorm o transient conditioning stimulus.

.. Current rends and Future Directions QS in

Acupuncture Research

...

Documents

Biophysical Basis for Meridian and Acupoint Functions