Involvement of peripheral opioid mechanisms in electroacupuncture analgesia

TRPM8's Role in the Shift Between Opioid and Cannabinoid Pathways in Electroacupuncture for Inflammatory Pain in Mice

The TRPM8 channel, a temperature-sensitive ion channel, plays a crucial role in various physiological processes, particularly in the modulation of inflammation and nociception. Although electroacupuncture (EA) is a recognized analgesic treatment for pain conditions, its interaction with TRPM8 remains underexplored. This study aims to determine TRPM8's role in EA-induced analgesia using a murine model of inflammatory pain. Mechanical allodynia, evidenced by a reduced paw withdrawal threshold (PWT), was induced in both wild-type and Trpm8-/- mice through CFA injection. EA applied at the GB34 and LR3 acupoints significantly alleviated mechanical allodynia in both groups. In wild-type mice, the analgesic effects of EA were partially reversed by naloxone (an opioid receptor antagonist) or AM251 (a CB1 receptor antagonist) and fully reversed by their combination. In contrast, only AM251 reversed EA-induced analgesia in Trpm8-/- or TRPM8-inhibited wild-type mice (via AMTB treatment, a TRPM8 antagonist), indicating no involvement of the opioid pathway. Additionally, the combination of menthol, a partial TRPM8 agonist, and EA enhanced analgesia in wild-type mice. In Trpm8-/- or AMTB-pretreated mice, the CB1 receptor agonist WIN 55,212-2 (WIN) exhibited stronger analgesic effects compared to wild-type controls. These findings suggest that EA at LR3 and GB34 mediates analgesia through both opioid and endocannabinoid pathways. TRPM8 is critical for EA to activate the opioid pathway, while its inhibition or deletion shifts the analgesic mechanism towards reliance on the cannabinoid system. Understanding this mechanistic shift may help optimize EA treatment strategies and improve pain management outcomes.

Short-term effect of frequency specific intramuscular electrical stimulation on post dry needling soreness of upper fibers of trapezius: A randomized controlled trial

OBJECTIVES

The purpose of this study was to compare the effect of frequency specific intramuscular electrical stimulation on post trigger point dry needling soreness.

BACKGROUND

Dry needling (DN) with intramuscular electrical stimulation (DN/IMES) has been shown to be effective in reducing post needling soreness. The effect of frequency specific intramuscular electrical stimulation on post needling soreness has not been studied abundantly, but initial results are favorable. This study investigated the effect of frequency specific intramuscular electrical stimulation on post needling soreness.

METHODS

A convenience sample of 45 (α = 0.05, power = 95%) subjects was recruited for this study and randomly assigned to DN (n = 15), DN/IMES [f-2Hz] (n = 15) and DN/IMES [f-100Hz] (n = 15) groups. Pain Pressure Threshold (PPT) and Numeric Pain Rating Scale (NPRS) were measured before and 24 hours after the intervention.

RESULT

Both DN/IMES [f-2Hz and 100 Hz] groups showed statistically significant improvement in NPRS (p = 0.001 and 0.00005, respectively) and PPT (p = 0.004 and 0.0002, respectively). No statistically significant changes were observed in DN group in NPRS (p = 0.726) and PPT (p = 0.238).

CONCLUSION

Both dry needling with Intramuscular electrical stimulation (DN/IMES [f-2Hz and 100Hz]) groups demonstrated statistically significant improvement in soreness as compared to DN group, but DN/IMES [f-100 Hz] group showed more significant improvement as compared to DN/IMES [f-2 Hz] group in reducing post needling soreness.

Effects of contralateral versus ipsilateral electroacupuncture for analgesia and rehabilitation after unilateral total knee arthroplasty: a randomized controlled trial

PURPOSE

Total knee arthroplasty (TKA) is a treatment for advanced knee osteoarthritis. Since postoperative pain affects rehabilitation, this study aimed to determine whether electroacupuncture (EA) contralateral to the surgical site is more effective than ipsilateral EA or sham EA in terms of relieving postoperative pain and promoting post-TKA rehabilitation.

METHODS

In this parallel, single-blind randomized controlled trial, 114 patients undergoing unilateral TKA were assigned to the contralateral EA (EA on the contralateral side + sham EA on the ipsilateral), ipsilateral EA (EA on the ipsilateral + sham EA on the contralateral side), or sham EA (sham EA on both sides) groups (n = 38 each). Treatment was performed once daily on postoperative days 1-3. The visual analog scale (VAS) scores, additional opioid doses via patient-controlled analgesia (PCA) pump, Hospital for Special Surgery (HSS) knee scores, active/passive range of motion (AROM/PROM), swelling around the knee joint, and Hamilton anxiety scale (HAMA) scores were used for postoperative evaluation.

RESULTS

At 3 days postoperatively, the VAS scores, HSS scores, AROM/PROM, swelling around the knee, and HAMA scores in the contralateral EA and ipsilateral EA groups were significantly improved compared with baseline. In addition, VAS scores, HSS scores, PROM and swelling around the knee were significantly better in the contralateral and ipsilateral EA groups than in the sham EA group, but similar in the two true EA groups. Furthermore, PCA additional dose release was significantly higher in the sham EA group than in the two true EA groups (which did not significantly differ). At 10 days postoperatively, the HSS scores, AROM/PROM, and HAMA scores were better in the contralateral and ipsilateral EA groups than in the sham EA group, but similar in the two true EA groups.

CONCLUSION

Contralateral EA is more effective than sham EA for treating postoperative pain following TKA, but has an analgesic effect similar to that of ipsilateral EA.

TRIAL REGISTRATION NUMBER

ChiCTR1800020297 (Chinese Clinical Trial Registry).

The Roles of Imaging Biomarkers in the Management of Chronic Neuropathic Pain

Chronic neuropathic pain (CNP) affects around 10% of the general population and has a significant social, emotional, and economic impact. Current diagnosis techniques rely mainly on patient-reported outcomes and symptoms, which leads to significant diagnostic heterogeneity and subsequent challenges in management and assessment of outcomes. As such, it is necessary to review the approach to a pathology that occurs so frequently, with such burdensome and complex implications. Recent research has shown that imaging methods can detect subtle neuroplastic changes in the central and peripheral nervous system, which can be correlated with neuropathic symptoms and may serve as potential markers. The aim of this paper is to review available imaging methods used for diagnosing and assessing therapeutic efficacy in CNP for both the preclinical and clinical setting. Of course, further research is required to standardize and improve detection accuracy, but available data indicate that imaging is a valuable tool that can impact the management of CNP.

Role of Neuroimmune Crosstalk in Mediating the Anti-inflammatory and Analgesic Effects of Acupuncture on Inflammatory Pain

Inflammatory pain is caused by peripheral tissue injury and inflammation. Inflammation leads to peripheral sensitization, which may further cause central sensitization, resulting in chronic pain and progressive functional disability. Neuroimmune crosstalk plays an essential role in the development and maintenance of inflammatory pain. Studies in recent years have shown that acupuncture can exert anti-inflammatory and analgesic effects by regulating peripheral (i.e., involving local acupoints and inflamed regions) and central neuroimmune interactions. At the local acupoints, acupuncture can activate the TRPV1 and TRPV2 channels of mast cells, thereby promoting degranulation and the release of histamine, adenosine, and other immune mediators, which interact with receptors on nerve endings and initiate neuroimmune regulation. At sites of inflammation, acupuncture enables the recruitment of immune cells, causing the release of opioid peptides, while also exerting direct analgesic effects via nerve endings. Furthermore, acupuncture promotes the balance of immune cells and regulates the release of inflammatory factors, thereby reducing the stimulation of nociceptive receptors in peripheral organs. Acupuncture also alleviates peripheral neurogenic inflammation by inhibiting the release of substance P (SP) and calcitonin gene-related peptide from the dorsal root ganglia. At the central nervous system level, acupuncture inhibits the crosstalk between glial cells and neurons by inhibiting the p38 MAPK, ERK, and JNK signaling pathways and regulating the release of inflammatory mediators. It also reduces the excitability of the pain pathway by reducing the release of excitatory neurotransmitters and promoting the release of inhibitory neurotransmitters from neurons and glial cells. In conclusion, the regulation of neuroimmune crosstalk at the peripheral and central levels mediates the anti-inflammatory and analgesic effects of acupuncture on inflammatory pain in an integrated manner. These findings provide novel insights enabling the clinical application of acupuncture in the treatment of inflammatory diseases.

The role of macrophage polarization and associated mechanisms in regulating the anti-inflammatory action of acupuncture: a literature review and perspectives

Acupuncture is used in the treatment of a variety of inflammatory conditions and diseases. However, the mechanisms of its anti-inflammatory action are complex and have not been systematically investigated. Macrophages are key components of the innate immune system, thus, balancing the M1/M2 macrophage ratio and modulating cytokine levels in the inflammatory environment may be desirable therapeutic goals. Evidence has shown that acupuncture has anti-inflammatory actions that affect multiple body systems, including the immune, locomotory, endocrine, nervous, digestive, and respiratory systems, by downregulating pro-inflammatory M1 and upregulating anti-inflammatory M2 macrophages, as well as by modulating associated cytokine secretion. Macrophage polarization is controlled by the interlocking pathways of extrinsic factors, the local tissue microenvironment, and the neural-endocrine-immune systems. It has been suggested that polarization of T lymphocytes and cytokine secretions resulting in modulation of the autonomic nervous system and the hypothalamic–pituitary–adrenal axis, may be upstream mechanisms of acupuncture-induced macrophage polarization. We further propose that macrophage polarization could be the principal pathway involved in acupuncture immune regulation and provide the scientific basis for the clinical application of acupuncture in inflammatory conditions.

Increasing Efficiency of Repetitive Electroacupuncture on Purine- and Acid-Induced Pain During a Three-Week Treatment Schedule

Acupuncture (AP) is an important constituent of the therapeutic repertoire of traditional Chinese medicine and has been widely used to alleviate chronic painful conditions all over the world. We studied in rats the efficiency of electroacupuncture (EAP) applied to the Zusanli acupoint (ST36) as an analgesic treatment over a 3-week period of time on purine (α,β-methylene ATP, dibenzoyl-ATP)- and acid (pH 6.0 medium)-induced pain in the rat paw. The two ATP derivatives stimulated P2X3 and P2X7 receptors, respectively, while the slightly acidic medium stimulated the “acid-sensitive ion channel 3” (ASIC3). It was found that the P2X7 receptor and ASIC-mediated pain was counteracted by EAP with greater efficiency at the end than at the beginning of the treatment schedule, while the P2X3 receptor–mediated pain was not. Our findings have important clinical and theoretical consequences, among others, because they are difficult to reconcile with the assumption that AP is primarily due to the release of peripheral and central opioid peptides causing the well-known tolerance to their effects. In consequence, AP is a convenient therapeutic instrument to treat subacute and chronic pain.

An Hypothesis for CXCL1/CXCR2 Signaling Regulating Neutrophil-Derived Opioid Peptides Involved in Acupuncture for Inflammatory Pain

Increasing evidences demonstrate that acupuncture is effective in treating inflammatory pain. Recent studies have found that peripheral endogenous opioid peptides in the area of inflammation are involved in acupuncture-treating inflammatory pain. However, the source of endogenous opioid peptides in local area of inflammation and the mechanism of acupuncture regulating these opioid peptides remain unclear. Studies have demonstrated that neutrophils infiltrated in the inflamed tissue contain and release opioid peptides. Chemokine (C-X-C motif) ligand 1 (CXCL1) is one of the key neutrophil chemokines and can promote the blood neutrophil recruitment to the area of inflammation. In our previous experiments, we found that acupuncture could alleviate inflammatory pain and significantly increase the concentration of chemokine CXCL1 in the blood of rats with inflammatory pain. So we suppose that increased concentration of CXCL1 by acupuncture could activate the blood opioid-containing neutrophils via its main receptor chemokine receptor type 2 (CXCR2) and promote them recruit to the inflamed tissue to release opioid peptides, participating in the analgesic effect of acupuncture.

Peripheral receptors and neuromediators involved in the antihyperalgesic effects of acupuncture: a state-of-the-art review

The present study aims to describe state-of-the-art of preclinical studies that have investigated peripheral receptors and neuromediators involved in the antihyperalgesic effects of acupuncture. The PubMed, Scopus, and Web of Science databases were searched using the integrative review method. Preclinical articles that involved the study of peripheral receptors and neuromediators on the pain control effects of acupuncture in rats or mice were selected using a predefined search strategy. From this search, 456 articles were found, and 29 of them met the inclusion criteria of the study. The selected articles addressed the following peripheral receptors: opioid (n = 9), adenosine (n = 5), cannabinoid (n = 5), transient receptor potential vanilloid (TRPV) (n = 3), histamine (n = 2), adrenergic (n = 1), muscarinic (n = 1), corticotrophin-releasing factor (CRF) (n = 2), IL-1 (n = 1), and endothelin (n = 1) receptors. The peripheral neuromediators correlated with the peripheral pain control effect were as follows: opioid peptides (n = 4), adenosine (n = 3), histamine (n = 1), substance P (n = 1) calcitonin gene-related peptide (CGRP) (n = 1), anandamide (n = 1), nitric oxide (n = 1), and norepinephrine (n = 1). This review summarizes the methods used to investigate the peripheral effects of acupuncture and discusses the main findings on each family of receptors and neuromediators. Ten families of peripheral receptors and 8 types of neuromediators were correlated with the antihyperalgesic effects of acupuncture in preclinical studies. Considering the benefits of a better understanding of the role of peripheral receptors and neuromediators in the context pain management, the findings of the present study highlight the importance of deepening the exploration of the peripheral mechanisms of acupuncture.

The neuro-immune microenvironment of acupoints-initiation of acupuncture effectiveness

Acupuncture is a centuried and unfading treatment of traditional Chinese medicine, which has been proved to exert curative effects on various disorders. Numerous works have been put in to uncover the effective mechanisms of acupuncture. And the interdependent interaction between acupuncture and acupoint microenvironment is a crucial topic. As a benign minimally invasive stimulation, the insertion and manipulation of needle at acupoint could cause deformation of local connective tissue and secretion of various molecules, such as high mobility group box 1 and ATP. The molecules are secreted into extracellular space and bind to the corresponding receptors thus active NF-κB, MAPK, ERK pathways on mast cells, fibroblasts, keratinocytes, and monocytes/macrophages, among others. This is supposed to trigger following transcription and translation of immune factors and neural active substance, as well as promote the free ion movement (such as Ca²⁺ influx) and the expansion of blood vessels to recruit more immune cells to acupoint. Finally, acupuncture could enhance network connectivity of local microenvironment at acupoints. The earlier mentioned substances further act on a variety of receptors in local nerve endings, transmitting electrical and biochemical signals to the CNS, and giving full play to the acupuncture action. In conclusion, we portrayed a neuro-immune microenvironment network of acupoints that medicates the acupuncture action, and would lay a foundation for the systematic study of the complex network relationship of acupoints in the future.

Comparing Verum and Sham Acupuncture in Fibromyalgia Syndrome: A Systematic Review and Meta-Analysis

OBJECTIVES

Acupuncture is often used for relieving symptoms of fibromyalgia syndrome (FMS). Our aim is to ascertain whether verum acupuncture is more effective than sham acupuncture in FMS.

METHODS

We collected RCTs to investigate the effects of verum acupuncture and sham acupuncture on pain, sleep quality, fatigue, and general status in FMS patients. The databases used for data retrieval were PubMed, Central Cochrane, EMBASE, PsycINFO, CNKI, VIP, OASIS, KoreaMed, and RISS. Selection/exclusion from the retrieved records was performed according to prespecified criteria, and the final selected records were assessed according to the Cochrane risk of bias tool. The results of the included trials were synthesized on the basis of outcomes, and subgroup analysis depended on the type of add-on sham acupuncture that was performed.

RESULTS

Ten RCTs (690 participants) were eligible, and eight RCTs were eventually included in the meta-analysis. The synthesis showed a sizable effect of verum acupuncture compared with sham acupuncture on pain relief (standardized mean difference (SMD) -0.49, Z = 3.26, P=0.001; I 2 = 59%), improving sleep quality (SMD -0.46, Z = 3.24, P=0.001; I 2 = 0%), and reforming general status (SMD -0.69, Z = 6.27, P < 0.00001; I 2 = 4%). However, efficacy on fatigue was insignificant (SMD -0.10, Z = 0.51, P=0.61; I 2 = 46%). When compared with a combination of simulation and improper location of needling, the effect of verum acupuncture for pain relief was the most obvious.

CONCLUSIONS

Verum acupuncture is more effective than sham acupuncture for pain relief, improving sleep quality, and reforming general status in FMS posttreatment. However, evidence that it reduces fatigue was not found.

Acupuncture for Post-stroke Shoulder-Hand Syndrome: A Systematic Review and Meta-Analysis

Background: Shoulder-hand syndrome (SHS) is prevalent in hemiplegic patients after stroke. Potential benefits of acupuncture were shown in recent clinical trials. This systematic review aimed to comprehensively evaluate the safety and efficacy of acupuncture for SHS in stroke patients.

Methods: Five English databases (PubMed, Embase, CINAHL, CENTRAL, and AMED) and four Chinese databases (CBM, CNKI, CQVIP, and Wanfang) were searched from their inceptions to January 2019. Randomized, controlled trials that evaluated the add-on effects of acupuncture to rehabilitation for post-stroke SHS were identified.

Results: Thirty-eight studies involving 3,184 participants fulfilled the eligible criteria and were included in the review. The overall meta-analysis showed that acupuncture combined with rehabilitation significantly improved motor function (upper-limb Fugl-Meyer Assessment (FMA): 34 studies, mean difference (MD) 8.01, 95% confidence interval (CI) [6.69,9.33]), and reduced pain (visual analog scale (VAS): 25 studies, MD −1.59, 95%CI [−1.86,−1.32]). It also improved activities of daily living (ADL) when compared with rehabilitation alone (ADL: 11 studies, MD 9.99, 95%CI [5.91,14.06]). However, the certainty of evidence of all these outcomes was assessed as “low.” Subgroup analyses of acupuncture stimulation types and treatment duration all showed significant add-on effects comparing with rehabilitation alone. The safety of acupuncture was unclear because there is a lack of detailed reporting of adverse events in most of the included studies.

Conclusions: Acupuncture therapy seems effective for motor function, pain relief and activities of daily living in stroke patients with mild SHS, when it is used in combination with rehabilitation. The low certainty of evidence downgrades our confidence in making recommendations to clinical practice.

A New Perspective of Acupuncture: The Interaction among Three Networks Leads to Neutralization

Acupuncture has been used to treat multiple medical conditions, but whether the diverse effects of acupuncture are intrinsically linked and how they might be connected have yet to be determined. More and more researches have shown that acupuncture is a kind of nociceptive stimulus, which can cause inflammatory reaction in the sites of acupuncture and then further activate the nerve-endocrine-immune systems to cause the cascade amplification of the acupuncture effect. This review seeks to provide a comprehensive summary of the existing literature concerning the role of "acupoint-meridian-disease network" in various effects of acupuncture and suggest a novel notion that acupuncture may restore homeostasis under different pathological conditions by regulating this network, resulting in the activation of different reaction cascades in response to pathological injury. We think that acupuncture acts on acupoints, first activating the small network of acupoints (Acupoint Network). The information of acupuncture is amplified by cascade, and the nerve endocrine immune system (NEI) is activated through the large network of meridians (Meridian Network) of the body itself. The nerve-endocrine-immune system (NEI) further outputs the effect information to the target organ through multilevel and multisystems and finally acts on the disease network (Disease Network) to produce acupuncture effect.

Acupuncture Resolves Persistent Pain and Neuroinflammation in a Mouse Model of Chronic Overlapping Pain Conditions

Patients with chronic overlapping pain conditions have decreased levels of catechol-O-methyltransferase (COMT), an enzyme that metabolizes catecholamines. Consistent with clinical syndromes, we previously demonstrated that COMT inhibition in rodents produces persistent pain and heightened immune responses. Here, we sought to determine the efficacy of manual acupuncture in resolving persistent pain and neuroinflammation in the classic inbred C57BL/6 strain and the rapid-wound healing MRL/MpJ strain. Mice received subcutaneous osmotic minipumps to deliver the COMT inhibitor OR486 or vehicle for 13 days. On day 7 after pump implantation, acupuncture was performed at the Zusanli (ST36) point or a non-acupoint for 6 consecutive days. Behavioral responses to mechanical stimuli were measured throughout the experiment. Immunohistochemical analysis of spinal phosphorylated p38 mitogen-activated protein kinase, a marker of inflammation, and glial fibrillary acidic protein, a marker of astrogliosis, was performed on day 13. Results demonstrated that ST36, but not sham, acupuncture resolved mechanical hypersensitivity and reduced OR486-dependent increases in phosphorylated p38 and glial fibrillary acidic protein in both strains. The magnitude of the analgesic response was greater in MRL/MpJ mice. These findings indicate acupuncture as an effective treatment for persistent pain linked to abnormalities in catecholamine signaling and, furthermore, that analgesic efficacy may be influenced by genetic differences. PERSPECTIVE: Chronic overlapping pain conditions remain ineffectively managed by conventional pharmacotherapies. Here, we demonstrate that acupuncture alleviates persistent pain and neuroinflammation linked to heightened catecholaminergic tone. Mice with superior healing capacity exhibit greater analgesic efficacy. Findings indicate acupuncture as an effective treatment for chronic overlapping pain conditions and provide insight into treatment response variability.

Electroacupuncture Alleviates Pain Responses and Inflammation in a Rat Model of Acute Gout Arthritis

Acute gout arthritis is one of the most painful inflammatory conditions. Treatments for gout pain are limited to colchicine, nonsteroidal anti-inflammatory drugs, and corticosteroids, which oftentimes result in severe adverse effects. Electroacupuncture (EA) has been proved to be effective in relieving many inflammatory pain conditions with few side effects. Here, we aim to investigate the therapeutic potentials of EA on pain and inflammation of a rat model of acute gout arthritis and underlying mechanisms. We found that 2/100 Hz EA produced the most robust analgesic effect on mechanical hyperalgesia of acute gout arthritis rat model compared with 2 and 100 Hz. EA produced similar analgesic effect compared with indomethacin. 2/100 Hz EA also significantly alleviates the ongoing pain behavior, thermal hyperalgesia, and ankle edema. Locally applied μ and κ-opioid receptor antagonists but not adenosine A₁ receptor antagonist significantly abolished the analgesic effect of EA. Locally applied μ and κ-opioid receptor agonists produced significant antiallodynia on acute gout arthritis rats, mimicking EA. Furthermore, 2/100 Hz EA upregulated β-endorphin expression in inflamed ankle skin tissue. Our results demonstrated, for the first time, that EA can be used for relieving acute gout arthritis with effect dependent on peripheral opioid system and comparable with the one obtained with indomethacin.

The endocannabinoid system, a novel and key participant in acupuncture's multiple beneficial effects

Acupuncture and its modified forms have been used to treat multiple medical conditions, but whether the diverse effects of acupuncture are intrinsically linked at the cellular and molecular level and how they might be connected have yet to be determined. Recently, an emerging role for the endocannabinoid system (ECS) in the regulation of a variety of physiological/pathological conditions has been identified. Overlap between the biological and therapeutic effects induced by ECS activation and acupuncture has facilitated investigations into the participation of ECS in the acupuncture-induced beneficial effects, which have shed light on the idea that the ECS may be a primary mediator and regulatory factor of acupuncture's beneficial effects. This review seeks to provide a comprehensive summary of the existing literature concerning the role of endocannabinoid signaling in the various effects of acupuncture, and suggests a novel notion that acupuncture may restore homeostasis under different pathological conditions by regulating similar networks of signaling pathways, resulting in the activation of different reaction cascades in specific tissues in response to pathological insults.

Acupuncture at Distant Myofascial Trigger Spots Enhances Endogenous Opioids in Rabbits: A Possible Mechanism for Managing Myofascial Pain

Background and Aim

Acupuncture applied at myofascial trigger points (MTrPs) of distant anatomical regions, to reduce pain in a patient's area of primary complaint, is one strategy that is available to manage myofascial pain. However, the endogenous opioid-mediated analgesic mechanism of distant acupuncture associated with pain control is still unclear. This aims of this study were to evaluate the changes in enkephalin and β-endorphin in serum, spinal cord, dorsal root ganglion (DRG) and muscle induced by acupuncture at distant myofascial trigger spots (MTrSs, similar to human MTrPs) in rabbits, to explore its underlying remote analgesic mechanism.

Methods

Acupuncture at MTrSs of a distant muscle (gastrocnemius) was performed either for one session or five daily sessions in rabbits. The levels of enkephalin and β-endorphin in proximal muscle (biceps femoris), serum, DRGs and spinal cords (L5-S2) were then determined by immunoassay immediately and 5 days after treatment.

Results

Immediately after treatment, acupuncture comprising both one dose and five doses significantly enhanced spinal enkephalin expression and serum β-endorphin levels (p<0.05). However, only five-dose acupuncture significantly enhanced the β-endorphin levels in the biceps femoris and DRGs (p<0.05), while 1-dose acupuncture did not (p>0.05). Furthermore, 5 days after treatment, significantly increased levels of spinal enkephalin and serum β-endorphin persisted in animals that received 5-dose acupuncture (p<0.05).

Conclusions

This study demonstrates that interactions within the endogenous opioid system may be involved in the remote effects of acupuncture treatment and could be a potential analgesic mechanism underlying MTrP pain management.

Acupuncture for the treatment of trigger finger in adults: a prospective case series

OBJECTIVE

To determine the effect of acupuncture performed at the synovial and ligamentous tendon sheath (A1 pulley site) on pain during snapping and the severity of the snapping phenomenon in patients with trigger finger.

METHODS

In this observational study, changes in the patients' condition were compared before and after acupuncture treatment. Acupuncture was performed on 19 fingers of 15 patients. Acupuncture needles were inserted into the radial and ulnar sides of the flexor tendon at the A1 pulley of the affected finger. Treatment was performed daily up to a maximum of five times. Before and after each treatment, pain during snapping and the severity of snapping were evaluated using a visual analogue scale (VAS).

RESULTS

VAS scores for pain and snapping severity were significantly improved immediately after the first treatment (p<0.001). Pain during snapping, assessed before each treatment, improved over time, reaching statistical significance from the second treatment onwards (p<0.001); similarly, a significant improvement in the severity of snapping was observed, also from the second treatment (p<0.001). Patients with clinically significant improvements (≥50%) in pain and snapping severity had a significantly shorter duration of the disorder than those with <50% improvement (p<0.05).

CONCLUSIONS

Acupuncture at the impaired A1 pulley site may be an effective treatment for trigger finger. We postulate that acupuncture may reduce inflammation/swelling of the synovial membrane of the tendon sheath, which predominates when the disorder is of short duration. Further research is required to confirm the efficacy/effectiveness of acupuncture for trigger finger and its mechanisms of action.

Probing the Effects and Mechanisms of Electroacupuncture at Ipsilateral or Contralateral ST36-ST37 Acupoints on CFA-induced Inflammatory Pain

Transient receptor potential vanilloid 1 (TRPV1) and associated signaling pathways have been reported to be increased in inflammatory pain signaling. There are accumulating evidences surrounding the therapeutic effect of electroacupuncture (EA). EA can reliably attenuate the increase of TRPV1 in mouse inflammatory pain models with unclear signaling mechanisms. Moreover, the difference in the clinical therapeutic effects between using the contralateral and ipsilateral acupoints has been rarely studied. We found that inflammatory pain, which was induced by injecting the complete Freund’s adjuvant (CFA), (2.14 ± 0.1, p < 0.05, n = 8) can be alleviated after EA treatment at either ipsilateral (3.91 ± 0.21, p < 0.05, n = 8) or contralateral acupoints (3.79 ± 0.25, p < 0.05, n = 8). EA may also reduce nociceptive Nav sodium currents in dorsal root ganglion (DRG) neurons. The expression of TRPV1 and associated signaling pathways notably increased after the CFA injection; this expression can be further attenuated significantly in EA treatment. TRPV1 and associated signaling pathways can be prevented in TRPV1 knockout mice, suggesting that TRPV1 knockout mice are resistant to inflammatory pain. Through this study, we have increased the understanding of the mechanism that both ipsilateral and contralateral EA might alter TRPV1 and associated signaling pathways to reduce inflammatory pain.

Acupuncture: Emerging evidence for its use as an analgesic (Review)

Acupuncture is an ancient Chinese technique, developed over >3,000 years, in which 'acupoints' are stimulated with the aim of treating various diseases. A number of previous studies have indicated that acupuncture may play a role in inducing analgesia. Acupuncture-induced analgesia has been hypothesized to act on various parts of the central nervous system, including the spinal cord, brain stem, cerebral ganglia and cerebral cortex. The mechanisms underlying the effects of acupuncture have been purported to include neurohumors and neurotransmitters, such as opioids and γ-aminobutyric acid, signaling pathways and the immune response, which are all involved in the induction of analgesia.

CXCL10 controls inflammatory pain via opioid peptide-containing macrophages in electroacupuncture

Acupuncture is widely used for pain treatment in patients with osteoarthritis or low back pain, but molecular mechanisms remain largely enigmatic. In the early phase of inflammation neutrophilic chemokines direct opioid-containing neutrophils in the inflamed tissue and stimulate opioid peptide release and antinociception. In this study the molecular pathway and neuroimmune connections in complete Freund's adjuvant (CFA)-induced hind paw inflammation and electroacupuncture for peripheral pain control were analyzed. Free moving Wistar rats with hind paw inflammation were treated twice with electroacupuncture at GB30 (Huan Tiao - gall bladder meridian) (day 0 and 1) and analyzed for mechanical and thermal nociceptive thresholds. The cytokine profiles as well as the expression of opioid peptides were quantified in the inflamed paw. Electroacupuncture elicited long-term antinociception blocked by local injection of anti-opioid peptide antibodies (beta-endorphin, met-enkephalin, dynorphin A). The treatment altered the cytokine profile towards an anti-inflammatory pattern but augmented interferon (IFN)-gamma and the chemokine CXCL10 (IP-10: interferon gamma-inducible protein) protein and mRNA expression with concomitant increased numbers of opioid peptide-containing CXCR3⁺ macrophages. In rats with CFA hind paw inflammation without acupuncture repeated injection of CXCL10 triggered opioid-mediated antinociception and increase opioid-containing macrophages. Conversely, neutralization of CXCL10 time-dependently decreased electroacupuncture-induced antinociception and the number of infiltrating opioid peptide-expressing CXCR3⁺ macrophages. In summary, we describe a novel function of the chemokine CXCL10 - as a regulator for an increase of opioid-containing macrophages and antinociceptive mediator in inflammatory pain and as a key chemokine regulated by electroacupuncture.

Electroacupuncture reduces hyperalgesia after injections of acidic saline in rats

Background. Injections of acidic saline into the gastrocnemius muscle in rats produce a bilateral long-lasting hyperalgesia similar to fibromyalgia in humans. No previous study investigated the effect of electroacupuncture (EA) on this acidic saline model. This study aimed to identify the effects of EA in the hyperalgesia produced by repeated intramuscular injections of acidic saline. Methods. Rats were divided into four groups (n = 6, each group): control, acupuncture, EA 15 Hz, and 100 Hz. Left gastrocnemius muscle was injected with 100 μL of pH 4.0 sterile saline twice five days apart. EA, acupuncture, or control therapy was daily administered (20 min) for 5 consecutive days under anesthesia. Needles were placed in the St36 and Sp6 acupoints. The assessment of secondary mechanical hyperalgesia, thermal hyperalgesia, and motor performance was performed before injections and before and after the treatment performed on each day. The paw withdrawal threshold was tested using the nonparametric Kruskal-Wallis test and differences within the group Wilcoxon Matched Pairs. The latency and motor performance were tested for ANOVA parametric test for independent measures, and for differences in the group, we used t-test for paired samples. Post hoc Tukey test was used for multiple corrections. P values less than 0.05 were considered statistically significant. Results. Indicate that there was a significant reduction of mechanical withdrawal threshold and paw withdrawal latency 24 hours following the second injection. Moreover, mechanical and thermal hyperalgesia were significantly reversed by EA 15, 100 Hz, and acupuncture. Conclusions. The results suggest that EA high and low frequency as well as acupuncture are effective in reducing hyperalgesia in chronic muscle pain model.

Mechanisms of acupuncture-electroacupuncture on persistent pain

In the last decade, preclinical investigations of electroacupuncture mechanisms on persistent tissue injury (inflammatory), nerve injury (neuropathic), cancer, and visceral pain have increased. These studies show that electroacupuncture activates the nervous system differently in health than in pain conditions, alleviates both sensory and affective inflammatory pain, and inhibits inflammatory and neuropathic pain more effectively at 2 to 10 Hz than at 100 Hz. Electroacupuncture blocks pain by activating a variety of bioactive chemicals through peripheral, spinal, and supraspinal mechanisms. These include opioids, which desensitize peripheral nociceptors and reduce proinflammatory cytokines peripherally and in the spinal cord, and serotonin and norepinephrine, which decrease spinal N-methyl-D-aspartate receptor subunit GluN1 phosphorylation. Additional studies suggest that electroacupuncture, when combined with low dosages of conventional analgesics, provides effective pain management which can forestall the side effects of often-debilitating pharmaceuticals.

Polycystic ovary syndrome: effect and mechanisms of acupuncture for ovulation induction

Polycystic ovary syndrome (PCOS), the most common endocrine disorder among women of reproductive age, is characterized by the coexistence of hyperandrogenism, ovulatory dysfunction, and polycystic ovaries (PCO). PCOS also represents the largest part of female oligoovulatory infertility, and the management of ovulatory and menstrual dysfunction, comprises a third of the high costs of PCOS treatment. Current pharmacological and surgical treatments for reproductive symptoms are effective, however, associated with negative side effects, such as cardiovascular complications and multiple pregnancies. For menstrual irregularities and ovulation induction in women with PCOS, acupuncture has indicated beneficial effects. This review will focus on the results from randomized controlled acupuncture trials for regulation of menstrual dysfunction and for inducing ovulation in women with PCOS although there are uncontrolled trials with nonetheless interesting results. Animal experimental studies will be further discussed when they can provide a more mechanistic explanatory view.

Understanding central mechanisms of acupuncture analgesia using dynamic quantitative sensory testing: a review

We discuss the emerging translational tools for the study of acupuncture analgesia with a focus on psychophysical methods. The gap between animal mechanistic studies and human clinical trials of acupuncture analgesia calls for effective translational tools that bridge neurophysiological data with meaningful clinical outcomes. Temporal summation (TS) and conditioned pain modulation (CPM) are two promising tools yet to be widely utilized. These psychophysical measures capture the state of the ascending facilitation and the descending inhibition of nociceptive transmission, respectively. We review the basic concepts and current methodologies underlying these measures in clinical pain research, and illustrate their application to research on acupuncture analgesia. Finally, we highlight the strengths and limitations of these research methods and make recommendations on future directions. The appropriate addition of TS and CPM to our current research armamentarium will facilitate our efforts to elucidate the central analgesic mechanisms of acupuncture in clinical populations.

Long-term antinociception by electroacupuncture is mediated via peripheral opioid receptors in free-moving rats with inflammatory hyperalgesia

BACKGROUND

Electroacupuncture (EA) has been widely accepted and applied as an important acupuncture-related technique for acupuncture analgesia (AA) research. The involvement of opioid peptides and receptors in acute AA has been shown via pre-EA application of opioid receptor/peptide antagonists. In this study, we intended to reproducibly institute acupoint position and needling excluding influences from anaesthesia or restrainers on rats with complete Freund's adjuvant (CFA) hind paw inflammatory pain, as well as to explore opioid-dependency and anti-inflammatory effects in sustained acupuncture analgesia.

METHODS

Accurate position and needling approach on acupoint GB30 was modelled by computer-based three-dimensional (3D) images and followed by an optimal EA treatment protocol (100 Hz, 2-3 mA, 20 min) at 0 and 24 h post-CFA in conscious free-moving rats. Opioid receptor antagonists, naloxone (NLX) and naltrindole (NTI) were applied intraplantarly post-EA at late phase (96 h) of CFA. Nociceptive thresholds were assessed by paw pressure threshold (Randall-Sellito) or paw withdrawal latency (Hargreaves), and anti-inflammatory effects were evaluated by measurement of plantar temperature and paw volume.

RESULTS

EA elicited significant sustained mechanical and thermal antinociception up to 144 h. Mechanical antinociception of EA was suppressed by peripheral intraplantar application of NLX and NTI. EA also reduced paw temperature and volume during the same time frame indicating anti-inflammatory effects.

CONCLUSIONS

By employing a reproducible EA treatment model on GB30 in free-moving rats, we demonstrated the involvement of peripheral opioid receptors mediated EA-induced long-term antinociception. Future studies should examine the specific neuroimmunological connection of EA-induced sustained antinociception in inflammation.

Differential effects of subcutaneous electrical stimulation (SQS) and transcutaneous electrical nerve stimulation (TENS) in rodent models of chronic neuropathic or inflammatory pain

OBJECTIVES

Electrical stimulation has been used for many years for the treatment of pain. Present-day research demonstrates that stimulation targets and parameters impact the induction of specific pain-modulating mechanisms. New targets are increasingly being investigated clinically, but the scientific rationale for a particular target is often not well established. This present study compares the behavioral effects of targeting peripheral axons by electrode placement in the subcutaneous space vs. electrode placement on the surface of the skin in a rodent model.

MATERIALS AND METHODS

Rodent models of inflammatory and neuropathic pain were used to investigate subcutaneous electrical stimulation (SQS) vs. transcutaneous electrical nerve stimulation (TENS). Electrical parameters and relative location of the leads were held constant under each condition.

RESULTS

SQS had cumulative antihypersensitivity effects in both inflammatory and neuropathic pain rodent models, with significant inhibition of mechanical hypersensitivity observed on days 3-4 of treatment. In contrast, reduction of thermal hyperalgesia in the inflammatory model was observed during the first four days of treatment with SQS, and reduction of cold allodynia in the neuropathic pain model was seen only on the first day with SQS. TENS was effective in the inflammation model, and in agreement with previous studies, tolerance developed to the antihypersensitivity effects of TENS. With the exception of a reversal of cold hypersensitivity on day 1 of testing, TENS did not reveal significant analgesic effects in the neuropathic pain rodent model.

CONCLUSIONS

The results presented show that TENS and SQS have different effects that could point to unique biologic mechanisms underlying the analgesic effect of each therapy. Furthermore, this study is the first to demonstrate in an animal model that SQS attenuates neuropathic and inflammatory-induced pain behaviors.

Electroacupuncture alleviates stress-induced visceral hypersensitivity through an opioid system in rats

AIM: To investigate whether stress-induced visceral hypersensitivity could be alleviated by electroacupuncture (EA) and whether EA effect was mediated by endogenous opiates.

METHODS: Six to nine week-old male Sprague-Dawley rats were used in this study. Visceral hypersensitivity was induced by a 9-d heterotypic intermittent stress (HIS) protocol composed of 3 randomly stressors, which included cold restraint stress at 4 °C for 45 min, water avoidance stress for 60 min, and forced swimming stress for 20 min, in adult male rats. The extent of visceral hypersensitivity was quantified by electromyography or by abdominal withdrawal reflex (AWR) scores of colorectal distension at different distention pressures (20 mmHg, 40 mmHg, 60 mmHg and 80 mmHg). AWR scores either 0, 1, 2, 3 or 4 were obtained by a blinded observer. EA or sham EA was performed at classical acupoint ST-36 (Zu-San-Li) or BL-43 (Gao-Huang) in both hindlimbs of rats for 30 min. Naloxone (NLX) or NLX methiodide (m-NLX) was administered intraperitoneally to HIS rats in some experiments.

RESULTS: HIS rats displayed an increased sensitivity to colorectal distention, which started from 6 h (the first measurement), maintained for 24 h, and AWR scores returned to basal levels at 48 h and 7 d after HIS compared to pre-HIS baseline at different distention pressures. The AWR scores before HIS were 0.6 ± 0.2, 1.3 ± 0.2, 1.9 ± 0.2 and 2.3 ± 0.2 for 20 mmHg, 40 mmHg, 60 mmHg and 80 mmHg distention pressures, respectively. Six hours after termination of the last stressor, the AWR scores were 2.0 ± 0.1, 2.5 ± 0.1, 2.8 ± 0.2 and 3.5 ± 0.2 for 20 mmHg, 40 mmHg, 60 mmHg and 80 mmHg distention pressures, respectively. EA given at classical acupoint ST-36 in both hindlimbs for 30 min significantly attenuated the hypersensitive responses to colorectal distention in HIS rats compared with sham EA treatment [AWRs at 20 mmHg: 2.0 ± 0.2 vs 0.7 ± 0.1, P = 4.23 711 E-4; AWRs at 40 mmHg: 2.6 ± 0.2 vs 1.5 ± 0.2, P = 0.00 163; AWRs at 60 mmHg: 3.1 ± 0.2 vs 1.9 ± 0.1, P = 0.003; AWRs at 80 mmHg: 3.6 ± 0.1 vs 2.4 ± 0.2, P = 0.0023; electromyographic (EMG) at 20 mmHg: 24 ± 4.7 vs 13.8 ± 3.5; EMG at 40 mmHg: 60.2 ± 6.6 vs 30 ± 4.9, P = 0.00 523; EMG at 60 mmHg: 83 ± 10 vs 39.8 ± 5.9, P = 0.00 029; EMG at 80 mmHg: 94.3 ± 10.8 vs 49.6 ± 5.9, P = 0.00 021]. In addition, EA at the acupuncture point BL-43 with same parameters did not alleviate visceral hypersensitivity in HIS rats. EA in healthy rats also did not have any effect on AWR scores to colorectal distention at distention pressures of 20 and 40 mmHg. The EA-mediated analgesic effect was blocked by pretreatment with NLX in HIS rats [AWR scores pretreated with NLX vs normal saline (NS) were 2.0 vs 0.70 ± 0.20, 2.80 ± 0.12 vs 1.50 ± 0.27, 3 vs 2.00 ± 0.15 and 3.60 ± 0.18 vs 2.60 ± 0.18 for 20 mmHg, 40 mmHg, 60 mmHg and 80 mmHg; P = 0.0087, 0.0104, 0.0117 and 0.0188 for 20, 40, 60 and 80 mmHg, respectively]. Furthermore, EA-mediated analgesic effect was completely reversed by administration of m-NLX, a peripherally restricted opioid antagonist (EMG pretreated with m-NLX vs NS were 30.84 ± 4.39 vs 13.33 ± 3.88, 74.16 ± 9.04 vs 36.28 ± 8.01, 96.45 ± 11.80 vs 50.19 ± 8.28, and 111.59 ± 13.79 vs 56.42 ± 8.43 for 20 mmHg, 40 mmHg, 60 mmHg and 80 mmHg; P = 0.05 026, 0.00 034, 0.00 005, 0.000 007 for 20 mmHg, 40 mmHg, 60 mmHg and 80 mmHg, respectively).

CONCLUSION: EA given at classical acupoint ST-36 alleviates stress-induced visceral pain, which is most likely mediated by opioid pathways in the periphery.

Neural acupuncture unit: a new concept for interpreting effects and mechanisms of acupuncture

When an acupuncture needle is inserted into a designated point on the body and mechanical or electrical stimulation is delivered, various neural and neuroactive components are activated. The collection of the activated neural and neuroactive components distributed in the skin, muscle, and connective tissues surrounding the inserted needle is defined as a neural acupuncture unit (NAU). The traditionally defined acupoints represent an anatomical landmark system that indicates local sites where NAUs may contain relatively dense and concentrated neural and neuroactive components, upon which acupuncture stimulation would elicit a more efficient therapeutic response. The NAU-based local mechanisms of biochemical and biophysical reactions play an important role in acupuncture-induced analgesia. Different properties of NAUs are associated with different components of needling sensation. There exist several central pathways to convey NAU-induced acupuncture signals, Electroacupuncture (EA) frequency-specific neurochemical effects are related to different peripheral and central pathways transmitting afferent signals from different frequency of NAU stimulation. More widespread and intense neuroimaging responses of brain regions to acupuncture may be a consequence of more efficient NAU stimulation modes. The introduction of the conception of NAU provides a new theoretical approach to interpreting effects and mechanisms of acupuncture in modern biomedical knowledge framework.

Electroacupuncture in reduction of discomfort associated with barostat-induced rectal distension--a randomized controlled study

BACKGROUND

This pilot study aims to explore the effectiveness of electroacupuncture in reduction of colorectal discomfort caused by Barostat-induced rectal distension.

METHOD

Subjects scheduled for a colonoscopy screening procedure were recruited and randomized to receive either electroacupuncture (EA) or sham acupuncture (SA) (short stud instead of needle) for 45 min to acupuncture points Hegu (LI4), Neiguan (PC6), and Zusanli (ST36). A balloon catheter attached to the Dual Drive Barostat machine was then inserted into the subjects' rectal region. Colorectal discomfort after each incremental pressure (4 mmHg) rise was assessed by visual analog and a four-point subjective discomfort scale. Blood beta-endorphin level was measured before, immediately after acupuncture, at 24 mmHg, and at maximal tolerable inflation pressure.

RESULTS

Forty subjects completed the study. Rectal discomfort was reported at a higher inflation pressure in the EA group compared to the SA group (p < 0.05). Twelve subjects in the EA group were able to tolerate the maximal inflation pressure (48 mmHg) compared to only four in the SA group. Beta-endorphin levels increased significantly in the EA group but not in the SA group.

CONCLUSION

Electroacupuncture appeared to be effective in reduction of colorectal discomfort during Barostat-induced rectal distension. The role of electroacupuncture during colonoscopy warrants further investigation.

Involvement of peripheral opioid receptors in electroacupuncture analgesia for carrageenan-induced hyperalgesia

Acupuncture is widely used to relieve pain; however, the mechanism underlying electroacupuncture analgesia (EAA) during inflammatory pain is unclear. We investigated whether endogenous peripheral opioid receptors participated in EAA during hyperalgesia elicited by carrageenan-induced inflammation. Moreover, we investigated which subtype of opioid receptor was involved in EAA. Carrageenan was subcutaneously administered by intraplanter (i.pl.) injection into the left hind paw. Nociceptive thresholds were measured using the paw pressure threshold (PPT). Rats received 3Hz electroacupuncture (EA) for 1h after carrageenan injection. The nonselective peripheral opioid receptor antagonist, naloxone methiodide, was administered by i.pl. injection of the inflamed paw 5min before EA. Also, animals received i.pl. or intravenous (i.v.) injection of selective antagonists against μ(D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-ThrNH2, CTOP), δ(naltrindole, NTI), or κ (nor-Binaltorphimine, nor-BNI) opioid receptors 1h before EA. PPT decreased significantly 3h after carrageenan injection. EA resulted in significant increases of PPT, moreover, PPT elevations persisted for 9h after carrageenan injection. PPT elevations produced by EA were antagonized by local i.pl. injection of naloxone methiodide at 3 and 5h after cessation of EA. NTI, nor-BNI and CTOP blocked EAA from immediately, 1h, and 3h after EA cessation, respectively. The EAA in the inflamed paw could not be blocked by i.v. injection of NTI, nor-BNI and CTOP. These findings suggest that peripheral μ, δ and κ receptors on peripheral nerve terminals are activated by EA, although there is a time difference among these activations.

Acupuncture analgesia for temporal summation of experimental pain: a randomised controlled study

BACKGROUND

Temporal summation of pain, a phenomenon of the central nervous system (CNS), represents enhanced painful sensation or reduced pain threshold upon repeated stimulation. This pain model has been used to evaluate the analgesic effect of various medications on the CNS.

AIMS

The present study aimed to evaluate the effects and characteristics of analgesia induced by electroacupuncture (EA), manual acupuncture (MA) and non-invasive sham-acupuncture (SA) in healthy humans on temporal summation of pain.

METHODS

Thirsty-six pain-free volunteers were randomised into one of the three groups EA (2/100 Hz), MA or SA. Acupuncture intervention was on ST36 and ST40 on the dominant leg delivered by an acupuncturist blinded to the outcome assessment. Both subjects and the evaluator were blinded to the treatment allocation. Pain thresholds to a single pulse (single pain threshold, SPT) and repeated pulses electrical stimulation (temporal summation thresholds, TST) were measured before, 30 min after and 24h after each treatment.

RESULTS

The baseline values of three groups were comparable. Compared to SA, EA significantly increased both SPT and TST immediately after the treatment on the treatment leg as well as 24h after on both the treatment and non-treatment legs (ANOVA, p<0.05). MA also increased SPT and TST, but the changes were not significantly different from those induced by SA.

CONCLUSION

EA induces bilateral, segmentally distributed and prolong analgesia on both SPT and TST, indicating a non-centrally specific effect. This effect needs to be verified with heat or mechanical model and in pain patients.

Neural mechanism underlying acupuncture analgesia

Acupuncture has been accepted to effectively treat chronic pain by inserting needles into the specific "acupuncture points" (acupoints) on the patient's body. During the last decades, our understanding of how the brain processes acupuncture analgesia has undergone considerable development. Acupuncture analgesia is manifested only when the intricate feeling (soreness, numbness, heaviness and distension) of acupuncture in patients occurs following acupuncture manipulation. Manual acupuncture (MA) is the insertion of an acupuncture needle into acupoint followed by the twisting of the needle up and down by hand. In MA, all types of afferent fibers (Abeta, Adelta and C) are activated. In electrical acupuncture (EA), a stimulating current via the inserted needle is delivered to acupoints. Electrical current intense enough to excite Abeta- and part of Adelta-fibers can induce an analgesic effect. Acupuncture signals ascend mainly through the spinal ventrolateral funiculus to the brain. Many brain nuclei composing a complicated network are involved in processing acupuncture analgesia, including the nucleus raphe magnus (NRM), periaqueductal grey (PAG), locus coeruleus, arcuate nucleus (Arc), preoptic area, nucleus submedius, habenular nucleus, accumbens nucleus, caudate nucleus, septal area, amygdale, etc. Acupuncture analgesia is essentially a manifestation of integrative processes at different levels in the CNS between afferent impulses from pain regions and impulses from acupoints. In the last decade, profound studies on neural mechanisms underlying acupuncture analgesia predominately focus on cellular and molecular substrate and functional brain imaging and have developed rapidly. Diverse signal molecules contribute to mediating acupuncture analgesia, such as opioid peptides (mu-, delta- and kappa-receptors), glutamate (NMDA and AMPA/KA receptors), 5-hydroxytryptamine, and cholecystokinin octapeptide. Among these, the opioid peptides and their receptors in Arc-PAG-NRM-spinal dorsal horn pathway play a pivotal role in mediating acupuncture analgesia. The release of opioid peptides evoked by electroacupuncture is frequency-dependent. EA at 2 and 100Hz produces release of enkephalin and dynorphin in the spinal cord, respectively. CCK-8 antagonizes acupuncture analgesia. The individual differences of acupuncture analgesia are associated with inherited genetic factors and the density of CCK receptors. The brain regions associated with acupuncture analgesia identified in animal experiments were confirmed and further explored in the human brain by means of functional imaging. EA analgesia is likely associated with its counter-regulation to spinal glial activation. PTX-sesntive Gi/o protein- and MAP kinase-mediated signal pathways as well as the downstream events NF-kappaB, c-fos and c-jun play important roles in EA analgesia.

Acupuncture for symptom management of rheumatoid arthritis: a pilot study

We investigated the feasibility of a future acupuncture trial in the symptom management of rheumatoid arthritis (RA). Twenty-five patients meeting the American College of Rheumatology (ACR) criteria were recruited and given 14 sessions of individualised acupuncture treatment for 6 weeks. Improvement in symptoms was assessed using ACR 20, 50 and 70; disease activity score (DAS28); tender joint count; swollen joint count; morning stiffness and health-related quality of life using the Korean Health Assessment Questionnaire and the SF-36 at baseline and after 6 weeks. Erythrocyte sedimentation rate (ESR) was also assessed. At 6 weeks, 44%, 20%, and 12% of patients achieved ACR 20, 50 and 70 responses, respectively. Acupuncture also produced statistically significant improvements in DAS28, pain and global activity, swollen joint count, health-related quality of life (SF-36) and ESR. No major acupuncture-related adverse events were reported. Acupuncture treatment as used in this pilot study was safe and well-tolerated. The use of acupuncture for symptom management in RA warrants further investigation.

EFNS guidelines on neurostimulation therapy for neuropathic pain

Pharmacological relief of neuropathic pain is often insufficient. Electrical neurostimulation is efficacious in chronic neuropathic pain and other neurological diseases. European Federation of Neurological Societies (EFNS) launched a Task Force to evaluate the evidence for these techniques and to produce relevant recommendations. We searched the literature from 1968 to 2006, looking for neurostimulation in neuropathic pain conditions, and classified the trials according to the EFNS scheme of evidence for therapeutic interventions. Spinal cord stimulation (SCS) is efficacious in failed back surgery syndrome (FBSS) and complex regional pain syndrome (CRPS) type I (level B recommendation). High-frequency transcutaneous electrical nerve stimulation (TENS) may be better than placebo (level C) although worse than electro-acupuncture (level B). One kind of repetitive transcranial magnetic stimulation (rTMS) has transient efficacy in central and peripheral neuropathic pains (level B). Motor cortex stimulation (MCS) is efficacious in central post-stroke and facial pain (level C). Deep brain stimulation (DBS) should only be performed in experienced centres. Evidence for implanted peripheral stimulations is inadequate. TENS and r-TMS are non-invasive and suitable as preliminary or add-on therapies. Further controlled trials are warranted for SCS in conditions other than failed back surgery syndrome and CRPS and for MCS and DBS in general. These chronically implanted techniques provide satisfactory pain relief in many patients, including those resistant to medication or other means.

The effect of physical therapy on beta-endorphin levels

Beta-endorphin (betaE) is an important reliever of pain. Various stressors and certain modalities of physiotherapy are potent inducers of the release of endogenous betaE to the blood stream. Most forms of exercise also increase blood betaE level, especially when exercise intensity involves reaching the anaerobic threshold and is associated with the elevation of serum lactate level. Age, gender, and mental activity during exercise also may influence betaE levels. Publications on the potential stimulating effect of manual therapy and massage on betaE release are controversial. Sauna, mud bath, and thermal water increase betaE levels through conveying heat to the tissues. The majority of the techniques for electrical stimulation have a similar effect, which is exerted both centrally and--to a lesser extent--peripherally. However, the parameters of electrotherapy have not yet been standardised. The efficacy of analgesia and the improvement of general well-being do not necessarily correlate with betaE level. Although in addition to blood, increased brain and cerebrospinal fluid betaE levels are also associated with pain, the majority of studies have concerned blood betaE levels. In general, various modalities of physical therapy might influence endorphin levels in the serum or in the cerebrospinal fluid--this is usually manifested by elevation with potential mitigation of pain. However, a causal relationship between the elevation of blood, cerebrospinal fluid or brain betaE levels and the onset of the analgesic action cannot be demonstrated with certainty.

Acupuncture stimulation to the sacral segment affects state of vigilance in rats

The effects of acupuncture stimulation to the sacral segment on electroencephalograms (EEGs) and activity of locus coeruleus (LC) neurons were examined in urethane-anesthetized rats. In 71 of 112 trials, when EEGs displayed small amplitude and high frequency, stimulation to the sacral segment-induced large amplitude and slow EEGs with a latency of <450s and duration ranged from 32s to >42 min. Stimulus-induced EEGs comprised significant increases in delta power and significant decreases in theta and beta powers. After intraperitoneal administration of bicuculline, stimulation to the sacral segment failed to induce changes in EEG pattern. Firing rate of noradrenergic LC neurons decreased significantly from 2.9+/-1.5 to 1.1+/-0.8 Hz (n=11, p<0.001). Decreased neuronal activity exhibited close relationships with increased EEG amplitude. These results suggest that acupuncture stimulation to the sacral segment changes the state of animals from light anesthesia to deep anesthesia, and that this change is mediated by GABAergic systems suppressing the activity of noradrenergic LC neurons.