Cholecystokinin receptors mediate tolerance to the analgesic effect of TENS in arthritic rats

A Co-MOF encapsulated microneedle patch activates hypoxia induction factor-1 to pre-protect transplanted flaps from distal ischemic necrosis

Avoiding ischemic necrosis after flap transplantation remains a significant clinical challenge. Developing an effective pretreatment method to promote flap survival postoperatively is crucial. Cobalt chloride (CoCl2) can increase cell tolerance to ischemia and hypoxia condition by stimulating hypoxia-inducible factor-1 (HIF-1) expression. However, the considerable toxic effects severely limit the clinical application of CoCl2. In this study, cobalt-based metal-organic frameworks (Co-MOF) encapsulated in a microneedle patch (Co-MOF@MN) was developed to facilitate the transdermal sustained release of Co2+ for rapid, minimally invasive rapid pretreatment of flap transplantation. The MN patch was composed of a fully methanol-based two-component cross-linked polymer formula, with a pyramid structure and high mechanical strength, which satisfied the purpose of penetrating the skin stratum corneum of rat back to achieve subcutaneous vascular area administration. Benefiting from the water-triggered disintegration of Co-MOF and the transdermal delivery via the MN patch, preoperative damage and side effects were effectively mitigated. Moreover, in both the oxygen-glucose deprivation/recovery (OGD/R) cell model and the rat dorsal perforator flap model, Co-MOF@MN activated the HIF-1α pathway and its associated downstream proteins, which reduced reperfusion oxidative damage, improved blood supply in choke areas, and increased flap survival rates post-transplantation. This preprotection strategy, combining MOF nanoparticles and the MN patch, meets the clinical demands for trauma minimization and uniform administration in flap transplantation. STATEMENT OF SIGNIFICANCE: Cobalt chloride (CoCl2) can stimulate the expression of hypoxia-inducible factor (HIF-1) and improve the tolerance of cells to ischemia and hypoxia conditions. However, the toxicity and narrow therapeutic window of CoCl2 severely limit its clinical application. Herein, we explored the role of Co-MOF as a biocompatible nanocage for sustained release of Co2+, showing the protective effect on vascular endothelial cells in the stress model of oxygen-glucose deprivation. To fit the clinical needs of minimal trauma in flap transplantation, a Co-MOF@MN system was developed to achieve local transdermal delivery at the choke area, significantly improving blood supply opening and flap survival rate. This strategy of two-step delivery of Co2+ realized the enhancement of biological functions while ensuring the biosafety.

Wireless Transcutaneous Electrical Nerve Stimulation (TENS) for Chronic Chemotherapy-Induced Peripheral Neuropathy (CIPN): A Proof-of-Concept Randomized Clinical Trial

Chemotherapy-induced peripheral neuropathy (CIPN) affects approximately 30 to 60% of people who receive neurotoxic chemotherapy. CIPN is associated with impaired quality of life and function and has few effective treatments. This 6-site, subject and assessor-blinded randomized clinical trial (RCT) was designed to assess 1) preliminary efficacy (ie, alpha pre-specified at .2) of a wearable, app-controlled, transcutaneous electrical nerve stimulation (TENS) device for chronic CIPN and 2) feasibility of conducting a confirmatory trial within the National Cancer Institute Community Oncology Research Program (NCORP) (NCT04367480). The primary outcome was the EORTC-CIPN20. The main secondary outcomes were individual symptoms assessed daily (via 0-10 numeric rating scales). The primary analysis was an analysis of covariance (outcome: EORTC-CIPN20, fixed effect: arm, covariates: baseline EORTC-CIPN20 and site). Secondary analyses used a similar analysis of covariance models (excluding site) for each symptom on subgroups of subjects with ≥4 out of 10 for that symptom at baseline. 142 eligible subjects were randomized and received a device; 130 (91%) completed the study. The difference between groups in the EORCT-CIPN20 at the endpoint (placebo-active) was 1.05 (95% Confidence Interval: -.56, 2.67; P = .199). The difference between groups for the individual symptoms was as follows: hot/burning pain: 1.37 (-.33, 3.08; P = .112), sharp/shooting pain: 1.21 (-.37, 2.79; P = .128), cramping: 1.35 (-.32, 3.02; P = .110), tingling: .23 (-.61, 1.08; P = .587), numbness: .27 (-.51, 1.05; P = .492). An RCT of an app-controlled TENS device for chronic CIPN with excellent retention is feasible in the NCORP. Preliminary efficacy evidence suggests that TENS is promising for pain and cramping from CIPN. A confirmatory RCT of TENS for painful CIPN is highly warranted. PERSPECTIVE: Daily, home-based TENS therapy demonstrates promising efficacy for painful CIPN symptoms in this proof-of-concept randomized clinical trial. Future confirmatory trial is warranted.

Transcutaneous Electric Nerve Stimulation in Animal Model Studies: From Neural Mechanisms to Biological Effects for Analgesia

OBJECTIVE

This systematic and meta-analysis review evaluated the transcutaneous electrical nerve stimulation (TENS)-induced action mechanisms for animal analgesia.

MATERIALS AND METHODS

Two independent investigators identified relevant articles published until February 2021 through a literature review, and a random-effects meta-analysis was performed to synthesize the results.

RESULTS

Of the 6984 studies found in the data base search, 53 full-text articles were selected and used in the systematic review. Most studies used Sprague Dawley rats (66.03%). High-frequency TENS was applied to at least one group in 47 studies, and most applications were performed for 20 minutes (64.15%). Mechanical hyperalgesia was analyzed as the primary outcome in 52.83% of the studies and thermal hyperalgesia in 23.07% of studies using a heated surface. More than 50% of the studies showed a low risk of bias on allocation concealment, random housing, selective outcome reporting, and acclimatization before the behavioral tests. Blinding was not performed in only one study and random outcome assessment in another study; acclimatization before the behavioral tests was not performed in just one study. Many studies had an uncertain risk of bias. Meta-analyses indicated no difference between low-frequency and high-frequency TENS with variations among the pain models.

CONCLUSIONS

This systematic review and meta-analysis suggests that TENS has presented a substantial scientific foundation for its hypoalgesic effect in preclinical studies for analgesia.

Physiotherapeutic Strategies and Their Current Evidence for Canine Osteoarthritis

Osteoarthritis (OA) is a common and debilitating condition in domestic dogs. Alongside pharmaceutical interventions and weight loss, exercise and physiotherapy (PT) are important measures in maintaining patient mobility and quality of life. Physiotherapy for OA aims to reduce pain, optimize muscular function and maintain joint function. Physiotherapeutic plans typically include PT exercises combined with therapeutic modalities, lifestyle and environmental modifications to improve the patient's overall quality of life and function. Information on therapeutic clinical efficacy of physiotherapeutic measures for canine OA is still very limited. Thus, physiotherapeutic strategies are still primarily based on evidence extrapolated from human protocols tailored to people with OA. The authors propose a simple systematic PT approach for canine OA, prioritizing measures according to simplicity, cost effectiveness and practicality. This guide (the "Physiotherapy Pyramid") aims to provide a clear stratified approach to simplify decision making and planning for owners, veterinarians and veterinary physiotherapists, leading to more straightforward design and implementation of treatment plans. Measures are implemented starting at the base of the pyramid, subsequently progressing to the top, allowing effective and practical interventions to be prioritized. The levels of the pyramid are in ascending order: environmental modification, exercise plan, OA-specific home exercises and treatment by a veterinary physiotherapist.

Effects of transcutaneous electrical nerve stimulation (TENS) in people with knee osteoarthritis: A systematic review and meta-analysis

OBJECTIVE

To evaluate the effects of Transcutaneous Electric Nerve Stimulation (TENS) on pain, function, walking ability and stiffness in people with Knee osteoarthritis (KOA).

DESIGN

Systematic review and meta-analysis of randomized controlled trials.

METHODS

We searched MEDLINE, EMBASE, PubMed, Cochrane Central Register of Controlled Trials, Physiotherapy Evidence Database (PEDro), clinicaltrials.gov and Web of Science (last search November 2021) for randomized controlled trials. The Cochrane Risk of Bias Tool was used for the included studies, and Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) was used to interpret the certainty of results. Standardized Mean Differences (SMDs) and 95% confidence interval (CI) were calculated for meta-analysis.

RESULTS

Twenty-nine studies were found (1398 people, age range 54-85, 74% are female) and fourteen were included in this review. Intervention duration was divided as short term (immediately after intervention), medium term (<four weeks) and long term (≥ four weeks). Active TENS showed greater improvement in Visual Analogue Scale (VAS) than sham TENS.Combining TENS with other interventions produced superior outcomes compared with other interventions for VAS in all the terms. In the meanwhile, TENS combined with other interventions was superior to other interventions for the pain subgroup of Western Ontario and McMaster Universities Arthritis Index in the medium term and long term. TENS combined with other interventions was superior to other interventions for function in the medium term and long term.

CONCLUSION

TENS could significantly relieve pain, decrease dysfunction and improve walking ability in people with KOA, but it is not effective for stiffness.

Resolving Long-Standing Uncertainty about the Clinical Efficacy of Transcutaneous Electrical Nerve Stimulation (TENS) to Relieve Pain: A Comprehensive Review of Factors Influencing Outcome

Pain is managed using a biopsychosocial approach and pharmacological and non-pharmacological treatments. Transcutaneous electrical nerve stimulation (TENS) is a technique whereby pulsed electrical currents are administered through the intact surface of the skin with the intention of alleviating pain, akin to 'electrically rubbing pain away'. Despite over 50 years of published research, uncertainty about the clinical efficacy of TENS remains. The purpose of this comprehensive review is to critically appraise clinical research on TENS to inform future strategies to resolve the 'efficacy-impasse'. The principles and practices of TENS are described to provide context for readers unfamiliar with TENS treatment. The findings of systematic reviews evaluating TENS are described from a historical perspective to provide context for a critical evaluation of factors influencing the outcomes of randomized controlled trials (RCTs); including sample populations, outcome measures, TENS techniques, and comparator interventions. Three possibilities are offered to resolve the impasse. Firstly, to conduct large multi-centered RCTs using an enriched enrolment with randomized withdrawal design, that incorporates a 'run-in phase' to screen for potential TENS responders and to optimise TENS treatment according to individual need. Secondly, to meta-analyze published RCT data, irrespective of type of pain, to determine whether TENS reduces the intensity of pain during stimulation, and to include a detailed assessment of levels of certainty and precision. Thirdly, to concede that it may be impossible to determine efficacy due to insurmountable methodological, logistical and financial challenges. The consequences to clinicians, policy makers and funders of this third scenario are discussed. I argue that patients will continue to use TENS irrespective of the views of clinicians, policy makers, funders or guideline panel recommendations, because TENS is readily available without prescription; TENS generates a pleasant sensory experience that is similar to easing pain using warming and cooling techniques; and technological developments such as smart wearable TENS devices will improve usability in the future. Thus, research is needed on how best to integrate TENS into existing pain management strategies by analyzing data of TENS usage by expert-patients in real-world settings.

Efficacy of transcutaneous electrical acupoint stimulation combined with general anesthesia for sedation and postoperative analgesia in minimally invasive lung cancer surgery: A randomized, double-blind, placebo-controlled trial

Background

Multimodal opioid‐sparing analgesia is a key component of an enhanced recovery pathway after surgery that aims to improve postoperative recovery. Transcutaneous electrical acupoint stimulation (TEAS) is assumed to alleviate pain and anxiety and to modify the autonomic nervous system. This study aimed to determine the efficacy of TEAS for sedation and postoperative analgesia in lung cancer patients undergoing thoracoscopic pulmonary resection.

Methods

A total of 80 patients were randomized into two groups: the TEAS group and the sham TEAS combined with general anesthesia group. Postoperative pain levels at six, 24, 48 hours, and one month after surgery were measured using the visual analogue scale (VAS). Bispectral index (BIS) score during the TEAS prior to anesthetic induction, Observer's Assessment of Alertness/Sedation (OAAS) score, sufentanil consumption during postoperative patient‐controlled intravenous analgesia (PCIA), number of total and effective attempts of PCIA pump use, and incidence of postoperative nausea and vomiting were recorded and analyzed statistically.

Results

Patients in the TEAS group had significantly lower VAS scores at six, 24, and 48 hours after surgery (P < 0.01); lower BIS scores at 10, 20, and 30 minutes before induction (P < 0.01); lower levels of postoperative sufentanil consumption; lower number of PCIA attempts and effective rates (P < 0.01); lower incidences of nausea at 0, six, 24, and 48 hours; and lower incidence of vomiting at 24 hours after surgery (P < 0.05). The postoperative OAAS scores were similar between the groups.

Conclusions

TEAS could be a feasible approach for sedation and postoperative analgesia in thoracoscopic pulmonary resection.

Expression of cholecystokinin by neurons in mouse spinal dorsal horn

Excitatory interneurons account for the majority of dorsal horn neurons, and are required for perception of normal and pathological pain. We have identified largely non-overlapping populations in laminae I-III, based on expression of substance P, gastrin-releasing peptide, neurokinin B, and neurotensin. Cholecystokinin (CCK) is expressed by many dorsal horn neurons, particularly in the deeper laminae. Here, we have used immunocytochemistry and in situ hybridization to characterize the CCK cells. We show that they account for ~7% of excitatory neurons in laminae I-II, but between a third and a quarter of those in lamina III. They are largely separate from the neurokinin B, neurotensin, and gastrin-releasing peptide populations, but show limited overlap with the substance P cells. Laminae II-III neurons with protein kinase Cγ (PKCγ) have been implicated in mechanical allodynia following nerve injury, and we found that around 50% of CCK cells were PKCγ-immunoreactive. Neurotensin is also expressed by PKCγ cells, and among neurons with moderate to high levels of PKCγ, ~85% expressed CCK or neurotensin. A recent transcriptomic study identified mRNA for thyrotropin-releasing hormone in a specific subpopulation of CCK neurons, and we show that these account for half of the CCK/PKCγ cells. These findings indicate that the CCK cells are distinct from other excitatory interneuron populations that we have defined. They also show that PKCγ cells can be assigned to different classes based on neuropeptide expression, and it will be important to determine the differential contribution of these classes to neuropathic allodynia.

Neurobiological mechanisms of TENS-induced analgesia

Pain inhibition by additional somatosensory input is the rationale for the widespread use of Transcutaneous Electrical Nerve Stimulation (TENS) to relieve pain. Two main types of TENS produce analgesia in animal models: high-frequency (∼50-100 Hz) and low-intensity 'conventional' TENS, and low-frequency (∼2-4 Hz) and high-intensity 'acupuncture-like' TENS. However, TENS efficacy in human participants is debated, raising the question of whether the analgesic mechanisms identified in animal models are valid in humans. Here, we used a sham-controlled experimental design to clarify the efficacy and the neurobiological effects of 'conventional' and 'acupuncture-like' TENS in 80 human volunteers. To test the analgesic effect of TENS we recorded the perceptual and brain responses elicited by radiant heat laser pulses that activate selectively Aδ and C cutaneous nociceptors. To test whether TENS has a long-lasting effect on brain state we recorded spontaneous electrocortical oscillations. The analgesic effect of 'conventional' TENS was maximal when nociceptive stimuli were delivered homotopically, to the same hand that received the TENS. In contrast, 'acupuncture-like' TENS produced a spatially-diffuse analgesic effect, coupled with long-lasting changes both in the state of the primary sensorimotor cortex (S1/M1) and in the functional connectivity between S1/M1 and the medial prefrontal cortex, a core region in the descending pain inhibitory system. These results demonstrate that 'conventional' and 'acupuncture-like' TENS have different analgesic effects, which are mediated by different neurobiological mechanisms.

Coping with Phantom Limb Pain

Phantom limb pain is a chronic neuropathic pain that develops in 45-85% of patients who undergo major amputations of the upper and lower extremities and appears predominantly during two time frames following an amputation: the first month and later about 1 year. Although in most patients the frequency and intensity of pain diminish over time, severe pain persists in about 5-10%. It has been proposed that factors in both the peripheral and central nervous systems play major roles in triggering the development and maintenance of pain associated with extremity amputations. Chronic pain is physically and mentally debilitating, affecting an individual's capacity for self-care, but also diminishing an individual's daily capacity for personal and economic independence. In addition, the pain may lead to depression and feelings of hopelessness. A National Center for Biotechnology Information study found that in the USA alone, the annual cost of dealing with neuropathic pain is more than $600 billion, with an estimated 20 million people in the USA suffering from this condition. Although the pain can be reduced by antiepileptic drugs and analgesics, they are frequently ineffective or their side effects preclude their use. The optimal approach for eliminating neuropathic pain and improving individuals' quality of life is the development of novel techniques that permanently prevent the development and maintenance of neuropathic pain, or that eliminate the pain once it has developed. What is still required is understanding when and where an effective novel technique must be applied, such as onto the nerve stump of the transected peripheral axons, dorsal root ganglion neurons, spinal cord, or cortex to induce the desired influences. This review, the second of two in this journal volume, examines the techniques that may be capable of reducing or eliminating chronic neuropathic pain once it has developed. Such an understanding will improve amputees' quality of life by blocking the mechanisms that trigger and/or maintain PLP and chronic neuropathic pain.

Wireless transcutaneous electrical nerve stimulation device for chemotherapy-induced peripheral neuropathy: an open-label feasibility study

Chemotherapy-induced peripheral neuropathy (CIPN) occurs in approximately 68% of patients who receive neurotoxic chemotherapy and lasts at least 6 months post-chemotherapy in approximately 30% of individuals. CIPN is associated with decreased quality of life and functional impairments. Evidence suggests that CIPN symptoms are caused, in part, by enhanced excitability and impaired inhibition in the central nervous system. Transcutaneous electrical nerve stimulation (TENS) decreases pain by counteracting both of these mechanisms and is efficacious in other conditions associated with neuropathic pain. This single-arm study (n = 29) assessed the feasibility of investigating TENS for CIPN after chemotherapy completion using a wireless, home-based TENS device. Eighty-one percent of eligible patients who were approached enrolled, and 85% of participants who received the TENS device completed the primary (6-week) study term. Qualitative interview data suggest that use of the device on the continuous setting that automatically alternates between 1-h stimulation and rest periods for 5 h/day would be acceptable to most participants. Significant (i.e., p < 0.05) improvements were observed with the EORTC-CIPN20 (percent change from baseline: 13%), SF-MPQ-2 (52%), numeric rating scale of pain (38%), tingling (30%), numbness (20%), and cramping (53%), and UENS large fiber sensation subscore (48%). Preliminary data that support the reliability and construct validity of the UENS for CIPN in cancer survivors are also provided. Together these data suggest that it is feasible to evaluate TENS for CIPN using a wireless, home-based device and that further evaluation of TENS for CIPN in a randomized clinical trial is warranted.

Rationale for electrical parameter determination in external trigeminal nerve stimulation (eTNS) for migraine: A narrative review

Background

Migraine is a primary headache disorder involving dysregulation of central and peripheral pain pathways. Medical treatment is often limited by drug side effects, comorbidities and poor compliance. This makes neuromodulation an ideal option for migraine treatment. Cefaly® is a transcutaneous electrical neurostimulator designed specifically for migraine treatment. It results in external trigeminal nerve stimulation of the supraorbital and supratrochlear nerves. External trigeminal nerve stimulation is effective for acute and preventive migraine treatment and may result in normalization of dysregulated pain pathways.

Objective

Our objective was to provide a narrative review of the neuroanatomical and pathophysiological basis of external trigeminal nerve stimulation for migraine treatment and to provide the rationale behind the choice of the electrical parameters used for external trigeminal nerve stimulation.

Methods

We reviewed external trigeminal nerve stimulation clinical trial publications, basic science neurostimulation literature, publications describing pathophysiological mechanisms in migraine, and documentation used in the application for the Food and Drug Administration approval of external trigeminal nerve stimulation.

Results

The electrical parameters used for external trigeminal nerve stimulation were chosen to maximize safety and efficacy. Critical parameters include generator characteristics, pulse shape, pulse duration, pulse frequency and session duration and frequency. We explain the rationale behind determination of each parameter. There is evidence of dysregulated central and peripheral pathways in migraine and evidence that external trigeminal nerve stimulation may normalize function of these pathways.

Conclusion

External trigeminal nerve stimulation is a safe and effective Food and Drug Administration-approved option for the acute and preventive treatment of migraine. The electrical parameters were optimized specifically for external stimulation of the trigeminal nerve to maximum safety, comfort and efficacy.

Heteromerization of μ-opioid receptor and cholecystokinin B receptor through the third transmembrane domain of the μ-opioid receptor contributes to the anti-opioid effects of cholecystokinin octapeptide

Activation of the cholecystokinin type B receptor (CCKBR) by cholecystokinin octapeptide (CCK-8) inhibits opioid analgesia. Chronic opiate treatment leads to an increase in the CCK-8 concentration and thus enhances the antagonism of CCK-8 against opioid analgesia; the underlying molecular mechanisms remain of great interest. In the present study, we validated the colocalization of the μ-opioid receptor (MOR) and CCKBR in pain signal transmission-related spinal cord dorsal horn and dorsal root ganglion neurons of rats. Co-immunoprecipitation (Co-IP) and fluorescence lifetime-imaging-microscopy-based fluorescence resonance energy transfer (FLIM-FRET) assays showed that MOR heteromerized with CCKBR directly in transfected HEK293 cells. Combined with MOR mutant construction, the third transmembrane domain of MOR (TM3_MOR) was demonstrated to participate in heteromerization with CCKBR. Receptor ligand binding, ERK phosphorylation and cAMP assays showed that MOR heteromerization with CCKBR weakened the activity of MOR. A cell-penetrating interfering peptide consisting of TM3_MOR and TAT (a transactivator of HIV-1) sequences from the N terminal to the C terminal disrupted the MOR-CCKBR interaction and restored the activity of MOR in transfected HEK293 cells. Furthermore, intrathecal application of the TM3_MOR-TAT peptide alleviated CCK-8-injection-induced antagonism to morphine analgesia in rats. These results suggest a new molecular mechanism for CCK-8 antagonism to opioid analgesia in terms of G-protein-coupled receptor (GPCR) interaction through direct heteromerization. Our study may provide a potential strategy for pain management with opioid analgesics.

Lack of Analgesic Synergy of the Cholecystokinin Receptor Antagonist Proglumide and Spinal Cord Stimulation for the Treatment of Neuropathic Pain in Rats

OBJECTIVE

Neuropathic pain is difficult to manage and treat. Spinal cord stimulation (SCS) has become an established procedure for treating chronic neuropathic pain that is refractory to pharmacological therapy. In order to achieve better analgesia, a number of studies have evaluated the effectiveness of combining drug therapy with SCS. Cholecystokinin antagonists, such as proglumide, enhance the analgesic efficacy of endogenous opioids in animal models of pain. We previously reported that both systemic and spinal administration of proglumide enhances analgesia produced by both low- and high-frequency transcutaneous electrical nerve stimulation (TENS). Since SCS produces analgesia through endogenous opioids, we hypothesized that the analgesic effect of SCS would be enhanced through co-administration with proglumide in animals with neuropathic pain.

MATERIALS AND METHODS

Male Sprague-Dawley rats (n = 40) with spared nerve injury were given proglumide (20 mg/kg, i.p.) or saline prior to treatment with SCS (sham, 4 Hz, and 60 Hz). Mechanical withdrawal thresholds of the paw were measured before and after induction of nerve injury, and after SCS. Physical activity levels were measured after SCS.

RESULTS

Both proglumide and SCS when given independently significantly increased withdrawal thresholds two weeks after nerve injury. However, there was no additional effect of combining proglumide and SCS on mechanical withdrawal thresholds or activity levels in animals with nerve injury.

DISCUSSION AND CONCLUSIONS

Proglumide may be a candidate for achieving analgesia for patients with refractory neuropathic pain conditions, but does not enhance analgesia produced by SCS.

Effect of low frequency transcutaneous electrical nerve stimulation of TE5 (waiguan) and PC6 (neiguan) acupoints on cold-induced pain

[Purpose] This study assesse the effect of low frequency transcutaneous electrical nerve stimulation (TENS) of theTE5 (waiguan) and PC6 (neiguan) acupoints on cold-induced pain. [Subjects and Methods] Forty-eight subjects were divided by convenience into three groups: TENS with electrodes of 1 cm(2) area, TENS with electrodes of area 15 cm(2) and a placebo group. The study consisted of three phases: cold-induced pain without electroanalgesia, cold-induced pain with electroanalgesia or placebo, and cold-induced pain post-electroanalgesia or placebo. [Results] Acupuncture like TENS increased the pain threshold latency during treatment (45.7 ± 11.7s) compared to pre-treatment (30.9 ± 8.9s) in the TENS group with 1 cm(2) electrodes. In the TENS group with 15 cm(2) electrodes, the pain threshold latency increased at post-treatment (36.2 ± 12.9s) compared to pre-treatment (25.5 ± 7.4s). The placebo group showed no significant changes. The group with 1 cm(2) electrodes showed a significantly higher pain threshold latency (45.7 ± 11.7s) than the other two groups. At post-treatment, the pain threshold latencies of both the 1 cm(2) (39.4 ± 11.5s) and 15 cm(2) (36.2 ± 12.9s) TENS group were higher than that of the placebo group (22.4 ± 7.4s). [Conclusion] Acupuncture like TENS applied to PC6 and TE5 acupoints increased the pain threshold latency. The pain intensity was reduced by TENS with an electrode area of 1 cm(2).

Using TENS for pain control: the state of the evidence

Transcutaneous electrical nerve stimulation (TENS) is a nonpharmacological intervention that activates a complex neuronal network to reduce pain by activating descending inhibitory systems in the central nervous system to reduce hyperalgesia. The evidence for TENS efficacy is conflicting and requires not only description but also critique. Population-specific systemic reviews and meta-analyses are emerging, indicating both HF and LF TENS being shown to provide analgesia, specifically when applied at a strong, nonpainful intensity. The purpose of this article is to provide a critical review of the latest basic science and clinical evidence for TENS. Additional research is necessary to determine if TENS has effects specific to mechanical stimuli and/or beyond reduction of pain and will improve activity levels, function and quality of life.

The New Portable Transcutaneous Electrical Nerve Stimulation Device Was Efficacious in the Control of Primary Dysmenorrhea Cramp Pain

INTRODUCTION

Transcutaneous electrical nerve stimulation (TENS) is an established method for pain relief in dysmenorrhea. A feasible advantage would be the study of a portable device. The purpose of the study was to evaluate the effectiveness and safety of a new portable TENS device (TANYX®) for menstruation cramps.

MATERIALS AND METHODS

Forty women were evaluated in a double-blind, prospective, randomized fashion, divided into sham and active groups. TENS was applied medially at the suprapubic region, for 30-min duration at eight-hour intervals, up to seven days. The placebo group (PG) received sham device. The TENS group (TG) applied an active 85 Hz frequency TENS. Efficacy measures were pain relief evaluated on a visual analog scale (VAS) and diclofenac intake, and quality of life represented by: 1) capacity to get out of the bed, 2) food or drink intake, 3) missing routine daily activities such as work or school, and 4) quality of sleep.

RESULTS

The active TENS device induced a prompt onset of pain relief in a strictly segmental manner nearby the dermatomes where the TENS was applied at the skin, and there was a drop in mean pain score from 8 to 2 cm (p < 0.001). Diclofenac consumption was also significantly reduced (p < 0.01), compared with the PG. Quality of life improved significantly in TG when compared with PG (p < 0.05). Three months after the beginning of the study, 14/20 of the women were still using the active device regularly. No adverse effects were observed.

CONCLUSIONS

The portable, disposable, active TENS device induced a prompt onset of pain relief and improved the quality of life, without adverse effects, in patients with painful cramps associated with dysmenorrhea.

A systematic review investigating the relationship between efficacy and stimulation parameters when using transcutaneous electrical nerve stimulation after knee arthroplasty

OBJECTIVE

To evaluate the clinical efficacy of transcutaneous electric nerve stimulation in the treatment of postoperative knee arthroplasty pain and to relate these results to the stimulation parameters used.

DATA SOURCES

PubMed, Pedro and Web of Knowledge were systematically screened for studies investigating effects of transcutaneous electric nerve stimulation on postoperative knee arthroplasty pain.

REVIEW METHODS

Studies were screened for their methodological and therapeutical quality. We appraised the influence of the stimulation settings used and indicated whether or not a neurophysiological and/or mechanistic rationale was given for these stimulation settings.

RESULTS

A total of 5 articles met the inclusion criteria. In total, 347 patients were investigated. The number of patients who received some form of transcutaneous electric nerve stimulation was 117, and 54 patients received sham transcutaneous electric nerve stimulation. Pain was the primary outcome in all studies. The stimulation settings used in the studies (n = 2) that reported significant effects differed from the others as they implemented a submaximal stimulation intensity. Stimulation parameters were heterogeneous, and only one study provided a rationale for them.

CONCLUSION

This review reveals that an effect of transcutaneous electric nerve stimulation might have been missed due to low methodological and therapeutical quality. Justifying the choice of transcutaneous electric nerve stimulation parameters may improve therapeutical quality.

Transcutaneous electrical nerve stimulation attenuates CFA-induced hyperalgesia and inhibits spinal ERK1/2-COX-2 pathway activation in rats

BACKGROUND

Transcutaneous electrical nerve stimulation (TENS) is a non-pharmacologic treatment for pain relief. In previous animal studies, TENS effectively alleviated Complete Freund's Adjuvant (CFA)- or carrageenan-induced inflammatory pain. Although TENS is known to produce analgesia via opioid activation in the brain and at the spinal level, few reports have investigated the signal transduction pathways mediated by TENS. Prior studies have verified the importance of the activation of extracellular signal-regulated kinase (ERK) signal transduction pathway in the spinal cord dorsal horn (SCDH) in acute and persistent inflammatory pains. Here, by using CFA rat model, we tested the efficacy of TENS on inhibiting the expressions of p-ERK1/2 and of its downstream cyclooxygenase-2 (COX-2) and the level of prostaglandin E2 (PGE2) at spinal level.

METHODS

Rats were randomly divided into control, model and TENS groups, and injected subcutaneously with 100 μl CFA or saline in the plantar surface of right hind paw. Rats in the TENS group were treated with TENS (constant aquare wave, 2 Hz and 100 Hz alternating frequencies, intensities ranging from 1 to 2 mA, lasting for 30 min each time) at 5 h and 24 h after injection. Paw withdrawal thresholds (PWTs) were measured with dynamic plantar aesthesiometer at 3d before modeling and 5 h, 6 h, and 25 h after CFA injection. The ipsilateral sides of the lumbar spinal cord dosral horns were harvested for detecting the expressions of p-ERK1/2 and COX-2 by western blot analysis and qPCR, and PGE2 by ELISA.

RESULTS

CFA-induced periphery inflammation decreased PWTs and increased paw volume of rats. TENS treatment significantly alleviated mechanical hyperalgesia caused by CFA. However, no anti-inflammatory effect of TENS was observed. Expression of p-ERK1/2 protein and COX-2 mRNA was significantly up-regualted at 5 h and 6 h after CFA injection, while COX-2 and PGE2 protein level only increased at 6 h after modeling. Furthermore, the high expression of p-ERK1/2 and COX-2, and over-production of PGE2 induced by CFA, were suppressed by TENS administration.

CONCLUSIONS

TENS may be an effective therapy in controlling inflammatory pain induced by CFA. Its analgesic effect may be associated with the inhibition of activation of the spinal ERK1/2-COX-2 pathway.

Increasing intensity of TENS prevents analgesic tolerance in rats

Transcutaneous electrical nerve stimulation (TENS) reduces hyperalgesia and pain. Both low-frequency (LF) and high-frequency (HF) TENS, delivered at the same intensity (90% motor threshold [MT]) daily, result in analgesic tolerance with repeated use by the fifth day of treatment. The current study tested 1) whether increasing intensity by 10% per day prevents the development of tolerance to repeated TENS; and 2) whether lower intensity TENS (50% MT) produces an equivalent reduction in hyperalgesia when compared to 90% MT TENS. Sprague-Dawley rats with unilateral knee joint inflammation (3% carrageenan) were separated according to the intensity of TENS used: sham, 50% LF, 50% HF, 90% LF, 90% HF, and increased intensity by 10% per day (LF and HF). The reduced mechanical withdrawal threshold following the induction of inflammation was reversed by application of TENS applied at 90% MT intensity and increasing intensity for the first 4 days. On the fifth day, the groups that received 90% MT intensity showed tolerance. Nevertheless, the group that received an increased intensity on each day still showed a reversal of the mechanical withdrawal threshold with TENS. These results show that the development of tolerance can be delayed by increasing intensity of TENS.

PERSPECTIVE

Our results showed that increasing intensity in both frequencies of TENS was able to prevent analgesic tolerance. Results from this study suggest that increasing intensities could be a clinical method to prevent analgesic tolerance and contribute to the effective use of TENS in reducing inflammatory pain and future clinical trials.

Effects of exogenous cholecystokinin octapeptide on acquisition of naloxone precipitated withdrawal induced conditioned place aversion in rats

Cholecystokinin octapeptide (CCK-8), a gut-brain peptide, regulates a variety of physiological behavioral processes. Previously, we reported that exogenous CCK-8 attenuated morphine-induced conditioned place preference, but the possible effects of CCK-8 on aversively motivated drug seeking remained unclear. To investigate the effects of endogenous and exogenous CCK on negative components of morphine withdrawal, we evaluated the effects of CCK receptor antagonists and CCK-8 on the naloxone-precipitated withdrawal-induced conditioned place aversion (CPA). The results showed that CCK2 receptor antagonist (LY-288,513, 10 µg, i.c.v.), but not CCK1 receptor antagonist (L-364,718, 10 µg, i.c.v.), inhibited the acquisition of CPA when given prior to naloxone (0.3 mg/kg) administration in morphine-dependent rats. Similarly, CCK-8 (0.1–1 µg, i.c.v.) significantly attenuated naloxone-precipitated withdrawal-induced CPA, and this inhibitory function was blocked by co-injection with L-364,718. Microinjection of L-364,718, LY-288,513 or CCK-8 to saline pretreated rats produced neither a conditioned preference nor aversion, and the induction of CPA by CCK-8 itself after morphine pretreatments was not significant. Our study identifies a different role of CCK1 and CCK2 receptors in negative affective components of morphine abstinence and an inhibitory effect of exogenous CCK-8 on naloxone-precipitated withdrawal-induced CPA via CCK1 receptor.

Cholecystokinin receptor-1 mediates the inhibitory effects of exogenous cholecystokinin octapeptide on cellular morphine dependence

Background

Cholecystokinin octapeptide (CCK-8), the most potent endogenous anti-opioid peptide, has been shown to regulate the processes of morphine dependence. In our previous study, we found that exogenous CCK-8 attenuated naloxone induced withdrawal symptoms. To investigate the precise effect of exogenous CCK-8 and the role of cholecystokinin (CCK) 1 and/or 2 receptors in morphine dependence, a SH-SY5Y cell model was employed, in which the μ-opioid receptor, CCK1/2 receptors, and endogenous CCK are co-expressed.

Results

Forty-eight hours after treating SH-SY5Y cells with morphine (10 μM), naloxone (10 μM) induced a cAMP overshoot, indicating that cellular morphine dependence had been induced. The CCK receptor and endogenous CCK were up-regulated after chronic morphine exposure. The CCK2 receptor antagonist (LY-288,513) at 1–10 μM inhibited the naloxone-precipitated cAMP overshoot, but the CCK1 receptor antagonist (L-364,718) did not. Interestingly, CCK-8 (0.1-1 μM), a strong CCK receptor agonist, dose-dependently inhibited the naloxone-precipitated cAMP overshoot in SH-SY5Y cells when co-pretreated with morphine. The L-364,718 significantly blocked the inhibitory effect of exogenous CCK-8 on the cAMP overshoot at 1–10 μM, while the LY-288,513 did not. Therefore, the CCK2 receptor appears to be necessary for low concentrations of endogenous CCK to potentiate morphine dependence in SH-SY5Y cells. An additional inhibitory effect of CCK-8 at higher concentrations appears to involve the CCK1 receptor.

Conclusions

This study reveals the difference between exogenous CCK-8 and endogenous CCK effects on the development of morphine dependence, and provides the first evidence for the participation of the CCK1 receptor in the inhibitory effects of exogenous CCK-8 on morphine dependence.

The effects of exogenous CCK-8 on the acquisition and expression of morphine-induced CPP

Cholecystokinin octapeptide (CCK-8) is the most potent endogenous anti-opioid peptide and regulates a variety of physiological processes. In our previous study, we found that exogenous CCK-8 attenuated naloxone-induced withdrawal symptoms, but the possible regulative effects of CCK-8 on the rewarding effects of morphine were not examined. In the present study, we aimed to determine the exact effects of exogenous CCK-8 at various doses on the rewarding action of morphine by utilizing the unbiased conditioned place preference (CPP) paradigm. We therefore examined the effects of CCK-8 on the acquisition, expression and extinction of morphine-induced CPP and on locomotor activity. The results showed that CCK-8 (0.01-1μg, i.c.v.), administered alone, induced neither CPP nor place aversion, but blocked the acquisition of CPP when administered with 10mg/kg morphine. The highest dose of CCK-8 (1μg) administered before CPP testing increased CPP and, along with lower doses (0.1μg), reduced its extinction. In addition, the highest dose (1μg) of CCK-8 suppressed locomotor activity. Our study provides the first behavioral evidence for the inhibitory effects of exogenous CCK-8 on rewarding activity and reveals significant effects of exogenous CCK-8 on various stages of place preference and the development of opioid dependence.

Endogenous opiates and behavior: 2010

This paper is the thirty-third consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2010 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration (Section 16); and immunological responses (Section 17).

Transcutaneous electrical nerve stimulation for the management of painful conditions: focus on neuropathic pain

The management of neuropathic pain is challenging, with medication being the first-line treatment. Transcutaneous electrical nerve stimulation (TENS) is an inexpensive, noninvasive, self-administered technique that is used as an adjunct to medication. Clinical experience suggests that TENS is beneficial providing it is administered at a sufficiently strong intensity, close to the site of pain. At present, there are too few randomized controlled trials on TENS for neuropathic pain to judge effectiveness. The findings of systematic reviews of TENS for other pain syndromes are inconclusive because trials have a low fidelity associated with inadequate TENS technique and infrequent treatments of insufficient duration. The use of electrode arrays to spatially target stimulation more precisely may improve the efficacy of TENS in the future.

An investigation of the development of analgesic tolerance to TENS in humans

Transcutaneous electrical nerve stimulation (TENS) is a noninvasive modality used to control pain. Animal models show that repeated TENS application produces analgesic tolerance and cross-tolerance at spinal opioid receptors. The aim of the present investigation was to examine whether repeated application of TENS produces analgesic tolerance in humans. One hundred healthy subjects were randomly assigned to 1 of 4 groups: control, placebo, low-frequency (4Hz) or high-frequency (100Hz) TENS. TENS was applied daily for 5days to the nondominant upper limb; pressure-pain threshold (PPT) measurements were recorded before and after TENS. Temporal summation to mechanical stimulation was recorded on days 1 and 5, before and after TENS. Diffuse noxious inhibitory control (DNIC) was tested on day 5 using the cold pressor test and PPT measurements. There was an initial increase in PPTs in both low- and high-frequency TENS groups when compared with placebo or control groups. However, by day 5 this TENS-induced increase in PPT did not occur, and there was no difference between active TENS and placebo or control groups. High-frequency TENS decreased temporal summation on day 1 when compared with day 5. DNIC increased the PPT similarly in all groups. These data suggest that repeated daily application of TENS results in a decrease in its hypoalgesic effect by the fifth day and that the tolerance-like effect to repeated TENS results from tolerance at centrally located opioid receptors. The lack of change in DNIC response suggests that TENS and DNIC utilize separate pathways to produce analgesia. Repeated high-frequency and low-frequency transcutaneous electrical nerve stimulation produce analgesic tolerance in humans by the fourth and fifth day of treatment, respectively.