Pain and sensory detection threshold response to acupuncture is modulated by coping strategy and acupuncture sensation

Modulation of Comorbid Chronic Neuropathic Pain and Anxiety-Like Behaviors by Glutamatergic Neurons in the Ventrolateral Periaqueductal Gray and the Analgesic and Anxiolytic Effects of Electroacupuncture

Comorbid chronic neuropathic pain and anxiety is a common disease that represents a major clinical challenge. The underlying mechanisms of chronic neuropathic pain and anxiety are not entirely understood, which limits the exploration of effective treatment methods. Glutamatergic neurons in the ventrolateral periaqueductal gray (vlPAG) have been implicated in regulating pain, but the potential roles of the vlPAG in neuropathic pain-induced anxiety have not been investigated. Herein, whole-cell recording and immunofluorescence showed that the excitability of CamkIIα neurons in the vlPAG (vlPAGCamkIIα+ neurons) was decreased in mice with spared nerve injury (SNI), while electroacupuncture (EA) activated these neurons. We also showed that chemogenetic inhibition of vlPAGCamkIIα+ neurons resulted in allodynia and anxiety-like behaviors in naive mice. Furthermore, chemogenetic activation of vlPAGCamkIIα+ neurons reduced anxiety-like behaviors and allodynia in mice with SNI, and EA had a similar effect in alleviating these symptoms. Nevertheless, EA combined with chemogenetic activation failed to further relieve allodynia and anxiety-like behaviors. Artificial inhibition of vlPAGCamkIIα+ neurons abolished the analgesic and anxiolytic effects of EA. Overall, our study reveals a novel mechanism of neuropathic pain-induced anxiety and shows that EA may relieve comorbid chronic neuropathic pain and anxiety by activating vlPAGCamkIIα+ neurons.

Effect of "needle sensation" and the real-time changes in autonomic nervous system activity during acupuncture analgesia

Introduction

Acupuncture analgesia (AA) is widely used in clinical practice. The autonomic nervous system (ANS) may be an important pathway for acupuncture signal transduction. However, real-time changes in autonomic function during AA and the effect of "needle sensation" remain unclear.

Methods

We established a human pain model in healthy adults and randomly assigned 128 participants to the model, sham acupuncture, and acupuncture groups in a 1:1:2 ratio. Heart rate variability (HRV), including total power (TP), low-frequency power (LF), high-frequency power (HF), ratio of LF to HF (LF/HF), standard deviation of the normal-normal intervals (SDNN), and root mean square of successive interval differences (RMSSD), were used to assess autonomic function. The visual analog scale (VAS) and efficiency were used to assess the analgesic effect of acupuncture. The Massachusetts General Hospital acupuncture sensation scale (MASS) was used to indicate the intensity of the needle sensation. Anxiety levels were also measured. Finally, the correlation of MASS with HRV, VAS, and anxiety levels was analyzed.

Results

VAS decreased after 10 min of needling and 5 min after needle withdrawal in the acupuncture group compared with those in the model group (p = 0.038, p = 0.020). The efficacy rates were 82.0, 50.0, and 61.3% in the acupuncture, model, and sham groups, respectively. These represent significant differences between the acupuncture group and the model and sham acupuncture groups (p < 0.001 in each case). No differences were observed between the model and sham acupuncture groups. HF, TP, SDNN, and RMSSD were all increased in the acupuncture group compared with those in the model group (p = 0.045, p = 0.041, p = 0.002, p = 0.006, respectively). No differences were observed in the sham acupuncture group compared to the model group (p = 0.632, p = 0.542, p = 0.093, p = 0.222, respectively). The LF and LF/HF did not differ among all three groups. A positive correlation was observed between MASS and RMSSD2, LF2, RMSSD4, TP4, VAS5, and anxiety levels.

Conclusion

AA was associated with enhanced vagal activity. The intensity of needle sensation was positively correlated with vagal and sympathetic nerve activities. Acupuncture is an effective means of regulating autonomic function, and needle sensation may be an important modulator.

Dropouts in randomized clinical trials of Korean medicine interventions: a systematic review and meta-analysis

BACKGROUND

The dropout rate is an important determinant of outcomes in randomized controlled trials (RCTs) and should be carefully controlled. This study explored the current dropout rate in studies of Korean medicine (KM) interventions by systematic evaluation of RCTs conducted in the past 10 years.

METHODS

Three clinical trial registries (Clinical Research Information Service, ClinicalTrials.gov, and World Health Organization International Clinical Trials Registry Platform) were searched to identify RCT protocols for KM interventions, such as acupuncture, herbal medicine, moxibustion, or cupping, and studies of mixed interventions, registered in Korea from 2009 to 2019. The PubMed, Embase, and OASIS databases were searched for the full reports of these RCTs, including published journal articles and theses. Dropout rates and the reasons for dropping out were analyzed in each report. The risk of bias in each of the included studies was assessed using the Cochrane risk of bias tool. The risk difference for dropping out between the treatment and control groups was calculated with the 95% confidence interval in a random effects model.

RESULTS

Forty-nine published studies were included in the review. The median dropout rate was 10% in the treatment group (interquartile range 6.7%, 17.0%) and 14% in the control group (interquartile range 5.4%, 16.3%) and was highest in acupuncture studies (12%), followed by herbal medicine (10%), moxibustion (8%), and cupping (7%). Loss to follow-up was the most common reason for dropping out. The risk difference for dropping out between the intervention and control groups was estimated to be 0.01 (95% confidence interval - 0.02, 0.03) in KM intervention studies.

CONCLUSIONS

This review found no significant difference in the dropout rate between studies according to the type of KM intervention. We recommend allowance for a minimum dropout rate of 15% in future RCTs of KM interventions.

REVIEW PROTOCOL REGISTRATION

PROSPERO CRD42020141011.

Influence of the Intensity, Components, and Spreading of the Deqi Sensation on the Analgesic Effect of SP6 Needling in Primary Dysmenorrhea Patients: A Secondary Analysis of a Randomised Controlled Trial

Although deqi, the phenomenon whereby excitation of Qi in the meridians occurs with needling, is critical to the practice of acupuncture and its efficacy, it is poorly understood. So we investigate the influence of the deqi sensation on the analgesic effects of acupuncture in patients who were enrolled in a randomised controlled trial for the treatment of patients with primary dysmenorrhea, a painful and common condition, and cold and dampness stagnation. Two groups were assessed: a deqi group (undergoing deep needling with thick needles and manipulation, n=17) and a non-deqi group (undergoing shallow needling with thin needles and no manipulation, n=51). The Sanyinjiao (SP6) was needled for 30 min in both groups. Pain scores at baseline, upon needle removal, and at 10, 20, and 30 min after needle removal were evaluated by the Visual Analogue Scale for pain. The deqi sensation was evaluated by the Acupuncture Deqi Clinical Assessment Scale. Patients who experienced a genuine deqi sensation (n=39) were selected for further analysis. Compared with patients in the non-deqi group who experienced deqi (n=25), patients who self-reported deqi in the deqi group (n=14) felt a stronger deqi sensation, experienced soreness and fullness more frequently, felt a greater intensity of soreness, fullness, electric sensation, spreading, and radiating, and experienced larger spreading distances. In those who experienced the deqi sensation in the deqi group, the intensity of the sensation, as well as their degree of soreness and fullness, was negatively correlated with pain reduction. In patients who experienced the deqi sensation in the non-deqi group, deqi intensity was positively correlated with pain reduction, while soreness was negatively correlated with pain reduction. The distance of spreading was not correlated with pain reduction in either group. We found, in SP6 needling of patients with primary dysmenorrhea with cold and dampness stagnation, that a moderate deqi response predicted a prolonged analgesic effect better than a strong deqi response.

Technical development of transcutaneous electrical nerve inhibition using medium-frequency alternating current

Background

Innovative technical approaches to controlling undesired sensory and motor activity, such as hyperalgesia or spasticity, may contribute to rehabilitation techniques for improving neural plasticity in patients with neurologic disorders. To date, transcutaneous electrical stimulation has used low frequency pulsed currents for sensory inhibition and muscle activation. Yet, few studies have attempted to achieve motor nerve inhibition using transcutaneous electrical stimulation. This study aimed to develop a technique for transcutaneous electrical nerve inhibition (TENI) using medium-frequency alternating current (MFAC) to suppress both sensory and motor nerve activity in humans.

Methods

Surface electrodes were affixed to the skin of eight young adults to stimulate the median nerve. Stimulation intensity was increased up to 50% and 100% of the pain threshold. To identify changes in sensory perception by transcutaneous MFAC (tMFAC) stimulation, we examined tactile and pressure pain thresholds in the index and middle fingers before and after stimulation at 10 kHz. To demonstrate the effect of tMFAC stimulation on motor inhibition, stimulation was applied while participants produced flexion forces with the index and middle fingers at target forces (50% and 90% of MVC, maximum voluntary contraction).

Results

tMFAC stimulation intensity significantly increased tactile and pressure pain thresholds, indicating decreased sensory perception. During the force production task, tMFAC stimulation with the maximum intensity immediately reduced finger forces by ~ 40%. Finger forces recovered immediately after stimulation cessation. The effect on motor inhibition was greater with the higher target force (90% MVC) than with the lower target (50% MVC). Also, higher tMFAC stimulation intensity provided a greater inhibition effect on both sensory and motor nerve activity.

Conclusion

We found that tMFAC stimulation immediately inhibits sensory and motor activity. This pre-clinical study demonstrates a novel technique for TENI using MFAC stimulation and showed that it can effectively inhibit both sensory perception and motor activity. The proposed technique can be combined with existing rehabilitation devices (e.g., a robotic exoskeleton) to inhibit undesired sensorimotor activities and to accelerate recovery after neurologic injury.

What intrinsic factors influence responsiveness to acupuncture in pain?: a review of pre-clinical studies that used responder analysis

BACKGROUND

Not many studies have investigated individual sensitivity to acupuncture. To explore the intrinsic factors related to individual responses to acupuncture, we reviewed published pre-clinical studies using responder analysis on pain.

METHODS

We searched the PubMed and EMBASE databases to June 2015. We included pre-clinical reports describing responders and non-responders to anti-nociceptive and analgesic effects of acupuncture in animal study. We identified the potential intrinsic factors which might be related with the response to acupuncture.

RESULTS

Totally, 216 potentially relevant articles were retrieved and 14 studies met our inclusion criteria. Rat (n = 1348) and rabbit (n = 56) were used, and only electroacupuncture (EA) was applied as an intervention. Results showed that high levels of cholecystokinin-8 and receptors were associated with poor responsiveness to EA. Endogenous opioids including β-endorphin and met-enkephalin, descending inhibitory norepinephrine and serotonin system, and hypothalamic 5'-AMP-activated protein kinase seemed to be associated with high-level responses. Spinal levels of neurotransmitters and pro-inflammatory cytokines were also differentially expressed depending on the EA sensitiveness. In the central nervous system, hypothalamus, periaqueductal grey, pituitary gland, and spinal cord were suggested to be involved in the EA responsiveness. Identified individual variations did not seem to be accidental, as the responsiveness to EA was replicated over time. However, methodological issues such as reproducibility, cut-off criteria, and clinical relevance need to be further elaborated.

CONCLUSION

Our study suggests that the identification of the biological factors differentiating responders from non-responders is necessary and it may aid in understanding how acupuncture modulates pain.

Comparison of the placebo effect between different non-penetrating acupuncture devices and real acupuncture in healthy subjects: a randomized clinical trial

Background

Several studies have used placebo acupuncture methods in recent years as a way for blinding therapeutic effect of acupuncture, however placebo method selection has not followed enough methodological criteria to the point of stabilishing a consensus of what should be the best method to be used. This study aimed to evaluate the effectiveness of three different placebo acupuncture methods for blinding applied in healthy subjects.

Methods

This study was approved by the Ethics Committee of the Federal University of Sergipe with the number 47193015.5.0000.5546 and all individuals participating in the study signed a free and informed consent. For this study, 321 healthy volunteers were randomly divided into seven groups using the abdominal point stomach (ST) 25 and seven groups using the lumbar point bladder (Bl) 52 for stimulation. For real acupuncture procedure, three different methods of placebo acupuncture plus a mix between real acupuncture and placebo applied in the same individual, totaling fourteen groups in this study. Outcome assessments were performed before and immediately after applying the technique. Investigator who assessed variables had no knowledgement about the method was applied. Identification, weight and height were measured before puncture by using. At the end, subjects were asked if they believed they were receiving real or placebo acupuncture.

Results

There was no significant difference between groups for the perception about the type o stimulation (wheter real or placebo puncture). Percentage of subjects who reported to have received real acupuncture in the abdominal point was 69.56% in real group, 86.95% in group Park Sham, 82.60% in needle + foam, 91.30% in insertion and removal, 78.26% in real + Park Sham, 86.36% in real + needle and foam, 86.95% in real + insertion and removal, and for the lumbar point was 86.36% in real group, 86.95% in group Park Sham, 69.56% in needle + foam, 72% in insertion and removal, 86.95% in real + Park Sham, 81.81% in real + needle and foam and 78.26% in real + insertion and removal.

Conclusion

All placebo acupuncture methods proposed in this study were equally effective for bliding the study participants using either abdominal or lumbar acupoints, and none of the placebo methods presented benefit compared to the other to be used in future clinical trials.

Ethics Committee

Federal University of Sergipe (UFS), number of approval: 47193015.5.0000.5546

Trial registration

ensaiosclinicos.gov.br RBR-3w2p32 Registered in 28th January 2016.

Effect of verbal persuasion on self-efficacy for pain-related diagnostic sensory testing in individuals with chronic neck pain and healthy controls - a randomized, controlled trial

The aim of this study was to investigate the differences in cold pain threshold (CTh), pressure pain threshold (PPT), cold pain tolerance (CPTo) tests, and the level of self-efficacy when self-efficacy for diagnostic sensory testing was manipulated by verbal persuasion before a testing situation in persons with neck pain and in healthy controls. A randomized experimental design was used. Twenty-one healthy volunteers and 22 individuals with either traumatic or nontraumatic chronic neck pain were recruited to participate in the study. The intervention consisted of two experimental verbal persuasion conditions: Increase self-efficacy and Decrease self-efficacy. The PPT was measured using a pressure algometer, the CTh was measured using a thermo test system, and CPTo was measured by submerging the participant’s hand in ice water up to the elbow joint. On three occasions, the participants reported their self-efficacy level in performing the sensory tests. In the chronic neck pain group, there were no differences in pain threshold or tolerance. There was a difference in the self-efficacy level after verbal persuasion between the experimental conditions. In the healthy control group, the CThs increased following the condition that aimed to increase self-efficacy. No other differences were observed in the healthy controls. A short verbal persuasion in the form of manipulative instructions seems to have a marginal effect on the individual’s self-efficacy levels in the chronic neck pain group and a slight influence on the results of sensory testing in healthy controls.