Auricular acupuncture and vagal regulation

Auricular Therapy for Migraine

PURPOSE OF REVIEW

Migraine brings hours or even days of disability, affecting 15% of the US population and one billion people worldwide. Migraine treatments have improved over the years and there is now a range of non-pharmacologic therapies that can be administered as monotherapy, combined with pharmacologic therapy or combined with other non-pharmacologic therapies to give greater options for those who do not tolerate, do not respond to, or who wish to reduce or avoid pharmacologic treatments.

RECENT FINDINGS

We conducted a review of the literature on auricular therapy as acute or preventive treatment for migraine, searching the databases of MEDLINE and ClinicalTrials.gov from 2013 to 2023. A total of 43 articles contained at least one search term, with three studies specific to acute or prevention of migraine (one for acute only, one for prevention only and one for both acute and prevention). The population was limited to, adults with migraine ages 18 or older, with the administration of auricular therapy as the intervention. While there have been studies on the use of auricular therapy for pain on two specific standardized auricular therapies, Battlefield Acupuncture (BFA) and National Acupuncture Detoxification Association (NADA), neither of these protocols were utilized in any of the studies specific to migraine management. Each of the three studies used different techniques, with one using acupuncture needles and five specific points and two using semi-permanent needles (remained in for a few days) that were placed in areas that showed high activity. Each of these studies showed auricular therapy to have benefit for the management of migraine. However, the authors of each of the studies recommended further studies. Auricular therapy may be a helpful adjunctive treatment to abort a current migraine attack or aid in reducing the frequency or severity of migraine attacks.

Transcutaneous auricular vagus nerve stimulation as a novel therapy connecting the central and peripheral systems: a review

Currently, clinical practice and scientific research mostly revolve around a single disease or system, but the single disease-oriented diagnostic and therapeutic paradigm needs to be revised. This review describes how transcutaneous auricular vagus nerve stimulation (taVNS), a novel non-invasive neuromodulation approach, connects the central and peripheral systems of the body. Through stimulation of the widely distributed vagus nerve from the head to the abdominal cavity, this therapy can improve and treat central system disorders, peripheral system disorders, and central-peripheral comorbidities caused by autonomic dysfunction. In the past, research on taVNS has focused on the treatment of central system disorders by modulating this brain nerve. As the vagus nerve innervates the heart, lungs, liver, pancreas, gastrointestinal tract, spleen and other peripheral organs, taVNS could have an overall modulatory effect on the region of the body where the vagus nerve is widespread. Based on this physiological basis, the authors summarize the existing evidence of the taVNS ability to regulate cardiac function, adiposity, glucose levels, gastrointestinal function, and immune function, among others, to treat peripheral system diseases, and complex diseases with central and peripheral comorbidities. This review shows the successful examples and research progress of taVNS using peripheral neuromodulation mechanisms from more perspectives, demonstrating the expanded scope and value of taVNS to provide new ideas and approaches for holistic therapy from both central and peripheral perspectives.

The Effectiveness of Auricular Acupressure on Chronic Musculoskeletal Pain: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Objectives: To assess the effectiveness of auricular acupressure (AA) in managing pain and disability in individuals with chronic musculoskeletal pain. Materials and Methods: A systematic search on six electronic databases was performed from their inception to May 7, 2023, to identified relevant randomized controlled trials (RCTs). Two independent reviewers screened the abstracts and full texts, extracted data, and assessed risk of bias using RoB 2. The primary outcomes were pain intensity and disability. The secondary outcomes were pain pressure thresholds, pain catastrophizing level, and fear avoidance beliefs. A random-effects model was used for meta-analyses. The certainty of evidence was evaluated using the Grading of Recommendations Assessment, Development, and Evaluation. Sensitivity analyses were conducted after removing low-quality papers. Results: Of 633 identified records, six studies involving 496 participants were included. All included studies compared the effectiveness of AA with sham controls in treating various chronic musculoskeletal pain. Four meta-analyses were conducted to compare the effectiveness of AA with sham controls. Low-quality evidence supported that AA had a large effect size on postintervention subjective pain reduction (standardized mean difference [SMD] = -0.95; 95% confidence interval [CI]: -1.36 to -0.54; p = 0.00; I2 = 52.61%); moderate-quality evidence substantiated that AA had a large effect size on enhancing postintervention pressure pain threshold (SMD = -0.55; 95% CI: -0.88 to -0.23; p = 0.00; I2 = 0%). There was low-quality evidence that AA had a large effect on reducing postintervention disability (SMD = -0.68; 95% CI: -1.24 to -0.12; p = 0.02; I2 = 51.33%). Our sensitivity analysis reaffirmed the same conclusion regarding pain reduction immediately after the intervention. Fourteen participants reported minimal adverse events, including soreness, tenderness, irritation, and redness, which disappeared within 1-7 days. Discussion: Our systematic review revealed that AA significantly improved pain, pressure pain thresholds, and disability in individuals with various chronic musculoskeletal pain conditions immediately post-treatment compared with sham treatment. Given the paucity of studies and inconsistent protocols, future RCTs are warranted to evaluate the effectiveness of AA in people with chronic musculoskeletal pain at a longer follow-up with detailed protocols, which allows researchers and clinicians to optimize AA intervention. Conclusion: AA has immediate post-treatment benefits for chronic musculoskeletal pain, whereas its effects at the 1- or 6-month follow-up remain uncertain.

Transcutaneous Auricular Vagal Nerve Stimulation in Healthy Non-Sedated Horses: A Feasibility Study

This study aimed to evaluate the feasibility of transcutaneous auricular vagal nerve stimulation (tAVNS) in healthy horses and its effect on heart rate variability (HRV). The study comprised three phases: the selection of mares, their acclimatization to the tAVNS, and the stimulation phase. Stimulation was performed with two electrodes positioned on the right pinna. The settings were 0.5 mA, 250 μs, and 25 Hz for pulse amplitude, pulse width, and pulse frequency, respectively. HRV was analysed before (B1), during (T), and after (B2) the tAVNS. From the 44 mares initially included, only 7 completed the three phases. In these mares, the heart rate (HR) was significantly lower, and frequency domain parameters showed an increased parasympathetic tone in B2 compared with B1. However, in 3/7 mares, the HR was significantly higher during T compared with B1 and B2, compatible with a decreased parasympathetic tone, while in 4/7 mares, the HR was significantly lower and the parasympathetic nervous system index was significantly higher during T and B2 compared with B1. The tAVNS is an economical and easy procedure to perform and has the potential to stimulate vagal activity; however, it was poorly tolerated in the mares included in this study.

An update on noninvasive neuromodulation in the treatment of patients with prolonged disorders of consciousness

BACKGROUND

With the improvement of emergency techniques, the survival rate of patients with severe brain injury has increased. However, this has also led to an annual increase in the number of patients with prolonged disorders of consciousness (pDoC). Hence, recovery of consciousness is an important part of treatment. With advancing techniques, noninvasive neuromodulation seems a promising intervention. The objective of this review was to summarize the latest techniques and provide the basis for protocols of noninvasive neuromodulations in pDoC.

METHODS

This review summarized the advances in noninvasive neuromodulation in the treatment of pDoC in the last 5 years.

RESULTS

Variable techniques of neuromodulation are used in pDoC. Transcranial ultrasonic stimulation (TUS) and transcutaneous auricular vagus nerve stimulation (taVNS) are very new techniques, while transcranial direct current stimulation (tDCS) and transcranial magnetic stimulation (TMS) are still the hotspots in pDoC. Median nerve electrical stimulation (MNS) has received little attention in the last 5 years.

CONCLUSIONS

Noninvasive neuromodulation is a valuable and promising technique to treat pDoC. Further studies are needed to determine a unified stimulus protocol to achieve optimal effects as well as safety.

Preventive noninvasive vagal nerve stimulation reduces insufficient sleep-induced depression by improving the autonomic nervous system

BACKGROUND

Depression is closely linked to an imbalance in the autonomic nervous system (ANS). However, the role of this imbalance in mediating the effects of sleep deprivation (SD) and vagus nerve stimulation (VNS) on emotional well-being is not fully understood.

METHODS

A population-based analysis was conducted to explore the relationship between sleep duration, depression scores, and heart rate variability (HRV). Additionally, the chronic SD mouse model was established to assess the impact of preventive transcutaneous auricular VNS (taVNS) on pathological and behavioral changes.

RESULTS

Our study found a significant link between sleep duration, depression severity, and HRV. Shorter sleep duration was associated with higher depression scores and lower RMSSD (a measure of HRV). In our rat model, insufficient sleep consistently impaired HRV. This effect was mitigated by taVNS, accompanied by corresponding changes in levels of IL-1β and IL-6, astrocyte and microglia activation, and tail suspension times.

CONCLUSIONS

Using VNS as a preventive treatment for depression-risk individuals with insufficient sleep shows promise. It not only broadens the potential applications of VNS but also sheds light on its mechanism-particularly its role in enhancing vagal nerve function and balancing the ANS, as evidenced by HRV measurements.

A scoping review of mechanisms of auricular acupuncture for treatment of pain

OBJECTIVES

Auricular acupuncture (AA) is becoming increasingly common in primary care clinics, emergency departments and peri-operatively for pain relief. Over the last decade, since the last comprehensive reviews were published, the literature has expanded. In this scoping review, we seek to document the efficacy of AA in treating both acute and chronic pain, describe the mechanism of action of AA in treating pain, and discuss how AA has been integrated into Western medicine to date.

METHODS

The authors performed a MEDLINE search inclusive of articles from 1966 to June 2023 including articles written in English identifying literature. We included human studies when more than 3 patients were included. Three hundred and fourteen unique articles were identified and 152 were selected by title screen. After abstract review, 117 were chosen for full-text review. Following full-text review, 33 articles were excluded and 21 added from references, totaling 105 articles included in our scoping review.

RESULTS

AA reduces pain severity in patients with both acute and chronic pain. The best studies in the acute settings have occurred in the peri-operative setting where sham AA is employed, multiple sessions of AA are given, and medication dosing is carefully monitored. In these cases, AA reduced pain and post-operative medications. In patients with chronic pain, multiple sessions of AA resulted not only in pain relief but also in improvements in function and disability. Literature suggests that AA works through multiple mechanisms with the most compelling data coupled to the autonomic nervous system and neuroendocrine system. Curriculums designed to teach AA and aid in implementation have been published.

CONCLUSION

AA is an accessible, effective means of pain relief. AA is relatively straightforward to learn, and protocols and curriculums exist to teach healthcare professionals this valuable skill. Overcoming implementation barriers, including patient education, are essential next steps.

Neural, Anti-Inflammatory, and Clinical Effects of Transauricular Vagus Nerve Stimulation in Major Depressive Disorder: A Systematic Review

BACKGROUND

The discovery of effective treatments for major depressive disorder (MDD) may help target different brain pathways. Invasive vagus nerve stimulation (VNS) is an effective neuromodulation technique for the treatment of MDD; however, the effectiveness of the noninvasive technique, transauricular VNS (taVNS), remains unknown. Moreover, a mechanistic understanding of the neural effects behind its biological and therapeutic effects is lacking. This review aimed to evaluate the clinical evidence and the neural and anti-inflammatory effects of taVNS in MDD.

METHODS

Two searches were conducted using a systematic search strategy reviewed the clinical efficacy and neural connectivity of taVNS in MDD in humans and evaluated the changes in inflammatory markers after taVNS in humans or animal models of depression. A risk of bias assessment was performed in all human studies.

RESULTS

Only 5 studies evaluated the effects of taVNS in patients with depression. Although the studies demonstrated the efficacy of taVNS in treating depression, they used heterogeneous methodologies and limited data, thus preventing the conduct of pooled quantitative analyses. Pooled analysis could not be performed for studies that investigated the modulation of connectivity between brain areas; of the 6 publications, 5 were based on the same experiment. The animal studies that analyzed the presence of inflammatory markers showed a reduction in the level of pro-inflammatory cytokines or receptor expression.

CONCLUSIONS

Data on the clinical efficacy of taVNS in the treatment of MDD are limited. Although these studies showed positive results, no conclusions can be drawn regarding this topic considering the heterogeneity of these studies, as in the case of functional connectivity studies. Based on animal studies, the application of taVNS causes a decrease in the level of inflammatory factors in different parts of the brain, which also regulate the immune system. Therefore, further studies are needed to understand the effects of taVNS in patients with MDD.

Advances in acupuncture regulation on the autonomic nervous system from 2013 to 2022: A bibliometric analysis via citespace

OBJECTIVE

To understand research advances and frontiers of acupuncture regulation on the autonomic nervous system (ANS) over the past decade through a bibliometric analysis.

METHODS

Publications related to acupuncture regulation on the ANS were retrieved from the Web of Science Core Collection (WoSCC) database. CiteSpace software was used to analyze the datasets and generate knowledge maps.

RESULTS

A total of 445 relevant publications published between 2013 and 2022 were included in this bibliometric analysis. The number of annual publications fluctuated from 2013 to 2016 but increased gradually from 2016 to 2022. China produced the highest number of publications, while the USA established the most extensive cooperation relationships. China Academy of Chinese Medical Science was the most productive institution. Chen Jiande D.Z. was the most prolific author and Rong Peijing holds the most extensive cooperation network. Han Jisheng was the most co-cited author. Relevant research involved mechanism exploration and clinical efficacy research, and "anti-inflammatory effect" was the most active research topic, especially cholinergic anti-inflammatory mechanisms. The most cited references mainly focused on inflammation. Gastrointestinal and cardiovascular disorders were the most active medical conditions studied in this field.

CONCLUSIONS

Research related to acupuncture regulation on the ANS mainly focused on anti-inflammation, and regulating gastrointestinal and cardiovascular function over the past decade. However, the mechanisms of the autonomic effects of acupuncture need further investigation. High-quality clinical studies are required to determine the optimal parameters of acupuncture for clinical application.

Efficacy of acupuncture therapy on cancer-related insomnia: a systematic review and network meta-analysis

Objectives

Cancer-related insomnia (CRI) takes a toll on many cancer survivors, causing distressing symptoms and deteriorating the quality of life. Acupuncture therapy has been used for CRI already. However, it is still uncertain which acupuncture regime is best for CRI. The primary objective of this review is to conduct a comparative evaluation and ranking of the effectiveness of different acupuncture therapies for CRI.

Methods

Randomized controlled trials (RCTs) that were published up to July 31, 2023, from 8 databases (PubMed, Embase, Cochrane library, Web of Science, China National Knowledge Infrastructure, Wanfang Database, VIP Database, and China Biology Medicine disc) were integrated in this study. Trials that met the inclusion criteria were evaluated the risk of bias. Pittsburgh sleep quality index (PSQI) was used to assess the efficacy of different acupuncture therapies as the primary outcome. Then, STATA 15, R, and OpenBUGS were applied to perform the network meta-analysis. PRISMA statements were followed in this network meta-analysis.

Results

A total of 37 studies were included in this review, involving 16 interventions with 3,246 CRI participants. Auriculotherapy + moxibustion [surface under the cumulative ranking curve (SUCRA) 98.98%] and auriculotherapy (SUCRA 77.47%) came out top of the ranking, which were more effective than control, medicine, usual care and sham acupuncture.

Conclusion

Auriculotherapy + moxibustion and auriculotherapy + acupuncture emerged as the top two acupuncture regimes for CRI and future studies should pay more attention to CRI.

Clinical trial registration

https://clinicaltrials.gov/, identifier INPLASY202210095.

Acupuncture Treatment for Generalized Anxiety Disorder by Activating the Vagus Nerve and Improving Heart-Rate Variability and Heart-Rhythm Coherence, A Case-Series Study

Objective

The goal of this case series was to observe the effectiveness of acupuncture for reducing sympathetic stress and anxiety-related symptoms in generalized anxiety disorder. The effect of acupuncture on the balance of the autonomic nervous system was also examined.

Materials and Methods

This was a case-series study with 10 participants enrolled. Each participant received acupuncture treatment 2 times per week for 4 weeks. Participants were evaluated with the Generalized Anxiety Disorder-7 (GAD-7) scale and the Body Perception Questionnaire-Short Form (BPQ-SF) before and after the treatment program. Heart-rate variability heart-rhythm coherence (HRC) was also assessed during each acupuncture session.

Results

Five participants completed the program. Both GAD-7 and BPQ mean scores showed significant reductions. The mean HRC high-coherence ratio also increased significantly after acupuncture treatment. No adverse effects occurred.

Conclusions

Acupuncture may be an effective therapy for sympathetic stress and anxiety-related symptoms. The mechanism of action may be through activating the vagus nerve and improving the HRC high coherence ratio. It is feasible to conduct larger clinical trials with random controls, longer treatment durations, and long-term follow-ups to support the results of this study.

Auricular Vagal Nerve Stimulation Inhibited Central Nerve Growth Factor/Tropomyosin Receptor Kinase A/Phospholipase C-Gamma Signaling Pathway in Functional Dyspepsia Model Rats With Gastric Hypersensitivity

OBJECTIVE

Functional dyspepsia (FD), which has a complicated pathophysiologic process, is a common functional gastrointestinal disease. Gastric hypersensitivity is the key pathophysiological factor in patients with FD with chronic visceral pain. Auricular vagal nerve stimulation (AVNS) has the therapeutic effect of reducing gastric hypersensitivity by regulating the activity of the vagus nerve. However, the potential molecular mechanism is still unclear. Therefore, we investigated the effects of AVNS on the brain-gut axis through the central nerve growth factor (NGF)/ tropomyosin receptor kinase A (TrkA)/phospholipase C-gamma (PLC-γ) signaling pathway in FD model rats with gastric hypersensitivity.

MATERIALS AND METHODS

We established the FD model rats with gastric hypersensitivity by means of colon administration of trinitrobenzenesulfonic acid on ten-day-old rat pups, whereas the control rats were given normal saline. AVNS, sham AVNS, K252a (an inhibitor of TrkA, intraperitoneally), and K252a + AVNS were performed on eight-week-old model rats for five consecutive days. The therapeutic effect of AVNS on gastric hypersensitivity was determined by the measurement of abdominal withdrawal reflex response to gastric distention. NGF in gastric fundus and NGF, TrkA, PLC-γ, and transient receptor potential vanilloid 1 (TRPV1) in the nucleus tractus solitaries (NTS) were detected separately by polymerase chain reaction, Western blot, and immunofluorescence tests.

RESULTS

It was found that a high level of NGF in gastric fundus and an upregulation of the NGF/TrkA/PLC-γ signaling pathway in NTS were manifested in model rats. Meanwhile, both AVNS treatment and the administration of K252a not only decreased NGF messenger ribonucleic acid (mRNA) and protein expressions in gastric fundus but also reduced the mRNA expressions of NGF, TrkA, PLC-γ, and TRPV1 and inhibited the protein levels and hyperactive phosphorylation of TrkA/PLC-γ in NTS. In addition, the expressions of NGF and TrkA proteins in NTS were decreased significantly after the immunofluorescence assay. The K252a + AVNS treatment exerted a more sensitive effect on regulating the molecular expressions of the signal pathway than did the K252a treatment.

CONCLUSION

AVNS can regulate the brain-gut axis effectively through the central NGF/TrkA/PLC-γ signaling pathway in the NTS, which suggests a potential molecular mechanism of AVNS in ameliorating visceral hypersensitivity in FD model rats.

Electro-acupuncture versus battle field auricular acupuncture in breast cancer survivors with chronic musculoskeletal pain: subgroup analysis of a randomized clinical trial

PURPOSE

Chronic musculoskeletal pain is common and debilitating among breast cancer survivors. The PEACE trial demonstrated that electro-acupuncture (EA) and battle field auricular acupuncture (BFAA) both reduced pain more than usual care (UC) in cancer survivors. However, the comparative effectiveness between EA and BFAA among breast cancer survivors is unknown.

METHODS

EA and BFAA received ten weekly treatments. UC was offered ten EA treatments after week 12. The primary endpoint was change in mean Brief Pain Inventory (BPI) pain severity from baseline to week 12. We analyzed the subset of 165 (46%) trial participants with a breast cancer primary diagnosis. We conducted constrained linear mixed model analyses, which constrained all arms to a common pre-randomization baseline mean. Model-based mean estimates at weeks 12 and 24 were compared between arms using model contrasts.

RESULTS

Among 165 breast cancer survivors, common pre-randomization mean pain severity was 5.35 [95% Confidence Interval (CI) 5.04, 5.66]. At week 12, BPI pain severity score was 2.69 (2.26. 3.13) in EA, 3.60 (3.17, 4.02) in BFAA, and 5.06 (4.47, 5.65) in UC. EA reduced pain severity significantly more than BFAA at weeks 12 [- 0.90 (- 1.45, - 0.36), p = 0.001] and 24 [- 0.82, (- 1.38, - 0.27), p = 0.004]. EA and BFAA significantly improved both Patient-Reported Outcomes Measurement Information System (PROMIS) - Global Health physical health and mental health component scores at week 12 compared to UC. Mild toxicities were reported.

CONCLUSION

EA was more effective than BFAA at reducing pain severity, but both similarly improved physical and mental health scores. Breast cancer survivors with chronic musculoskeletal pain may consider EA before BFAA.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02979574. https://clinicaltrials.gov/ct2/show/NCT02979574.

Management of auricular transcutaneous neuromodulation and electro-acupuncture of the vagus nerve for chronic migraine: a systematic review

Background

Migraine is a type of primary headache that is accompanied by symptoms such as nausea, vomiting, or sensitivity to light and sound.

Objective

The aim of this study was to conduct a systematic review on the effectiveness of non-invasive neuromodulation, auricular transcutaneous vagus nerve stimulation (at-VNS), and electro-ear acupuncture of the vagus nerve in patients with migraine headaches.

Methods

Six databases were searched from inception to 15 June 2022 for clinical trials, in which at least one group received any form of non-invasive neuromodulation of the vagus nerve for managing migraine with outcomes collected on pain intensity and related disability. Data, including participants, interventions, blinding strategy, outcomes, and results, were extracted by two reviewers. The methodological quality was assessed with the PEDro scale, ROB, and Oxford scale.

Results

The search identified 1,117 publications with nine trials eligible for inclusion in the review. The methodological quality scores ranged from 6 to 8 (mean: 7.3, SD: 0.8) points. Low-quality evidence suggests some positive clinical effects for the treatment of chronic migraine with 1 Hz with at-VNS and ear-electro-acupuncture compared with the control group at post-treatment. Some of the studies provided evidence of the relationship between chronic migraine and a possible positive effect as a treatment with at-VNS and the neurophysiological effects using fMRI. Six of the studies provided evidence using fMRI of the relationship between chronic migraine and a possible positive effect as a treatment with at-VNS and the neurophysiological effects. Regarding all included studies, the level of evidence with the Oxford scale was level 1 (11.17%), six studies were graded as level 2 (66.66%), and two studies were graded as level 3 (22.2%). With the PEDro score, five studies got a low methodological score < 5 and only four got a score superior to 5, being highly methodological quality studies. For ROB, most of the studies were high risk and only a few of them received a low risk of bias. The pain intensity, migraine attacks, frequency, and duration were measured by three studies with positive results at post-treatment. And only 7% reported adverse events using at-VNS. All studies reported results at a post-treatment period in their respective main outcomes. And all studies with fMRI provided strong evidence of the relationship between the Locus Coeruleus, Frontal Cortex, and other superior brain areas with the auricular branch of the Vagus nerve with at-VNS.

Conclusion

Some positive effects regarding the effect of non-invasive neuromodulation, auricular transcutaneous vagus nerve stimulation (at-VNS), and electro-ear acupuncture of the vagus nerve on migraine is reported in the current literature, but there are not enough data to obtain strong conclusions.

Systematic review registration

This systematic review was registered in the PROSPERO database (registration number: CRD42021265126).

Reflex Auriculo-Cardiac (RAC) Induced by Auricular Laser and Needle Acupuncture: New Case Results Using a Smartphone

The reflex auriculo-cardiac (RAC), dynamic pulse reaction (Nogier reflex), or vascular autonomic signal was proposed by Nogier. It refers to the pulse changes that can occur in the radial artery immediately after auricular acupuncture is performed. RAC is helpful for the clinical practice of auricular acupuncture, but there is a lack of objective verification methods. Photoplethysmography (PPG) has been used to objectively calculate radial artery blood flow. This study used PPG via a smartphone to measure RAC induced by auricular acupuncture. Thirty subjects without major diseases were recruited to receive traditional needle and laser acupuncture. The Shen Men ear point and control points were stimulated for 20 s. PPG was continuously measured during the acupuncture. The PPG data were tested for differences with a paired t-test. The results showed that there were no statistical differences in the frequency and amplitude of PPG obtained before and after acupuncture, either with a traditional needle or laser acupuncture. However, interestingly, it was found that one patient with insomnia, one patient with viral respiratory symptoms, and two menstruating females exhibited changes in PPG within five seconds of needle placement. We hypothesized that RAC might be induced by auricular acupuncture and could be quantified by PPG, even among subjects suffering from mild diseases; however, auricular acupuncture might not induce a measurable RAC in totally healthy subjects.

Optimizing the modulation paradigm of transcutaneous auricular vagus nerve stimulation in patients with disorders of consciousness: A prospective exploratory pilot study protocol

Background

Transcutaneous auricular vagus nerve stimulation (taVNS) is a non-invasive neuromodulation technique. Several studies have reported the effectiveness of taVNS in patients with disorders of consciousness (DOC); however, differences in the modulation paradigm have led to inconsistent treatment outcomes.

Methods/design

This prospective exploratory trial will include 15 patients with a minimally conscious state (MCS) recruited according to the coma recovery scale-revised (CRS-R). Each patient will receive 5 different frequencies of taVNS (1, 10, 25, 50, and 100 Hz); sham stimulation will be used as a blank control. The order of stimulation will be randomized, and the patients' CRS-R scores and resting electroencephalography (EEG) before and after stimulation will be recorded.

Discussion

The overall study of taVNS used in treating patients with DOC is still in the preliminary stage of exploration. Through this experiment, we aim to explore the optimal stimulation frequency parameters of taVNS for the treatment of DOC patients. Furthermore, we expect to achieve a stable improvement of consciousness in DOC patients by continuously optimizing the neuromodulation paradigm of taVNS for the treatment of DOC patients.

Clinical trial registration

https://www.chictr.org.cn/index.aspx, identifier ChiCTR 2200063828.

Acupuncture and moxibustion in patients with cancer-related insomnia: A systematic review and network meta-analysis

OBJECTIVES

Cancer-related insomnia (CRI) is one of the most common and serious symptoms in patients with cancer. Acupuncture and moxibustion have been widely applied in the treatment of CRI. Nevertheless, the comparative efficacy and safety of different acupuncture and moxibustion techniques remain unclear. This study aimed to evaluate and compare the efficacy and safety of different acupuncture and moxibustion techniques in the treatment of CRI.

METHODS

Eight medical databases were comprehensively searched for relevant randomized controlled trials (RCTs) as of June 2022. Two independent reviewers assessed the risk of bias and conducted the research selection, data extraction, and quality assessment of the included RCTs. A network meta-analysis (NMA) was performed using frequency models, combining all available direct and indirect evidence from RCTs. The Pittsburgh Sleep Quality Index (PSQI) was set as the primary outcome, and adverse events and effective rates were set as the secondary outcomes. The efficacy rate was calculated as the ratio of patients with insomnia symptom relief to the total number of patients.

RESULTS

Thirty-one RCTs with 3,046 participants were included, including 16 acupuncture- and moxibustion-related therapies. Transcutaneous electrical acupoint stimulation [surface under the cumulative ranking curve (SUCRA) 85.7%] and acupuncture and moxibustion (SUCRA 79.1%) were more effective than Western medicine, routine care, and placebo-sham acupuncture. Furthermore, Western medicine showed significantly better effects than placebo-sham acupuncture. In the NMA, the acupuncture and moxibustion treatments with the best therapeutic effects for CRI were transcutaneous electrical acupoint stimulation (SUCRA 85.7%), acupuncture and moxibustion (SUCRA 79.1%), auricular acupuncture (SUCRA 62.9%), routine care combined with intradermal needling (SUCRA 55.0%), and intradermal needling alone (SUCRA 53.3%). No serious acupuncture- or moxibustion-related adverse events were reported in the included studies.

CONCLUSION

Acupuncture and moxibustion are effective and relatively safe in treating CRI. The relatively conservative recommended order of acupuncture- and moxibustion-related therapies for CRI is as follows: transcutaneous electrical acupoint stimulation, acupuncture and moxibustion, and auricular acupuncture. However, the methodological quality of the included studies was generally poor, and further high-quality RCTs are needed to strengthen the evidence base.

Efficacy of auricular acupuncture in improving dry mouth among an institutionalised older population: A randomised controlled study

AIMS

To investigate the efficacy of applying auricular acupuncture (AA) treatment in improving dry mouth in institution-dwelling older adults.

BACKGROUND

Dry mouth (xerostomia) is a common distressing problem in older populations, especially for institution-dwelling older adults that can affect oral health and quality of life.

DESIGN

A randomised controlled trial was conducted from December 2020 to March 2021 and performed according to STRICTA guidelines extended from the CONSORT statement.

METHODS

Older adults aged more than 65 years were randomly allocated to an AA group (n = 37) with an 8-week actual auricular points treatment or a control group (n = 38) receiving sham auricular point acupuncture. Measurements comprised a subjective assessment of the level of dry mouth as assessed by a visual analogue scale in a xerostomia questionnaire, and an objective assessment of the physiological wetness of the lingual mucosa measured with a moisture-checking device. A generalised estimating equation model was used for data analyses.

RESULTS

After completing an 8-week AA intervention stimulating the Shenmen, Point Zero and Salivary Gland 2-prime points, the AA group exhibited significantly improved subjective symptoms of dry mouth comprised of difficulty speaking (B = -6.47, p < .001), difficulty swallowing (B = -6.73, p < .001), the amount of oral saliva (B = -5.38, p < .001), a dry throat (B = -7.53, p < .001) and thirst (B = -8.06, p < .001) compared with the control group. Moreover, the AA group had higher objective oral saliva flow than the control group (B = 4.73, p < .001).

CONCLUSION

AA is an effective non-pharmacological method for improving subjective symptoms of dry mouth and objective saliva secretion in older populations living in nursing homes.

RELEVANT TO CLINICAL PRACTICE

Performing regular AA on the Shenmen, Point Zero and Salivary Gland 2-prime auricular points can be considered an alternative treatment approach to improve dry mouth in institution-dwelling older adults.

A bibliometric analysis of 100 top-cited journal articles related to acupuncture regulation of the autonomic nervous system

Purpose

Research on the effects of acupuncture on autonomic function has been conducted for several decades, and a few notable studies have emerged in recent years. This study used bibliometric analysis to assess 100 top-cited articles to characterize the current status and research trends over the last three decades.

Methods

The 100 top-cited publications were identified from the Web of Science Core Collection database. The bibliometrix package in R was used for quantitative and qualitative analyses of the publication patterns and the country/region, institution, and author contributions. VOSviewer was used to construct networks based on co-citation analysis of the journals and the keyword co-occurrence.

Results

The 100 top-cited articles were identified with a total of 8,123 citations (range: 37-345). The majority of the articles came from the USA (n = 42), followed by Japan (n = 14) and mainland China (n = 13). Articles from the USA exhibited the largest number of citations (3,582 citations), followed by articles from Japan (1,189 citations), then articles from mainland China (755 citations). Neurosciences/Neurology was the most studied research area (n = 41). The Autonomic Neuroscience: Basic and Clinical published the largest number of papers (n = 14), while Brain Research received the largest number of citations (205 citations). Longhurst JC was the most productive author (10 publications), and Sato A was first among the cited authors (87 citations). The most frequently cited articles that focused on gastrointestinal, cardiovascular, or gynecologic responses to acupuncture regulation of the autonomic nervous system first appeared in the 1990s, peaked in the 2000s, then decreased after 2010. Publication of articles focused on the anti-inflammatory effects of acupuncture associated with autonomic function demonstrated an increasing trend over the last three decades.

Conclusion

From the initial studies focusing on the autonomic mechanism of visceral responses to acupuncture, researchers concentrated on exploring the autonomic mechanism of acupuncture in the control of systemic inflammation. Non-invasive electrical methods that activate somato-autonomic reflexes are current translational directions in clinical practice. Additional investigation of the underlying neuroanatomical basis of somato-autonomic reflexes also is needed.

Vagus Nerve Stimulation: A Personalized Therapeutic Approach for Crohn's and Other Inflammatory Bowel Diseases

Inflammatory bowel diseases, including Crohn's disease and ulcerative colitis, are incurable autoimmune diseases characterized by chronic inflammation of the gastrointestinal tract. There is increasing evidence that inappropriate interaction between the enteric nervous system and central nervous system and/or low activity of the vagus nerve, which connects the enteric and central nervous systems, could play a crucial role in their pathogenesis. Therefore, it has been suggested that appropriate neuroprosthetic stimulation of the vagus nerve could lead to the modulation of the inflammation of the gastrointestinal tract and consequent long-term control of these autoimmune diseases. In the present paper, we provide a comprehensive overview of (1) the cellular and molecular bases of the immune system, (2) the way central and enteric nervous systems interact and contribute to the immune responses, (3) the pathogenesis of the inflammatory bowel disease, and (4) the therapeutic use of vagus nerve stimulation, and in particular, the transcutaneous stimulation of the auricular branch of the vagus nerve. Then, we expose the working hypotheses for the modulation of the molecular processes that are responsible for intestinal inflammation in autoimmune diseases and the way we could develop personalized neuroprosthetic therapeutic devices and procedures in favor of the patients.

Non-invasive tragus stimulation improves cardiac post-ischemic remodeling by regulating cardiac parasympathetic activity

AIMS

Our previous study proved that low-level tragus nerve stimulation (LL-TS) could improve left ventricular remodelling by cardiac down-stream mechanisms. However, the cardiac up-stream mechanisms remain unknown.

METHODS AND RESULTS

Twenty-eight adult beagle dogs were randomly divided into an MI group (myocardial infarction was induced by permanent ligation of the left coronary artery, n = 10), an LL-TS group (MI plus intermittent LL-TS treatment, n = 10), and a control group (sham ligation with the same stimulation as the LL-TS group, n = 8). Auricular tragus nerve was bilaterally delivered to the tragus via ear-clips connected to a custom-made stimulator. The voltage slowing sinus rate was used as the threshold to set the LL-TS 80% below this level. At the end of 4 weeks post-MI, LL-TS could significantly increase atrial ganglion plex (GP) activity, decreased left stellate ganglion (LSG) activity, reduced LV dilation, and improved ventricular functions. Chronic intermittent LL-TS treatment significantly attenuated left ventricular remodelling via the up-regulation of α7nAChR expression and the down-regulation of MMP-9 level in post-MI LV tissue. The elevated protein and mRNA of MMP-9 levels in remote areas were significantly ameliorated by LL-TS treatment.

CONCLUSIONS

Chronic LL-TS increased GP neural activity and improved ventricular remodelling possibly via α7nAChR/MMP-9 axis.

Single-Cell Transcriptional Profiling Reveals Low-Level Tragus Stimulation Improves Sepsis-Induced Myocardial Dysfunction by Promoting M2 Macrophage Polarization

Background

Sepsis can lead to multiple organ damage, of which the heart is one of the most vulnerable organs. Vagal nerve stimulation can reduce myocardial injury in sepsis and improve survival rates. However, the potential impact of low-level tragus stimulation and disparate cell populations on sepsis-induced myocardial dysfunction remains undetermined.

Methods

A cardiac single-cell transcriptomic approach was used for characterizing cardiac cell populations that form the heart. Single-cell mRNA sequencing data were used for selecting all cardiac macrophages from CD45+ cells. Then, echocardiography, western blot, flow cytometry, immunofluorescence, and immunohistochemistry were performed to verify the single-cell mRNA sequencing results.

Results

Using single-cell mRNA sequencing data, we uncovered the multiple cell populations contributing to myocardial injury in sepsis under low-level tragus stimulation, thereby illustrating a comprehensive map of the cardiac cellular landscape. Pseudotiming analysis in single-cell sequencing showed that low-level vagal nerve stimulation played an anti-inflammatory role by promoting cardiac monocytes into M2 macrophages, which significantly increased α7nAChR expression in heart tissues. Echocardiography assessment indicated that low-level vagal nerve stimulation could also improve cardiac functions in mice with sepsis-induced myocardial dysfunction. In addition, the heart tissues of mice from the sepsis group with low-level tragus stimulation had significantly lower interleukin-1β expression levels than those from the sepsis group. Flow cytometry analysis showed that different acetylcholine concentrations promoted cardiac monocytes into M2 macrophages in in vitro experiments.

Conclusion

Low-level tragus stimulation could improve sepsis-induced myocardial dysfunction by promoting cardiac monocytes to M2 macrophages.

Transauricular Vagal Nerve Stimulation at 40 Hz Inhibits Hippocampal P2X7R/NLRP3/Caspase-1 Signaling and Improves Spatial Learning and Memory in 6-Month-Old APP/PS1 Mice

OBJECTIVES

Transauricular vagal nerve stimulation (taVNS) at 40 Hz attenuates hippocampal amyloid load in 6-month-old amyloid precursor protein/presenilin 1 (APP/PS1) transgenic mice, but it is unclear whether 40-Hz taVNS can improve cognition in these mice. Moreover, the underlying mechanisms are still unclear.

MATERIALS AND METHODS

6-month-old C57BL/6 (wild type [WT]) and APP/PS1 mice were subjected to 40-Hz taVNS. Novel Object Recognition and the Morris Water Maze were used to evaluate cognition. Hippocampal amyloid-β (Aβ)1-40, Aβ1-42, pro-interleukin (IL)-1β, and pro-IL-18 were measured using enzyme-linked immunosorbent assays. Hippocampal Aβ42, purinergic 2X7 receptor (P2X7R), nucleotide-binding oligomerization domain-like receptor pyrin domain containing 3 (NLRP3), Caspase-1, IL-1β, and IL-18 expression were evaluated by western blotting. Histologic assessments including immunofluorescence, immunohistochemistry, Nissl staining, and Congo red staining were used to assess microglial phagocytosis, neuroprotective effects, and Aβ plaque load.

RESULTS

40-Hz taVNS improved spatial memory and learning in 6-month-old APP/PS1 mice but did not affect recognition memory. There were no effects on the cognitive behaviors of 6-month-old WT mice. taVNS at 40 Hz modulated microglia; significantly decreased levels of Aβ1-40, Aβ1-42, pro-IL-1β, and pro-IL-18; inhibited Aβ42, P2X7R, NLRP3, Caspase-1, IL-1β, and IL-18 expression; reduced Aβ deposits; and had neuroprotective effects in the hippocampus of 6-month-old APP/PS1 mice. These changes were not observed in 6-month-old WT mice.

CONCLUSION

Our results show that 40-Hz taVNS inhibits the hippocampal P2X7R/NLRP3/Caspase-1 signaling and improves spatial learning and memory in 6-month-old APP/PS1 mice.

Auricular Acupuncture During Chemotherapy Infusion in Breast Cancer Patients: A Feasibility Study

Introduction: Breast cancer patients undergoing chemotherapy experience multiple distressing symptoms. The authors investigated the feasibility and potential benefits of auricular acupuncture during chemotherapy infusion in this population. Materials and Methods: Women with stage I-III breast cancer undergoing chemotherapy were enrolled and followed for three chemotherapy cycles. During the first cycle of chemotherapy that participants received after study enrollment, they were provided with educational materials. During the second and third cycles of chemotherapy after enrollment, they received auricular acupuncture. The primary outcome was feasibility, assessed by recruitment, retention, and completion of assessments. Secondary outcomes included symptom burden (Edmonton Symptom Assessment System-Revised Version) and anxiety (State-Trait Anxiety Inventory-State), assessed at four timepoints for each cycle: day 1, pre-education/acupuncture (T1); day 1, post-education/acupuncture (T2); day 2 (T3); and day 5 (T4). Nausea and vomiting (Multinational Association of Supportive Care in Cancer [MASCC] Antiemesis Tool) were assessed on days 2 and 5. Paired t test was used to compare patient-reported outcomes during cycle 1 (education) versus an average of outcomes during cycles 2 and 3 (acupuncture). Results: Twenty-six patients were enrolled, of which 24 completed all acupuncture sessions and 22 completed all outcome assessments. In cycles 2 and 3 versus cycle 1, participants experienced significant reductions in symptom burden (change from T1 to T4: -7.9 ± 13.6, p = 0.02), anxiety (change from T1 to T2: -3.3 ± 6.5, p = 0.02), and nausea severity on day 2 (-1.3 ± 2.6, p = 0.04). Conclusions: The delivery of auricular acupuncture during chemotherapy infusion was feasible and associated with reduction of symptom burden, anxiety, and nausea in breast cancer patients. Larger-scale clinical studies are needed to confirm these findings. Clinical Trial Registration number: NCT03170648.

Auricular Acupressure for Hemodialysis Patients with Insomnia: A Multicenter Double-Blind Randomized Sham-Controlled Trial

Background and objectives: The effect of auricular acupressure (AA) for maintenance hemodialysis (MHD) patients with insomnia has been controversial. This study assessed the efficacy and safety of AA for MHD patients with chronic insomnia. Design, setting, participants, and measurements: This was a multicenter, double-blind (participant and assessor), randomized sham-controlled trial. A total of 133 subjects were randomized to receive AA on active points (AA group, n = 64) or on sham auricular acupressure (SAA) points (SAA group, n = 69) for 8 weeks and followed up for 12 weeks. AA was provided by assigned qualified nurses who were not involved in assessment. The primary outcome was the clinical response rate, which was defined as the percentage of participants who reached a reduction of Pittsburgh Sleep Quality Index (PSQI) global score ≥3 in each group. Secondary outcomes included changes in PSQI scores over time, PSQI scores and hypnotics use at each visit, and changes in the weekly dose of hypnotics for drug-dependent subjects. Results: At week 8, the AA group yielded a higher clinical response rate than the SAA group (AA: 55% vs. SAA: 36%, odds ratio: 1.5, 95% confidence interval: 1.0-2.2, p = 0.033). Both groups showed a reduction in PSQI global scores during treatment and follow-up, compared with the baseline, respectively. A significant change of PSQI global score was observed over time (F = 28.387, p < 0.001). PSQI global score of the AA group was relatively lower than that of the SAA group at each visit (p < 0.05 at week 16 and 20). For those depending on hypnotics, AA reduced their consumption of hypnotics. The intervention was safe, and its adherence was satisfactory. Conclusion: AA could serve as a complementary or alternative therapy for MHD patients with insomnia by improving their sleep quality and reducing their use of hypnotics. Clinical trial registration: Clinicaltrials.gov, Identifier: NCT03015766.

Toward Diverse or Standardized: A Systematic Review Identifying Transcutaneous Stimulation of Auricular Branch of the Vagus Nerve in Nomenclature

OBJECTIVES

After 20 years of development, there is confusion in the nomenclature of transcutaneous stimulation of the auricular branch of the vagus nerve (ABVN). We performed a systematic review of transcutaneous stimulation of ABVN in nomenclature.

MATERIALS AND METHODS

A systematic search of the literature was carried out, using the bibliographic search engine PubMed. The search covered articles published up until June 11, 2020. We recorded the full nomenclature and abbreviated nomenclature same or similar to transcutaneous stimulation of ABVN in the selected eligible studies, as well as the time and author information of this nomenclature.

RESULTS

From 261 studies, 67 full nomenclatures and 27 abbreviated nomenclatures were finally screened out, transcutaneous vagus nerve stimulation and tVNS are the most common nomenclature, accounting for 38.38% and 42.06%, respectively. In a total of 97 combinations of full nomenclatures and abbreviations, the most commonly used nomenclature for the combination of transcutaneous vagus nerve stimulation and tVNS, accounting for 30.28%. Interestingly, the combination of full nomenclatures and abbreviations is not always a one-to-one relationship, there are ten abbreviated nomenclatures corresponding to transcutaneous vagus nerve stimulation, and five full nomenclatures corresponding to tVNS. In addition, based on the analysis of the usage habits of nomenclature in 21 teams, it is found that only three teams have fixed habits, while other different teams or the same team do not always use the same nomenclature in their paper.

CONCLUSIONS

The phenomenon of confusion in the nomenclature of transcutaneous stimulation of ABVN is obvious and shows a trend of diversity. The nomenclature of transcutaneous stimulation of ABVN needs to become more standardized in the future.

Transcutaneous auricular vagal nerve stimulation inhibits limbic-regional P2X7R expression and reverses depressive-like behaviors in Zucker diabetic fatty rats

Zucker diabetic fatty (ZDF) rats develop type 2 diabetes (T2D) along with depressive-like behaviors. Transcutaneous auricular vagal nerve stimulation (taVNS) has antidiabetic and antidepressant-like effects in ZDF rats; however, the underlying antidepressant-like mechanisms are unclear. The purinergic receptor P2X7R, which is related to inflammation and depression, is upregulated in the limbic brain regions of depressed patients and rodents and is considered as a potential therapeutic target. Thus, this study aimed to provide preliminary evidence at the molecular level of taVNS antidepressant-like effect in ZDF rats through testing their limbic-regional P2X7R expression. ZDF rats were subjected to taVNS and transcutaneous non-vagal nerve stimulation (tnVNS). Body weight and blood glucose levels were monitored weekly. Depressive-like behaviors were evaluated with the open-field test (OFT) and forced swimming test (FST). Limbic-regional P2X7R expression was examined by western blotting (WB). P2X7R expressing cells were detected by immunohistochemistry (IHC). Compared to their lean littermates (ZL rats), ZDF rats developed obesity, hyperglycemia, and depressive-like behaviors with elevated limbic-regional P2X7R expression. taVNS but not tnVNS lowered body weight, reduced and stabilized blood glucose levels, suppressed limbic-regional P2X7R expression, and reversed the depressive-like behaviors. P2X7R was found primarily expressed in ZDF rats' limbic-regional astrocytes. In conclusion, taVNS inhibits ZDF rats' limbic-regional P2X7R expression, which may be one of the taVNS antidepressant-like mechanisms.

Auricular Vagus Nerve Stimulation Attenuates Lipopolysaccharide-Induced Acute Lung Injury by Inhibiting Neutrophil Infiltration and Neutrophil Extracellular Traps Formation

ABSTRACT

Vagus nerve stimulation has been shown to exert anti-inflammation activities in sepsis. However, surgical implantation of stimulation devices is performed under general anesthesia, which limits its clinical application. Auricular vagus nerve stimulation (AVNS) is a minimal invasive technique that delivers electrical currents to the auricular branch of the vagus nerve. The purpose of this study was to determine the effects of AVNS on systemic inflammation, lung injury, neutrophil infiltration, and neutrophil extracellular traps (NETs) formation in the lung. In a LPS challenge lung-injury mice model, AVNS was applied to bilateral ears. Twelve hours after LPS administration, samples of blood, bronchoalveolar lavage fluid (BALF), and lung tissues were processed for investigations. We found that the treatment with AVNS significantly attenuated histopathological changes and neutrophil infiltration in the lung tissue, inhibited inflammatory cytokine elevations in serum and BALF, and decreased protein concentrations in BALF. Besides, AVNS decreased leukocyte and neutrophil accounts in BALF. Furthermore, colocalization of citrullination of histone H3 and myeloperoxidase expressions (highly specific marker of NETs) was reduced in AVNS mice. In conclusion, AVNS reduced systemic inflammation, attenuated lung edema, and inhibited neutrophil infiltration and NETs formation in the lung in LPS mice.

A potential treatment approach for subclinical mastitis in dairy cows: auriculotherapy of the auricular branch of the vagus nerve

This research aims to test the hypothesis that neural therapy (NT) on the auricular branch of the vagus nerve (ABVN) in dairy cows diagnosed with subclinical mastitis (SCM) results in a reduction of the somatic cell count. Therapeutic options for SCM are mostly based on use of antibiotics and often lead to unsatisfactory results. An alternative therapy targeting the anti-inflammatory properties of the vagus nerve showing good efficacy, economic viability and without major side effects would be of considerable interest. Auriculotherapy (AT) was performed using three repeated infiltrations of 8.0 mg (0.4 ml) procaine hydrochloride (2%) at the location of the ear tag associated with the auricular acupuncture point (AAP) of the udder. Some 85 clinically healthy cows from nine dairy farms were sampled for evaluation of quarter somatic cell count (QSCC) on four days (d0, d2, d4 and d6). Quarters with a QSCC > 100 000 cells/ml on d0 were included in the analysis. Over the study period, a total of 784 quarters were analysed, 385 control (CON) quarters from 40 cows and 399 treated (TRE) quarters from 45 cows. Results showed that AT of the ABNV resulted in a significant reduction of the QSCC after three treatments. The effect was independent of bacteriological culture results of the quarter milk samples. The bacteriological cure rate, however, was not influenced by AT. To our knowledge this is the first report of AT reducing QSCC in dairy cows with SCM. Before AT can be regarded as an alternative therapeutic approach, further research should focus on possible long-term effects of AT on the reduction of SCC, any bacterial elimination and the neural pathways of AT in dairy cows with SCM.

Mechanisms underlying antidepressant effect of transcutaneous auricular vagus nerve stimulation on CUMS model rats based on hippocampal α7nAchR/NF-κB signal pathway

Background

Stress-induced neuroinflammation was considered to play a critical role in the pathogenesis of depression. Transcutaneous auricular vagus nerve stimulation (taVNS) is a relatively non-invasive alternative treatment for patients suffering from major depressive disorder. The anti-inflammatory signal of vagus nerve is mediated by α7 nicotinic acetylcholine receptor (α7nAchR), and the hippocampus, the region with the most distribution of α7nAchR, regulates emotions. Here, we investigated the role of α7nAchR mediating hippocampal neuroinflammation in taVNS antidepressant effect though homozygous α7nAChR (−/−) gene knockout and α7nAchR antagonist (methyllycaconitine, MLA).

Methods

There were control, model, taVNS, α7nAChR(−/−) + taVNS, hippocampus (Hi) MLA + taVNS and Hi saline + taVNS groups. We used the chronic unpredicted mild stress (CUMS) method to establish depressive model rats for 42 days, excepting control group. After the successful modeling, except the control and model, the rats in the other groups were given taVNS, which was applied through an electroacupuncture apparatus at the auricular concha (2/15 Hz, 2 mA, 30 min/days) for 21 days. Behavioral tests were conducted at baseline, after modeling and after taVNS intervention, including sucrose preference test (SPT), open field test (OFT) and forced swimming test (FST). These tests are widely used to evaluate depression-like behavior in rats. The samples were taken after experiment, the expressions of α7nAchR, NF-κB p65, IL-1β and the morphology of microglia were detected.

Results

Depression-like behavior and hippocampal neuroinflammation in CUMS model rats were manifested by down-regulated expression of α7nAchR, up-regulated expression of NF-κB p65 and IL-1β, and the morphology of microglia was in amoebic-like activated state. TaVNS could significantly reverse the above-mentioned phenomena, but had rare improvement effect for α7nAChR(−/−) rats and Hi MLA rats.

Conclusion

The antidepressant effect of taVNS is related to hippocampal α7nAchR/NF-κB signal pathway.

Ear acupuncture as an adjunct in a treatment protocol for anorexia nervosa: utilization rate and nurses' experience

BACKGROUND

Anorexia nervosa (AN) is a life-threatening illness. Sometimes long inpatient treatment is necessary, increasing the anxiety that comes with hospitalization and the necessary weight gain. Safe, non-pharmacological adjunctive therapies that improve subjective health are called for.

OBJECTIVE

The aim of this non-randomized, mixed-methods observational study was to describe the utilization rate and nurses' experiences of ear acupuncture in a highly specialized clinic for eating disorders in Sweden, in which acupuncture had been implemented as part of routine clinical care. Twenty-five patients with AN-treated voluntarily or by law were included. The semi-standardized National Acupuncture Detoxification Association (NADA) ear acupuncture protocol, sometimes combined with needling at 2 traditional acupuncture point locations on the body, had been implemented as a voluntary adjunct to usual care, twice weekly. To evaluate the acceptance of acupuncture, the study examined how often patients chose acupuncture when offered on schedule, and how often they asked for extra acupuncture sessions. Patients rated their subjective health using the hospital anxiety and depression scale (HADS) and visual analogue scale (VAS), treatment satisfaction with usual care and acupuncture, and health-related quality of life with the RAND36 instrument. A credibility/expectancy questionnaire (CEQ) was used to measure confidence in treatment. Body mass index (BMI) was calculated to follow the patients' recovery. Nurses' experiences of giving acupuncture as a part of routine care were captured in interviews, and analysed with content analysis. Ethical approval was obtained.

RESULTS

Despite an initially moderate level of trust in acupuncture, the utilization rate of the scheduled acupuncture was 89% and patients asked for extra acupuncture sessions on 28 occasions. No serious side effects were reported. Nurses' experiences of providing acupuncture were positive. They were generally enthusiastic, although they reported finding it difficult to organize group treatments and to find time for acupuncture sessions if they were not scheduled.

CONCLUSION

Further research into the effectiveness and costs of acupuncture in psychiatric care is needed. This study provides relevant information for clinicians as well as researchers planning future randomized controlled trials.

Reassessment of the Effect of Transcutaneous Auricular Vagus Nerve Stimulation Using a Novel Burst Paradigm on Cardiac Autonomic Function in Healthy Young Adults

BACKGROUND

Transcutaneous auricular vagus nerve stimulation (taVNS) may modulate cardiac autonomic function. However, the response rate of the traditional tonic paradigm is low, and the results remain inconsistent. A recent pilot study presented a novel burst paradigm to activate the cardiac parasympathetic system, which might offer a new approach to treat cardiac autonomic function. The present study reassessed the effect of burst taVNS on modulating heart rate variability and explored the difference between burst and traditional tonic paradigms.

MATERIALS AND METHODS

Forty-two young adults were recruited for this study. Each participant underwent three types of taVNS with sham (30 sec of stimulation), tonic (25 Hz, 500 μsec), and burst (five pulses at 500 Hz every 200 msec) paradigms, respectively, with simultaneous electrocardiogram recording. One-way analysis of variance, multivariate analysis of variance, and linear regression were used for analysis. Multiple testing was performed using Bonferroni correction.

RESULTS

Both burst and tonic paradigms induced a significant decrease in heart rate, which continued until poststimulation, and increased cardiac parasympathetic activity. Moreover, two parasympathetic system indicators showed significant increase only in burst taVNS. The response rates during burst (35.7%) and tonic (38.1%) stimulations were both higher than that during sham stimulation (11.9%). The response to taVNS showed parameter specificity with few nonresponders to the tonic paradigm responding to the burst paradigm. The overall response rate increased from 38.1% in tonic taVNS to 54.8% in taVNS using both burst and tonic paradigms. For both burst and tonic responders, baseline cardiac parasympathetic activity was found to be significantly negatively correlated with changes during stimulation.

CONCLUSION

The burst parameter could be used as an alternative strategy for regulating cardiac parasympathetic function by taVNS, which has the potential to be used as a complementary paradigm to traditional tonic taVNS for promoting clinical treatment efficacy.

Auricular Neuromodulation for Mass Vagus Nerve Stimulation: Insights From SOS COVID-19 a Multicentric, Randomized, Controlled, Double-Blind French Pilot Study

Importance: An exacerbated inflammatory response to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is believed to be one of the major causes of the morbidity and mortality of the coronavirus disease 2019 (COVID-19). Neuromodulation therapy, based on vagus nerve stimulation, was recently hypothesized to control both the SARS-CoV-2 replication and the ensuing inflammation likely through the inhibition of the nuclear factor kappa-light-chain-enhancer of activated B cells pathway and could improve the clinical outcomes as an adjunct treatment. We proposed to test it by the stimulation of the auricular branch of the vagus nerve, i.e., auricular neuromodulation (AN), a non-invasive procedure through the insertion of semipermanent needles on the ears.

Objective: The aim of this study was to assess the effect of AN on the clinical outcomes in patients affected by COVID-19.

Design, Setting, and Participants: A multicenter, randomized, placebo-controlled, double-blind clinical trial included 31 patients with respiratory failure due to COVID-19 requiring hospitalization. Within 72 h after admission, patients received either AN (n = 14) or sham neuromodulation (SN, n = 15) in addition to the conventional treatments.

Main Outcome and Measures: The primary endpoint of the study was the rate of a clinical benefit conferred by AN at Day 14 (D14) as assessed by a 7-point Clinical Progression Scale. The secondary endpoint of the study was the impact of AN on the rate of transfer to the intensive care unit (ICU) and on the survival rate at D14.

Results: The AN procedure was well-tolerated without any reported side effects but with no significant improvement for the measures of both primary (p > 0.3) and secondary (p > 0.05) endpoints at the interim analysis. None of the AN-treated patients died but one in the SN group did (81 years). Two AN-treated patients (73 and 79 years, respectively) and one SN-treated patient (59 years) were transferred to ICU. Remarkably, AN-treated patients were older with more representation by males than in the SN arm (i.e., the median age of 75 vs. 65 years, 79% male vs. 47%).

Conclusion: The AN procedure, which was used within 72 h after the admission of patients with COVID-19, was safe and could be successfully implemented during the first two waves of COVID-19 in France. Nevertheless, AN did not significantly improve the outcome of the patients in our small preliminary study. It is pertinent to explore further to validate AN as the non-invasive mass vagal stimulation solution for the forthcoming pandemics.

Clinical Trial Registration: [https://clinicaltrials.gov/], identifier [NCT04341415].

Efficacy of auricular acupressure in maintenance haemodialysis patients: A systematic review and meta-analysis

OBJECTIVES

To systematically evaluate the efficacy of auricular acupressure on sleep disorders, depression, pruritus, xerostomia and daily net weight gain (%) in maintenance haemodialysis patients.

BACKGROUND

Auricular acupressure has been used for various complications in maintenance haemodialysis patients, such as sleep disorders, depression, pruritus and xerostomia, but the efficacy has not yet been unified.

DESIGN

Systematic review and meta-analysis.

METHODS

Randomised controlled trials comparing auricular acupressure intervention with non-AA intervention in maintenance haemodialysis patients were included. We searched English databases (PubMed, Cochrane Library, Embase, Web of Science) and Chinese databases (CNKI, WanFang, CBM and VIP database) from the inception to 27 November 2020. The risk of bias was assessed by the Cochrane risk of bias tool. The RevMan 5.3 software was used to perform the meta-analysis. A descriptive analysis was conducted if the data were high of heterogeneity or could not be meta-analysed. The PRISMA statement was used to report systematic review and meta-analysis.

RESULTS

A total of 12 RCTs with 805 MHD patients were included. Meta-analysis showed that auricular acupressure had a significant difference for improving sleep disorders (MD = -1.97 points, 95% CI: -2.62 to -1.32, p < .0001), pruritus (MD = -1.55 points, 95% CI: -2.01 to -1.08, p < .0001), and daily net weight gain (%) (MD = -0.29, 95% CI: -0.37 to -0.21, p < .0001). The efficacy of depression and xerostomia were analysed descriptively due to insufficient data.

CONCLUSIONS

The meta-analysis results indicated that auricular acupressure had a positive efficacy in maintenance haemodialysis patients to improve sleep disorders, pruritus and daily net weight gain (%). But the results should be treated conservatively on account of the low quality of included studies. Future researchers need to conduct more high-quality, large sample, multi-centre randomised controlled studies to provide a solid basis to demonstrate of the efficacy of auricular acupressure in maintenance haemodialysis patients.

RELEVANCE TO CLINICAL PRACTICE

Auricular acupressure has the advantages of low cost, non-invasive and easy to be accepted by patients. This review suggested that auricular acupressure could be considered a non-pharmacological intervention for maintenance haemodialysis patients. Medical staff could teach maintenance haemodialysis patients auricular acupressure to help them self-manage some complications at home.

Cerebral Hemodynamic Correlates of Transcutaneous Auricular Vagal Nerve Stimulation in Consciousness Restoration: An Open-Label Pilot Study

This study aimed to preliminarily illustrate the cerebral hemodynamic correlates of transcutaneous auricular vagal nerve stimulation (taVNS) in consciousness restoration. Arterial spin labeling (ASL) was adopted with functional magnetic resonance imaging (fMRI) to measure cerebral blood flow (CBF) changes before and after taVNS in 10 qualified patients with disorders of consciousness (DOC). Before taVNS, five patients responded to auditory stimuli (RtAS), and five did not respond to auditory stimuli (nRtAS). The RtAS DOC patients obtained favorable prognoses after the 4-week taVNS treatment, whereas the nRtAS ones did not. Simultaneously, taVNS increased CBF of multiple brain regions in the RtAS DOC patients, but hardly in the nRtAS ones. In conclusion, the preserved auditory function might be the prior key factor of the taVNS responders in DOC patients, and taVNS might alleviate RtAS DOC by activating the salience network, the limbic system, and the interoceptive system.

Transcutaneous auricular VNS applied to experimental pain: A paired behavioral and EEG study using thermonociceptive CO2 laser

Background

Transcutaneous auricular Vagal Nerve Stimulation (taVNS) is a non-invasive neurostimulation technique with potential analgesic effects. Several studies based on subjective behavioral responses suggest that taVNS modulates nociception differently with either pro-nociceptive or anti-nociceptive effects.

Objective

This study aimed to characterize how taVNS alters pain perception, by investigating its effects on event-related potentials (ERPs) elicited by different types of spinothalamic and lemniscal somatosensory stimuli, combined with quantitative sensory testing (detection threshold and intensity ratings).

Methods

We performed 3 experiments designed to study the time-dependent effects of taVNS and compare with standard cervical VNS (cVNS). In Experiment 1, we assessed the effects of taVNS after 3 hours of stimulation. In Experiment 2, we focused on the immediate effects of the duty cycle (OFF vs. ON phases). Experiments 1 and 2 included 22 and 15 healthy participants respectively. Both experiments consisted of a 2-day cross-over protocol, in which subjects received taVNS and sham stimulation sequentially. In addition, subjects received a set of nociceptive (thermonociceptive CO₂ laser, mechanical pinprick) and non-nociceptive (vibrotactile, cool) stimuli, for which we recorded detection thresholds, intensity of perception and ERPs. Finally, in Experiment 3, we tested 13 epileptic patients with an implanted cVNS by comparing OFF vs. ON cycles, using a similar experimental procedure.

Results

Neither taVNS nor cVNS appeared to modulate the cerebral and behavioral aspects of somatosensory perception.

Conclusion

The potential effect of taVNS on nociception requires a cautious interpretation, as we found no objective change in behavioral and cerebral responses to spinothalamic and lemniscal somatosensory stimulations.

Risks and Safety of Extended Auricular Therapy: A Review of Reviews and Case Reports of Adverse Events

OBJECTIVE

Auricular acupuncture (AA) and extended auricular therapy (AT) are a part of acupuncture practice shown to benefit patients with pain, anxiety, and other conditions, with cost-effective access enhanced when given in a group setting. Yet there are safety concerns and risks, perhaps unnecessary risks, that attend embedded, indwelling needles applied to the ear as a means of extended AT.

METHODS

Electronic searches were conducted in PubMed, MEDLINE, CINAHL and Cochrane Central Register of Controlled Trials (CENTRAL) for "auriculotherapy," "auricular acupuncture" or "auricular acupressure," "safety," "adverse events," "chondritis," and "perichondritis," with additional manual review of titles, links, and reference lists. Individual auricular therapy adverse event (AE) case reports were included, as well as systematic reviews and or meta-analyses if they evaluated AEs associated with AT.

RESULTS

Nineteen auricular AE case reports and nine safety reviews of or including auriculotherapy were included. Ten systematic reviews of AT with eight specific reviews of auricular acupressure (AP) were also included.

CONCLUSIONS

The primary AE risks is infection, perichondritis, and chondritis stemming from embedded or indwelling needles or potential inadvertent needlesticks from contaminated roaming sharps. Extended AP i.e., application of spheres, preferably seeds (natural, nontoxic botanical Vaccaria seeds) provides clinical benefit without the risks associated with embedded needles. More research is needed to establish if embedded needles at the ear are even necessary or have any advantage over in-session auricular acupuncture for immediate pain relief followed by ear acupressure.

Electroacupuncture Ameliorates Acute Pancreatitis: A Role for the Vagus Nerve-Mediated Cholinergic Anti-Inflammatory Pathway

Organ failure resulting from excessive inflammation is the leading cause of death in the early phase of acute pancreatitis (AP). The autonomic nervous system was reported to be involved in AP, and the vagus nerve could exert anti-inflammatory effects through α7 nicotinic acetylcholine receptor (α7nAChR) signaling. Acupuncture has been widely used in traditional Asian medicine, and recent studies suggested the inflammation modulating effect of electroacupuncture (EA) might be mediated by the autonomic nervous system. In this study, we aimed to investigate the effects of EA in AP animal models. Two independent AP mouse models were used, namely, caerulein hyperstimulation and pancreatic duct ligation. We found that EA at Zusanli acupoint increased vagus nerve activity, suppressed systemic inflammation, and alleviated the histopathological manifestations and leukocyte infiltrations of the pancreas. Induction of AP resulted in a remarkable decrease in the frequency of α7nAchR⁺ macrophages in the pancreas, while EA counteracted this phenomenon. The anti-inflammatory, pancreatic protective and upregulation of α7nAchR effects of EA were reduced in mice with vagotomy. Moreover, the therapeutic effects of EA were attenuated in mice treated with methyllycaconitine citrate, a selective α7nAChR antagonist. Taken together, EA could modulate inflammation, thereby exerting protective effects in AP. The mechanism may include activating the vagus nerve through the cholinergic anti-inflammatory pathway.

Auricular Vagus Neuromodulation-A Systematic Review on Quality of Evidence and Clinical Effects

Background: The auricular branch of the vagus nerve runs superficially, which makes it a favorable target for non-invasive stimulation techniques to modulate vagal activity. For this reason, there have been many early-stage clinical trials on a diverse range of conditions. These trials often report conflicting results for the same indication. Methods: Using the Cochrane Risk of Bias tool we conducted a systematic review of auricular vagus nerve stimulation (aVNS) randomized controlled trials (RCTs) to identify the factors that led to these conflicting results. The majority of aVNS studies were assessed as having "some" or "high" risk of bias, which makes it difficult to interpret their results in a broader context. Results: There is evidence of a modest decrease in heart rate during higher stimulation dosages, sometimes at above the level of sensory discomfort. Findings on heart rate variability conflict between studies and are hindered by trial design, including inappropriate washout periods, and multiple methods used to quantify heart rate variability. There is early-stage evidence to suggest aVNS may reduce circulating levels and endotoxin-induced levels of inflammatory markers. Studies on epilepsy reached primary endpoints similar to previous RCTs testing implantable vagus nerve stimulation therapy. Preliminary evidence shows that aVNS ameliorated pathological pain but not evoked pain. Discussion: Based on results of the Cochrane analysis we list common improvements for the reporting of results, which can be implemented immediately to improve the quality of evidence. In the long term, existing data from aVNS studies and salient lessons from drug development highlight the need for direct measures of local neural target engagement. Direct measures of neural activity around the electrode will provide data for the optimization of electrode design, placement, and stimulation waveform parameters to improve on-target engagement and minimize off-target activation. Furthermore, direct measures of target engagement, along with consistent evaluation of blinding success, must be used to improve the design of controls-a major source of concern identified in the Cochrane analysis. The need for direct measures of neural target engagement and consistent evaluation of blinding success is applicable to the development of other paresthesia-inducing neuromodulation therapies and their control designs.

Transcutaneous auricular vagal nerve stimulation inhibits hypothalamic P2Y1R expression and attenuates weight gain without decreasing food intake in Zucker diabetic fatty rats

Zucker diabetic fatty (ZDF) rats that harbor a mutation in the leptin receptor innately develop type 2 diabetes (T2D) with obesity. Transcutaneous auricular vagal nerve stimulation (taVNS) has an antidiabetic effect in ZDF rats. However, the underlying mechanisms of the weight-gain attenuating effect in ZDF rats by taVNS is still unclear. This study aimed to assess whether the weight-gain attenuating effect of taVNS in ZDF rats is associated with changes in the central nervous system (CNS) expression of P2Y1 receptors (P2Y1R). Adult male ZDF rats were subjected to taVNS and transcutaneous non-vagal nerve stimulation (tnVNS). Their food intake and body weight were recorded daily and weekly, respectively. P2Y1R expression in the hypothalamus, amygdala, and hippocampus was evaluated by western blotting. Hypothalamic P2Y1R expressing cells were detected using immunohistochemistry. Naïve ZDF rats were much heavier (p < 0.05) than their lean littermates (ZL rats), with elevated hypothalamic P2Y1R expression (p < 0.05). Further, taVNS but not tnVNS attenuated weight gain (p < 0.05) without decreasing food intake (p > 0.05) and suppressed hypothalamic P2Y1R expression in ZDF rats (p < 0.05). Moreover, P2Y1R showed major expression in astrocytes of ZDF rats' hypothalamus. ZDF rats innately develop obesity associated with elevated hypothalamic P2Y1R expression. taVNS attenuates weight gain in ZDF rats without changes in food intake, suggesting increased energy expenditure. Whether the reduced hypothalamic P2Y1R expression in response to taVNS is mechanistically linked to the increased energy expenditure remains to be determined.

Additional value of auricular intradermal acupuncture alongside selective serotonin reuptake inhibitors: a single-blinded, randomized, sham-controlled preliminary clinical study

BACKGROUND

To evaluate the antidepressant effects of auricular intradermal acupuncture (AIA) of areas innervated by both the auricular branch of the vagus nerve and the trigeminal nerve.

METHODS

Forty-nine patients with depression were randomly allocated into an AIA group (n = 25) and a sham AIA group (n = 24). Both groups received selective serotonin reuptake inhibitors (SSRIs) as conventional treatment. The AIA group received AIA stimulation, and the sham AIA group received sham AIA, which constituted being subjected to an attached needle that did not penetrate the skin. The needles were retained for 4 h each session, with five sessions a week for a total duration of 2 weeks. The outcomes were assessed by the 17-item Hamilton depression rating scale (HAMD-17), five factors (sleep disorder, retardation, cognitive dysfunction, anxiety/somatization, and weight) and self-rating depression scale (SDS) at weeks 0, 1, and 2.

RESULTS

Fifty-four patients were randomly assigned to the AIA (n = 27) and sham AIA group (n = 27), of whom 25 patients in the AIA and 24 patients in the sham AIA group were analyzed. AIA-treated patients displayed a significantly greater reduction from baseline in HAMD-17 scores (p = 0.03) and SDS scores (p = 0.02) at week 2 compared to patients receiving sham AIA. The AIA intervention also produced a higher rate of clinically significant responses in sleep disorders (p = 0.07) compared to sham AIA. No adverse events occurred in either group.

CONCLUSION

According to the findings of this preliminary study, AIA appears to have additional value compared to SSRIs alone in treating patients with depressive disorder.

Activation of the cholinergic antiinflammatory reflex by occipitoatlantal decompression and transcutaneous auricular vagus nerve stimulation

CONTEXT

The parasympathetic-mediated inflammatory reflex inhibits excessive proinflammatory cytokine production. Noninvasive techniques, including occipitoatlantal decompression (OA-D) and transcutaneous auricular vagus nerve stimulation (taVNS), have been demonstrated to increase parasympathetic tone.

OBJECTIVES

To test the hypothesis that OA-D and taVNS increase parasympathetic nervous system activity and inhibit proinflammatory cytokine mobilization and/or production.

METHODS

Healthy adult participants were randomized to receive OA-D (5 min of OA-D followed by 10 min of rest; n=8), taVNS (15 min; n=9), or no intervention (15 min, time control; n=10) on three consecutive days. Before and after these interventions, saliva samples were collected for determination of the cytokines interleukin-1β (IL-1β), interleukin-6 (IL-6), interleukin-8 (IL-8), and tumor necrosis factor α (TNF-α). Arterial blood pressure and the electrocardiogram were recorded for a 30-min baseline, throughout the intervention, and during a 30-min recovery period to derive heart rate and blood pressure variability markers as indices of vagal and sympathetic control.

RESULTS

OA-D and taVNS increased root mean square of successive RR interval differences (RMSSD) and high frequency heart rate variability, which are established markers for parasympathetic modulation of cardiac function. In all three groups, the experimental protocol was associated with a significant increase in salivary cytokine concentrations. However, the increase in IL-1β was significantly less in the taVNS group (+66 ± 13 pg/mL; p<0.05) than in the time control group (+142 ± 24 pg/mL). A similar trend was observed in the taVNS group for TNF-α (+1.7 ± 0.3 pg/mL vs. 4.1 ± 1.3 pg/mL; p<0.10). In the OA-D group baseline IL-6, IL-8, and TNF-α levels on the third study day were significantly lower than on the first study day (IL-6: 2.3 ± 0.4 vs. 3.2 ± 0.6 pg/mL, p<0.05; IL-8: 190 ± 61 vs. 483 ± 125 pg/mL, p <0.05; TNF-α: 1.2 ± 0.3 vs. 2.3 ± 0.4 pg/mL, p<0.05). OA-D decreased mean blood pressure from the first (100 ± 8 mmHg) to the second (92 ± 6 mmHg; p<0.05) and third (93 ± 8 mmHg; p<0.05) study days and reduced low frequency spectral power of systolic blood pressure variability (19 ± 3 mmHg² after OA-D vs. 28 ± 5 mmHg² before OA-D; p<0.05), a marker of sympathetic modulation of vascular tone. OA-D also increased baroreceptor-heart rate reflex sensitivity from the first (13.7 ± 3.0 ms/mmHg) to the second (18.4 ± 4.3 ms/mmHg; p<0.05) and third (16.9 ± 4.2 ms/mmHg; p<0.05) study days.

CONCLUSIONS

Both OA-D and taVNS elicited antiinflammatory responses that were associated with increases in heart rate variability-derived markers for parasympathetic function. These findings suggest that OA-D and taVNS activate the parasympathetic antiinflammatory reflex. Furthermore, an antihypertensive effect was observed with OA-D that may be mediated by reduced sympathetic modulation of vascular tone and/or increased baroreceptor reflex sensitivity.

Baroreceptor Modulation of the Cardiovascular System, Pain, Consciousness, and Cognition

Baroreceptors are mechanosensitive elements of the peripheral nervous system that maintain cardiovascular homeostasis by coordinating the responses to external and internal environmental stressors. While it is well known that carotid and cardiopulmonary baroreceptors modulate sympathetic vasomotor and parasympathetic cardiac neural autonomic drive, to avoid excessive fluctuations in vascular tone and maintain intravascular volume, there is increasing recognition that baroreceptors also modulate a wide range of non-cardiovascular physiological responses via projections from the nucleus of the solitary tract to regions of the central nervous system, including the spinal cord. These projections regulate pain perception, sleep, consciousness, and cognition. In this article, we summarize the physiology of baroreceptor pathways and responses to baroreceptor activation with an emphasis on the mechanisms influencing cardiovascular function, pain perception, consciousness, and cognition. Understanding baroreceptor-mediated effects on cardiac and extra-cardiac autonomic activities will further our understanding of the pathophysiology of multiple common clinical conditions, such as chronic pain, disorders of consciousness (e.g., abnormalities in sleep-wake), and cognitive impairment, which may result in the identification and implementation of novel treatment modalities. © 2021 American Physiological Society. Compr Physiol 11:1373-1423, 2021.

Transcutaneous Auricular Vagus Nerve Stimulation: From Concept to Application

Whether in the West or the East, the connection between the ear and the rest of the body has been explored for a long time. Especially in the past century or more, the relevant theoretical and applied research on the ear has greatly promoted the development of ear therapy, and finally the concept of transcutaneous auricular vagus nerve stimulation (taVNS) has been proposed. The purpose of taVNS is to treat a disease non-invasively by applying electrical current to the cutaneous receptive field formed by the auricular branch of the vagus nerve in the outer ear. In the past two decades, taVNS has been a topic of basic, clinical, and transformation research. It has been applied as an alternative to drug treatment for a variety of diseases. Based on the rapid understanding of the application of taVNS to human health and disease, some limitations in the development of this field have also been gradually exposed. Here, we comprehensively review the origin and research status of the field.

The vagus nerve somatosensory evoked potential in the intact brain: state-of-evidence and some representative vignettes

OBJECTIVE

Scalp-recorded evoked potentials elicited by applying afferent electrical stimulation at the tragus region of the human external ear have shown inconsistent results. We aim to disentangle discrepant findings and interpretations, and put forward novel physiological explanations on the origin of the vagus nerve somatosensory evoked potentials (VSEP).

METHODS

We systematically search and critically appraise in PubMed, Web of Science, and Scielo databases the scientific reports publishing VSEP findings elicited by afferent electrical stimulation at the tragus region from individuals without brain disorders. Eligible studies published from January 2000 to April 2020 were extracted. The following information was identified from each article: number of participants; age; gender; stimulating/recording and grounding electrodes as well as stimulus side, intensity, duration, frequency, and polarity. Information about physiological parameters and neurobiological variables was also extracted. Representative vignettes with novel scalp responses induced by stimulating the tragus were also included to add support to our conclusions.

RESULTS

140 healthy participants were identified from six selected reports. Mean age ranged from 24.3 to 61.5 years. Stimulating and recording aspects were miscellaneous among studies. Scalp responses marked as the VSEP were recorded in 76% of participants, and showed high variability, low validity and poor reproducibility. Age correlated with response latencies. There were not gender differences in scalp response parameters. Cardiovascular function was unaltered by tragus stimulation. Vignettes showed that the VSEP was scalp muscle responses.

CONCLUSION

VSEP did not fulfil evoked potential guidelines. VSEP corresponded to volume conduction propagating from muscles surrounding scalp recording sites.

Non-invasive Recording of Parasympathetic Nervous System Activity on Auricular Vagal Nerve Branch

The function of the autonomic nervous system (ANS) influences most of the physiological mechanisms. The popular non-invasive method to estimate the activities of the autonomic nervous system (ANS) is the heart rate variability (HRV). However, the HRV cannot provide real-time information of the ANS function. The skin sympathetic nerve activity (SKNA) is a novel method to evaluate sympathetic nerve system (SNS) activity. The SKNA technique has shown promise in clinical applications but is limited to evaluating SNS activities. To date, a direct non-invasive method for measuring the parasympathetic nerve system (PNS) function is urgently needed. According to anatomy, the auricular branch of the vagus nerve (aVN) is near the concha surface. In this study, we hypothesize that we can measure the aVN activity (aVNA) with the same technique developed for SKNA recording. Flexible auricular electrodes were developed for continuous long-term recording of aVN activity. The SKNA and aVNA were simultaneously recorded during the experiment. The cold face test and cold pressor test were performed to physiologically activate ANS. The SKNA and aVNA can be obtained simultaneously, and they are correlated with the heart rate change during the physiological challenge. The aVNA has a high potential to be developed into a novel method to measure the PNS activity.

[Improving parasympathetic functioning to contain the inflammatory response of COVID-19 infection]

COVID-19 infection results in an unrestrained inflammatory reaction in serious cases. The autonomic nervous system (ANS), in particular the parasympathetic branch, helps to regulate the inflammatory response. A dysfunction of this branch, frequent in people at risk of developing COVID-19, favours a pro-inflammatory effect. Reinforcing and stimulating the parasympathetic ANS is possible and accessible to paramedical and medical professionals.