Bioelectric neuromodulation for gastrointestinal disorders: effectiveness and mechanisms

Force-Based Neuromodulation

Technologies for neuromodulation have rapidly developed in the past decade with a particular emphasis on creating noninvasive tools with high spatial and temporal precision. The existence of such tools is critical in the advancement of our understanding of neural circuitry and its influence on behavior and neurological disease. Existing technologies have employed various modalities, such as light, electrical, and magnetic fields, to interface with neural activity. While each method offers unique advantages, many struggle with modulating activity with high spatiotemporal precision without the need for invasive tools. One modality of interest for neuromodulation has been the use of mechanical force. Mechanical force encapsulates a broad range of techniques, ranging from mechanical waves delivered via focused ultrasound (FUS) to torque applied to the cell membrane.Mechanical force can be delivered to the tissue in two forms. The first form is the delivery of a mechanical force through focused ultrasound. Energy delivery facilitated by FUS has been the foundation for many neuromodulation techniques, owing to its precision and penetration depth. FUS possesses the potential to penetrate deeply (∼centimeters) into tissue while maintaining relatively precise spatial resolution, although there exists a trade-off between the penetration depth and spatial resolution. FUS may work synergistically with ultrasound-responsive nanotransducers or devices to produce a secondary energy, such as light, heat, or an electric field, in the target region. This layered technology, first enabled by noninvasive FUS, overcomes the need for bulky invasive implants and also often improves the spatiotemporal precision of light, heat, electrical fields, or other techniques alone. Conversely, the second form of mechanical force modulation is the generation of mechanical force from other modalities, such as light or magnetic fields, for neuromodulation via mechanosensitive proteins. This approach localizes the mechanical force at the cellular level, enhancing the precision of the original energy delivery. Direct interaction of mechanical force with tissue presents translational potential in its ability to interface with endogenous mechanosensitive proteins without the need for transgenes.In this Account, we categorize force-mediated neuromodulation into two categories: 1) methods where mechanical force is the primary stimulus and 2) methods where mechanical force is generated as a secondary stimulus in response to other modalities. We summarize the general design principles and current progress of each respective approach. We identify the key advantages of the limitations of each technology, particularly noting features in spatiotemporal precision, the need for transgene delivery, and the potential outlook. Finally, we highlight recent technologies that leverage mechanical force for enhanced spatiotemporal precision and advanced applications.

Orally Ingested Self-Powered Stimulators for Targeted Gut-Brain Axis Electrostimulation to Treat Obesity and Metabolic Disorders

Obesity is a significant health concern that often leads to metabolic dysfunction and chronic diseases. This study introduces a novel approach to combat obesity using orally ingested self-powered electrostimulators. These electrostimulators consist of piezoelectric BaTiO3 (BTO) particles conjugated with capsaicin (Cap) and aim to activate the vagus nerve. Upon ingestion by diet-induced obese (DIO) mice, the BTO@Cap particles specifically target and bind to Cap-sensitive sensory nerve endings in the gastric mucosa. In response to stomach peristalsis, these particles generate electrical signals. The signals travel via the gut-brain axis, ultimately influencing the hypothalamus. By enhancing satiety signals in the brain, this neuromodulatory intervention reduces food intake, promotes energy metabolism, and demonstrates minimal toxicity. Over a 3-week period of daily treatments, DIO mice treated with BTO@Cap particles show a significant reduction in body weight compared to control mice, while maintaining their general locomotor activity. Furthermore, this BTO@Cap particle-based treatment mitigates various metabolic alterations associated with obesity. Importantly, this noninvasive and easy-to-administer intervention holds potential for addressing other intracerebral neurological diseases.

Exploring Electrical Neuromodulation as an Alternative Therapeutic Approach in Inflammatory Bowel Diseases

Background and Objectives: This review systematically evaluates the potential of electrical neuromodulation techniques-vagus nerve stimulation (VNS), sacral nerve stimulation (SNS), and tibial nerve stimulation (TNS)-as alternative treatments for inflammatory bowel disease (IBD), including ulcerative colitis (UC) and Crohn's Disease (CD). It aims to synthesize current evidence on the efficacy and safety of these modalities, addressing the significant burden of IBD on patient quality of life and the limitations of existing pharmacological therapies. Materials and Methods: We conducted a comprehensive analysis of studies from PubMed, focusing on research published between 1978 and 2024. The review included animal models and clinical trials investigating the mechanisms, effectiveness, and safety of VNS, SNS, and TNS in IBD management. Special attention was given to the modulation of inflammatory responses and its impact on gastrointestinal motility and functional gastrointestinal disorders associated with IBD. Results: Preliminary findings suggest that VNS, SNS, and TNS can significantly reduce inflammatory markers and improve symptoms in IBD patients. These techniques also show potential in treating related gastrointestinal disorders during IBD remission phases. However, the specific mechanisms underlying these benefits remain to be fully elucidated, and there is considerable variability in treatment parameters. Conclusions: Electrical neuromodulation holds promise as a novel therapeutic avenue for IBD, offering an alternative to patients who do not respond to traditional treatments or experience adverse effects. The review highlights the need for further rigorous studies to optimize stimulation parameters, understand long-term outcomes, and integrate neuromodulation effectively into IBD treatment protocols.

Ameliorating effects of transcutaneous auricular vagus nerve stimulation on a mouse model of constipation-predominant irritable bowel syndrome

Limited treatment options have been shown to alter the natural course of constipation-predominant irritable bowel syndrome (IBS-C). Therefore, safer and more effective approaches are urgently needed. We investigated the effects of transcutaneous auricular vagus nerve stimulation (taVNS) in a mouse model of IBS-C. In the current study, C57BL/6 mice were randomly divided into normal control, IBS-C model control, sham-electrostimulation (sham-ES), taVNS, and drug treatment groups. The effects of taVNS on fecal pellet number, fecal water content, and gastrointestinal transit were evaluated in IBS-C model mice. We assessed the effect of taVNS on visceral hypersensitivity using the colorectal distention test. 16S rRNA sequencing was used to analyze the fecal microbiota of the experimental groups. First, we found that taVNS increased fecal pellet number, fecal water content, and gastrointestinal transit in IBS-C model mice compared with the sham-ES group. Second, taVNS significantly decreased the abdominal withdrawal reflex (AWR) score compared with the sham-ES group, thus relieving visceral hyperalgesia. Third, the gut microbiota outcomes showed that taVNS restored Lactobacillus abundance while increasing Bifidobacterium probiotic abundance at the genus level. Notably, taVNS increased the number of c-kit-positive interstitial cells of Cajal (ICC) in the myenteric plexus region in IBS-C mice compared with the sham-ES group. Therefore, our study indicated that taVNS effectively ameliorated IBS-C in the gut microbiota and ICC.

Transcutaneous Auricular Vagal Nerve Stimulation Is Effective for the Treatment of Functional Dyspepsia: A Multicenter, Randomized Controlled Study

INTRODUCTION

Vagal nerve stimulation (VNS) can be used to modulate gastrointestinal motility, inflammation, and nociception. However, it remains unclear whether VNS is effective in adult patients with functional dyspepsia (FD). We investigated the effectiveness of transcutaneous auricular VNS (taVNS) in patients with FD.

METHODS

Consecutive patients with FD meeting Rome IV criteria with modified FD Symptom Diary score ≥10 were enrolled. Patients were randomly allocated to 10-Hz taVNS (V10 group), 25-Hz taVNS (V25 group), or sham group, with 30 minutes of treatment twice a day for 4 weeks. The primary outcome was the response rate at week 4, defined as the proportion of patients whose modified FD Symptom Diary score was reduced ≥5 when compared with the baseline. Secondary outcomes included adequate relief rate and adverse events.

RESULTS

A total of 300 patients were randomized to V10 (n = 101), V25 (n = 99), and sham groups (n = 100). After 4 weeks of treatment, V10 and V25 groups had a higher response rate (81.2% vs 75.9% vs 47%, both P < 0.001) and adequate relief rate (85.1% vs 80.8% vs 67%, both P < 0.05) compared with the sham group. There was no significant difference between V10 and V25 in response rate and adequate relief rate (both P > 0.05). The efficacy of taVNS (both 10 and 25 Hz) lasted at week 8 and week 12 during follow-up period. Adverse events were all mild and comparable among the 3 groups (1%-3%).

DISCUSSION

Our study firstly showed that 4-week taVNS (both 10 and 25 Hz) was effective and safe for the treatment of adult FD ( clinicaltrials.gov number: NCT04668534).

Excite the unexcitable: engineering cells and redox signaling for targeted bioelectronic control

The ever-growing influence of technology in our lives has led to an increasing interest in the development of smart electronic devices to interrogate and control biological systems. Recently, redox-mediated electrogenetics introduced a novel avenue that enables direct bioelectronic control at the genetic level. In this review, we discuss recent advances in methodologies for bioelectronic control, ranging from electrical stimulation to engineering efforts that allow traditionally unexcitable cells to be electrically 'programmable.' Alongside ion-transport signaling, we suggest redox as a route for rational engineering because it is a native form of electronic communication in biology. Using redox as a common language allows the interfacing of electronics and biology. This newfound connection opens a gateway of possibilities for next-generation bioelectronic tools.

Sacral Nerve Stimulation Alleviates Intestinal Inflammation Through Regulating the Autophagy of Macrophages and Activating the Inflammasome Mediated by a Cholinergic Antiinflammatory Pathway in Colitis Rats

BACKGROUND

Inflammatory bowel disease (IBD) is characterized by chronic progressive intestinal inflammation. Sacral nerve stimulation (SNS) ameliorates colon inflammation caused by IBD. The aim of this study was to investigate the antiinflammatory benefits of SNS in colitis rats and explore the roles of the cholinergic antiinflammatory pathway, macrophage autophagy, and nucleotide oligomerization domain-like receptor thermal protein domain associated protein 3 (NLRP3) inflammatory bodies.

MATERIALS AND METHODS

Rats were divided into four groups: healthy control, dextran sulfate sodium (DSS), DSS + sham-SNS, and DSS + SNS groups. An electrode was surgically placed in the right sacral nerve (S3) for stimulation. The disease activity index (DAI) score was recorded each day, and the degree of inflammatory injury was evaluated using hematoxylin and eosin staining. The alpha7 nicotinic acetylcholine receptor (α7nAChR) and autophagy- and NLRP3-related factors were assessed using immunofluorescence staining and Western blotting.

RESULTS

The DSS group showed a higher DAI score, colon shortening, upregulated proinflammatory action, and colon damage, and the DSS + SNS group showed significantly improved symptoms. The number of α7nAChR+ cells and the expression level of autophagy decreased in the DSS group but increased in the DSS + SNS group. Conversely, the DSS group showed increased activation of NLRP3 inflammatory bodies, whereas the DSS + SNS group showed decreased activation of NLRP3 inflammatory bodies.

CONCLUSION

In this study, SNS ameliorated colon inflammation by enhancing macrophage autophagy and inhibiting the activation of NLRP3 inflammatory bodies, which may be related to the opening of the cholinergic antiinflammatory pathway.

A flexible, thin-film microchannel electrode array device for selective subdiaphragmatic vagus nerve recording

The vagus nerve (VN) plays an important role in regulating physiological conditions in the gastrointestinal (GI) tract by communicating via the parasympathetic pathway to the enteric nervous system (ENS). However, the lack of knowledge in the neurophysiology of the VN and GI tract limits the development of advanced treatments for autonomic dysfunctions related to the VN. To better understand the complicated underlying mechanisms of the VN-GI tract neurophysiology, it is necessary to use an advanced device enabled by microfabrication technologies. Among several candidates including intraneural probe array and extraneural cuff electrodes, microchannel electrode array devices can be used to interface with smaller numbers of nerve fibers by securing them in the separate channel structures. Previous microchannel electrode array devices to interface teased nerve structures are relatively bulky with thickness around 200 µm. The thick design can potentially harm the delicate tissue structures, including the nerve itself. In this paper, we present a flexible thin film based microchannel electrode array device (thickness: 11.5 µm) that can interface with one of the subdiaphragmatic nerve branches of the VN in a rat. We demonstrated recording evoked compound action potentials (ECAP) from a transected nerve ending that has multiple nerve fibers. Moreover, our analysis confirmed that the signals are from C-fibers that are critical in regulating autonomic neurophysiology in the GI tract.

The nerve cells in gastrointestinal cancers: from molecular mechanisms to clinical intervention

Gastrointestinal (GI) cancer is a formidable malignancy with significant morbidity and mortality rates. Recent studies have shed light on the complex interplay between the nervous system and the GI system, influencing various aspects of GI tumorigenesis, such as the malignance of cancer cells, the conformation of tumor microenvironment (TME), and the resistance to chemotherapies. The discussion in this review first focused on exploring the intricate details of the biological function of the nervous system in the development of the GI tract and the progression of tumors within it. Meanwhile, the cancer cell-originated feedback regulation on the nervous system is revealed to play a crucial role in the growth and development of nerve cells within tumor tissues. This interaction is vital for understanding the complex relationship between the nervous system and GI oncogenesis. Additionally, the study identified various components within the TME that possess a significant influence on the occurrence and progression of GI cancer, including microbiota, immune cells, and fibroblasts. Moreover, we highlighted the transformation relationship between non-neuronal cells and neuronal cells during GI cancer progression, inspiring the development of strategies for nervous system-guided anti-tumor drugs. By further elucidating the deep mechanism of various neuroregulatory signals and neuronal intervention, we underlined the potential of these targeted drugs translating into effective therapies for GI cancer treatment. In summary, this review provides an overview of the mechanisms of neuromodulation and explores potential therapeutic opportunities, providing insights into the understanding and management of GI cancers.

Electrical carotid sinus nerve stimulation attenuates experimental colitis induced by acetic acid in rats

AIMS

The carotid bodies are sensors that detect physiological signals and convey them to the central nervous system, where the stimuli are processed inducing reflexes through efferent pathways. Recent studies have demonstrated that electrical stimulation of the carotid sinus nerve (CSN) triggers the anti-inflammatory reflex under different conditions. However, whether this electrical stimulation attenuates colitis was never examined. This study aimed to evaluate if the electrical CSN stimulation attenuates the experimental colitis induced by intrarectal administration of acetic acid in rats.

METHODS

Electrodes were implanted around the CSN to stimulate the CSN, and a catheter was inserted into the left femoral artery to record the arterial pressure. The observation of hypotensive responses confirmed the effectiveness of the electrical CNS stimulation. This maneuver was followed by a 4 % acetic acid or saline administered intrarectally. After 24 h, colons were segmented into distal and proximal parts for macroscopy, histological and biochemical assessment.

KEY FINDINGS

As expected, the electrical CSN stimulation was effective in decreasing arterial pressure in saline and colitis rats. Moreover, electrical CSN stimulation effectively reduced colonic tissue lesions, colitis scores, and histopathologic parameters associated with colitis. In addition, the CSN stimulation also reduced the colonic mucosa pro-inflammatory cytokine interleukin-1 beta, and increased the anti-inflammatory interleukin-10, in rats submitted to colitis.

SIGNIFICANCE

These findings indicated that electrical CSN stimulation breaks the vicious cycle of local colon inflammation in colitis, which might contribute to its better outcome.

Acute sub-diaphragmatic anterior vagus nerve stimulation increases peripheral glucose uptake in anaesthetized rats

The sub-diaphragmatic vagus innervates various organs involved in the control of glucose homeostasis including the liver, pancreas and the intestines. In the current study, we investigated the effect of acute electrical stimulation of the anterior trunk of the sub-diaphragmatic vagus on glucose fluxes in anaesthetized adult male rats. After overnight fast, rats underwent either vagus nerve stimulation (VNS+, n = 11; rectangular pulses at 5 Hz, 1.5 mA, 1 msec pulse width) or sham stimulation (VNS-; n = 11) for 120 min under isoflurane anesthesia. Before stimulation, the rats received an i.v. bolus of 1 mL/kg of a sterilized aqueous solution containing 125 mg/mL of D-[6,6-²H₂] glucose. Endogenous glucose production (EGP) and glucose clearance rate (GCR) were calculated by kinetic analysis from the wash-out of injected D-[6,6-²H₂]glucose from the circulation. VNS+ resulted in lower glucose levels compared to the VNS- group (p < 0.05), with similar insulin levels. EGP was similar in both groups, but the GCR was higher in the VNS+ group compared to the VNS- group (p < 0.001). Circulating levels of the sympathetic transmitter norepinephrine were reduced by VNS+ relative to VNS- treatment (p < 0.01). It is concluded that acute anterior sub-diaphragmatic VNS causes stimulation of peripheral glucose uptake, while plasma insulin levels remained similar, and this is associated with lower activity of the sympathetic nervous system.

Association between Red Blood Cell Distribution Width and Short-Term Mortality in Patients with Paralytic Intestinal Obstruction: Retrospective Data Analysis Based on the MIMIC-III Database

Objective

Elevated red cell distribution (RDW) has been reported to be associated with mortality in patients with acute pancreatitis and cholecystitis admitted to the intensive care unit (ICU). However, evidence for the relationship between RDW and paralytic intestinal obstruction is lacking. Therefore, the article aims to investigate the relationship between RDW and 28-day mortality of the patients with paralytic intestinal obstruction. Patients and Methods. This is a single-center retrospective study. Based on a particular screening criterion, 773 patients with paralytic intestinal obstruction were selected from the Medical Information Mart for Intensive Care III (MIMIC-III) database. Indicators of the first 24 h into the ICU were used to analyze the relationship between RDW and 28-day death from paralytic intestinal obstruction by Kaplan-Meier (K-M) analysis, logistic regression analysis, and stratification analysis.

Results

The curve fitting exhibited a nonlinear relationship. The K-M curve showed that groups with higher RDW values had lower survival rates. The logistic regression analysis revealed that RDW increased with 28-day mortality in patients with paralytic intestinal obstruction in the fully adjusted model. In the fully adjusted model, OR value and 95% CI from the second to the third quantiles compared to the first quartile (reference group) were 1.89 (1.04, 3.44) and 3.29 (1.82, 5.93), respectively. The results of stratified analysis of each layer had the same trend as those of regression analysis, and the interaction results were not significant.

Conclusion

Elevated RDW was associated with increased 28-day mortality from paralytic intestinal obstruction in the ICU. This study can help to further explore the relationship between RDW and death in patients with paralytic intestinal obstruction.

Villi Inspired Mechanical Interlocking for Intestinal Retentive Devices

Intestinal retentive devices have applications ranging from sustained oral drug delivery systems to indwelling ingestible medical devices. Current strategies to retain devices in the small intestine primarily focus on chemical anchoring using mucoadhesives or mechanical coupling using expandable devices or structures that pierce the intestinal epithelium. Here, the feasibility of intestinal retention using devices containing villi-inspired structures that mechanically interlock with natural villi of the small intestine is evaluated. First the viability of mechanical interlocking as an intestinal retention strategy is estimated by estimating the resistance to peristaltic shear between simulated natural villi and devices with various micropost geometries and parameters. Simulations are validated in vitro by fabricating micropost array patches via multistep replica molding and performing lap-shear tests to evaluate the interlocking performance of the fabricated microposts with artificial villi. Finally, the optimal material and design parameters of the patches that can successfully achieve retention in vivo are predicted. This study represents a proof-of-concept for the viability of micropost-villi mechanical interlocking strategy to develop nonpenetrative multifunctional intestinal retentive devices for the future.

Pharmacological and Electroceutical Targeting of the Cholinergic Anti-Inflammatory Pathway in Autoimmune Diseases

Continuous dialogue between the immune system and the brain plays a key homeostatic role in various immune responses to environmental cues. Several functions are under the control of the vagus nerve-based inflammatory reflex, a physiological mechanism through which nerve signals regulate immune functions. In the cholinergic anti-inflammatory pathway, the vagus nerve, its pivotal neurotransmitter acetylcholine, together with the corresponding receptors play a key role in modulating the immune response of mammals. Through communications of peripheral nerves with immune cells, it modulates proliferation and differentiation activities of various immune cell subsets. As a result, this pathway represents a potential target for treating autoimmune diseases characterized by overt inflammation and a decrease in vagal tone. Consistently, converging observations made in both animal models and clinical trials revealed that targeting the cholinergic anti-inflammatory pathway using pharmacologic approaches can provide beneficial effects. In parallel, bioelectronic medicine has recently emerged as an alternative approach to managing systemic inflammation. In several studies, nerve electrostimulation was reported to be clinically relevant in reducing chronic inflammation in autoimmune diseases, including rheumatoid arthritis and diabetes. In the future, these new approaches could represent a major therapeutic strategy for autoimmune and inflammatory diseases.

Modifying functional brain networks in focal epilepsy by manual visceral-osteopathic stimulation of the vagus nerve at the abdomen

Non-invasive transcutaneous vagus nerve stimulation elicits similar therapeutic effects as invasive vagus nerve stimulation, offering a potential treatment alternative for a wide range of diseases, including epilepsy. Here, we present a novel, non-invasive stimulation of the vagus nerve, which is performed manually viscero-osteopathically on the abdomen (voVNS). We explore the impact of short-term voVNS on various local and global characteristics of EEG-derived, large-scale evolving functional brain networks from a group of 20 subjects with and without epilepsy. We observe differential voVNS-mediated alterations of these characteristics that can be interpreted as a reconfiguration and modification of networks and their stability and robustness properties. Clearly, future studies are necessary to assess the impact of such a non-pharmaceutical intervention on clinical decision-making in the treatment of epilepsy. However, our findings may add to the current discussion on the importance of the gut-brain axis in health and disease. Clinical Trial Registration: https://drks.de/search/en/trial/DRKS00029914, identifier DRKS00029914.

Sympathetic components in left and right human cervical vagus nerve: implications for vagus nerve stimulation

Cervical vagus nerve stimulation is in a great variety of clinical situations indicated as a form of treatment. It is textbook knowledge that at the cervical level the vagus nerve contains many different fiber classes. Yet, recently, several reports have shown that this nerve also may contain an additional class of potentially noradrenergic fibers, suggested to denote efferent sympathetic fibers. As such, the nature and presence of these fibers should be considered when choosing a stimulation protocol. We have studied human vagus material extracted from dissection room cadavers in order to further confirm the presence of this class of fibers, to study their origin and direction within the nerve and to determine their distribution and variability between subjects and pairs of left and right nerves of the same individual. Sections were studied with immunohistochemical techniques using antibodies against tyrosine hydroxylase (TH: presumed to indicate noradrenergic fibers), myelin basic protein and neurofilament. Our results show that at least part of the TH-positive fibers derive from the superior cervical ganglion or sympathetic trunk, do not follow a cranial but take a peripheral course through the nerve. The portion of TH-positive fibers is highly variable between individuals but also between the left and right pairs of the same individual. TH-positive fibers can distribute and wander throughout the fascicles but maintain a generally clustered appearance. The fraction of TH-positive fibers generally diminishes in the left cervical vagus nerve when moving in a caudal direction but remains more constant in the right nerve. These results may help to determine optimal stimulation parameters for cervical vagus stimulation in clinical settings.

Combined optogenetic and electrical stimulation of the sciatic nerve for selective control of sensory fibers

Introduction

Electrical stimulation offers a drug-free alternative for the treatment of many neurological conditions, such as chronic pain. However, it is not easy to selectively activate afferent or efferent fibers of mixed nerves, nor their functional subtypes. Optogenetics overcomes these issues by controlling activity selectively in genetically modified fibers, however the reliability of responses to light are poor compared to electrical stimulation and the high intensities of light required present considerable translational challenges. In this study we employed a combined protocol of optical and electrical stimulation to the sciatic nerve in an optogenetic mouse model to allow for better selectivity, efficiency, and safety to overcome fundamental limitations of electrical-only and optical-only stimulation.

Methods

The sciatic nerve was surgically exposed in anesthetized mice (n = 12) expressing the ChR2-H134R opsin via the parvalbumin promoter. A custom-made peripheral nerve cuff electrode and a 452 nm laser-coupled optical fiber were used to elicit neural activity utilizing optical-only, electrical-only, or combined stimulation. Activation thresholds for the individual and combined responses were measured.

Results

Optically evoked responses had a conduction velocity of 34.3 m/s, consistent with ChR2-H134R expression in proprioceptive and low-threshold mechanoreceptor (Aα/Aβ) fibers which was also confirmed via immunohistochemical methods. Combined stimulation, utilizing a 1 ms near-threshold light pulse followed by an electrical pulse 0.5 ms later, approximately halved the electrical threshold for activation (p = 0.006, n = 5) and resulted in a 5.5 dB increase in the Aα/Aβ hybrid response amplitude compared to the electrical-only response at equivalent electrical levels (p = 0.003, n = 6). As a result, there was a 3.25 dB increase in the therapeutic stimulation window between the Aα/Aβ fiber and myogenic thresholds (p = 0.008, n = 4).

Discussion

The results demonstrate that light can be used to prime the optogenetically modified neural population to reside near threshold, thereby selectively reducing the electrical threshold for neural activation in these fibers. This reduces the amount of light needed for activation for increased safety and reduces potential off-target effects by only stimulating the fibers of interest. Since Aα/Aβ fibers are potential targets for neuromodulation in chronic pain conditions, these findings could be used to develop effective strategies to selectively manipulate pain transmission pathways in the periphery.

Bioinspired, ingestible electroceutical capsules for hunger-regulating hormone modulation

The gut-brain axis, which is mediated via enteric and central neurohormonal signaling, is known to regulate a broad set of physiological functions from feeding to emotional behavior. Various pharmaceuticals and surgical interventions, such as motility agents and bariatric surgery, are used to modulate this axis. Such approaches, however, are associated with off-target effects or post-procedure recovery time and expose patients to substantial risks. Electrical stimulation has also been used to attempt to modulate the gut-brain axis with greater spatial and temporal resolution. Electrical stimulation of the gastrointestinal (GI) tract, however, has generally required invasive intervention for electrode placement on serosal tissue. Stimulating mucosal tissue remains challenging because of the presence of gastric and intestinal fluid, which can influence the effectiveness of local luminal stimulation. Here, we report the development of a bioinspired ingestible fluid-wicking capsule for active stimulation and hormone modulation (FLASH) capable of rapidly wicking fluid and locally stimulating mucosal tissue, resulting in systemic modulation of an orexigenic GI hormone. Drawing inspiration from Moloch horridus, the "thorny devil" lizard with water-wicking skin, we developed a capsule surface capable of displacing fluid. We characterized the stimulation parameters for modulation of various GI hormones in a porcine model and applied these parameters to an ingestible capsule system. FLASH can be orally administered to modulate GI hormones and is safely excreted with no adverse effects in porcine models. We anticipate that this device could be used to treat metabolic, GI, and neuropsychiatric disorders noninvasively with minimal off-target effects.

Flexible IrOx neural electrode for mouse vagus nerve stimulation

Vagus nerve stimulation (VNS) is being actively explored as a treatment for multiple conditions as part of bioelectronic medicine research. Reliable and safe VNS in mouse models is a critical need for understanding mechanisms of these. We report on the development and evaluation of a microfabricated cuff electrode (MouseFlex) constructed of polyimide (PI) and with iridium oxide (IrOx) electrodes that is thermoformed to 86 µm ± 12 µm radius to interface the mouse cervical vagus nerve (r ≈ 50 µm). Innovative bench-top methods were used to evaluate the stimulation stability and electrochemical properties of electrodes. Our aggressive stimulation stability (Stim-Stab) test utilized 1 billion pulses at a 1000 Hz with a current density of 6.28 A/cm2 (1.51 mC/cm2/phase) delivering 3023 × 103 C/cm2 to evaluate electrode lifetimes, and all electrodes remained functional. We also investigated the effects of thermoforming on their impedance, charge storage capacity (CSC), and charge injection capacity (CIC). The modest changes in electrochemical properties indicate that the thermoforming process was well tolerated. Thermoformed electrode safety and efficacy were evaluated in-vivo by performing acute VNS in mice and monitoring their heart and respiration rate as biomarkers. Their electrochemical properties were also measured before, during and after VNS. Bradycardia and bradypnea were reliably induced at stimulation currents of 100 to 200 µA, well below the in-vivo CIC of ∼1250 µA (∼0.5 mC/cm2), supporting their safety and efficacy. The electrode impedance increased and CIC decreased during in-vivo use, but largely reversed these changes in in-vitro testing after enzymatic cleaning, supporting their tolerance for surgical use. STATEMENT OF SIGNIFICANCE: Vagus nerve stimulation (VNS) is a rapidly growing aspect of healthcare and bioelectronic medicine research. Reliable and safe VNS in mice with small diameter (d ≈ 100 µm) nerves has been a challenge due to achieving intimate contact with the nerve, and the stimulation stability of commonly used electrodes. We demonstrate a microfabricated (MouseFlex) cuff electrode constructed of polyimide with IrOx electrodes that is thermoformed to contact the mouse cervical vagus. Bench studies highlight the stimulation stability exceeded 109 pulses at 6.28 A/cm2 and their electrochemical properties were measured before, during, and after bench and nerve stimulation. Nerve stimulation induced bradycardia and bradypnea at currents below the in-vivo charge injection capacity, supporting their safety, efficacy, and tolerance for surgical handling.

Computational models of autonomic regulation in gastric motility: Progress, challenges, and future directions

The stomach is extensively innervated by the vagus nerve and the enteric nervous system. The mechanisms through which this innervation affects gastric motility are being unraveled, motivating the first concerted steps towards the incorporation autonomic regulation into computational models of gastric motility. Computational modeling has been valuable in advancing clinical treatment of other organs, such as the heart. However, to date, computational models of gastric motility have made simplifying assumptions about the link between gastric electrophysiology and motility. Advances in experimental neuroscience mean that these assumptions can be reviewed, and detailed models of autonomic regulation can be incorporated into computational models. This review covers these advances, as well as a vision for the utility of computational models of gastric motility. Diseases of the nervous system, such as Parkinson’s disease, can originate from the brain-gut axis and result in pathological gastric motility. Computational models are a valuable tool for understanding the mechanisms of disease and how treatment may affect gastric motility. This review also covers recent advances in experimental neuroscience that are fundamental to the development of physiology-driven computational models. A vision for the future of computational modeling of gastric motility is proposed and modeling approaches employed for existing mathematical models of autonomic regulation of other gastrointestinal organs and other organ systems are discussed.

Gastroparesis syndromes: emerging drug targets and potential therapeutic opportunities

INTRODUCTION

Gastroparesis (Gp) and related disorders such as chronic unexplained nausea and vomiting and functional dyspepsia, known as gastropareis syndromes (GpS), have large unmet needs. Mainstays of GpS treatments are diet and drugs.

AREAS COVERED

The purpose of this review is to explore potential new medications and other therapies for gastroparesis. Before discussing possible new drugs, the currently used drugs are discussed. These include dopamine receptor antagonists, 5-hydroxytryptamine receptor agonists and antagonists, neurokinin-1 receptor antagonists and other anti-emetics. The article also considers future drugs that may be used for Gp, based on currently known pathophysiology.

EXPERT OPINION

Gaps in knowledge about the pathophysiology of gastroparesis and related syndromes are critical to developing therapeutic agents that will be successful. Recent major developments in the gastroparesis arena are related to microscopic anatomy, cellular function, and pathophysiology. The major challenges moving forward will be to develop the genetic and biochemical correlates of these major developments in gastroparesis research.

Electroceuticals for Neurogastroenterology and Motility Disorders

PURPOSE OF REVIEW

To provide an updated overview on use of electrostimulation in gastrointestinal motility disorders and obesity, with a focus on gastric electrical stimulation, vagal nerve stimulation and sacral nerve stimulation.

RECENT FINDINGS

Recent studies on gastric electrical stimulation for chronic vomiting showed a decrease in frequency of vomiting, but without significant improvement in quality of life. Percutaneous vagal nerve stimulation shows some promise for both symptoms of gastroparesis and IBS. Sacral nerve stimulation does not appear effective for constipation. Studies of electroceuticals for treatment of obesity have quite varied results with less clinical penetrance of the technology. Results of studies on the efficacy of electroceuticals have been variable depending on pathology but this area remains promising. Improved mechanistic understanding, technology and more controlled trials will be helpful to establish a clearer role for electrostimulation in treatment of various GI disorders.

One-Dimensional Ferroelectric Nanoarrays with Wireless Switchable Static and Dynamic Electrical Stimulation for Selective Regulating Osteogenesis and Antiosteosarcoma

Preventing local tumor recurrence and simultaneously improving bone-tissue regeneration are in great demand for osteosarcoma therapy. However, the current therapeutic implants fail to selectively suppress tumor growth and enhance osteogenesis, and antitumor therapy may compromise osseointegration of the bone implant. Here, based on the different responses of bone tumor cells and osteoblasts to different electric stimulations, we constructed ferroelectric BaTiO₃ nanorod arrays (NBTO) on the surface of titanium implants with switchable dynamic and static electrical stimulation for selective bone-tumor therapy and bone tissue regeneration. Polarized NBTO (PNBTO) generated a sustained dynamic electrical stimulus in response to wireless ultrasonic irradiation ("switch-on"), which disrupted the orientation of the spindle filaments of the tumor cell, blocked the G2/M phase of mitosis, and ultimately led to tumor cell death, whereas it had almost no cytotoxic effect on normal bone cells. Under the switch-off state, PNBTO with a high surface potential provided static electrical stimulation, accelerating osteogenic differentiation of mesenchymal stem cells and enhancing the quality of bone regeneration both in vitro and in vivo. This study broadens the biomedical potential of electrical stimulation therapy and provides a comprehensive and clinically feasible strategy for the overall treatment and tissue regeneration in osteosarcoma.

Abdominal vagus nerve stimulation alleviates collagen-induced arthritis in rats

Rheumatoid arthritis (RA) is a chronic, autoimmune inflammatory disease. Despite therapeutic advances, a significant proportion of RA patients are resistant to pharmacological treatment. Stimulation of the cervical vagus nerve is a promising alternative bioelectric neuromodulation therapeutic approach. However, recent clinical trials show cervical vagus nerve stimulation (VNS) was not effective in a significant proportion of drug resistant RA patients. Here we aim to assess if abdominal vagus nerve stimulation reduces disease severity in a collagen-induced arthritis (CIA) rat model. The abdominal vagus nerve of female Dark Agouti rats was implanted and CIA induced using collagen type II injection. VNS (1.6 mA, 200 μs pulse width, 50 μs interphase gap, 27 Hz frequency) was applied to awake freely moving rats for 3 h/day (days 11–17). At 17 days following the collagen injection, unstimulated CIA rats (n = 8) had significantly worse disease activity index, tumor necrosis factor-alpha (TNF-α) and receptor activator of NFκB ligand (RANKL) levels, synovitis and cartilage damage than normal rats (n = 8, Kruskal–Wallis: P &lt; 0.05). However, stimulated CIA rats (n = 5–6) had significantly decreased inflammatory scores and ankle swelling (Kruskal–Wallis: P &lt; 0.05) compared to unstimulated CIA rats (n = 8). Levels of tumor necrosis factor-alpha (TNF-α) remained at undetectable levels in stimulated CIA rats while levels of receptor activator of NFκB ligand (RANKL) were significantly less in stimulated CIA rats compared to unstimulated CIA rats (P &lt; 0.05). Histopathological score of inflammation and cartilage loss in stimulated CIA rats were no different from that of normal (P &gt; 0.05). In conclusion, abdominal VNS alleviates CIA and could be a promising therapy for patients with RA.

kHz-frequency electrical stimulation selectively activates small, unmyelinated vagus afferents

BACKGROUND

Vagal reflexes regulate homeostasis in visceral organs and systems through afferent and efferent neurons and nerve fibers. Small, unmyelinated, C-type afferents comprise over 80% of fibers in the vagus and form the sensory arc of autonomic reflexes of the gut, lungs, heart and vessels and the immune system. Selective bioelectronic activation of C-afferents could be used to mechanistically study and treat diseases of peripheral organs in which vagal reflexes are involved, but it has not been achieved.

METHODS

We stimulated the vagus in rats and mice using trains of kHz-frequency stimuli. Stimulation effects were assessed using neuronal c-Fos expression, physiological and nerve fiber responses, optogenetic and computational methods.

RESULTS

Intermittent kHz stimulation for 30 min activates specific motor and, preferentially, sensory vagus neurons in the brainstem. At sufficiently high frequencies (>5 kHz) and at intensities within a specific range (7-10 times activation threshold, T, in rats; 15-25 × T in mice), C-afferents are activated, whereas larger, A- and B-fibers, are blocked. This was determined by measuring fiber-specific acute physiological responses to kHz stimulus trains, and by assessing fiber excitability around kHz stimulus trains through compound action potentials evoked by probing pulses. Aspects of selective activation of C-afferents are explained in computational models of nerve fibers by how fiber size and myelin shape the response of sodium channels to kHz-frequency stimuli.

CONCLUSION

kHz stimulation is a neuromodulation strategy to robustly and selectively activate vagal C-afferents implicated in physiological homeostasis and disease, over larger vagal fibers.

Electrical neuromodulation therapy for inflammatory bowel disease

Inflammatory bowel disease (IBD) is an inflammatory disease of the gastrointestinal (GI) tract. It has financial and quality of life impact on patients. Although there has been a significant advancement in treatments, a considerable number of patients do not respond to it or have severe side effects. Therapeutic approaches such as electrical neuromodulation are being investigated to provide alternate options. Although bioelectric neuromodulation technology has evolved significantly in the last decade, sacral nerve stimulation (SNS) for fecal incontinence remains the only neuromodulation protocol commonly utilized use for GI disease. For IBD treatment, several electrical neuromodulation techniques have been studied, such as vagus NS, SNS, and tibial NS. Several animal and clinical experiments were conducted to study the effectiveness, with encouraging results. The precise underlying mechanisms of action for electrical neuromodulation are unclear, but this modality appears to be promising. Randomized control trials are required to investigate the efficacy of intrinsic processes. In this review, we will discuss the electrical modulation therapy for the IBD and the data pertaining to it.

Modulation of the autonomic nervous system by one session of spinal low-level laser therapy in patients with chronic colonic motility dysfunction

Patients with a defecation disorder may not evoke a normal defecation reflex, or the reflex may be excessive, as a dysfunction of the spinal autonomic nervous system. Treatment with various forms of lumbar and sacral neuromodulation have shown symptom improvement, but potential changes in autonomic functioning are rarely studied. Here we evaluate the effects on autonomic function of a single session of low-level laser therapy (LLLT) on the lumbar and sacral spine in 41 patients with chronic gastrointestinal motor dysfunction. The LLLT protocol used red LED light at a wavelength of 660 nm for 10 min and infrared LED light at a wavelength of 840 nm for 10 min, followed by infrared laser light at a wavelength of 825 nm for 10 min. Effects on the autonomic nervous system were assessed by measuring heart rate variability (HRV) changes. Respiratory Sinus Arrhythmia (RSA) and Root Mean Square of Successive Differences (RMSSD) were used to quantify parasympathetic reactivity; the Baevsky’s Stress Index (SI) reflected sympathetic activity while the ratios SI/RSA and SI/RMSSD were used to show shifts in autonomic dominance. The results indicate that lumbar and sacral neuromodulation using light arrays reduced, whereas stimulation by the laser probes significantly increased parasympathetic activity. The light arrays increased whereas the laser probes significantly decreased sympathetic activity (SI). The entire protocol shifted the autonomic balance toward parasympathetic activity. The comparison of actual vs. sham neuromodulation proved that the change in HRV parameters was due to actual light stimulation and not due to the arrays and probe touching the skin. In conclusion, a single session of LLLT markedly affects autonomic nervous system activity reflected in changes in HRV which is only possible by generating activity in the spinal autonomic nerves. These results warrant a study into the effects of LLLT on restoring autonomic dysfunction in chronic refractory colonic motility disorders.

Impact of intravenous dexmedetomidine on gastrointestinal function recovery after laparoscopic hysteromyomectomy: a randomized clinical trial

Postoperative intestinal ileus is common after laparoscopic surgery, the incidence of those after hysterectomy was 9.2%. Anesthesia is one of the independent risk factors of postoperative ileus. Dexmedetomidine has been widely used in perioperative anesthesia and previous reports suggested that intraoperative dexmedetomidine may be associated with the improvement of gastrointestinal function recovery after abdominal surgery. We hypothesized that dexmedetomidine could improve gastrointestinal function recovery after laparoscopic hysteromyomectomy. Participants in elective laparoscopic hysteromyomectomy were enrolled with a single dose of 0.5 μg kg⁻¹ dexmedetomidine or the same volume of placebo intravenously administered for 15 min, followed by continuous pumping of 0.2 μg kg⁻¹ h⁻¹ of corresponding drugs until 30 min before the end of surgery. The primary outcome was the time to first flatus. Secondary outcomes were the time to first oral feeding and the first defecation, the occurrence of flatulence, pain score and postoperative nausea and vomiting until 48 h after the surgery. Eventually, 106 participants (54 in dexmedetomidine group and 52 in placebo group) were included for final analysis. The time to first flatus (SD, 25.83 [4.18] vs 27.67 [3.77], P = 0.019), oral feeding time (SD, 27.29 [4.40] vs 28.92 [3.82], P = 0.044), the time to first defecation (SD, 59.82 [10.49] vs 63.89 [7.71], P = 0.025), abdominal distension (n%, 12 (22.2) vs 21 (40.4), P = 0.044), PONV at 24 h (n%, 10 (18.5) vs 19 (36.5), P = 0.037), NRS 6 h (3.15(0.68) vs 3.46 (0.87), P = 0.043) and NRS 12 h (3.43 (0.88) vs 3.85 (0.85), P = 0.014) of dexmedetomidine group were significantly shorter than those of the placebo group. Intraoperative dexmedetomidine reduced the time to first flatus, first oral feeding, and first defecation. These results suggested that this treatment may be a feasible strategy for improving postoperative gastrointestinal function recovery in patients undergoing laparoscopic hysteromyomectomy.

Effects of the Ultrasound-Guided Stellate Ganglion Block on Hemodynamics, Stress Response, and Gastrointestinal Function in Postoperative Patients with Colorectal Cancer

Objective

The aim of the study was to study the effects of the ultrasound-guided stellate ganglion block on hemodynamics, stressful response, and postoperative gastrointestinal functions in patients with colorectal cancer.

Methods

A total of 100 patients with colorectal cancer hospitalized from January 2021 to December 2021 were selected. After anesthesia induction, the right stellate ganglion block was performed under ultrasound guidance in the research group and the general anesthesia was performed in the control group. The heart rate (HR), mean arterial pressure (MAP), epinephrine, cortisol, self-rating anxiety scale (SAS), Ramsay sedation score (RSS), postoperative bowel sound recovery time, anal exhaust time, and the incidence of gastrointestinal adverse reactions 24 hours after operation were studied pre-and post-24-hour anesthesia induction.

Results

Following 24-hour operation, the HR and MAP values were largely reduced (p < 0.05). Following 24-hour operation, epinephrine and cortisol became obviously higher (p < 0.05). After 24-hour operation, the levels of epinephrine and cortisol in the research group were greatly lower. The score of the SAS in the study cohort was less than that of the controls (p < 0.05). The RSS of the research group was obviously increased (p < 0.05). The recovery time of intestinal sound and the anal exhaust time of the study cohort became remarkably shorter (p < 0.05). The incidence of gastrointestinal adverse reactions 24 hours after operation of the study cohort was much less common (p < 0.05).

Conclusion

The ultrasound-guided stellate ganglion block can reduce the fluctuation of blood circulation during radical resection of colorectal cancer, reduce postoperative gastrointestinal dysfunction and stress reaction, relieve patients' anxiety, and contribute to the recovery of gastrointestinal function.

New Understanding on the Pathophysiology and Treatment of Constipation in Parkinson’s Disease

Constipation, one of the most common prodromal non-motor symptoms of Parkinson’s disease (PD), usually occurs several years earlier than the onset of motor symptoms. Previous studies have shown that constipation occurrence increases as the disease progresses. However, the mechanism underlying this pathologic disorder is not clear yet. Moreover, chronic constipation causes slowness in gastric emptying and, therefore, may lead to a delay in the absorption of medications for PD, including levodopa and dopamine agonists. Accordingly, it is necessary to understand how the pathophysiological factors contribute to constipation during PD as well as pursue precise and effective treatment strategies. In this review, we encapsulate the molecular mechanism of constipation underlying PD and update the progress in the treatments of PD-associated constipation.

Clinical perspectives on vagus nerve stimulation: present and future

The vagus nerve, the great wanderer, is involved in numerous processes throughout the body and vagus nerve stimulation (VNS) has the potential to modulate many of these functions. This wide-reaching capability has generated much interest across a range of disciplines resulting in several clinical trials and studies into the mechanistic basis of VNS. This review discusses current preclinical and clinical evidence supporting the efficacy of VNS in different diseases and highlights recent advancements. Studies that provide insights into the mechanism of VNS are considered.

Care of the Patient After Metabolic and Bariatric Surgery

Weight loss surgery, also known as metabolic and bariatric surgery (MBS), is an effective weight loss treatment and is associated with reduced mortality and improvements in obesity-related health conditions and quality of life. Postsurgical anatomical and physiologic changes include decreased absorption of micronutrients and alterations in gut-brain hormonal regulation that affect many aspects of health. Patients require ongoing monitoring of their physical and mental health for lasting success. Internists, particularly primary care clinicians, are in an ideal position to monitor for nonserious complications in the short and long term, adjust management of chronic diseases accordingly, and monitor for mental health changes. This article reviews key issues that internists should be aware of for supporting patients' health in the short and long term after MBS.

Pediatric gastrointestinal neuromodulation: A review

Neuromodulation, also known as bioelectric neuromodulation or neurostimulation, is the therapeutic use of electrical stimulation of nerves or brain centers. Neuromodulation has been trialed in an increasing range of human diseases as well as gastrointestinal disorders. The application of neuromodulation to treat pediatric motility and functional disorders is an exciting recent development. This review aims to briefly discuss the use of neuromodulation for the treatment of pediatric gastroparesis, constipation, and visceral hyperalgesia.

Low-frequency electrical stimulation promotes the recovery of gastrointestinal motility following gynecological laparoscopy (Review)

The rapid recovery of gastrointestinal transit is critical for clinical recovery following laparoscopic procedures, including gynecological laparoscopies (GLs). Rehabilitation interventions post-surgery may provide significant prevention against early post-operative gastrointestinal motility disorders and maid aid in the acceleration of post-operative recovery in patients undergoing GLs. Among others, low-frequency electrical stimulation (LFES) has been demonstrated to pronouncedly mitigate the symptoms caused by gastrointestinal motility disorders; thus, this has attracted increasing attention over the past decade. The present study aimed to present an overview of the efficacy and application of LFES in gastrointestinal motility recovery following GL procedures.

Anorexia nervosa and gut microbiome: implications for weight change and novel treatments

INTRODUCTION

Host-microbiota interactions may be involved in many physical and psychological functions ranging from the digestion of food, maintenance of immune homeostasis, to the regulation of mood and cognition. Microbiome dysbiosis has been consistently described in many diseases. The pathogenesis and weight regulation mechanism in anorexia nervosa (AN) also seem to be implicated in the dynamic bidirectional adjustment of the microbiota-gut-brain axis. This review aims at elucidating this relationship.

AREA COVERED

This review starts with a description of pathogenic gut-brain pathways. Next, we focus on the latest research on the associations between gut microbiota and weight change in the condition of AN. The strategies to alter the intestinal microbiome for the treatment of this disorder are discussed, including dietary, probiotics, prebiotics, synbiotics, and fecal microbiota transplantation.

EXPERT OPINION

Gut microbiome is inextricably linked to AN. It may regulate weight gain in the process of refeeding via the microbiota-gut-brain axis, while the specific mechanism has yet to be clearly established. In the future, a better understanding of gut microbiome could have implications for developing microbiome-based prevention, diagnostics and therapies.

Brain circuits for promoting homeostatic and non-homeostatic appetites

As the principal means of acquiring nutrients, feeding behavior is indispensable to the survival and well-being of animals. In response to energy or nutrient deficits, animals seek and consume food to maintain energy homeostasis. On the other hand, even when animals are calorically replete, non-homeostatic factors, such as the sight, smell, and taste of palatable food, or environmental cues that predict food, can stimulate feeding behavior. These homeostatic and non-homeostatic factors have traditionally been investigated separately, but a growing body of literature highlights that these factors work synergistically to promote feeding behavior. Furthermore, recent breakthroughs in cell type-specific and circuit-specific labeling, recording, and manipulation techniques have markedly accelerated the discovery of well-defined neural populations underlying homeostatic and non-homeostatic appetite control, as well as overlapping circuits that contribute to both types of appetite. This review aims to provide an update on our understanding of the neural circuit mechanisms for promoting homeostatic and non-homeostatic appetites, focusing on the function of recently identified, genetically defined cell types.

Research on the neural circuit mechanisms underlying feeding behaviors is critical to identifying therapeutic targets for food-related disorders like obesity and anorexia. Sung-Yon Kim and colleagues at Seoul National University, South Korea, reviewed the current understanding of neural circuits promoting feeding behavior, which is regulated by homeostatic and non-homeostatic appetites. In response to deficits in energy (caloric) or nutrients, specific populations of neurons sensitive to hormones leptin and ghrelin generate homeostatic appetite and promote feeding. In addition, diverse neural populations stimulate non-homeostatic appetite in the absence of immediate internal needs and are thought to drive overconsumption in the modern obesogenic environment. These appetites extensively interact through overlapping neural circuits to jointly promote feeding behaviors.

Recent Progress in Materials Chemistry to Advance Flexible Bioelectronics in Medicine

Designing bioelectronic devices that seamlessly integrate with the human body is a technological pursuit of great importance. Bioelectronic medical devices that reliably and chronically interface with the body can advance neuroscience, health monitoring, diagnostics, and therapeutics. Recent major efforts focus on investigating strategies to fabricate flexible, stretchable, and soft electronic devices, and advances in materials chemistry have emerged as fundamental to the creation of the next generation of bioelectronics. This review summarizes contemporary advances and forthcoming technical challenges related to three principal components of bioelectronic devices: i) substrates and structural materials, ii) barrier and encapsulation materials, and iii) conductive materials. Through notable illustrations from the literature, integration and device fabrication strategies and associated challenges for each material class are highlighted.

[Ultrasound-guided stellate ganglion block accelerates postoperative gastrointestinal function recovery following laparoscopic radical gastrectomy for gastric cancer]

OBJECTIVE

To explore the effects of ultrasound-guided stellate ganglion block (SGB) on perioperative stress response, gastrointestinal hormones and postoperative gastrointestinal function recovery in patients undergoing laparoscopic radical gastrectomy for gastric cancer.

METHODS

This study was conducted among 60 American Society of Anesthesiologists (ASA) class II-III patients with gastric cancer (regardless of gender, aged 35-75 years with BMI of 18.5-26 kg/m2) undergoing elective laparoscopic radical gastrectomy. The patients were randomized into experimental group (S group, n=30) and control group (NS group, n=30). In S group, SGB at the C6 level of the right cervical spine was performed under ultrasound guidance 15 min before induction of anesthesia by injection of 7 mL 0.5% ropivacaine; the patients in NS group received injections of normal saline in the same manner. Peripheral venous blood samples were collected before SGB (T1), after surgery (T2), and on the 2nd and 6th days after surgery (T3 and T4) for determination of the levels of motitin (MOT), vasoactive intestinal peptide (VIP), cortisol (COR), and blood glucose (GLU). Intraoperative usage of sufentanil, recovery rate of intestinal sounds at 36, 48, 60, 72, 84 and 96 h after operation and the time of first passage of flatus were recorded and compared between the two groups.

RESULTS

There was no significant difference in the total amount of sufentanil consumption between the two groups. Compared with those in NS group, the patients in S group had significant lower COR and VIP levels (P < 0.05) and higher MOT level (P < 0.05) at T2, T3 and T4. Glu level at T2 and T3 was also significantly lower in S group (P < 0.05). The recovery rates of intestinal sounds at 36, 48, 60, 72 and 84 h after surgery were significantly higher (P < 0.05) and the time of the first passage of flatus was earlier in S group than in NS group (P < 0.05).

CONCLUSION

In patients with gastric cancer undergoing laparoscopic radical gastrectomy, ultrasound-guided SGB can reduce postoperative stress level, promote the recovery of gastrointestinal hormone secretion, and accelerate postoperative recovery of gastrointestinal functions.

Different Transcutaneous Auricular Vagus Nerve Stimulation Parameters Modulate the Anti-Inflammatory Effects on Lipopolysaccharide-Induced Acute Inflammation in Mice

Vagus nerve stimulation (VNS) is considered a potential method for anti-inflammation due to the involvement of the VN in the cholinergic anti-inflammatory pathway (CAP) formation of a connection between the central nervous system and peripheral immune cells that help relieve inflammation. However, whether a non-invasive transcutaneous auricular VNS (taVNS) modulates the inflammation levels via altering the parameter of taVNS is poorly understood. This study aimed to determine the differential inhibitory effects of taVNS on lipopolysaccharide (LPS)-induced systemic inflammation using electrical stimulation parameters such as pulse frequency and time. The taVNS-promoted CAP activity significantly recovered LPS-induced tissue injuries (lung, spleen, and intestine) and decreased inflammatory cytokine levels and tissue-infiltrated immune cells. Interestingly, the anti-inflammatory capacity of taVNS with 15 Hz was much higher than that of taVNS with 25 Hz. When a cytokine array was used to investigate the changes of inflammation and immune response-related cytokines/chemokines expression in taVNS with 15 Hz or 25 Hz treatment in LPS-induced endotoxemia in mice, most of the expression of cytokines/chemokines associated with pro-inflammation was severely decreased in taVNS with 15 Hz compared to 25 Hz. This study demonstrated that the taVNS parameter could differentially modulate the inflammation levels of animals, suggesting the importance of taVNS parameter selection for use in feasible interventions for acute inflammation treatment.

Vagus Nerve Stimulation Reduces Indomethacin-Induced Small Bowel Inflammation

Crohn's disease is a chronic, idiopathic condition characterized by intestinal inflammation and debilitating gastrointestinal symptomatology. Previous studies of inflammatory bowel disease (IBD), primarily in colitis, have shown reduced inflammation after electrical or pharmacological activation of the vagus nerve, but the scope and kinetics of this effect are incompletely understood. To investigate this, we studied the effect of electrical vagus nerve stimulation (VNS) in a rat model of indomethacin-induced small intestinal inflammation. 1 min of VNS significantly reduced small bowel total inflammatory lesion area [(mean ± SEM) sham: 124 ± 14 mm2, VNS: 62 ± 14 mm2, p = 0.002], intestinal peroxidation and chlorination rates, and intestinal and systemic pro-inflammatory cytokine levels as compared with sham-treated animals after 24 h following indomethacin administration. It was not known whether this observed reduction of inflammation after VNS in intestinal inflammation was mediated by direct innervation of the gut or if the signals are relayed through the spleen. To investigate this, we studied the VNS effect on the small bowel lesions of splenectomized rats and splenic nerve stimulation (SNS) in intact rats. We observed that VNS reduced small bowel inflammation also in splenectomized rats but SNS alone failed to significantly reduce small bowel lesion area. Interestingly, VNS significantly reduced small bowel lesion area for 48 h when indomethacin administration was delayed. Thus, 1 min of electrical activation of the vagus nerve reduced indomethacin-induced intestinal lesion area by a spleen-independent mechanism. The surprisingly long-lasting and spleen-independent effect of VNS on the intestinal response to indomethacin challenge has important implications on our understanding of neural control of intestinal inflammation and its potential translation to improved therapies for IBD.

Electrical Stimulation for Immune Modulation in Cancer Treatments

Immunotherapy is becoming a very common treatment for cancer, using approaches like checkpoint inhibition, T cell transfer therapy, monoclonal antibodies and cancer vaccination. However, these approaches involve high doses of immune therapeutics with problematic side effects. A promising approach to reducing the dose of immunotherapeutic agents given to a cancer patient is to combine it with electrical stimulation, which can act in two ways; it can either modulate the immune system to produce the immune cytokines and agents in the patient's body or it can increase the cellular uptake of these immune agents via electroporation. Electrical stimulation in form of direct current has been shown to reduce tumor sizes in immune-competent mice while having no effect on tumor sizes in immune-deficient mice. Several studies have used nano-pulsed electrical stimulations to activate the immune system and drive it against tumor cells. This approach has been utilized for different types of cancers, like fibrosarcoma, hepatocellular carcinoma, human papillomavirus etc. Another common approach is to combine electrochemotherapy with immune modulation, either by inducing immunogenic cell death or injecting immunostimulants that increase the effectiveness of the treatments. Several therapies utilize electroporation to deliver immunostimulants (like genes encoded with cytokine producing sequences, cancer specific antigens or fragments of anti-tumor toxins) more effectively. Lastly, electrical stimulation of the vagus nerve can trigger production and activation of anti-tumor immune cells and immune reactions. Hence, the use of electrical stimulation to modulate the immune system in different ways can be a promising approach to treat cancer.

Neural signalling of gut mechanosensation in ingestive and digestive processes

Eating and drinking generate sequential mechanosensory signals along the digestive tract. These signals are communicated to the brain for the timely initiation and regulation of diverse ingestive and digestive processes - ranging from appetite control and tactile perception to gut motility, digestive fluid secretion and defecation - that are vital for the proper intake, breakdown and absorption of nutrients and water. Gut mechanosensation has been investigated for over a century as a common pillar of energy, fluid and gastrointestinal homeostasis, and recent discoveries of specific mechanoreceptors, contributing ion channels and the well-defined circuits underlying gut mechanosensation signalling and function have further expanded our understanding of ingestive and digestive processes at the molecular and cellular levels. In this Review, we discuss our current understanding of the generation of mechanosensory signals from the digestive periphery, the neural afferent pathways that relay these signals to the brain and the neural circuit mechanisms that control ingestive and digestive processes, focusing on the four major digestive tract parts: the oral and pharyngeal cavities, oesophagus, stomach and intestines. We also discuss the clinical implications of gut mechanosensation in ingestive and digestive disorders.

White matter tract transcranial ultrasound stimulation, a computational study

Low-intensity transcranial ultrasound stimulation (TUS) is poised to become one of the most promising treatments for neurological disorders. However, while recent animal model experiments have successfully quantified the alterations of the functional activity coupling between a sonicated target cortical region and other cortical regions of interest (ROIs), the varying degree of alteration between these different connections remains unexplained. We hypothesise here that the incidental sonication of the tracts leaving the target region towards the different ROIs could participate in explaining these differences. To this end, we propose a tissue level phenomenological numerical model of the coupling between the ultrasound waves and the white matter electrical activity. The model is then used to reproduce in silico the sonication of the anterior cingulate cortex (ACC) of a macaque monkey and measure the neuromodulation power within the white matter tracts leaving the ACC for five cortical ROIs. The results show that the more induced power a white matter tract proximal to the ACC and connected to a secondary ROI receives, the more altered the connectivity fingerprint of the ACC to this region will be after sonication. These results point towards the need to isolate the sonication to the cortical region and minimise the spillage on the neighbouring tracts when aiming at modulating the target region without losing the functional connectivity with other ROIs. Those results further emphasise the potential role of the white matter in TUS and the need to account for white matter topology when designing TUS protocols.

The Predictive Role of ADRA2A rs1800544 and HTR3B rs3758987 Polymorphisms in Motion Sickness Susceptibility

Motion sickness is a common central nervous system response, the primary sign of which is vomiting. Its susceptibility varies between individuals. To find predictive factors, we investigated the association of ADRA2A rs1800544 and HTR3B rs3758987 with motion sickness susceptibility and examined their mRNA changes during actual voyages. A total of 315 healthy college students were enrolled for SNP genotyping by the PCR-RFLP method. Blood samples were collected from another 42 subjects during two separate voyages to detect their mRNA expression changes at three time points. The frequency of the rs1800544 GG genotype in the susceptibility group was significantly higher (52.26%), and allele G increased the risk of motion sickness (OR = 1.585, 95% CI = 1.136-2.208). In the logistic regression model, the rs3758987 CC+TC genotype and rs1800544 GG genotype increased the risk of motion sickness-induced vomiting (OR = 2.105, 95% CI = 1.112-3.984; OR = 1.992, 95% CI = 1.114-3.571). The ADRA2A mRNA baseline was lower in the GG carriers and the HTR3B mRNA baseline was lower in the TC/CC carriers before sailing, then increased significantly within 24 h and then decreased after a long-term voyage. People carrying the rs1800544 GG genotype seem more susceptible to motion sickness. In combination with the incidence of vomiting during the actual-voyage experiments, our results indicate the involvement of rs1800544 and rs3758987 in motion sickness-induced vomiting.

Neuronal regulation of the gut immune system and neuromodulation for treating inflammatory bowel disease

The gut immune system in the healthy intestine is anti-inflammatory, but can move to a pro-inflammatory state when the gut is challenged by pathogens or in disease. The nervous system influences the level of inflammation through enteric neurons and extrinsic neural connections, particularly vagal and sympathetic innervation of the gastrointestinal tract, each of which exerts anti-inflammatory effects. Within the enteric nervous system (ENS), three neuron types that influence gut immune cells have been identified, intrinsic primary afferent neurons (IPANs), vasoactive intestinal peptide (VIP) neurons that project to the mucosa, and cholinergic neurons that influence macrophages in the external muscle layers. The enteric neuropeptides, calcitonin gene-related peptide (CGRP), tachykinins, and neuromedin U (NMU), which are contained in IPANs, and VIP produced by the mucosa innervating neurons, all influence immune cells, notably innate lymphoid cells (ILCs). ILC2 are stimulated by VIP to release IL-22, which promotes microbial defense and tissue repair. Enteric neurons are innervated by the vagus, and, in the large intestine, by the pelvic nerves. Vagal nerve stimulation reduces gut inflammation, which may be both by stimulation of efferent (motor) pathways to the ENS, and stimulation of afferent pathways that connect to integrating centers in the CNS. Efferent pathways from the CNS have their anti-inflammatory effects through either or both vagal efferent neurons and sympathetic pathways. The final neurons in sympathetic pathways reduce gut inflammation by the action of noradrenaline on β2 adrenergic receptors expressed by immune cells. Activation of neural anti-inflammatory pathways is an attractive option to treat inflammatory bowel disease that is refractory to other treatments. Further investigation of the ways in which enteric reflexes, vagal pathways and sympathetic pathways integrate their effects to modulate the gut immune system and gut inflammation is needed to optimize neuromodulation therapy.

Understanding the physiology of human defaecation and disorders of continence and evacuation

The act of defaecation, although a ubiquitous human experience, requires the coordinated actions of the anorectum and colon, pelvic floor musculature, and the enteric, peripheral and central nervous systems. Defaecation is best appreciated through the description of four phases, which are, temporally and physiologically, reasonably discrete. However, given the complexity of this process, it is unsurprising that disorders of defaecation are both common and problematic; almost everyone will experience constipation at some time in their life and many will develop faecal incontinence. A detailed understanding of the normal physiology of defaecation and continence is critical to inform management of disorders of defaecation. During the past decade, there have been major advances in the investigative tools used to assess colonic and anorectal function. This Review details the current understanding of defaecation and continence. This includes an overview of the relevant anatomy and physiology, a description of the four phases of defaecation, and factors influencing defaecation (demographics, stool frequency/consistency, psychobehavioural factors, posture, circadian rhythm, dietary intake and medications). A summary of the known pathophysiology of defaecation disorders including constipation, faecal incontinence and irritable bowel syndrome is also included, as well as considerations for further research in this field.

Gastric neurons in the nucleus tractus solitarius are selective to the orientation of gastric electrical stimulation

Objective.Gastric electrical stimulation (GES) is a bioelectric intervention for gastroparesis, obesity, and other functional gastrointestinal disorders. In a potential mechanism of action, GES activates the nerve endings of vagal afferent neurons and induces the vago-vagal reflex through the nucleus tractus solitarius (NTS) in the brainstem. However, it is unclear where and how to stimulate in order to optimize the vagal afferent responses.Approach.To address this question with electrophysiology in rats, we applied mild electrical currents to two serosal targets on the distal forestomach with dense distributions of vagal intramuscular arrays (IMAs) that innervated the circular and longitudinal smooth muscle layers. During stimulation, we recorded single and multi-unit responses from gastric neurons in NTS and evaluated how the recorded responses depended on the stimulus orientation and amplitude.Main results.We found that NTS responses were highly selective to the stimulus orientation for a range of stimulus amplitudes. The strongest responses were observed when the applied current flowed in the same direction as the IMAs in parallel with the underlying smooth muscle fibers. Our results suggest that gastric neurons in NTS may encode the orientation-specific activity of gastric smooth muscles relayed by vagal afferent neurons.Significance.This finding suggests that the orientation of GES is critical to effective engagement of vagal afferents and should be considered in light of the structural phenotypes of vagal terminals in the stomach.