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Jiang L, Yang J, Gao X, Huang J, Liu Q, Fu L. In vivo imaging of vagal-induced myenteric plexus responses in gastrointestinal tract with an optical window. Nat Commun 2024; 15:8123. [PMID: 39285207 PMCID: PMC11405534 DOI: 10.1038/s41467-024-52397-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2024] [Accepted: 09/03/2024] [Indexed: 09/20/2024] Open
Abstract
The vagus nerve (VN) extensively innervates the gastric enteric nervous system (ENS), but its influence on gastric ENS functionality and motility in vivo remains unclear due to technical challenges. Here we describe a method for stable, long-term observation of gastric ENS activity and muscle dynamics at cellular resolution, which can also be extended to intestinal applications. This method involves ENS-specific labeling and the implantation of an abdominal wall window for optical recording in male mice. In vivo calcium imaging reveals a linear relationship between vagal stimulation frequency and myenteric neuron activation in gastric antrum. Furthermore, the motility of gastric antrum is significantly enhanced and shows a positive correlation with the intensity and number of activated myenteric neurons. While vagal stimulation also activates proximal colonic myenteric neurons, this activation is not frequency-dependent and does not induce proximal colonic motility. The method and results provide important insights into VN-ENS interactions in vivo, advancing our understanding of gastrointestinal motility regulation.
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Affiliation(s)
- Longjie Jiang
- Britton Chance Center for Biomedical Photonics, Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, Hubei, China
- MoE Key Laboratory for Biomedical Photonics, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Jie Yang
- Britton Chance Center for Biomedical Photonics, Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, Hubei, China
- MoE Key Laboratory for Biomedical Photonics, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Xiujuan Gao
- Britton Chance Center for Biomedical Photonics, Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, Hubei, China
- MoE Key Laboratory for Biomedical Photonics, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Jiangfeng Huang
- Britton Chance Center for Biomedical Photonics, Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, Hubei, China
- MoE Key Laboratory for Biomedical Photonics, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Qian Liu
- School of Biomedical Engineering, Hainan University, Haikou, Hainan, China
| | - Ling Fu
- Britton Chance Center for Biomedical Photonics, Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, Hubei, China.
- MoE Key Laboratory for Biomedical Photonics, Huazhong University of Science and Technology, Wuhan, Hubei, China.
- School of Biomedical Engineering, Hainan University, Haikou, Hainan, China.
- School of Physics and Optoelectronics Engineering, Hainan University, Haikou, Hainan, China.
- Advanced Biomedical Imaging Facility, Huazhong University of Science and Technology, Wuhan, Hubei, China.
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Wang X, Alkaabi F, Choi M, Di Natale MR, Scheven UM, Noll DC, Furness JB, Liu Z. Surface mapping of gastric motor functions using MRI: a comparative study between humans and rats. Am J Physiol Gastrointest Liver Physiol 2024; 327:G345-G359. [PMID: 38915290 PMCID: PMC11427095 DOI: 10.1152/ajpgi.00045.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/12/2024] [Accepted: 06/16/2024] [Indexed: 06/26/2024]
Abstract
The stomach's ability to store, mix, propel, and empty its content requires highly coordinated motor functions. However, current diagnostic tools cannot simultaneously assess these motor processes. This study aimed to use magnetic resonance imaging (MRI) to map multifaceted gastric motor functions, including accommodation, tonic and peristaltic contractions, and emptying, through a single noninvasive experiment for both humans and rats. Ten humans and 10 Sprague-Dawley rats consumed MRI-visible semisolid meals and underwent MRI scans. We used a surface model to analyze MRI data, capturing the deformation of the stomach wall on ingestion or during digestion. We inferred muscle activity, mapped motor processes, parcellated the stomach into functional regions, and revealed cross-species distinctions. In humans, both the fundus and antrum distended postmeal, followed by sustained tonic contractions to regulate intragastric pressure. Peristaltic contractions initiated from the distal fundus, including three concurrent wavefronts oscillating at 3.3 cycles/min and traveling at 1.7 to 2.9 mm/s. These motor functions facilitated linear gastric emptying with a 61-min half-time. In contrast, rats exhibited peristalsis from the midcorpus, showing two wavefronts oscillating at 5.0 cycles/min and traveling at 0.4 to 0.9 mm/s. For both species, motility features allowed functional parcellation of the stomach along a midcorpus division. This study maps region- and species-specific gastric motor functions. We demonstrate the value of MRI with surface modeling in understanding gastric physiology and its potential to become a new standard for clinical and preclinical investigations of gastric disorders at both individual and group levels.NEW & NOTEWORTHY A novel MRI technique can visualize how the stomach accommodates, mixes, and propels food for digestion in humans and animals alike. Digital models of gastric MRI reveal the functional maps, organization, and distinction of the stomach across individuals and species. This technique holds the unique potential to advance basic and clinical studies of functional gastric disorders.
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Affiliation(s)
- Xiaokai Wang
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, United States
| | - Fatimah Alkaabi
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, United States
| | - Minkyu Choi
- Division of Electrical and Computer Engineering, University of Michigan, Ann Arbor, Michigan, United States
| | - Madeleine R Di Natale
- Department of Anatomy and Physiology, University of Melbourne, Parkville, Victoria, Australia
- Florey Institute of Neuroscience and Mental Health, Parkville, Victoria, Australia
| | - Ulrich M Scheven
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan, United States
| | - Douglas C Noll
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, United States
- Department of Radiology, University of Michigan, Ann Arbor, Michigan, United States
| | - John B Furness
- Department of Anatomy and Physiology, University of Melbourne, Parkville, Victoria, Australia
- Florey Institute of Neuroscience and Mental Health, Parkville, Victoria, Australia
| | - Zhongming Liu
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, United States
- Division of Electrical and Computer Engineering, University of Michigan, Ann Arbor, Michigan, United States
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Reardon C. Comment on "No consistent evidence for the anti-inflammatory effect of vagus nerve stimulation in humans: A systematic review and meta-analysis". Brain Behav Immun 2024; 119:1018. [PMID: 38447885 DOI: 10.1016/j.bbi.2024.03.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/08/2024] [Revised: 01/18/2024] [Accepted: 03/03/2024] [Indexed: 03/08/2024] Open
Affiliation(s)
- Colin Reardon
- Department of Anatomy, Physiology and Cell Biology, School of Veterinary Medicine, UC Davis, Davis, CA, United States
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Sévoz-Couche C, Liao W, Foo HYC, Bonne I, Lu TB, Tan Qi Hui C, Azhar SH, Peh WYX, Yen SC, Wong WSF. Direct vagus nerve stimulation: A new tool to control allergic airway inflammation through α7 nicotinic acetylcholine receptor. Br J Pharmacol 2024; 181:1916-1934. [PMID: 38430056 DOI: 10.1111/bph.16334] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2023] [Revised: 11/24/2023] [Accepted: 01/08/2024] [Indexed: 03/03/2024] Open
Abstract
BACKGROUND AND PURPOSE Asthma is characterized by airway inflammation, mucus hypersecretion, and airway hyperresponsiveness. The use of nicotinic agents to mimic the cholinergic anti-inflammatory pathway (CAP) controls experimental asthma. Yet, the effects of vagus nerve stimulation (VNS)-induced CAP on allergic inflammation remain unknown. EXPERIMENTAL APPROACH BALB/c mice were sensitized and challenged with house dust mite (HDM) extract and treated with active VNS (5 Hz, 0.5 ms, 0.05-1 mA). Bronchoalveolar lavage (BAL) fluid was assessed for total and differential cell counts and cytokine levels. Lungs were examined by histopathology and electron microscopy. KEY RESULTS In the HDM mouse asthma model, VNS at intensities equal to or above 0.1 mA (VNS 0.1) but not sham VNS reduced BAL fluid differential cell counts and alveolar macrophages expressing α7 nicotinic receptors (α7nAChR), goblet cell hyperplasia, and collagen deposition. Besides, VNS 0.1 also abated HDM-induced elevation of type 2 cytokines IL-4 and IL-5 and was found to block the phosphorylation of transcription factor STAT6 and expression level of IRF4 in total lung lysates. Finally, VNS 0.1 abrogated methacholine-induced hyperresponsiveness in asthma mice. Prior administration of α-bungarotoxin, a specific inhibitor of α7nAChR, but not propranolol, a specific inhibitor of β2-adrenoceptors, abolished the therapeutic effects of VNS 0.1. CONCLUSION AND IMPLICATIONS Our data revealed the protective effects of VNS on various clinical features in allergic airway inflammation model. VNS, a clinically approved therapy for depression and epilepsy, appears to be a promising new strategy for controlling allergic asthma.
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Affiliation(s)
- Caroline Sévoz-Couche
- INSERM, UMRS1158 Neurophysiologie Respiratoire et Clinique, Sorbonne Université, Paris, France
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Wupeng Liao
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
- Singapore-HUJ Alliance for Research and Enterprise (SHARE), National University of Singapore, Singapore
| | - Hazel Y C Foo
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
- Singapore-HUJ Alliance for Research and Enterprise (SHARE), National University of Singapore, Singapore
| | - Isabelle Bonne
- Electron Microscopy Unit, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
- Department of Microbiology & Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Thong Beng Lu
- Electron Microscopy Unit, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
- Department of Microbiology & Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Caris Tan Qi Hui
- Advanced imaging and Histology Core, Immunology Program, Life Science Institute, National University of Singapore, Singapore
| | - Syaza Hazwany Azhar
- Advanced imaging and Histology Core, Immunology Program, Life Science Institute, National University of Singapore, Singapore
| | - Wendy Yen Xian Peh
- The N.1 Institute for Health, National University of Singapore, Singapore
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore
| | - Shih-Cheng Yen
- The N.1 Institute for Health, National University of Singapore, Singapore
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore
| | - W S Fred Wong
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
- Singapore-HUJ Alliance for Research and Enterprise (SHARE), National University of Singapore, Singapore
- Drug Discovery and Optimization Platform, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
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Tovbis D, Yoo PB. Vagus nerve stimulation in bursts can efficiently modulate gastric contractions and contraction frequency at varying gastric pressures. Neurogastroenterol Motil 2024; 36:e14815. [PMID: 38735698 DOI: 10.1111/nmo.14815] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/29/2023] [Revised: 03/25/2024] [Accepted: 04/26/2024] [Indexed: 05/14/2024]
Abstract
OBJECTIVE There has been recent clinical interest in the use of vagus nerve stimulation (VNS) for treating gastrointestinal disorders as an alternative to drugs or gastric electrical stimulation. However, effectiveness of burst stimulation has not been demonstrated. We investigated the ability of bursting and continuous VNS to influence gastric and pyloric activity under a range of stimulation parameters and gastric pressures. The goals of this study were to determine which parameters could optimally excite or inhibit gastric activity. MATERIALS AND METHODS Data were collected from 21 Sprague-Dawley rats. Under urethane anesthesia, a rubber balloon was implanted into the stomach, connected to a pressure transducer and a saline infusion pump. A pressure catheter was inserted at the pyloric sphincter and a bipolar nerve cuff was implanted onto the left cervical vagus nerve. The balloon was filled to 15 cmH2O. Stimulation trials were conducted in a consistent order; the protocol was then repeated at 25 and 35 cmH2O. The nerve was then transected and stimulation repeated to investigate directionality of effects. RESULTS Bursting stimulation at the bradycardia threshold caused significant increases in gastric contraction amplitude with entrainment to the bursting frequency. Some continuous stimulation trials could also cause increased contractions but without frequency changes. Few significant changes were observed at the pylorus, except for frequency entrainment. These effects could not be uniquely attributed to afferent or efferent activity. SIGNIFICANCE Our findings further elucidate the effects of different VNS parameters on the stomach and pylorus and provide a basis for future studies of bursting stimulation for gastric neuromodulation.
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Affiliation(s)
- D Tovbis
- Institute of Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada
| | - P B Yoo
- Institute of Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada
- Edward S. Rogers Sr. Department of Electrical and Computer Engineering, University of Toronto, Toronto, Ontario, Canada
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Athavale ON, Avci R, Clark AR, Di Natale MR, Wang X, Furness JB, Liu Z, Cheng LK, Du P. Neural regulation of slow waves and phasic contractions in the distal stomach: a mathematical model. J Neural Eng 2024; 20:066040. [PMID: 38100816 PMCID: PMC10765034 DOI: 10.1088/1741-2552/ad1610] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2023] [Revised: 11/06/2023] [Accepted: 12/15/2023] [Indexed: 12/17/2023]
Abstract
Objective.Neural regulation of gastric motility occurs partly through the regulation of gastric bioelectrical slow waves (SWs) and phasic contractions. The interaction of the tissues and organs involved in this regulatory process is complex. We sought to infer the relative importance of cellular mechanisms in inhibitory neural regulation of the stomach by enteric neurons and the interaction of inhibitory and excitatory electrical field stimulation.Approach.A novel mathematical model of gastric motility regulation by enteric neurons was developed and scenarios were simulated to determine the mechanisms through which enteric neural influence is exerted. This model was coupled to revised and extended electrophysiological models of gastric SWs and smooth muscle cells (SMCs).Main results.The mathematical model predicted that regulation of contractile apparatus sensitivity to intracellular calcium in the SMC was the major inhibition mechanism of active tension development, and that the effect on SW amplitude depended on the inhibition of non-specific cation currents more than the inhibition of calcium-activated chloride current (kiNSCC= 0.77 vs kiAno1= 0.33). The model predicted that the interaction between inhibitory and excitatory neural regulation, when applied with simultaneous and equal intensity, resulted in an inhibition of contraction amplitude almost equivalent to that of inhibitory stimulation (79% vs 77% decrease), while the effect on frequency was overall excitatory, though less than excitatory stimulation alone (66% vs 47% increase).Significance.The mathematical model predicts the effects of inhibitory and excitatory enteric neural stimulation on gastric motility function, as well as the effects when inhibitory and excitatory enteric neural stimulation interact. Incorporation of the model into organ-level simulations will provide insights regarding pathological mechanisms that underpin gastric functional disorders, and allow forin silicotesting of the effects of clinical neuromodulation protocols for the treatment of these disorders.
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Affiliation(s)
- Omkar N Athavale
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Recep Avci
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Alys R Clark
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Madeleine R Di Natale
- Florey Institute of Neuroscience and Mental Health, Parkville, VIC, Australia
- Department of Anatomy & Physiology, University of Melbourne, Parkville, VIC, Australia
| | - Xiaokai Wang
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, United States of America
| | - John B Furness
- Florey Institute of Neuroscience and Mental Health, Parkville, VIC, Australia
- Department of Anatomy & Physiology, University of Melbourne, Parkville, VIC, Australia
| | - Zhongming Liu
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, United States of America
| | - Leo K Cheng
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Peng Du
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
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7
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Di Natale MR, Hunne B, Stebbing MJ, Wang X, Liu Z, Furness JB. Characterization of neuromuscular transmission and projections of muscle motor neurons in the rat stomach. Am J Physiol Gastrointest Liver Physiol 2024; 326:G78-G93. [PMID: 37987773 PMCID: PMC11208016 DOI: 10.1152/ajpgi.00194.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/14/2023] [Revised: 11/09/2023] [Accepted: 11/14/2023] [Indexed: 11/22/2023]
Abstract
The stomach is the primary reservoir of the gastrointestinal tract, where ingested content is broken down into small particles. Coordinated relaxation and contraction is essential for rhythmic motility and digestion, but how the muscle motor innervation is organized to provide appropriate graded regional control is not established. In this study, we recorded neuromuscular transmission to the circular muscle using intracellular microelectrodes to investigate the spread of the influence of intrinsic motor neurons. In addition, microanatomical investigations of neuronal projections and pharmacological analysis were conducted to investigate neuromuscular relationships. We found that inhibitory neurotransmission to the circular muscle is graded with stimulus strength and circumferential distance from the stimulation site. The influence of inhibitory neurons declined between 1 and 11 mm from the stimulation site. In the antrum, corpus, and fundus, the declines at 11 mm were about 20%, 30%, and 50%, respectively. Stimulation of inhibitory neurons elicited biphasic hyperpolarizing potentials often followed by prolonged depolarizing events in the distal stomach, but only hyperpolarizing events in the proximal stomach. Excitatory neurotransmission influence varied greatly between proximal stomach, where depolarizing events occurred, and distal stomach, where no direct electrical effects in the muscle were observed. Structural studies using microlesion surgeries confirmed a dominant circumferential projection. We conclude that motor neuron influences extend around the gastric circumference, that the effectiveness can be graded by the recruitment of different numbers of motor neuron nerve terminals to finely control gastric motility, and that the ways in which the neurons influence the muscle differ between anatomical regions.NEW & NOTEWORTHY This study provides a detailed mapping of nerve transmission to the circular muscle of the different anatomical regions of rat stomach. It shows that excitatory and inhibitory influences extend around the gastric circumference and that there is a summation of neural influence that allows for finely graded control of muscle tension and length. Nerve-mediated electrical events are qualitatively and quantitatively different between regions, for example, excitatory neurons have direct effects on fundus but not antral muscle.
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Affiliation(s)
- Madeleine R Di Natale
- Department of Anatomy and Physiology, University of Melbourne, Parkville, Victoria, Australia
- Florey Institute of Neuroscience and Mental Health, Parkville, Victoria, Australia
| | - Billie Hunne
- Department of Anatomy and Physiology, University of Melbourne, Parkville, Victoria, Australia
| | - Martin J Stebbing
- Department of Anatomy and Physiology, University of Melbourne, Parkville, Victoria, Australia
- Florey Institute of Neuroscience and Mental Health, Parkville, Victoria, Australia
| | - Xiaokai Wang
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, United States
- Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan, United States
| | - Zhongming Liu
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, United States
- Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan, United States
| | - John B Furness
- Department of Anatomy and Physiology, University of Melbourne, Parkville, Victoria, Australia
- Florey Institute of Neuroscience and Mental Health, Parkville, Victoria, Australia
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Athavale ON, Cheng LK, Avci R, Clark AR, Du P. Cervical Vagus Nerve Stimulation Disrupts Gastric Slow Wave Activity in Rats. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2023; 2023:1-4. [PMID: 38082764 DOI: 10.1109/embc40787.2023.10340367] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2023]
Abstract
Cervical vagus nerve stimulation (cVNS) is a promising neuromodulation therapy for treating symptoms of disease in peripheral organs. The rat is a common animal model for studying and trialing new applications of cVNS therapy, but the stomach and its activity in rats is less well characterized than other animals, such as pigs. We sought to investigate the effects of acute, in vivo cVNS on gastric bioelectrical activity as an intermediate step to computational modeling of the effects of cVNS on gastric smooth muscle electromechanical coupling. Here we show a method of detecting bioelectrical gastric slow wave events using a non-linear energy operator. The marked events are compared to the underlying bioelectrical slow wave activity.The mean propagation velocity before stimulation was 0.79 ± 0.31 mm s-1, and the mean interval was 17.4 ± 1.4 s. During cVNS, there was a significant increase in velocity (1.02 ± 0.69 mm s-1; p < 0.001), and decrease in interval (15.4 ± 2.9 s; p = 0.0196). At stimulation onset, premature slow waves were induced at an ectopic pacemaker location and waves originating at the ectopic and initial pacemaker sites continued to collide following the cessation of cVNS.This work forms the basis for more thorough investigation of the effects of cVNS on gastric bioelectrical slow wave activity and consequential smooth muscle contractions in rats. A better understanding of the effects of cVNS on gastric function will allow the refinement of cVNS therapy to target the stomach, and avoid off-target effects on the stomach.Clinical relevance- This work presents a signal processing and analysis approach for the investigation of cervical vagus nerve stimulation on gastric bioelectrical activity in rats. Vagus nerve stimulation may enable the control and amelioration of hunger, gastric emptying, or functional gastric disorders.
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Wang X, Cao J, Han K, Choi M, She Y, Scheven UM, Avci R, Du P, Cheng LK, Natale MRD, Furness JB, Liu Z. Diffeomorphic Surface Modeling for MRI-Based Characterization of Gastric Anatomy and Motility. IEEE Trans Biomed Eng 2023; 70:2046-2057. [PMID: 37018592 PMCID: PMC10443119 DOI: 10.1109/tbme.2023.3234509] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
OBJECTIVE Gastrointestinal magnetic resonance imaging (MRI) provides rich spatiotemporal data about the movement of the food inside the stomach, but does not directly report muscular activity on the stomach wall. Here we describe a novel approach to characterize the motility of the stomach wall that drives the volumetric changes of the ingesta. METHODS A neural ordinary differential equation was optimized to model a diffeomorphic flow that ascribed the deformation of the stomach wall to a continuous biomechanical process. Driven by this diffeomorphic flow, the surface of the stomach progressively changes its shape over time, while preserving its topology and manifoldness. RESULTS We tested this approach with MRI data collected from 10 rats under a lightly anesthetized condition, and demonstrated accurate characterization of gastric motor events with an error in the order of sub-millimeters. Uniquely, we characterized gastric anatomy and motility with a surface coordinate system common at both individual and group levels. Functional maps were generated to reveal the spatial, temporal, and spectral characteristics of muscle activity and its coordination across different regions. The peristalsis at the distal antrum had a dominant frequency and peak-to-peak amplitude of [Formula: see text] cycles per minute and [Formula: see text] mm, respectively. The relationship between muscle thickness and gastric motility was found to be distinct between two functional regions in the proximal and distal stomach. CONCLUSION These results demonstrate the efficacy of using MRI to model gastric anatomy and function. SIGNIFICANCE The proposed approach is expected to enable non-invasive and accurate mapping of gastric motility for preclinical and clinical studies.
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Cao J, Wang X, Chen J, Zhang N, Liu Z. The vagus nerve mediates the stomach-brain coherence in rats. Neuroimage 2022; 263:119628. [PMID: 36113737 PMCID: PMC10008817 DOI: 10.1016/j.neuroimage.2022.119628] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2022] [Revised: 08/20/2022] [Accepted: 09/12/2022] [Indexed: 11/26/2022] Open
Abstract
Interactions between the brain and the stomach shape both cognitive and digestive functions. Recent human studies report spontaneous synchronization between brain activity and gastric slow waves in the resting state. However, this finding has not been replicated in any animal models. The neural pathways underlying this apparent stomach-brain synchrony is also unclear. Here, we performed functional magnetic resonance imaging while simultaneously recording body-surface gastric slow waves from anesthetized rats in the fasted vs. postprandial conditions and performed a bilateral cervical vagotomy to assess the role of the vagus nerve. The coherence between brain fMRI signals and gastric slow waves was found in a distributed "gastric network", including subcortical and cortical regions in the sensory, motor, and limbic systems. The stomach-brain coherence was largely reduced by the bilateral vagotomy and was different between the fasted and fed states. These findings suggest that the vagus nerve mediates the spontaneous coherence between brain activity and gastric slow waves, which is likely a signature of real-time stomach-brain interactions. However, its functional significance remains to be established.
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Affiliation(s)
- Jiayue Cao
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, USA
| | - Xiaokai Wang
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, USA
| | - Jiande Chen
- Division of Gastroenterology and Hepatology, University of Michigan, Ann Arbor, USA
| | - Nanyin Zhang
- Department of Biomedical Engineering, Huck Institutes of the life sciences, Pennsylvania State University, USA
| | - Zhongming Liu
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, USA; Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, USA.
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O'Grady G, Gharibans AA, Du P, Huizinga JD. The gastric conduction system in health and disease: a translational review. Am J Physiol Gastrointest Liver Physiol 2021; 321:G527-G542. [PMID: 34549598 DOI: 10.1152/ajpgi.00065.2021] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Gastric peristalsis is critically dependent on an underlying electrical conduction system. Recent years have witnessed substantial progress in clarifying the operations of this system, including its pacemaking units, its cellular architecture, and slow-wave propagation patterns. Advanced techniques have been developed for assessing its functions at high spatiotemporal resolutions. This review synthesizes and evaluates this progress, with a focus on human and translational physiology. A current conception of the initiation and conduction of slow-wave activity in the human stomach is provided first, followed by a detailed discussion of its organization at the cellular and tissue level. Particular emphasis is then given to how gastric electrical disorders may contribute to disease states. Gastric dysfunction continues to grow in their prevalence and impact, and while gastric dysrhythmia is established as a clear and pervasive feature in several major gastric disorders, its role in explaining pathophysiology and informing therapy is still emerging. New insights from high-resolution gastric mapping are evaluated, together with historical data from electrogastrography, and the physiological relevance of emerging biomarkers from body surface mapping such as retrograde propagating slow waves. Knowledge gaps requiring further physiological research are highlighted.
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Affiliation(s)
- Gregory O'Grady
- Department of Surgery, The University of Auckland, Auckland, New Zealand.,Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
| | - Armen A Gharibans
- Department of Surgery, The University of Auckland, Auckland, New Zealand.,Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
| | - Peng Du
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
| | - Jan D Huizinga
- Department of Medicine, Farncombe Family Digestive Health Research Institute, McMaster University, Hamilton, Ontario, Canada
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Cao J, Wang X, Powley TL, Liu Z. Gastric neurons in the nucleus tractus solitarius are selective to the orientation of gastric electrical stimulation. J Neural Eng 2021; 18:10.1088/1741-2552/ac2ec6. [PMID: 34634781 PMCID: PMC8625070 DOI: 10.1088/1741-2552/ac2ec6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Accepted: 10/11/2021] [Indexed: 01/02/2023]
Abstract
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.
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Affiliation(s)
- Jiayue Cao
- Department of Biomedical Engineering, University of Michigan Ann Arbor
| | - Xiaokai Wang
- Department of Biomedical Engineering, University of Michigan Ann Arbor
| | - Terry L. Powley
- Department of Psychological Sciences, Purdue University West Lafayette
| | - Zhongming Liu
- Department of Biomedical Engineering, University of Michigan Ann Arbor
- Department of Electrical Engineering and Computer Science, University of Michigan Ann Arbor
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Zhang Y, Lu T, Dong Y, Chen Y, Chen JDZ. Auricular vagal nerve stimulation enhances gastrointestinal motility and improves interstitial cells of Cajal in rats treated with loperamide. Neurogastroenterol Motil 2021; 33:e14163. [PMID: 33991455 DOI: 10.1111/nmo.14163] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/19/2020] [Revised: 03/25/2021] [Accepted: 04/06/2021] [Indexed: 12/12/2022]
Abstract
BACKGROUND Gastrointestinal (GI) motility disorders affect a large proportion of the population with limited treatment options. The aims of this study were to investigate the potential of a non-invasive method of auricular vagal nerve stimulation (aVNS) for treating GI dysmotility and to explore possible mechanisms involving slow waves and interstitial cells of Cajal (ICC). METHODS Normal rats were treated daily with loperamide for 1 week and then treated, while still on daily loperamide, with aVNS/Sham-aVNS for another 1 week. Gastric emptying (GE), small intestine transit (SIT), and GI slow waves were measured. The plasma level of pancreatic polypeptide (PP) and noradrenaline (NE) was assessed by ELISA. ICC in the gastric antrum were detected by immunohistochemistry. KEY RESULTS (a) aVNS significantly increased the percentage of normal GI slow waves (p < 0.05 for both fasting and postprandial states, vs. Sham-aVNS) and accelerated GE (p < 0.05, vs. Sham-aVNS) and SIT (p < 0.05, vs. Sham-aVNS) impaired by loperamide. (b) aVNS increased plasma PP (p < 0.01) and decreased plasma NE (p < 0.01), compared with Sham-aVNS. (c) Gastric ICC was decreased by loperamide (p < 0.01) but increased after aVNS (p < 0.01, vs. Sham aVNS). CONCLUSIONS & INFERENCES Loperamide induces upper GI dysmotility. aVNS accelerates upper GI transit and improving pace-making activity mediated via the ICC. Non-invasive aVNS may have a therapeutic potential for upper GI dysmotility.
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Affiliation(s)
- Yiling Zhang
- School of Life Sciences, Beijing University of Chinese Medicine, Beijing, China.,Division of Gastroenterology and Hepatology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Tao Lu
- School of Life Sciences, Beijing University of Chinese Medicine, Beijing, China
| | - Yan Dong
- Division of Gastroenterology and Hepatology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Yan Chen
- Division of Gastroenterology and Hepatology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Jiande D Z Chen
- Division of Gastroenterology and Hepatology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
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Cheng LK, Nagahawatte ND, Avci R, Du P, Liu Z, Paskaranandavadivel N. Strategies to Refine Gastric Stimulation and Pacing Protocols: Experimental and Modeling Approaches. Front Neurosci 2021; 15:645472. [PMID: 33967679 PMCID: PMC8100207 DOI: 10.3389/fnins.2021.645472] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2020] [Accepted: 03/22/2021] [Indexed: 12/13/2022] Open
Abstract
Gastric pacing and stimulation strategies were first proposed in the 1960s to treat motility disorders. However, there has been relatively limited clinical translation of these techniques. Experimental investigations have been critical in advancing our understanding of the control mechanisms that innervate gut function. In this review, we will discuss the use of pacing to modulate the rhythmic slow wave conduction patterns generated by interstitial cells of Cajal in the gastric musculature. In addition, the use of gastric high-frequency stimulation methods that target nerves in the stomach to either inhibit or enhance stomach function will be discussed. Pacing and stimulation protocols to modulate gastric activity, effective parameters and limitations in the existing studies are summarized. Mathematical models are useful to understand complex and dynamic systems. A review of existing mathematical models and techniques that aim to help refine pacing and stimulation protocols are provided. Finally, some future directions and challenges that should be investigated are discussed.
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Affiliation(s)
- Leo K Cheng
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand.,Department of General Surgery, Vanderbilt University Medical Center, Nashville, TN, United States.,Riddet Institute, Palmerston North, New Zealand
| | - Nipuni D Nagahawatte
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Recep Avci
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Peng Du
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Zhongming Liu
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, United States.,Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI, United States
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