1
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Wensveen FM, Šestan M, Polić B. The immunology of sickness metabolism. Cell Mol Immunol 2024; 21:1051-1065. [PMID: 39107476 PMCID: PMC11364700 DOI: 10.1038/s41423-024-01192-4] [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] [Received: 03/26/2024] [Accepted: 05/29/2024] [Indexed: 09/01/2024] Open
Abstract
Everyone knows that an infection can make you feel sick. Although we perceive infection-induced changes in metabolism as a pathology, they are a part of a carefully regulated process that depends on tissue-specific interactions between the immune system and organs involved in the regulation of systemic homeostasis. Immune-mediated changes in homeostatic parameters lead to altered production and uptake of nutrients in circulation, which modifies the metabolic rate of key organs. This is what we experience as being sick. The purpose of sickness metabolism is to generate a metabolic environment in which the body is optimally able to fight infection while denying vital nutrients for the replication of pathogens. Sickness metabolism depends on tissue-specific immune cells, which mediate responses tailored to the nature and magnitude of the threat. As an infection increases in severity, so do the number and type of immune cells involved and the level to which organs are affected, which dictates the degree to which we feel sick. Interestingly, many alterations associated with metabolic disease appear to overlap with immune-mediated changes observed following infection. Targeting processes involving tissue-specific interactions between activated immune cells and metabolic organs therefore holds great potential for treating both people with severe infection and those with metabolic disease. In this review, we will discuss how the immune system communicates in situ with organs involved in the regulation of homeostasis and how this communication is impacted by infection.
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Affiliation(s)
| | - Marko Šestan
- University of Rijeka Faculty of Medicine, Rijeka, Croatia
| | - Bojan Polić
- University of Rijeka Faculty of Medicine, Rijeka, Croatia
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2
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Stebbing MJ, Shafton AD, Davey CE, Di Natale MR, Furness JB, McAllen RM. A ganglionic intestinointestinal reflex activated by acute noxious challenge. Am J Physiol Gastrointest Liver Physiol 2024; 326:G360-G373. [PMID: 38226653 DOI: 10.1152/ajpgi.00145.2023] [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: 07/11/2023] [Revised: 12/13/2023] [Accepted: 01/07/2024] [Indexed: 01/17/2024]
Abstract
To investigate noxious stimulation-responsive neural circuits that could influence the gut, we recorded from intestinally directed (efferent) nerve filaments dissected from mesenteric nerves close to the small intestine in anesthetized rats. These exhibited baseline multiunit activity that was almost unaffected by vagotomy (VagX) and reduced only slightly by cutting the splanchnic nerves. The activity was halved by hexamethonium (Hex) treatment. When an adjacent gut segment received an intraluminal stimulus 2,4,6-trinitrobenzenesulfonate (TNBS) in 30% ethanol, mesenteric efferent nerve activity increased for more than 1 h. The increased activity was almost unaffected by bilateral vagotomy or splanchnic nerve section, indicating a lack of central nervous involvement, but it was 60% reduced by hexamethonium. Spike sorting discriminated efferent single and predominantly single-unit spike trains that responded to TNBS, were unaffected by splachnectomy but were silenced by hexamethonium. After noxious stimulation of one segment, the adjacent segment showed no evidence of suppression of gut motility or vasoconstriction. We conclude that luminal application of a noxious stimulus to the small intestine activates an entirely peripheral, intestinointestinal reflex pathway. This pathway involves enteric intestinofugal neurons that excite postganglionic sympathetic neurons via a nicotinic synapse. We suggest that the final sympathetic efferent neurons that respond to a tissue damaging stimulus are distinct from vasoconstrictor, secretomotor, and motility inhibiting neurons.NEW & NOTEWORTHY An intraluminal noxious chemical stimulus applied to one segment of small intestine increased mesenteric efferent nerve activity to an adjacent segment. This was identified as a peripheral ganglionic reflex that did not require vagal or spinal connections. Hexamethonium blocked most, but not all, ongoing and reflex mesenteric efferent activity. The prevertebral sympathetic efferent neurons that are activated likely affect inflammatory and immune functions of other gut segments.
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Affiliation(s)
- Martin J Stebbing
- Florey Institute of Neuroscience and Mental Health, Parkville, Victoria, Australia
- Department of Anatomy and Physiology, University of Melbourne, Parkville, Victoria, Australia
| | - Anthony D Shafton
- Florey Institute of Neuroscience and Mental Health, Parkville, Victoria, Australia
| | - Catherine E Davey
- Department of Biomedical Engineering, University of Melbourne, Parkville, Victoria, Australia
| | | | - John B Furness
- Florey Institute of Neuroscience and Mental Health, Parkville, Victoria, Australia
- Department of Anatomy and Physiology, University of Melbourne, Parkville, Victoria, Australia
| | - Robin M McAllen
- Florey Institute of Neuroscience and Mental Health, Parkville, Victoria, Australia
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3
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Borgmann D, Fenselau H. Vagal pathways for systemic regulation of glucose metabolism. Semin Cell Dev Biol 2024; 156:244-252. [PMID: 37500301 DOI: 10.1016/j.semcdb.2023.07.010] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2022] [Revised: 06/20/2023] [Accepted: 07/20/2023] [Indexed: 07/29/2023]
Abstract
Maintaining blood glucose at an appropriate physiological level requires precise coordination of multiple organs and tissues. The vagus nerve bidirectionally connects the central nervous system with peripheral organs crucial to glucose mobilization, nutrient storage, and food absorption, thereby presenting a key pathway for the central control of blood glucose levels. However, the precise mechanisms by which vagal populations that target discrete tissues participate in glucoregulation are much less clear. Here we review recent advances unraveling the cellular identity, neuroanatomical organization, and functional contributions of both vagal efferents and vagal afferents in the control of systemic glucose metabolism. We focus on their involvement in relaying glucoregulatory cues from the brain to peripheral tissues, particularly the pancreatic islet, and by sensing and transmitting incoming signals from ingested food to the brain. These recent findings - largely driven by advances in viral approaches, RNA sequencing, and cell-type selective manipulations and tracings - have begun to clarify the precise vagal neuron populations involved in the central coordination of glucose levels, and raise interesting new possibilities for the treatment of glucose metabolism disorders such as diabetes.
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Affiliation(s)
- Diba Borgmann
- Synaptic Transmission in Energy Homeostasis Group, Max Planck Institute for Metabolism Research, Gleueler Strasse 50, 50931 Cologne, Germany; Center for Physical Activity Research (CFAS), Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen, Denmark
| | - Henning Fenselau
- Synaptic Transmission in Energy Homeostasis Group, Max Planck Institute for Metabolism Research, Gleueler Strasse 50, 50931 Cologne, Germany; Center for Endocrinology, Diabetes and Preventive Medicine (CEDP), University Hospital Cologne, Kerpener Strasse 26, 50937 Cologne, Germany; Excellence Cluster on Cellular Stress Responses in Aging Associated Diseases (CECAD), University of Cologne, Joseph-Stelzmann-Straße 26, Cologne 50931, Germany.
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4
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Shaffer C, Barrett LF, Quigley KS. Signal processing in the vagus nerve: Hypotheses based on new genetic and anatomical evidence. Biol Psychol 2023; 182:108626. [PMID: 37419401 PMCID: PMC10563766 DOI: 10.1016/j.biopsycho.2023.108626] [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: 01/09/2023] [Revised: 06/25/2023] [Accepted: 07/03/2023] [Indexed: 07/09/2023]
Abstract
Each organism must regulate its internal state in a metabolically efficient way as it interacts in space and time with an ever-changing and only partly predictable world. Success in this endeavor is largely determined by the ongoing communication between brain and body, and the vagus nerve is a crucial structure in that dialogue. In this review, we introduce the novel hypothesis that the afferent vagus nerve is engaged in signal processing rather than just signal relay. New genetic and structural evidence of vagal afferent fiber anatomy motivates two hypotheses: (1) that sensory signals informing on the physiological state of the body compute both spatial and temporal viscerosensory features as they ascend the vagus nerve, following patterns found in other sensory architectures, such as the visual and olfactory systems; and (2) that ascending and descending signals modulate one another, calling into question the strict segregation of sensory and motor signals, respectively. Finally, we discuss several implications of our two hypotheses for understanding the role of viscerosensory signal processing in predictive energy regulation (i.e., allostasis) as well as the role of metabolic signals in memory and in disorders of prediction (e.g., mood disorders).
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Affiliation(s)
- Clare Shaffer
- Department of Psychology, College of Science, Northeastern University, Boston, MA, USA.
| | - Lisa Feldman Barrett
- Department of Psychology, College of Science, Northeastern University, Boston, MA, USA; Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA
| | - Karen S Quigley
- Department of Psychology, College of Science, Northeastern University, Boston, MA, USA.
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5
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Sharkey KA, Mawe GM. The enteric nervous system. Physiol Rev 2023; 103:1487-1564. [PMID: 36521049 PMCID: PMC9970663 DOI: 10.1152/physrev.00018.2022] [Citation(s) in RCA: 58] [Impact Index Per Article: 58.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2022] [Revised: 12/12/2022] [Accepted: 12/15/2022] [Indexed: 12/23/2022] Open
Abstract
Of all the organ systems in the body, the gastrointestinal tract is the most complicated in terms of the numbers of structures involved, each with different functions, and the numbers and types of signaling molecules utilized. The digestion of food and absorption of nutrients, electrolytes, and water occurs in a hostile luminal environment that contains a large and diverse microbiota. At the core of regulatory control of the digestive and defensive functions of the gastrointestinal tract is the enteric nervous system (ENS), a complex system of neurons and glia in the gut wall. In this review, we discuss 1) the intrinsic neural control of gut functions involved in digestion and 2) how the ENS interacts with the immune system, gut microbiota, and epithelium to maintain mucosal defense and barrier function. We highlight developments that have revolutionized our understanding of the physiology and pathophysiology of enteric neural control. These include a new understanding of the molecular architecture of the ENS, the organization and function of enteric motor circuits, and the roles of enteric glia. We explore the transduction of luminal stimuli by enteroendocrine cells, the regulation of intestinal barrier function by enteric neurons and glia, local immune control by the ENS, and the role of the gut microbiota in regulating the structure and function of the ENS. Multifunctional enteric neurons work together with enteric glial cells, macrophages, interstitial cells, and enteroendocrine cells integrating an array of signals to initiate outputs that are precisely regulated in space and time to control digestion and intestinal homeostasis.
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Affiliation(s)
- Keith A Sharkey
- Hotchkiss Brain Institute and Snyder Institute for Chronic Diseases, Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Gary M Mawe
- Department of Neurological Sciences, Larner College of Medicine, University of Vermont, Burlington, Vermont
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6
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Watts AG, Kanoski SE, Sanchez-Watts G, Langhans W. The physiological control of eating: signals, neurons, and networks. Physiol Rev 2022; 102:689-813. [PMID: 34486393 PMCID: PMC8759974 DOI: 10.1152/physrev.00028.2020] [Citation(s) in RCA: 54] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Accepted: 08/30/2021] [Indexed: 02/07/2023] Open
Abstract
During the past 30 yr, investigating the physiology of eating behaviors has generated a truly vast literature. This is fueled in part by a dramatic increase in obesity and its comorbidities that has coincided with an ever increasing sophistication of genetically based manipulations. These techniques have produced results with a remarkable degree of cell specificity, particularly at the cell signaling level, and have played a lead role in advancing the field. However, putting these findings into a brain-wide context that connects physiological signals and neurons to behavior and somatic physiology requires a thorough consideration of neuronal connections: a field that has also seen an extraordinary technological revolution. Our goal is to present a comprehensive and balanced assessment of how physiological signals associated with energy homeostasis interact at many brain levels to control eating behaviors. A major theme is that these signals engage sets of interacting neural networks throughout the brain that are defined by specific neural connections. We begin by discussing some fundamental concepts, including ones that still engender vigorous debate, that provide the necessary frameworks for understanding how the brain controls meal initiation and termination. These include key word definitions, ATP availability as the pivotal regulated variable in energy homeostasis, neuropeptide signaling, homeostatic and hedonic eating, and meal structure. Within this context, we discuss network models of how key regions in the endbrain (or telencephalon), hypothalamus, hindbrain, medulla, vagus nerve, and spinal cord work together with the gastrointestinal tract to enable the complex motor events that permit animals to eat in diverse situations.
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Affiliation(s)
- Alan G Watts
- The Department of Biological Sciences, Dornsife College of Letters, Arts and Sciences, University of Southern California, Los Angeles, California
| | - Scott E Kanoski
- The Department of Biological Sciences, Dornsife College of Letters, Arts and Sciences, University of Southern California, Los Angeles, California
| | - Graciela Sanchez-Watts
- The Department of Biological Sciences, Dornsife College of Letters, Arts and Sciences, University of Southern California, Los Angeles, California
| | - Wolfgang Langhans
- Physiology and Behavior Laboratory, Eidgenössische Technische Hochschule-Zürich, Schwerzenbach, Switzerland
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7
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Yin Y, Zhu ZX, Li Z, Chen YS, Zhu WM. Role of mesenteric component in Crohn’s disease: A friend or foe? World J Gastrointest Surg 2021; 13:1536-1549. [PMID: 35070062 PMCID: PMC8727179 DOI: 10.4240/wjgs.v13.i12.1536] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Revised: 08/01/2021] [Accepted: 11/25/2021] [Indexed: 02/06/2023] Open
Abstract
Crohn’s disease (CD) is a complex and relapsing gastrointestinal disease with mesenteric alterations. The mesenteric neural, vascular, and endocrine systems actively take part in the gut dysbiosis-adaptive immunity-mesentery-body axis, and this axis has been proven to be bidirectional. The abnormalities of morphology and function of the mesenteric component are associated with intestinal inflammation and disease progress of CD via responses to afferent signals, neuropeptides, lymphatic drainage, adipokines, and functional cytokines. The hypertrophy of mesenteric adipose tissue plays important roles in the pathogenesis of CD by secreting large amounts of adipokines and representing a rich source of proinflammatory or profibrotic cytokines. The vascular alteration, including angiogenesis and lymphangiogenesis, is concomitant in the disease course of CD. Of note, the enlarged and obstructed lymphatic vessels, which have been described in CD patients, are likely related to the early onset submucosa edema and being a cause of CD. The function of mesenteric lymphatics is influenced by endocrine of mesenteric nerves and adipocytes. Meanwhile, the structure of the mesenteric lymphatic vessels in hypertrophic mesenteric adipose tissue is mispatterned and ruptured, which can lead to lymph leakage. Leaky lymph factors can in turn stimulate adipose tissue to proliferate and effectively elicit an immune response. The identification of the role of mesentery and the crosstalk between mesenteric tissues in intestinal inflammation may shed light on understanding the underlying mechanism of CD and help explore new therapeutic targets.
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Affiliation(s)
- Yi Yin
- Department of General Surgery, Jinling Hospital, Medical School of Nanjing University, Nanjing 210002, Jiangsu Province, China
| | - Zhen-Xing Zhu
- Department of General Surgery, Jinling Hospital, Medical School of Nanjing University, Nanjing 210002, Jiangsu Province, China
| | - Zhun Li
- Department of General Surgery, Jinling Hospital, Medical School of Nanjing University, Nanjing 210002, Jiangsu Province, China
| | - Yu-Sheng Chen
- Department of General Surgery, Jinling Hospital, Medical School of Nanjing University, Nanjing 210002, Jiangsu Province, China
| | - Wei-Ming Zhu
- Department of General Surgery, Jinling Hospital, Medical School of Nanjing University, Nanjing 210002, Jiangsu Province, China
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8
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An Z, Wang H, Mokadem M. Role of the Autonomic Nervous System in Mechanism of Energy and Glucose Regulation Post Bariatric Surgery. Front Neurosci 2021; 15:770690. [PMID: 34887725 PMCID: PMC8649921 DOI: 10.3389/fnins.2021.770690] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2021] [Accepted: 10/15/2021] [Indexed: 01/06/2023] Open
Abstract
Even though lifestyle changes are the mainstay approach to address obesity, Sleeve gastrectomy (SG) and Roux-en-Y gastric bypass (RYGB) are the most effective and durable treatments facing this pandemic and its associated metabolic conditions. The traditional classifications of bariatric surgeries labeled them as “restrictive,” “malabsorptive,” or “mixed” types of procedures depending on the anatomical rearrangement of each one of them. This conventional categorization of bariatric surgeries assumed that the “restrictive” procedures induce their weight loss and metabolic effects by reducing gastric content and therefore having a smaller reservoir. Similarly, the “malabsorptive” procedures were thought to induce their main energy homeostatic effects from fecal calorie loss due to intestinal malabsorption. Observational data from human subjects and several studies from rodent models of bariatric surgery showed that neither of those concepts is completely true, at least in explaining the multiple metabolic changes and the alteration in energy balance that those two surgeries induce. Rather, neuro-hormonal mechanisms have been postulated to underly the physiologic effects of those two most performed bariatric procedures. In this review, we go over the role the autonomic nervous system plays- through its parasympathetic and sympathetic branches- in regulating weight balance and glucose homeostasis after SG and RYGB.
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Affiliation(s)
- Zhibo An
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, Carver College of Medicine, The University of Iowa, Iowa City, IA, United States
| | - Haiying Wang
- Department of Physiology, Basic Medical School of Jining Medical University, Jining, China
| | - Mohamad Mokadem
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, Carver College of Medicine, The University of Iowa, Iowa City, IA, United States.,Fraternal Order of Eagles Diabetes Research Center, The University of Iowa, Iowa City, IA, United States.,Obesity Research and Education Initiative, The University of Iowa, Iowa City, IA, United States.,Iowa City Veterans Affairs Health Care System, Iowa City, IA, United States
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9
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Powley TL. Brain-gut communication: vagovagal reflexes interconnect the two "brains". Am J Physiol Gastrointest Liver Physiol 2021; 321:G576-G587. [PMID: 34643086 PMCID: PMC8616589 DOI: 10.1152/ajpgi.00214.2021] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Revised: 09/24/2021] [Accepted: 09/28/2021] [Indexed: 01/31/2023]
Abstract
The gastrointestinal tract has its own "brain," the enteric nervous system or ENS, that executes routine housekeeping functions of digestion. The dorsal vagal complex in the central nervous system (CNS) brainstem, however, organizes vagovagal reflexes and establishes interconnections between the entire neuroaxis of the CNS and the gut. Thus, the dorsal vagal complex links the "CNS brain" to the "ENS brain." This brain-gut connectome provides reflex adjustments that optimize digestion and assimilation of nutrients and fluid. Vagovagal circuitry also generates the plasticity and adaptability needed to maintain homeostasis to coordinate among organs and to react to environmental situations. Arguably, this dynamic flexibility provided by the vagal circuitry may, in some circumstances, lead to or complicate maladaptive disorders.
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Affiliation(s)
- Terry L Powley
- Department of Psychological Sciences, Purdue University, West Lafayette, Indiana
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10
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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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11
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Gershon MD, Margolis KG. The gut, its microbiome, and the brain: connections and communications. J Clin Invest 2021; 131:143768. [PMID: 34523615 PMCID: PMC8439601 DOI: 10.1172/jci143768] [Citation(s) in RCA: 68] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Modern research on gastrointestinal behavior has revealed it to be a highly complex bidirectional process in which the gut sends signals to the brain, via spinal and vagal visceral afferent pathways, and receives sympathetic and parasympathetic inputs. Concomitantly, the enteric nervous system within the bowel, which contains intrinsic primary afferent neurons, interneurons, and motor neurons, also senses the enteric environment and controls the detailed patterns of intestinal motility and secretion. The vast microbiome that is resident within the enteric lumen is yet another contributor, not only to gut behavior, but to the bidirectional signaling process, so that the existence of a microbiota-gut-brain "connectome" has become apparent. The interaction between the microbiota, the bowel, and the brain now appears to be neither a top-down nor a bottom-up process. Instead, it is an ongoing, tripartite conversation, the outline of which is beginning to emerge and is the subject of this Review. We emphasize aspects of the exponentially increasing knowledge of the microbiota-gut-brain "connectome" and focus attention on the roles that serotonin, Toll-like receptors, and macrophages play in signaling as exemplars of potentially generalizable mechanisms.
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Affiliation(s)
| | - Kara Gross Margolis
- Department of Pediatrics, Columbia University Vagelos College of Physicians and Surgeons, New York, New York, USA
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12
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Pitra S, Smith BN. Musings on the wanderer: What's new in our understanding of vago-vagal reflexes? VI. Central vagal circuits that control glucose metabolism. Am J Physiol Gastrointest Liver Physiol 2021; 320:G175-G182. [PMID: 33205998 PMCID: PMC7938771 DOI: 10.1152/ajpgi.00368.2020] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Neurons in the brain stem dorsal vagal complex (DVC) take part in a continuous bidirectional crosstalk, in which they receive and respond to a vast array of signaling molecules, including glucose. Importantly, chronic dysregulation of blood glucose concentration, a hallmark of high prevalence pathologies, such as diabetes and metabolic syndrome, can induce neuroplasticity in DVC neural networks, which is hypothesized to either contribute to or compensate for the glycemic or insulinemic dysregulation observed in these conditions. Here, we revisit the topic of vagal reflexes to review recent research on the importance of DVC function in regulating systemic glucose homeostasis and the neuroplastic changes in this brain region that are associated with systemic glucose alterations. We also discuss the critical connection between these nuclei and the gut and the role of central vagal circuits in the favorable outcomes associated with bariatric surgical procedures for metabolic disorders.
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Affiliation(s)
- Soledad Pitra
- 1Department of Neuroscience, University of Kentucky, Lexington, Kentucky
| | - Bret N. Smith
- 1Department of Neuroscience, University of Kentucky, Lexington, Kentucky,2Department of Physiology, College of Medicine, University of Kentucky, Lexington, Kentucky
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13
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Blanke EN, Holmes GM, Besecker EM. Altered physiology of gastrointestinal vagal afferents following neurotrauma. Neural Regen Res 2021; 16:254-263. [PMID: 32859772 PMCID: PMC7896240 DOI: 10.4103/1673-5374.290883] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The adaptability of the central nervous system has been revealed in several model systems. Of particular interest to central nervous system-injured individuals is the ability for neural components to be modified for regain of function. In both types of neurotrauma, traumatic brain injury and spinal cord injury, the primary parasympathetic control to the gastrointestinal tract, the vagus nerve, remains anatomically intact. However, individuals with traumatic brain injury or spinal cord injury are highly susceptible to gastrointestinal dysfunctions. Such gastrointestinal dysfunctions attribute to higher morbidity and mortality following traumatic brain injury and spinal cord injury. While the vagal efferent output remains capable of eliciting motor responses following injury, evidence suggests impairment of the vagal afferents. Since sensory input drives motor output, this review will discuss the normal and altered anatomy and physiology of the gastrointestinal vagal afferents to better understand the contributions of vagal afferent plasticity following neurotrauma.
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Affiliation(s)
- Emily N Blanke
- Department of Neural and Behavioral Sciences, Penn State University College of Medicine, Hershey, PA, USA
| | - Gregory M Holmes
- Department of Neural and Behavioral Sciences, Penn State University College of Medicine, Hershey, PA, USA
| | - Emily M Besecker
- Department of Health Sciences, Gettysburg College, Gettysburg, PA, USA
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14
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Toniolo I, Fontanella CG, Foletto M, Carniel EL. Biomechanical Investigation of the Stomach Following Different Bariatric Surgery Approaches. Bioengineering (Basel) 2020; 7:bioengineering7040159. [PMID: 33317122 PMCID: PMC7764040 DOI: 10.3390/bioengineering7040159] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Revised: 12/02/2020] [Accepted: 12/07/2020] [Indexed: 12/15/2022] Open
Abstract
Background: The stomach is a hollow organ of the gastrointestinal tract, on which bariatric surgery (BS) is performed for the treatment of obesity. Even though BS is the most effective treatment for severe obesity, drawbacks and complications are still present because the intervention design is largely based on the surgeon’s expertise and intraoperative decisions. Bioengineering methods can be exploited to develop computational tools for more rational presurgical design and planning of the intervention. Methods: A computational mechanical model of the stomach was developed, considering the actual complexity of the biological structure, as the nonhomogeneous and multilayered configuration of the gastric wall. Mechanical behavior was characterized by means of an anisotropic visco-hyperelastic constitutive formulation of fiber-reinforced conformation, nonlinear elastic response, and time-dependent behavior, which assume the typical features of gastric wall mechanics. Model applications allowed for an analysis of the influence of BS techniques on stomach mechanical functionality through different computational analyses. Results: Computational results showed that laparoscopic sleeve gastrectomy and endoscopic sleeve gastroplasty drastically alter stomach capacity and stiffness, while laparoscopic adjustable gastric banding modestly affects stomach stiffness and capacity. Moreover, the mean elongation strain values, which are correlated to the mechanical stimulation of gastric receptors, were elevated in laparoscopic adjustable gastric banding compared to other procedures. Conclusions: The investigation of stomach mechanical response through computational models provides information on different topics such as stomach capacity and stiffness and the mechanical stimulation of gastric receptors, which interact with the brain to control satiety. These data can provide reliable support to surgeons in the presurgical decision-making process.
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Affiliation(s)
- Ilaria Toniolo
- Department of Industrial Engineering, University of Padova, Via Venezia 1, 35131 Padova, Italy; (I.T.); (E.L.C.)
| | - Chiara Giulia Fontanella
- Department of Industrial Engineering, University of Padova, Via Venezia 1, 35131 Padova, Italy; (I.T.); (E.L.C.)
- Centre for Mechanics of Biological Materials, University of Padova, Via F. Marzolo 9, 35131 Padova, Italy;
- Correspondence: ; Tel.: +39-049-8276754
| | - Mirto Foletto
- Centre for Mechanics of Biological Materials, University of Padova, Via F. Marzolo 9, 35131 Padova, Italy;
- IFSO Bariatric Center of Excellence, Padova University Hospital, Via Ospedale Civile, 35121 Padova, Italy
| | - Emanuele Luigi Carniel
- Department of Industrial Engineering, University of Padova, Via Venezia 1, 35131 Padova, Italy; (I.T.); (E.L.C.)
- Centre for Mechanics of Biological Materials, University of Padova, Via F. Marzolo 9, 35131 Padova, Italy;
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15
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Dodds KN, Kyloh MA, Travis L, Beckett EAH, Spencer NJ. Morphological identification of thoracolumbar spinal afferent nerve endings in mouse uterus. J Comp Neurol 2020; 529:2029-2041. [PMID: 33190293 DOI: 10.1002/cne.25070] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Revised: 09/30/2020] [Accepted: 11/09/2020] [Indexed: 11/06/2022]
Abstract
Major sensory innervation to the uterus is provided by spinal afferent nerves, whose cell bodies lie predominantly in thoracolumbar dorsal root ganglia (DRG). While the origin of the cell bodies of uterine spinal afferents is clear, the identity of their sensory endings has remained unknown. Hence, our major aim was to identify the location, morphology, and calcitonin gene-related peptide (CGRP)-immunoreactivity of uterine spinal afferent endings supplied by thoracolumbar DRG. We also sought to determine the degree of uterine afferent innervation provided by the vagus nerve. Using an anterograde tracing technique, nulliparous female C57BL/6 mice were injected unilaterally with biotinylated dextran into thoracolumbar DRG (T13-L3). After 7-9 days, uterine horns were stained to visualize traced nerve axons and endings immunoreactive to CGRP. Whole uteri from a separate cohort of animals were injected with retrograde neuronal tracer (DiI) and dye uptake in nodose ganglia was examined. Anterogradely labeled axons innervated each uterine horn, these projected rostrally or caudally from their site of entry, branching to form varicose endings in the myometrium and/or vascular plexus. Most spinal afferent endings were CGRP-immunoreactive and morphologically classified as "simple-type." Rarely, uterine nerve cell bodies were labeled in nodose ganglia. Here, we provide the first detailed description of spinal afferent nerve endings in the uterus of a vertebrate. Distinct morphological types of spinal afferent nerve endings were identified throughout multiple anatomical layers of the uterine wall. Compared to other visceral organs, uterine spinal afferent endings displayed noticeably less morphological diversity. Few neurons in nodose ganglia innervate the uterus.
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Affiliation(s)
- Kelsi N Dodds
- College of Medicine and Public Health, Flinders Health and Medical Research Institute, Flinders University of South Australia, Bedford Park, South Australia, Australia
| | - Melinda A Kyloh
- College of Medicine and Public Health, Flinders Health and Medical Research Institute, Flinders University of South Australia, Bedford Park, South Australia, Australia
| | - Lee Travis
- College of Medicine and Public Health, Flinders Health and Medical Research Institute, Flinders University of South Australia, Bedford Park, South Australia, Australia
| | - Elizabeth A H Beckett
- Discipline of Physiology, Adelaide Medical School, University of Adelaide, Adelaide, South Australia, Australia
| | - Nick J Spencer
- College of Medicine and Public Health, Flinders Health and Medical Research Institute, Flinders University of South Australia, Bedford Park, South Australia, Australia
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16
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Impact of 3D-CT-Based Gastric Wall Volume on Weight Loss after Laparoscopic Sleeve Gastrectomy. Obes Surg 2020; 30:4226-4233. [DOI: 10.1007/s11695-020-04783-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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17
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Lu KH, Cao J, Phillips R, Powley TL, Liu Z. Acute effects of vagus nerve stimulation parameters on gastric motility assessed with magnetic resonance imaging. Neurogastroenterol Motil 2020; 32:e13853. [PMID: 32297404 PMCID: PMC7872206 DOI: 10.1111/nmo.13853] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/19/2019] [Revised: 02/24/2020] [Accepted: 03/19/2020] [Indexed: 12/13/2022]
Abstract
BACKGROUND Vagus nerve stimulation (VNS) is an emerging bioelectronic therapy for regulating food intake and controlling gastric motility. However, the effects of different VNS parameters and polarity on postprandial gastric motility remain incompletely characterized. METHODS In anesthetized rats (N = 3), we applied monophasic electrical stimuli to the left cervical vagus and recorded compound nerve action potential (CNAP) as a measure of nerve response. We evaluated to what extent afferent or efferent pathway could be selectively activated by monophasic VNS. In a different group of rats (N = 13), we fed each rat a gadolinium-labeled meal and scanned the rat stomach with oral contrast-enhanced magnetic resonance imaging (MRI) while the rat was anesthetized. We evaluated the antral and pyloric motility as a function of pulse amplitude (0.13, 0.25, 0.5, 1 mA), width (0.13, 0.25, 0.5 ms), frequency (5, 10 Hz), and polarity of VNS. KEY RESULTS Monophasic VNS activated efferent and afferent pathways with about 67% and 82% selectivity, respectively. Primarily afferent VNS increased antral motility across a wide range of parameters. Primarily efferent VNS induced a significant decrease in antral motility as the stimulus intensity increased (R = -.93, P < .05 for 5 Hz, R = -.85, P < .05 for 10 Hz). The VNS with either polarity tended to promote pyloric motility to a greater extent given increasing stimulus intensity. CONCLUSIONS AND INFERENCES Monophasic VNS biased toward the afferent pathway is potentially more effective for facilitating occlusive contractions than that biased toward the efferent pathway.
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Affiliation(s)
- Kun-Han Lu
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA,Purdue Institute for Integrative Neuroscience, Purdue University, West Lafayette, IN, USA,Correspondence: Kun-Han Lu, PhD, Postdoctoral Research Associate, Weldon School of Biomedical Engineering, College of Engineering, Purdue University, 206 S. Martin Jischke Dr., West Lafayette, IN 47907, USA, Phone: +1 765 714 8776,
| | - Jiayue Cao
- Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - Robert Phillips
- Department of Psychological Sciences, Purdue University, West Lafayette, IN, USA
| | - Terry L Powley
- Department of Psychological Sciences, Purdue University, West Lafayette, IN, USA,Purdue Institute for Integrative Neuroscience, Purdue University, West Lafayette, IN, USA
| | - Zhongming Liu
- Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA,Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI, USA
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18
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Sensory nerve endings arising from single spinal afferent neurons that innervate both circular muscle and myenteric ganglia in mouse colon: colon-brain axis. Cell Tissue Res 2020; 381:25-34. [DOI: 10.1007/s00441-020-03192-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2019] [Accepted: 02/19/2020] [Indexed: 10/25/2022]
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19
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Spencer NJ, Kyloh MA, Travis L, Dodds KN. Identification of spinal afferent nerve endings in the colonic mucosa and submucosa that communicate directly with the spinal cord: The gut–brain axis. J Comp Neurol 2020; 528:1742-1753. [DOI: 10.1002/cne.24854] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2019] [Revised: 01/01/2020] [Accepted: 01/02/2020] [Indexed: 12/12/2022]
Affiliation(s)
- Nick J. Spencer
- Visceral Neurophysiology Laboratory, College of Medicine and Public Health, Centre for Neuroscience Flinders University Bedford Park South Australia Australia
| | - Melinda A. Kyloh
- Visceral Neurophysiology Laboratory, College of Medicine and Public Health, Centre for Neuroscience Flinders University Bedford Park South Australia Australia
| | - Lee Travis
- Visceral Neurophysiology Laboratory, College of Medicine and Public Health, Centre for Neuroscience Flinders University Bedford Park South Australia Australia
| | - Kelsi N. Dodds
- Visceral Neurophysiology Laboratory, College of Medicine and Public Health, Centre for Neuroscience Flinders University Bedford Park South Australia Australia
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20
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Abstract
Gastric acid secretion (i) facilitates digestion of protein as well as absorption of micronutrients and certain medications, (ii) kills ingested microorganisms, including Helicobacter pylori, and (iii) prevents bacterial overgrowth and enteric infection. The principal regulators of acid secretion are the gastric peptides gastrin and somatostatin. Gastrin, the major hormonal stimulant for acid secretion, is synthesized in pyloric mucosal G cells as a 101-amino acid precursor (preprogastrin) that is processed to yield biologically active amidated gastrin-17 and gastrin-34. The C-terminal active site of gastrin (Trp-Met-Asp-Phe-NH2 ) binds to gastrin/CCK2 receptors on parietal and, more importantly, histamine-containing enterochromaffin-like (ECL) cells, located in oxyntic mucosa, to induce acid secretion. Histamine diffuses to the neighboring parietal cells where it binds to histamine H2 -receptors coupled to hydrochloric acid secretion. Gastrin is also a trophic hormone that maintains the integrity of gastric mucosa, induces proliferation of parietal and ECL cells, and is thought to play a role in carcinogenesis. Somatostatin, present in D cells of the gastric pyloric and oxyntic mucosa, is the main inhibitor of acid secretion, particularly during the interdigestive period. Somatostatin exerts a tonic paracrine restraint on gastrin secretion from G cells, histamine secretion from ECL cells, and acid secretion from parietal cells. Removal of this restraint, for example by activation of cholinergic neurons during ingestion of food, initiates and maximizes acid secretion. Knowledge regarding the structure and function of gastrin, somatostatin, and their respective receptors is providing novel avenues to better diagnose and manage acid-peptic disorders and certain cancers. Published 2020. Compr Physiol 10:197-228, 2020.
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Affiliation(s)
- Mitchell L Schubert
- Division of Gastroenterology, Department of Medicine, Virginia Commonwealth University Health System, Richmond, Virginia, USA.,Hunter Holmes McGuire Veterans Affairs Medical Center, Richmond, Virginia, USA
| | - Jens F Rehfeld
- Department of Clinical Biochemistry, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
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21
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Besecker EM, Blanke EN, Deiter GM, Holmes GM. Gastric vagal afferent neuropathy following experimental spinal cord injury. Exp Neurol 2019; 323:113092. [PMID: 31697943 DOI: 10.1016/j.expneurol.2019.113092] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2019] [Revised: 09/11/2019] [Accepted: 10/23/2019] [Indexed: 01/01/2023]
Abstract
Dramatic impairment of gastrointestinal (GI) function accompanies high-thoracic spinal cord injury (T3-SCI). The vagus nerve contains mechano- and chemosensory fibers as well as the motor fibers necessary for the central nervous system (CNS) control of GI reflexes. Cell bodies for the vagal afferent fibers are located within the nodose gangla (NG) and the majority of vagal afferent axons are unmyelinated C fibers that are sensitive to capsaicin through activation of transient receptor potential vanilloid-1 (TRPV1) channels. Vagal afferent fibers also express receptors for GI hormones, including cholecystokinin (CCK). Previously, T3-SCI provokes a transient GI inflammatory response as well as a reduction of both gastric emptying and centrally-mediated vagal responses to GI peptides, including CCK. TRPV1 channels and CCK-A receptors (CCKar) expressed in vagal afferents are upregulated in models of visceral inflammation. The present study investigated whether T3-SCI attenuates peripheral vagal afferent sensitivity through plasticity of TRPV1 and CCK receptors. Vagal afferent response to graded mechanical stimulation of the stomach was significantly attenuated by T3-SCI at 3-day and 3-week recovery. Immunocytochemical labeling for CCKar and TRPV1 demonstrated expression on dissociated gastric-projecting NG neurons. Quantitative assessment of mRNA expression by qRT-PCR revealed significant elevation of CCKar and TRPV1 in the whole NG following T3-SCI in 3-day recovery, but levels returned to normal after 3-weeks. Three days after injury, systemic administration of CCK-8 s showed a significantly diminished gastric vagal afferent response in T3-SCI rats compared to control rats while systemic capsaicin infusion revealed a significant elevation of vagal response in T3-SCI vs control rats. These findings demonstrate that T3-SCI provokes peripheral remodeling and prolonged alterations in the response of vagal afferent fibers to the physiological signals associated with digestion.
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Affiliation(s)
- Emily M Besecker
- Department of Neural and Behavioral Sciences, Penn State University College of Medicine, Hershey, PA 17033, United States of America; Department of Health Sciences, Gettysburg College, Gettysburg, PA 17325, United States of America
| | - Emily N Blanke
- Department of Neural and Behavioral Sciences, Penn State University College of Medicine, Hershey, PA 17033, United States of America
| | - Gina M Deiter
- Department of Neural and Behavioral Sciences, Penn State University College of Medicine, Hershey, PA 17033, United States of America
| | - Gregory M Holmes
- Department of Neural and Behavioral Sciences, Penn State University College of Medicine, Hershey, PA 17033, United States of America.
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22
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Maniscalco JW, Rinaman L. Vagal Interoceptive Modulation of Motivated Behavior. Physiology (Bethesda) 2019; 33:151-167. [PMID: 29412062 DOI: 10.1152/physiol.00036.2017] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
In addition to regulating the ingestion and digestion of food, sensory feedback from gut to brain modifies emotional state and motivated behavior by subconsciously shaping cognitive and affective responses to events that bias behavioral choice. This focused review highlights evidence that gut-derived signals impact motivated behavior by engaging vagal afferents and central neural circuits that generally serve to limit or terminate goal-directed approach behaviors, and to initiate or maintain behavioral avoidance.
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Affiliation(s)
- J W Maniscalco
- Department of Psychology, University of Illinois at Chicago, Chicago, Illionois
| | - L Rinaman
- Department of Psychology, Florida State University , Tallahassee, Florida
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23
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Margolis KG, Gershon MD, Bogunovic M. Cellular Organization of Neuroimmune Interactions in the Gastrointestinal Tract. Trends Immunol 2016; 37:487-501. [PMID: 27289177 PMCID: PMC5003109 DOI: 10.1016/j.it.2016.05.003] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2016] [Revised: 04/19/2016] [Accepted: 05/09/2016] [Indexed: 02/06/2023]
Abstract
The gastrointestinal (GI) tract is the largest immune organ; in vertebrates, it is the only organ whose function is controlled by its own intrinsic enteric nervous system (ENS), but it is additionally regulated by extrinsic (sympathetic and parasympathetic) innervation. The GI nervous and immune systems are highly integrated in their common goal, which is to unite digestive functions with protection from ingested environmental threats. This review discusses the physiological relevance of enteric neuroimmune integration by summarizing the current knowledge of evolutionary and developmental pathways, cellular organization, and molecular mechanisms of neuroimmune interactions in health and disease.
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Affiliation(s)
- Kara Gross Margolis
- Department of Pediatrics, Morgan Stanley Children's Hospital, Columbia University College of Physicians and Surgeons, New York, NY, USA
| | - Michael David Gershon
- Department of Pathology and Cell Biology, Columbia University College of Physicians and Surgeons, New York, NY, USA
| | - Milena Bogunovic
- Department of Microbiology and Immunology, Penn State University College of Medicine, Hershey, PA, USA.
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24
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Li Y, Zhu W, Zuo L, Shen B. The Role of the Mesentery in Crohn's Disease: The Contributions of Nerves, Vessels, Lymphatics, and Fat to the Pathogenesis and Disease Course. Inflamm Bowel Dis 2016; 22:1483-95. [PMID: 27167572 DOI: 10.1097/mib.0000000000000791] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Crohn's disease (CD) is a complex gastrointestinal disorder involving multiple levels of cross talk between the immunological, neural, vascular, and endocrine systems. The current dominant theory in CD is based on the unidirectional axis of dysbiosis-innate immunity-adaptive immunity-mesentery-body system. Emerging clinical evidence strongly suggests that the axis be bidirectional. The morphologic and/or functional abnormalities in the mesenteric structures likely contribute to the disease progression of CD, to a less extent the disease initiation. In addition to adipocytes, mesentery contains nerves, blood vessels, lymphatics, stromal cells, and fibroblasts. By the secretion of adipokines that have endocrine functions, the mesenteric fat tissue exerts its activity in immunomodulation mainly through response to afferent signals, neuropeptides, and functional cytokines. Mesenteric nerves are involved in the pathogenesis and prognosis of CD mainly through neuropeptides. In addition to angiogenesis observed in CD, lymphatic obstruction, remodeling, and impaired contraction maybe a cause and consequence of CD. Lymphangiogenesis and angiogenesis play a concomitant role in the progress of chronic intestinal inflammation. Finally, the interaction between neuropeptides, adipokines, and vascular and lymphatic endothelia leads to adipose tissue remodeling, which makes the mesentery an active participator, not a bystander, in the disease initiation and precipitation CD. The identification of the role of mesentery, including the structure and function of mesenteric nerves, vessels, lymphatics, and fat, in the intestinal inflammation in CD has important implications in understanding its pathogenesis and clinical management.
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Affiliation(s)
- Yi Li
- *Department of General Surgery, Jinling Hospital, Medical School of Nanjing University, Nanjing, Jiangsu, China; and †Center for Inflammatory Bowel Disease, Digestive Disease Institute, The Cleveland Clinic Foundation, Cleveland, Ohio
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25
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Browning KN. Role of central vagal 5-HT3 receptors in gastrointestinal physiology and pathophysiology. Front Neurosci 2015; 9:413. [PMID: 26578870 PMCID: PMC4625078 DOI: 10.3389/fnins.2015.00413] [Citation(s) in RCA: 76] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Accepted: 10/15/2015] [Indexed: 12/21/2022] Open
Abstract
Vagal neurocircuits are vitally important in the co-ordination and modulation of GI reflexes and homeostatic functions. 5-hydroxytryptamine (5-HT; serotonin) is critically important in the regulation of several of these autonomic gastrointestinal (GI) functions including motility, secretion and visceral sensitivity. While several 5-HT receptors are involved in these physiological responses, the ligand-gated 5-HT3 receptor appears intimately involved in gut-brain signaling, particularly via the afferent (sensory) vagus nerve. 5-HT is released from enterochromaffin cells in response to mechanical or chemical stimulation of the GI tract which leads to activation of 5-HT3 receptors on the terminals of vagal afferents. 5-HT3 receptors are also present on the soma of vagal afferent neurons, including GI vagal afferent neurons, where they can be activated by circulating 5-HT. The central terminals of vagal afferents also exhibit 5-HT3 receptors that function to increase glutamatergic synaptic transmission to second order neurons of the nucleus tractus solitarius within the brainstem. While activation of central brainstem 5-HT3 receptors modulates visceral functions, it is still unclear whether central vagal neurons, i.e., nucleus of the tractus solitarius (NTS) and dorsal motor nucleus of the vagus (DMV) neurons themselves also display functional 5-HT3 receptors. Thus, activation of 5-HT3 receptors may modulate the excitability and activity of gastrointestinal vagal afferents at multiple sites and may be involved in several physiological and pathophysiological conditions, including distention- and chemical-evoked vagal reflexes, nausea, and vomiting, as well as visceral hypersensitivity.
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Affiliation(s)
- Kirsteen N Browning
- Department of Neural and Behavioral Sciences, Penn State University College of Medicine Hershey, PA, USA
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26
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Powley TL, Hudson CN, McAdams JL, Baronowsky EA, Phillips RJ. Vagal Intramuscular Arrays: The Specialized Mechanoreceptor Arbors That Innervate the Smooth Muscle Layers of the Stomach Examined in the Rat. J Comp Neurol 2015; 524:713-37. [PMID: 26355387 DOI: 10.1002/cne.23892] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Revised: 08/18/2015] [Accepted: 08/19/2015] [Indexed: 01/14/2023]
Abstract
The fundamental roles that the stomach plays in ingestion and digestion notwithstanding, little morphological information is available on vagal intramuscular arrays (IMAs), the afferents that innervate gastric smooth muscle. To characterize IMAs better, rats were given injections of dextran biotin in the nodose ganglia, and, after tracer transport, stomach whole mounts were collected. Specimens were processed for avidin-biotin permanent labeling, and subsets of the whole mounts were immunohistochemically processed for c-Kit or stained with cuprolinic blue. IMAs (n = 184) were digitized for morphometry and mapping. Throughout the gastric muscle wall, IMAs possessed common phenotypic features. Each IMA was generated by a parent neurite arborizing extensively, forming an array of multiple (mean = 212) branches averaging 193 µm in length. These branches paralleled, and coursed in apposition with, bundles of muscle fibers and interstitial cells of Cajal. Individual arrays averaged 4.3 mm in length and innervated volumes of muscle sheet, presumptive receptive fields, averaging 0.1 mm(3) . Evaluated by region and by muscle sheet, IMAs displayed architectural adaptations to the different loci. A subset (32%) of circular muscle IMAs issued specialized polymorphic collaterals to myenteric ganglia, and a subset (41%) of antral longitudinal muscle IMAs formed specialized net endings associated with the serosal boundary. IMAs were concentrated in regional patterns that correlated with the unique biomechanical adaptations of the stomach, specifically proximal stomach reservoir functions and antral emptying operations. Overall, the structural adaptations and distributions of the IMAs were consonant with the hypothesized stretch receptor roles of the afferents.
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Affiliation(s)
- Terry L Powley
- Department of Psychological Sciences, Purdue University, West Lafayette, Indiana, 47907-2081
| | - Cherie N Hudson
- Department of Psychological Sciences, Purdue University, West Lafayette, Indiana, 47907-2081
| | - Jennifer L McAdams
- Department of Psychological Sciences, Purdue University, West Lafayette, Indiana, 47907-2081
| | - Elizabeth A Baronowsky
- Department of Psychological Sciences, Purdue University, West Lafayette, Indiana, 47907-2081
| | - Robert J Phillips
- Department of Psychological Sciences, Purdue University, West Lafayette, Indiana, 47907-2081
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27
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Sleeve gastrectomy and Roux-en-Y gastric bypass alter the gut-brain communication. Neural Plast 2015; 2015:601985. [PMID: 25722893 PMCID: PMC4333325 DOI: 10.1155/2015/601985] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2014] [Revised: 10/15/2014] [Accepted: 10/17/2014] [Indexed: 12/15/2022] Open
Abstract
This study investigated the anatomical integrity of vagal innervation of the gastrointestinal tract following vertical sleeve gastrectomy (VSG) and Roux-en-Y gastric bypass (RYGB) operations. The retrograde tracer fast blue (FB) was injected into the stomach to label vagal neurons originating from nodose ganglion (NG) and dorsal motor nucleus of the vagus (DMV). Microglia activation was determined by quantifying changes in the fluorescent staining of hindbrain sections against an ionizing calcium adapter binding molecule 1 (Iba1). Reorganization of vagal afferents in the hindbrain was studied by fluorescent staining against isolectin 4 (IB4). The density of Iba1- and IB4-immunoreactivity was analyzed using Nikon Elements software. There was no difference in the number of FB-labeled neurons located in NG and DMV between VSG and VSG-sham rats. RYGB, but not RYGB-sham rats, showed a dramatic reduction in number of FB-labeled neurons located in the NG and DMV. VSG increased, while the RYGB operation decreased, the density of vagal afferents in the nucleus tractus solitarius (NTS). The RYGB operation, but not the VSG procedure, significantly activated microglia in the NTS and DMV. Results of this study show that the RYGB, but not the VSG procedure, triggers microglia activation in vagal structures and remodels gut-brain communication.
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28
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Ripken D, van der Wielen N, van der Meulen J, Schuurman T, Witkamp R, Hendriks H, Koopmans S. Cholecystokinin regulates satiation independently of the abdominal vagal nerve in a pig model of total subdiaphragmatic vagotomy. Physiol Behav 2015; 139:167-76. [DOI: 10.1016/j.physbeh.2014.11.031] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2014] [Revised: 09/16/2014] [Accepted: 11/10/2014] [Indexed: 11/25/2022]
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Vagal pathways for microbiome-brain-gut axis communication. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014; 817:115-33. [PMID: 24997031 DOI: 10.1007/978-1-4939-0897-4_5] [Citation(s) in RCA: 307] [Impact Index Per Article: 30.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
There is now strong evidence from animal studies that gut microorganism can activate the vagus nerve and that such activation plays a critical role in mediating effects on the brain and behaviour. The vagus appears to differentiate between non-pathogenic and potentially pathogenic bacteria even in the absence of overt inflammation and vagal pathways mediate signals that can induce both anxiogenic and anxiolytic effects, depending on the nature of the stimulus. Certain vagal signals from the gut can instigate an anti-inflammatory reflex with afferent signals to the brain activating an efferent response, releasing mediators including acetylcholine that, through an interaction with immune cells, attenuates inflammation. This immunomodulatory role of the vagus nerve may also have consequences for modulation of brain function and mood.What is currently lacking are relevant data on the electrophysiology of the system. Certainly, important advances in our understanding of the gut-brain and microbiome- gut-brain axis will come from studies of how distinct microbial and nutritional stimuli activate the vagus and the nature of the signals transmitted to the brain that lead to differential changes in the neurochemistry of the brain and behaviour.Understanding the induction and transmission of signals in the vagus nerve may have important implications for the development of microbial-or nutrition based therapeutic strategies for mood disorders.
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30
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Greene JG. Causes and consequences of degeneration of the dorsal motor nucleus of the vagus nerve in Parkinson's disease. Antioxid Redox Signal 2014; 21:649-67. [PMID: 24597973 DOI: 10.1089/ars.2014.5859] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
SIGNIFICANCE Parkinson's disease (PD) is no longer considered merely a movement disorder caused by degeneration of dopamine neurons in the midbrain. It is now recognized as a widespread neuropathological syndrome accompanied by a variety of motor and nonmotor clinical symptoms. As such, any hypothesis concerning PD pathogenesis and pathophysiology must account for the entire spectrum of disease and not solely focus on the dopamine system. RECENT ADVANCES Based on its anatomy and the intrinsic properties of its neurons, the dorsal motor nucleus of the vagus nerve (DMV) is uniquely vulnerable to damage from PD. Fibers in the vagus nerve course throughout the gastrointestinal (GI) tract to and from the brainstem forming a close link between the peripheral and central nervous systems and a point of proximal contact between the environment and areas where PD pathology is believed to start. In addition, DMV neurons are under high levels of oxidative stress due to their high level of α-synuclein expression, fragile axons, and specific neuronal physiology. Moreover, several consequences of DMV damage, namely, GI dysfunction and unrestrained inflammation, may propagate a vicious cycle of injury affecting vulnerable brain regions. CRITICAL ISSUES Current evidence to suggest the vagal system plays a pivotal role in PD pathogenesis is circumstantial, but given the current state of the field, the time is ripe to obtain direct experimental evidence to better delineate it. FUTURE DIRECTIONS Better understanding of the DMV and vagus nerve may provide insight into PD pathogenesis and a neural highway with direct brain access that could be harnessed for novel therapeutic interventions.
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Affiliation(s)
- James G Greene
- Department of Neurology, Emory University , Atlanta, Georgia
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Powley TL, Hudson CN, McAdams JL, Baronowsky EA, Martin FN, Mason JK, Phillips RJ. Organization of vagal afferents in pylorus: mechanoreceptors arrayed for high sensitivity and fine spatial resolution? Auton Neurosci 2014; 183:36-48. [PMID: 24656895 DOI: 10.1016/j.autneu.2014.02.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2014] [Revised: 02/24/2014] [Accepted: 02/26/2014] [Indexed: 01/16/2023]
Abstract
The pylorus is innervated by vagal mechanoreceptors that project to gastrointestinal smooth muscle, but the distributions and specializations of vagal endings in the sphincter have not been fully characterized. To evaluate their organization, the neural tracer dextran biotin was injected into the nodose ganglia of rats. Following tracer transport, animals were perfused, and their pylori and antra were prepared as whole mounts. Specimens were processed to permanently label the tracer, and subsets were counterstained with Cuprolinic blue or immunostained for c-Kit. Intramuscular arrays (IMAs) in the circular muscle comprised the principal vagal afferent innervation of the sphincter. These pyloric ring IMAs were densely distributed and evidenced a variety of structural specializations. Morphometric comparisons between the arbors innervating the pylorus and a corresponding sample of IMAs in the adjacent antral circular muscle highlighted that sphincter IMAs branched profusely, forming more than twice as many branches as did antral IMAs (means of 405 vs. 165, respectively), and condensed their numerous neurites into compact receptive fields (∼48% of the area of antral IMAs) deep in the circular muscle (∼6μm above the submucosa). Separate arbors of IMAs in the sphincter interdigitated and overlapped to form a 360° band of mechanoreceptors encircling the pyloric canal. The annulus of vagal IMA arbors, putative stretch receptors tightly intercalated in the sphincter ring and situated near the lumen of the pyloric canal, creates an architecture with the potential to generate gut reflexes on the basis of pyloric sensory maps of high sensitivity and fine spatial resolution.
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Affiliation(s)
- Terry L Powley
- Purdue University, Department of Psychological Sciences, West Lafayette, IN 47907-2081, United States.
| | - Cherie N Hudson
- Purdue University, Department of Psychological Sciences, West Lafayette, IN 47907-2081, United States
| | - Jennifer L McAdams
- Purdue University, Department of Psychological Sciences, West Lafayette, IN 47907-2081, United States
| | - Elizabeth A Baronowsky
- Purdue University, Department of Psychological Sciences, West Lafayette, IN 47907-2081, United States
| | - Felecia N Martin
- Purdue University, Department of Psychological Sciences, West Lafayette, IN 47907-2081, United States
| | - Jacqueline K Mason
- Purdue University, Department of Psychological Sciences, West Lafayette, IN 47907-2081, United States
| | - Robert J Phillips
- Purdue University, Department of Psychological Sciences, West Lafayette, IN 47907-2081, United States.
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Azpiroz F, Feinle-Bisset C, Grundy D, Tack J. Gastric sensitivity and reflexes: basic mechanisms underlying clinical problems. J Gastroenterol 2014; 49:206-18. [PMID: 24306100 DOI: 10.1007/s00535-013-0917-8] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/03/2013] [Accepted: 11/19/2013] [Indexed: 02/04/2023]
Abstract
Both reflex and sensory mechanisms control the function of the stomach, and disturbances in these mechanisms may explain the pathophysiology of disorders of gastric function. The objective of this report is to perform a literature-based critical analysis of new, relevant or conflicting information on gastric sensitivity and reflexes, with particular emphasis on the comprehensive integration of basic and clinical research data. The stomach exerts both phasic and tonic muscular (contractile and relaxatory) activity. Gastric tone determines the capacity of the stomach and mediates both gastric accommodation to a meal as well as gastric emptying, by partial relaxation or progressive recontraction, respectively. Perception and reflex afferent pathways from the stomach are activated independently by specific stimuli, suggesting that the terminal nerve endings operate as specialized receptors. Particularly, perception appears to be related to stimulation of tension receptors, while the existence of volume receptors in the stomach is uncertain. Reliable techniques have been developed to measure gastric perception and reflexes both in experimental and clinical conditions, and have facilitated the identification of abnormal responses in patients with gastric disorders. Gastroparesis is characterised by impaired gastric tone and contractility, whereas patients with functional dyspepsia have impaired accommodation, associated with antral distention and increased gastric sensitivity. An integrated view of fragmented knowledge allows the design of pathophysiological models in an attempt to explain disorders of gastric function, and may facilitate the development of mechanistically orientated treatments.
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Affiliation(s)
- Fernando Azpiroz
- Digestive System Research Unit, Hospital General Vall d'Hebron, Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (Ciberehd), 08035, Barcelona, Spain,
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VanElzakker MB. Chronic fatigue syndrome from vagus nerve infection: A psychoneuroimmunological hypothesis. Med Hypotheses 2013; 81:414-23. [DOI: 10.1016/j.mehy.2013.05.034] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2012] [Revised: 05/15/2013] [Accepted: 05/23/2013] [Indexed: 12/20/2022]
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Raybould HE. The heat is on: does direct application of capsaicin to autonomic nerves produce a specific deafferentation? J Physiol 2013; 591:1405. [PMID: 23504233 DOI: 10.1113/jphysiol.2013.251868] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Affiliation(s)
- Helen E Raybould
- Department of Anatomy, Physiology and Cell Biology, UC Davis School of Veterinary Medicine, UC Davis, CA 95616, USA.
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Goldberg D, Borojevic R, Anderson M, Chen JJ, Gershon MD, Ratcliffe EM. Slit/Robo-mediated chemorepulsion of vagal sensory axons in the fetal gut. Dev Dyn 2013; 242:9-15. [PMID: 23161783 PMCID: PMC3688041 DOI: 10.1002/dvdy.23898] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/17/2012] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND The vagus nerve descends from the brain to the gut during fetal life to reach specific targets in the bowel wall. Vagal sensory axons have been shown to respond to the axon guidance molecule netrin and to its receptor, deleted in colorectal cancer (DCC). As there are regions of the gut wall into which vagal axons do and do not extend, it is likely that a combination of attractive and repellent cues are involved in how vagal axons reach specific targets. We tested the hypothesis that Slit/Robo chemorepulsion can contribute to the restriction of vagal sensory axons to specific targets in the gut wall. RESULTS Transcripts encoding Robo1 and Robo2 were expressed in the nodose ganglia throughout development and mRNA encoding the Robo ligands Slit1, Slit2, and Slit3 were all found in the fetal and adult bowel. Slit2 protein was located in the outer gut mesenchyme in regions that partially overlap with the secretion of netrin-1. Neurites extending from explanted nodose ganglia were repelled by Slit2. CONCLUSIONS These observations suggest that vagal sensory axons are responsive to Slit proteins and are thus repelled by Slits secreted in the gut wall and prevented from reaching inappropriate targets.
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Affiliation(s)
- David Goldberg
- School of Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Rajka Borojevic
- Department of Pediatrics, McMaster University, Hamilton, Ontario, Canada
- Farncombe Family Digestive Health Research Institute, McMaster University, Hamilton, Ontario, Canada
| | - Monique Anderson
- School of Medicine, University of Virginia, Charlottesville, Virginia
| | - Jason J. Chen
- Department of Pathology and Cell Biology, Columbia University, New York, New York
| | - Michael D. Gershon
- Department of Pathology and Cell Biology, Columbia University, New York, New York
| | - Elyanne M. Ratcliffe
- Department of Pediatrics, McMaster University, Hamilton, Ontario, Canada
- Farncombe Family Digestive Health Research Institute, McMaster University, Hamilton, Ontario, Canada
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Holmes GM. Upper gastrointestinal dysmotility after spinal cord injury: is diminished vagal sensory processing one culprit? Front Physiol 2012; 3:277. [PMID: 22934031 PMCID: PMC3429051 DOI: 10.3389/fphys.2012.00277] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2012] [Accepted: 06/27/2012] [Indexed: 12/12/2022] Open
Abstract
Despite the widely recognized prevalence of gastric, colonic, and anorectal dysfunction after spinal cord injury (SCI), significant knowledge gaps persist regarding the mechanisms leading to post-SCI gastrointestinal (GI) impairments. Briefly, the regulation of GI function is governed by a mix of parasympathetic, sympathetic, and enteric neurocircuitry. Unlike the intestines, the stomach is dominated by parasympathetic (vagal) control whereby gastric sensory information is transmitted via the afferent vagus nerve to neurons of the nucleus tractus solitarius (NTS). The NTS integrates this sensory information with signals from throughout the central nervous system. Glutamatergic and GABAergic NTS neurons project to other nuclei, including the preganglionic parasympathetic neurons of the dorsal motor nucleus of the vagus (DMV). Finally, axons from the DMV project to gastric myenteric neurons, again, through the efferent vagus nerve. SCI interrupts descending input to the lumbosacral spinal cord neurons that modulate colonic motility and evacuation reflexes. In contrast, vagal neurocircuitry remains anatomically intact after injury. This review presents evidence that unlike the post-SCI loss of supraspinal control which leads to colonic and anorectal dysfunction, gastric dysmotility occurs as an indirect or secondary pathology following SCI. Specifically, emerging data points toward diminished sensitivity of vagal afferents to GI neuroactive peptides, neurotransmitters and, possibly, macronutrients. The neurophysiological properties of rat vagal afferent neurons are highly plastic and can be altered by injury or energy balance. A reduction of vagal afferent signaling to NTS neurons may ultimately bias NTS output toward unregulated GABAergic transmission onto gastric-projecting DMV neurons. The resulting gastroinhibitory signal may be one mechanism leading to upper GI dysmotility following SCI.
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Affiliation(s)
- Gregory M. Holmes
- Neural and Behavioral Sciences, Penn State University College of MedicineHershey, PA, USA
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Jacobs IJ, Ku WY, Que J. Genetic and cellular mechanisms regulating anterior foregut and esophageal development. Dev Biol 2012; 369:54-64. [PMID: 22750256 DOI: 10.1016/j.ydbio.2012.06.016] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2012] [Revised: 06/07/2012] [Accepted: 06/20/2012] [Indexed: 12/22/2022]
Abstract
Separation of the single anterior foregut tube into the esophagus and trachea involves cell proliferation and differentiation, as well as dynamic changes in cell-cell adhesion and migration. These biological processes are regulated and coordinated at multiple levels through the interplay of the epithelium and mesenchyme. Genetic studies and in vitro modeling have shed light on relevant regulatory networks that include a number of transcription factors and signaling pathways. These signaling molecules exhibit unique expression patterns and play specific functions in their respective territories before the separation process occurs. Disruption of regulatory networks inevitably leads to defective separation and malformation of the trachea and esophagus and results in the formation of a relatively common birth defect, esophageal atresia with or without tracheoesophageal fistula (EA/TEF). Significantly, some of the signaling pathways and transcription factors involved in anterior foregut separation continue to play important roles in the morphogenesis of the individual organs. In this review, we will focus on new findings related to these different developmental processes and discuss them in the context of developmental disorders or birth defects commonly seen in clinics.
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Affiliation(s)
- Ian J Jacobs
- Department of Biology, University of Rochester, Rochester, NY 14642, USA
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Kinch DC, Peters JH, Simasko SM. Comparative pharmacology of cholecystokinin induced activation of cultured vagal afferent neurons from rats and mice. PLoS One 2012; 7:e34755. [PMID: 22514663 PMCID: PMC3326049 DOI: 10.1371/journal.pone.0034755] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2011] [Accepted: 03/05/2012] [Indexed: 12/18/2022] Open
Abstract
Cholecystokinin (CCK) facilitates the process of satiation via activation of vagal afferent neurons innervating the upper gastrointestinal tract. Recent findings indicate CCK acts on these neurons via a ruthenium red (RuR) sensitive pathway that involves members of the vanilloid (V) subfamily of transient receptor potential (TRP) channels. To further test this mechanism, the mouse provides an ideal model in which genetic tools could be applied. However, whether CCK acts by similar mechanism(s) in mice has not been determined. In the present study we explored the actions of CCK on nodose neurons isolated from Sprague Dawley (SD) rat and two strains of mice; C57BL/6 and BalbC using fluorescence-based calcium imaging. With minor exceptions nodose neurons isolated from all species/strains behaved similarly. They all respond to brief depolarization with a large calcium transient. A significant subset of neurons responded to capsaicin (CAP), a TRPV1 agonist, although neurons from C57BL/6 were 10-fold more sensitive to CAP than SD rats or BalbC mice, and a significantly smaller fraction of neurons from BalbC mice responded to CAP. CCK-8 dose-dependently activated a subpopulation of neurons with similar dose dependency, percent responders, and overlap between CCK and CAP responsiveness. In all species/strains CCK-8 induced activation was significantly attenuated (but not completely blocked) by pretreatment with the TRPV channel blocker RuR. Surprisingly, the CCK analogue JMV-180, which is reported to have pure antagonistic properties in rat but mixed agonist/antagonist properties in mice, behaved as a pure antagonist to CCK in both rat and mouse neurons. The pure antagonistic action of JMV-180 in this in vitro preparation suggests that prior reported differential effects of JMV-180 on satiation in rats versus mouse must be mediated by a site other than vagal afferent activation.
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Affiliation(s)
- Dallas C. Kinch
- Program in Neuroscience, Department of Veterinary and Comparative Anatomy, Pharmacology, and Physiology, Washington State University, Pullman, Washington, United States of America
| | - James H. Peters
- Program in Neuroscience, Department of Veterinary and Comparative Anatomy, Pharmacology, and Physiology, Washington State University, Pullman, Washington, United States of America
| | - Steven M. Simasko
- Program in Neuroscience, Department of Veterinary and Comparative Anatomy, Pharmacology, and Physiology, Washington State University, Pullman, Washington, United States of America
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40
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Abstract
BACKGROUND The vagus nerve is the major neural connection between the gastrointestinal tract and the central nervous system. During fetal development, axons from the cell bodies of the nodose ganglia and the dorsal motor nucleus grow into the gut to find their enteric targets, providing the vagal sensory and motor innervations respectively. Vagal sensory and motor axons innervate selective targets, suggesting a role for guidance cues in the establishment of the normal pattern of enteric vagal innervation. PURPOSE This review explores known molecular mechanisms that guide vagal innervation in the gastrointestinal tract. Guidance and growth factors, such as netrin-1 and its receptor, deleted in colorectal cancer, extracellular matrix molecules, such as laminin-111, and members of the neurotrophin family of molecules, such as brain-derived neurotrophic factor have been identified as mediating the guidance of vagal axons to the fetal mouse gut. In addition to increasing our understanding of the development of enteric innervation, studies of vagal development may also reveal clinically relevant insights into the underlying mechanisms of vago-vagal communication with the gastrointestinal tract.
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Affiliation(s)
- E M Ratcliffe
- Division of Gastroenterology and Nutrition, Department of Pediatrics, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada.
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Ratcliffe EM, Fan L, Mohammed TJ, Anderson M, Chalazonitis A, Gershon MD. Enteric neurons synthesize netrins and are essential for the development of the vagal sensory innervation of the fetal gut. Dev Neurobiol 2011; 71:362-73. [PMID: 21485011 DOI: 10.1002/dneu.20869] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
During fetal life, vagal sensory fibers establish a reproducible distribution in the gut that includes an association with myenteric ganglia. Previous work has shown that netrin is expressed in the bowel wall and, by acting on its receptor, deleted in colorectal cancer (DCC), mediates the guidance of vagal sensory axons to the developing gut. Because the highest concentration of netrins in fetal bowel is in the endoderm, we tested the hypothesis that the ingrowth of vagal afferents to the gut would be independent of the presence of enteric neurons, although enteric neurons might influence the internal distribution of these fibers. Surprisingly, experiments indicated that the vagal sensory innervation is intrinsic neuron-dependent. To examine the vagal innervation in the absence of enteric ganglia, fetal Ret -/- mice were labeled by applying DiI bilaterally to nodose ganglia. In Ret -/- mice, DiI-labeled vagal sensory axons descended in paraesophageal trunks as far as the proximal stomach, which contains neurons, but did not enter the aganglionic bowel. To determine whether neurons produce netrins, enteric neural-crest-derived cells (ENCDCs) were immunoselected from E15 rat gut. Transcripts encoding netrin-1 and -3 were not detected in the ENCDCs, but appeared after they had given rise to neurons. When these neurons were cocultured with cells expressing c-Myc-tagged netrin-1, the neurons displayed netrin-1, but not c-Myc, immunoreactivity. Enteric neurons thus synthesize netrins. The extent to which neuronal netrin accounts for the dependence of the vagal sensory innervation on intrinsic neurons, remains to be determined.
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Affiliation(s)
- Elyanne M Ratcliffe
- Department of Pediatrics, Division of Gastroenterology and Nutrition, McMaster University, Hamilton, Ontario.
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Powley TL, Phillips RJ. Vagal intramuscular array afferents form complexes with interstitial cells of Cajal in gastrointestinal smooth muscle: analogues of muscle spindle organs? Neuroscience 2011; 186:188-200. [PMID: 21530617 PMCID: PMC3110524 DOI: 10.1016/j.neuroscience.2011.04.036] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2011] [Revised: 04/12/2011] [Accepted: 04/14/2011] [Indexed: 01/11/2023]
Abstract
Intramuscular arrays (IMAs), vagal mechanoreceptors that innervate gastrointestinal smooth muscle, have not been completely described structurally or functionally. To delineate more fully the architecture of IMAs and to consider the structure-function implications of the observations, the present experiment examined the organization of the IMA terminal arbors and the accessory tissue elements of those arbors. IMA terminal fields, labeled by injection of biotinylated dextran into the nodose ganglia, were examined in whole mounts of rat gastric smooth muscle double-labeled with immunohistochemistry for interstitial cells of Cajal (ICCs; c-Kit) and/or inputs of different neuronal efferent transmitter (markers: tyrosine hydroxylase (TH), vesicular acetylcholine transporter (VAChT), and nitric oxide synthase (NOS)) or afferent neuropeptidergic (calcitonin gene-related peptide (CGRP)) phenotypes. IMAs make extensive varicose and lamellar contacts with ICCs. In addition, axons of the multiple efferent and afferent phenotypes examined converge and articulate with IMA terminal arbors innervating ICCs. This architecture is consistent with the hypothesis that IMAs, or the multiply innervated IMA-ICC complexes they form, can function as stretch receptors. The tissue organization is also consonant with the proposal that those units can operate as functional analogues of muscle spindle organs. For electrophysiological assessments of IMA functions, experiments will need protocols that preserve both the complex architecture and the dynamic operations of IMA-ICC complexes.
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Affiliation(s)
- T L Powley
- Purdue University, West Lafayette, IN 47906, USA.
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Calmont A, Thapar N, Scambler PJ, Burns AJ. Absence of the vagus nerve in the stomach of Tbx1-/- mutant mice. Neurogastroenterol Motil 2011; 23:125-30. [PMID: 20939858 DOI: 10.1111/j.1365-2982.2010.01615.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
BACKGROUND Tbx1 is a member of the Tbox family of binding domain transcription factors. TBX1 maps within the region of chromosome 22q11 deleted in humans with DiGeorge syndrome (DGS), a common genetic disorder characterized by numerous physical manifestations including craniofacial and cardiac anomalies. Mice with homozygous null mutations in Tbx1 phenocopy this disorder and have defects including abnormal cranial ganglia formation and cardiac neural crest cell migration. These defects prompted us to investigate whether extrinsic vagus nerve or intrinsic enteric nervous system abnormalities are prevalent in the gastrointestinal tract of Tbx1 mutant mice. METHODS We used in situ hybridization for Ret, and immunohistochemical staining for neurofilament, HuC/D and βIII-tubulin to study cranial ganglia, vagus nerve, and enteric nervous system development in Tbx1 mutant and control mice. KEY RESULTS In Tbx1(-/-) embryos, cranial ganglia of the glossopharyngeal (IXth) and vagus (Xth) nerves were malformed and abnormally fused. In the gastrointestinal tract, the vagus nerves adjacent to the esophagus were severely hypoplastic and they did not extend beyond the gastro-esophageal junction nor project branches within the stomach wall, as was observed in Tbx1(+/+) mice. CONCLUSIONS & INFERENCES Although cranial ganglia morphology appeared normal in Tbx1(+/-) mice, these animals had a spectrum of stomach vagus innervation defects ranging from mild to severe. In all Tbx1 genotypes, the intrinsic enteric nervous system developed normally. The deficit in vagal innervation of the stomach in mice mutant for a gene implicated in DGS raises the possibility that similar defects may underlie a number of as yet unidentified/unreported congenital disorders affecting gastrointestinal function.
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Affiliation(s)
- A Calmont
- Molecular Medicine Unit, UCL Institute of Child Health, London, UK
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44
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Ratcliffe EM. Molecular development of the extrinsic sensory innervation of the gastrointestinal tract. Auton Neurosci 2010; 161:1-5. [PMID: 21147045 DOI: 10.1016/j.autneu.2010.11.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2009] [Revised: 10/27/2010] [Accepted: 11/02/2010] [Indexed: 12/19/2022]
Abstract
The extrinsic sensory innervation of the gastrointestinal tract is the conduit through which the gut and the central nervous system communicate. The hindbrain receives information directly from the bowel via the vagus nerve, while information from spinal afferents arrives in the central nervous system through the dorsal root ganglia. This review focuses on the molecular development of these vagal and spinal innervations, with an emphasis on mechanisms that involve axon guidance. During development, axons from both the nodose ganglia and dorsal root ganglia grow into the gut, innervate their appropriate enteric targets and avoid inappropriate cells in the gut wall. These developmental outcomes suggest that both attractive and repellent molecules are important in establishing the normal pattern of the extrinsic sensory innervation. In the fetal mouse gut, the guidance of vagal sensory axons is mediated by axon guidance molecules, such as netrin and the netrin receptor, deleted in colorectal cancer (DCC), as well as extracellular matrix molecules, such as laminin-111. Dorsal root ganglion neurons are known to express, and their axons to respond to, axon guidance molecules. The question of whether or not these molecules are involved in guiding spinal afferents to the bowel, however, has not yet been examined. It is anticipated that a better understanding of how vagal and spinal afferents innervate the fetal gut and reach specific enteric locations will provide deeper insights into the underlying mechanisms of normal and abnormal sensation from the gastrointestinal tract.
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Affiliation(s)
- Elyanne M Ratcliffe
- Division of Gastroenterology and Nutrition, Department of Pediatrics, McMaster University, Canada.
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45
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Phillips RJ, Walter GC, Powley TL. Age-related changes in vagal afferents innervating the gastrointestinal tract. Auton Neurosci 2010; 153:90-8. [PMID: 19665435 PMCID: PMC2818053 DOI: 10.1016/j.autneu.2009.07.009] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2009] [Revised: 07/11/2009] [Accepted: 07/13/2009] [Indexed: 12/16/2022]
Abstract
Recent progress in understanding visceral afferents, some of it reviewed in the present issue, serves to underscore how little is known about the aging of the visceral afferents in the gastrointestinal (GI) tract. In spite of the clinical importance of the issue-with age, GI function often becomes severely compromised-only a few initial observations on age-related structural changes of visceral afferents are available. Primary afferent cell bodies in both the nodose ganglia and dorsal root ganglia lose Nissl material and accumulate lipofucsin, inclusions, aggregates, and tangles. Additionally, in changes that we focus on in the present review, vagal visceral afferent terminals in both the muscle wall and the mucosa of the GI tract exhibit age-related structural changes. In aged animals, both of the vagal terminal types examined, namely intraganglionic laminar endings and villus afferents, exhibit dystrophic or regressive morphological changes. These neuropathies are associated with age-related changes in the structural integrity of the target organs of the affected afferents, suggesting that local changes in trophic environment may give rise to the aging of GI innervation. Given the clinical relevance of GI tract aging, a more complete understanding both of how aging alters the innervation of the gut and of how such changes might be mitigated should be made research priorities.
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Affiliation(s)
- Robert J Phillips
- Purdue University, Ingestive Behavior Research Center, Department of Psychological Sciences, West Lafayette, IN 47907-2081, USA.
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46
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Abstract
Evidence for the regulation of body energy is reviewed from the homeostatic perspective of Claude Bernard and Walter Cannon. The complementary roles of food intake and energy expenditure in the maintenance and defense of energy balance are considered. Particular attention is paid to the roles adjustments in energy expenditure play in this process and to recent investigations identifying their metabolic underpinnings. This is followed by a consideration of the many newly identified signals of body energy status and the pathways and feedback loops they utilize to inform the central regulating system. Finally, various naturally occurring and experimentally induced alterations in the regulated level of body energy are described and discussed. It is concluded that, though early investigators did not expressly consider energy a regulated feature of the milieu interieur, more recent research has provided a sound basis for judging the regulation of body energy to be another homeostatic process.
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Ratcliffe EM, D'Autréaux F, Gershon MD. Laminin terminates the Netrin/DCC mediated attraction of vagal sensory axons. Dev Neurobiol 2008; 68:960-71. [PMID: 18418846 DOI: 10.1002/dneu.20634] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Vagal sensory axons navigate to specific sites in the bowel during fetal life. Netrin/deleted in colorectal cancer (DCC) were found to mediate the attraction of vagal sensory axons to the fetal mouse gut. We tested the hypothesis that laminin-111 can reverse the chemoattractive effects of netrin and act as a stop signal for vagal sensory axons. Laminin-111-expressing cells were located in the E12 and E16 mouse bowel by in situ hybridization. At E12, these cells extended centrifugally from the endoderm; by E16, laminin-111 expressing cells were found in the mucosa and outer gut mesenchyme. A similar pattern was seen in preparations of E13 and E15 mouse gut labeled with antibodies to laminin. Application of DiI to nodose ganglia identified vagal sensory axons growing into the fetal bowel. These terminals were found to avoid concentrations of laminin or to terminate at laminin-delimited boundaries. Soluble laminin inhibited the preferential growth of nodose neurites toward netrin-secreting cells (p < 0.01). This effect was mimicked by a peptide, YIGSR, a sequence within the beta1 chain of laminin-111 (p < 0.004) and antagonized by a peptide, IKVAV, a sequence within the alpha1 chain of laminin-111. Antibodies to beta1-integrins were also able to reverse the inhibitive effects of laminin and restore the attraction of nodose neurites towards netrin-1-secreting cells. Soluble laminin inhibited the preferential growth of nodose neurites toward a cocultured explant of foregut. These findings suggest that laminin terminates the attraction of vagal sensory axons towards sources of netrin in the developing bowel.
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Weiss R. Devices for the treatment of obesity: will understanding the physiology of satiety unravel new targets for intervention? J Diabetes Sci Technol 2008; 2:501-8. [PMID: 19885218 PMCID: PMC2769726 DOI: 10.1177/193229680800200323] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The rise in the prevalence of obesity in the last few decades and its growing impact on health has driven the scientific community to investigate the physiological basis of energy homeostasis and mechanisms of satiety, and seek targets for intervention against this burgeoning epidemic. Recent findings highlight the role of gut-derived, hormonal signals in the regulation of satiety. These hormones act together with the dense and intricate enteric nervous system to coordinate and regulate gastrointestinal satiety signals, motility, and digestive processes. Bariatric surgical approaches attempt to take advantage of these mechanisms to facilitate early satiety and weight loss. Some of these procedures, by altering the anatomical structure of the upper gastrointestinal tract, also modify the hormonal response to food. Similarly, devices such as volume-occupying elements and nerve stimulators attempt to alter the gastrointestinal milieu in a manner that will ultimately lead to long-term weight loss. Novel surgical, endoscopic, and device-oriented methodologies seem to be promising approaches to treat obesity, yet further research is needed to appreciate their long-term effect.
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Affiliation(s)
- Ram Weiss
- Department of Human Nutrition and Metabolism, and the Department of Pediatrics, Hebrew University Medical School, Jerusalem, Israel.
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Powley TL, Wang XY, Fox EA, Phillips RJ, Liu LWC, Huizinga JD. Ultrastructural evidence for communication between intramuscular vagal mechanoreceptors and interstitial cells of Cajal in the rat fundus. Neurogastroenterol Motil 2008; 20:69-79. [PMID: 17931338 DOI: 10.1111/j.1365-2982.2007.00990.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
To assess whether afferent vagal intramuscular arrays (IMAs), putative gastrointestinal mechanoreceptors, form contacts with interstitial cells of Cajal of the intramuscular type (ICC-IM) and to describe any such contacts, electron microscopic analyses were performed on the external muscle layers of the fundus containing dextran-labelled diaminobenzidin (DAB)-stained IMAs. Special staining and embedding techniques were developed to preserve ultrastructural features. Within the muscle layers, IMA varicosities were observed in nerve bundles traversing major septa without contact with ICC-IM, contacting unlabelled neurites and glial cells. IMA varicosities were encountered in minor septa in contact with ICC-IM which were not necessarily in close contact with muscle cells. In addition, IMA varicosities were observed within muscle bundles in close contact with ICC-IM which were in gap junction contact with muscle cells. IMAs formed varicosities containing predominantly small agranular vesicles, occasionally large granular vesicles and prejunctional thickenings in apposition to ICC-IM processes, indicating communication between ICC and IMA via synapse-like contacts. Taken together, these different morphological features are consistent with a hypothesized mechanoreceptor role for IMA-ICC complexes. Intraganglionic laminar ending varicosities contacted neuronal somata and dendrites in the myenteric plexus of the fundus, but no contacts with ICC associated with Auerbach's plexus were encountered.
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Affiliation(s)
- T L Powley
- Department of Psychological Sciences, Purdue University, West Lafayette, IN, USA
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Phillips RJ, Powley TL. Innervation of the gastrointestinal tract: patterns of aging. Auton Neurosci 2007; 136:1-19. [PMID: 17537681 PMCID: PMC2045700 DOI: 10.1016/j.autneu.2007.04.005] [Citation(s) in RCA: 189] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2006] [Revised: 04/10/2007] [Accepted: 04/24/2007] [Indexed: 12/12/2022]
Abstract
The gastrointestinal (GI) tract is innervated by intrinsic enteric neurons and by extrinsic projections, including sympathetic and parasympathetic efferents as well as visceral afferents, all of which are compromised by age to different degrees. In the present review, we summarize and illustrate key structural changes in the aging innervation of the gut, and suggest a provisional list of the general patterns of aging of the GI innervation. For example, age-related neuronal losses occur in both the myenteric plexus and submucosal plexus of the intestines. These losses start in adulthood, increase over the rest of the life span, and are specific to cholinergic neurons. Parallel losses of enteric glia also occur. The extent of neuronal and glial loss varies along an oral-to-anal gradient, with the more distal GI tract being more severely affected. Additionally, with aging, dystrophic axonal swellings and markedly dilated varicosities progressively accumulate in the sympathetic, vagal, dorsal root, and enteric nitrergic innervation of the gut. These dramatic and consistent patterns of neuropathy that characterize the aging autonomic nervous system of the GI tract are candidate mechanisms for some of the age-related declines in function evidenced in the elderly.
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Affiliation(s)
- Robert J Phillips
- Purdue University, Department of Psychological Sciences, 703 Third Street, West Lafayette, IN 47907-2081, USA.
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