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Neyens DM, Brenner L, Calkins R, Winzenried ET, Ritter RC, Appleyard SM. CCK-sensitive C fibers activate NTS leptin receptor-expressing neurons via NMDA receptors. Am J Physiol Regul Integr Comp Physiol 2024; 326:R383-R400. [PMID: 38105761 DOI: 10.1152/ajpregu.00238.2022] [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: 09/27/2022] [Revised: 12/07/2023] [Accepted: 12/07/2023] [Indexed: 12/19/2023]
Abstract
The hormone leptin reduces food intake through actions in the peripheral and central nervous systems, including in the hindbrain nucleus of the solitary tract (NTS). The NTS receives viscerosensory information via vagal afferents, including information from the gastrointestinal tract, which is then relayed to other central nervous system (CNS) sites critical for control of food intake. Leptin receptors (lepRs) are expressed by a subpopulation of NTS neurons, and knockdown of these receptors increases both food intake and body weight. Recently, we demonstrated that leptin increases vagal activation of lepR-expressing neurons via increased NMDA receptor (NMDAR) currents, thereby potentiating vagally evoked firing. Furthermore, chemogenetic activation of these neurons was recently shown to inhibit food intake. However, the vagal inputs these neurons receive had not been characterized. Here we performed whole cell recordings in brain slices taken from lepRCre × floxedTdTomato mice and found that lepR neurons of the NTS are directly activated by monosynaptic inputs from C-type afferents sensitive to the transient receptor potential vanilloid type 1 (TRPV1) agonist capsaicin. CCK administered onto NTS slices stimulated spontaneous glutamate release onto lepR neurons and induced action potential firing, an effect mediated by CCKR1. Interestingly, NMDAR activation contributed to the current carried by spontaneous excitatory postsynaptic currents (EPSCs) and enhanced CCK-induced firing. Peripheral CCK also increased c-fos expression in these neurons, suggesting they are activated by CCK-sensitive vagal afferents in vivo. Our results indicate that the majority of NTS lepR neurons receive direct inputs from CCK-sensitive C vagal-type afferents, with both peripheral and central CCK capable of activating these neurons and NMDARs able to potentiate these effects.
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Affiliation(s)
- Drew M Neyens
- Department of Integrated Physiology and Neuroscience, Washington State University, Pullman, Washington, United States
| | - Lynne Brenner
- Department of Integrated Physiology and Neuroscience, Washington State University, Pullman, Washington, United States
| | - Rowan Calkins
- Department of Integrated Physiology and Neuroscience, Washington State University, Pullman, Washington, United States
| | - Eric T Winzenried
- Department of Integrated Physiology and Neuroscience, Washington State University, Pullman, Washington, United States
| | - Robert C Ritter
- Department of Integrated Physiology and Neuroscience, Washington State University, Pullman, Washington, United States
| | - Suzanne M Appleyard
- Department of Integrated Physiology and Neuroscience, Washington State University, Pullman, Washington, United States
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2
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McVey Neufeld KA, Mao YK, West CL, Ahn M, Hameed H, Iwashita E, Stanisz AM, Forsythe P, Barbut D, Zasloff M, Kunze WA. Squalamine reverses age-associated changes of firing patterns of myenteric sensory neurons and vagal fibres. Commun Biol 2024; 7:80. [PMID: 38200107 PMCID: PMC10781697 DOI: 10.1038/s42003-023-05623-2] [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: 05/01/2023] [Accepted: 11/21/2023] [Indexed: 01/12/2024] Open
Abstract
Vagus nerve signaling is a key component of the gut-brain axis and regulates diverse physiological processes that decline with age. Gut to brain vagus firing patterns are regulated by myenteric intrinsic primary afferent neuron (IPAN) to vagus neurotransmission. It remains unclear how IPANs or the afferent vagus age functionally. Here we identified a distinct ageing code in gut to brain neurotransmission defined by consistent differences in firing rates, burst durations, interburst and intraburst firing intervals of IPANs and the vagus, when comparing young and aged neurons. The aminosterol squalamine changed aged neurons firing patterns to a young phenotype. In contrast to young neurons, sertraline failed to increase firing rates in the aged vagus whereas squalamine was effective. These results may have implications for improved treatments involving pharmacological and electrical stimulation of the vagus for age-related mood and other disorders. For example, oral squalamine might be substituted for or added to sertraline for the aged.
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Affiliation(s)
| | - Yu-Kang Mao
- Brain-Body Institute, McMaster University, Hamilton, ON, Canada
| | - Christine L West
- Brain-Body Institute, McMaster University, Hamilton, ON, Canada
- Department of Biology, McMaster University, Hamilton, ON, Canada
| | - Matthew Ahn
- Brain-Body Institute, McMaster University, Hamilton, ON, Canada
| | - Hashim Hameed
- Brain-Body Institute, McMaster University, Hamilton, ON, Canada
| | - Eiko Iwashita
- Brain-Body Institute, McMaster University, Hamilton, ON, Canada
| | | | - Paul Forsythe
- Department of Medicine, 569 Heritage Medical Research Center, University of Alberta, Edmonton, AB, Canada
| | | | - Michael Zasloff
- Enterin, Inc., Philadelphia, PA, USA.
- MedStar-Georgetown Transplant Institute, Georgetown University School of Medicine, Washington, DC, USA.
| | - Wolfgang A Kunze
- Brain-Body Institute, McMaster University, Hamilton, ON, Canada.
- Department of Biology, McMaster University, Hamilton, ON, Canada.
- Department of Psychiatry and Behavioural Neurosciences, McMaster University, Hamilton, ON, Canada.
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3
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Sundaresan S, Johnson C, Dixon KB, Dole M, Kilkelly D, Antoun J, Flynn CR, Abumrad NN, Tamboli R. Intraduodenal nutrient infusion differentially alters intestinal nutrient sensing, appetite, and satiety responses in lean and obese subjects. Am J Clin Nutr 2023; 118:646-656. [PMID: 37661107 PMCID: PMC10517208 DOI: 10.1016/j.ajcnut.2023.06.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 06/02/2023] [Accepted: 06/12/2023] [Indexed: 09/05/2023] Open
Abstract
BACKGROUND Intestinal nutrient sensing regulates food intake and energy metabolism by acting locally and relaying nutritional status to the brain. It is unclear whether these mechanisms are altered in obese humans. OBJECTIVES We aimed to investigate differences in duodenal nutrient sensing in humans with or without obesity and the effects of transiently blocking vagal transmission on nutrient sensing, hunger, and appetite. METHODS In a single-blinded, randomized, cross-over design, subjects with or without obesity (n = 14 and n = 11, respectively) were infused intraduodenally with saline or a combination of glucose and oleic acid for 90 min (glucose load: 22.5 g, 1 kcal/min; oleic acid load: 10 g, 1 kcal/min) in the presence or absence of local anesthetic (benzocaine). Blood was sampled at 10-min intervals (120-240 min) and 15-min intervals until termination of the study for measurements of gut hormones, insulin, leptin, and C-peptide. Hunger and satiety sensations were scored using the visual analog scale, and hepatic glucose production and glucose oxidation rates were measured. RESULTS Duodenal nutrient infusion in lean subjects led to a 65% drop in acyl ghrelin release and robustly increased cholecystokinin 8 (CCK-8) release (65%; P = 0.023); benzocaine infusion delayed this response (2-factor repeated-measures analysis of variance, P = 0.0065). In contrast, subjects with obesity had significantly blunted response to nutrient infusion, and no further effects were observed with benzocaine. Additionally, significant delays were observed in peptide YY (3-36), pancreatic polypeptide, glucose inhibitory peptide, and glucagon-like peptide 1 (7-36) response. No significant interactions were found between body mass index (BMI) or baseline hormone levels and areas under the curve for hormones except CCK-8 (BMI, P = 0.018; baseline CCK, P = 0.013). Nutrient-induced hunger and satiety sensations were impeded by benzocaine only in the lean cohort. Hunger and satiety sensations in subjects with obesity were not responsive to nutrient entry into the duodenum, and no additional effects were observed by blocking neural signaling. CONCLUSION Nutrient-induced gut hormone release and response to transient vagal blockade are significantly blunted in subjects with obesity. This trial was registered at clinicaltrials.org as NCT02537314.
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Affiliation(s)
- Sinju Sundaresan
- Department of Physiology, Midwestern University, Downers Grove, IL; Department of Surgery, Vanderbilt University Medical Center, Nashville, TN.
| | - Connor Johnson
- Department of Surgery, Vanderbilt University Medical Center, Nashville, TN
| | - Kala B Dixon
- Department of Surgery, Vanderbilt University Medical Center, Nashville, TN
| | - Michael Dole
- Department of Surgery, Vanderbilt University Medical Center, Nashville, TN
| | - Donna Kilkelly
- Department of Surgery, Vanderbilt University Medical Center, Nashville, TN
| | - Joseph Antoun
- Department of Surgery, Vanderbilt University Medical Center, Nashville, TN
| | - Charles Robb Flynn
- Department of Surgery, Vanderbilt University Medical Center, Nashville, TN
| | - Naji N Abumrad
- Department of Surgery, Vanderbilt University Medical Center, Nashville, TN
| | - Robyn Tamboli
- Department of Surgery, Vanderbilt University Medical Center, Nashville, TN
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4
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Li H, Page AJ. Altered Vagal Signaling and Its Pathophysiological Roles in Functional Dyspepsia. Front Neurosci 2022; 16:858612. [PMID: 35527812 PMCID: PMC9072791 DOI: 10.3389/fnins.2022.858612] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Accepted: 03/28/2022] [Indexed: 11/20/2022] Open
Abstract
The vagus nerve is crucial in the bidirectional communication between the gut and the brain. It is involved in the modulation of a variety of gut and brain functions. Human studies indicate that the descending vagal signaling from the brain is impaired in functional dyspepsia. Growing evidence indicate that the vagal signaling from gut to brain may also be altered, due to the alteration of a variety of gut signals identified in this disorder. The pathophysiological roles of vagal signaling in functional dyspepsia is still largely unknown, although some studies suggested it may contribute to reduced food intake and gastric motility, increased psychological disorders and pain sensation, nausea and vomiting. Understanding the alteration in vagal signaling and its pathophysiological roles in functional dyspepsia may provide information for new potential therapeutic treatments of this disorder. In this review, we summarize and speculate possible alterations in vagal gut-to-brain and brain-to-gut signaling and the potential pathophysiological roles in functional dyspepsia.
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Affiliation(s)
- Hui Li
- Vagal Afferent Research Group, Adelaide Medical School, The University of Adelaide, Adelaide, SA, Australia
- Nutrition, Diabetes and Gut Health, Lifelong Health Theme, South Australian Health and Medical Research Institute, Adelaide, SA, Australia
- *Correspondence: Hui Li,
| | - Amanda J. Page
- Vagal Afferent Research Group, Adelaide Medical School, The University of Adelaide, Adelaide, SA, Australia
- Nutrition, Diabetes and Gut Health, Lifelong Health Theme, South Australian Health and Medical Research Institute, Adelaide, SA, Australia
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5
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West CL, Neufeld KAM, Mao YK, Stanisz AM, Forsythe P, Bienenstock J, Barbut D, Zasloff M, Kunze WA. Identification of SSRI-evoked antidepressant sensory signals by decoding vagus nerve activity. Sci Rep 2021; 11:21130. [PMID: 34702901 PMCID: PMC8548562 DOI: 10.1038/s41598-021-00615-w] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Accepted: 10/11/2021] [Indexed: 12/25/2022] Open
Abstract
The vagus nerve relays mood-altering signals originating in the gut lumen to the brain. In mice, an intact vagus is required to mediate the behavioural effects of both intraluminally applied selective serotonin reuptake inhibitors and a strain of Lactobacillus with antidepressant-like activity. Similarly, the prodepressant effect of lipopolysaccharide is vagus nerve dependent. Single vagal fibres are broadly tuned to respond by excitation to both anti- and prodepressant agents, but it remains unclear how neural responses encode behaviour-specific information. Here we demonstrate using ex vivo experiments that for single vagal fibres within the mesenteric neurovascular bundle supplying the mouse small intestine, a unique neural firing pattern code is common to both chemical and bacterial vagus-dependent antidepressant luminal stimuli. This code is qualitatively and statistically discernible from that evoked by lipopolysaccharide, a non-vagus-dependent antidepressant or control non-antidepressant Lactobacillus strain and are not affected by sex status. We found that all vagus dependent antidepressants evoked a decrease in mean spike interval, increase in spike burst duration, decrease in gap duration between bursts and increase in intra-burst spike intervals. Our results offer a novel neuronal electrical perspective as one explanation for mechanisms of action of gut-derived vagal dependent antidepressants. We expect that our ex vivo individual vagal fibre recording model will improve the design and operation of new, extant electroceutical vagal stimulation devices currently used to treat major depression. Furthermore, use of this vagal antidepressant code should provide a valuable screening tool for novel potential oral antidepressant candidates in preclinical animal models.
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Affiliation(s)
- Christine L West
- Brain-Body Institute, St. Joseph's Healthcare, Hamilton, ON, Canada.,Department of Biology, McMaster University, Hamilton, ON, Canada
| | - Karen-Anne McVey Neufeld
- Brain-Body Institute, St. Joseph's Healthcare, Hamilton, ON, Canada.,Department of Pathology and Molecular Medicine, McMaster University, Hamilton, ON, Canada
| | - Yu-Kang Mao
- Brain-Body Institute, St. Joseph's Healthcare, Hamilton, ON, Canada
| | - Andrew M Stanisz
- Brain-Body Institute, St. Joseph's Healthcare, Hamilton, ON, Canada
| | - Paul Forsythe
- Brain-Body Institute, St. Joseph's Healthcare, Hamilton, ON, Canada.,Department of Medicine, McMaster University, Hamilton, ON, Canada.,Firestone Institute for Respiratory Health, St. Joseph's Healthcare, Hamilton, ON, Canada
| | - John Bienenstock
- Brain-Body Institute, St. Joseph's Healthcare, Hamilton, ON, Canada.,Department of Pathology and Molecular Medicine, McMaster University, Hamilton, ON, Canada.,Department of Medicine, McMaster University, Hamilton, ON, Canada
| | | | - Michael Zasloff
- Enterin, Inc., Philadelphia, PA, USA.,MedStar-Georgetown Transplant Institute, Georgetown University School of Medicine, Washington, DC, USA
| | - Wolfgang A Kunze
- Brain-Body Institute, St. Joseph's Healthcare, Hamilton, ON, Canada. .,Department of Biology, McMaster University, Hamilton, ON, Canada. .,Department of Psychiatry and Behavioural Neurosciences, McMaster University, Hamilton, ON, Canada.
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6
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O'Brien R, Buckley MM, O'Malley D. Divergent effects of exendin-4 and interleukin-6 on rat colonic secretory and contractile activity are associated with changes in regional vagal afferent signaling. Neurogastroenterol Motil 2021; 33:e14160. [PMID: 33945195 DOI: 10.1111/nmo.14160] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Revised: 03/10/2021] [Accepted: 03/24/2021] [Indexed: 12/13/2022]
Abstract
BACKGROUND The pro-inflammatory cytokine, interleukin (IL)-6 is elevated in individuals with the functional bowel disorder, irritable bowel syndrome (IBS). IL-6 can independently modify intestinal secreto-motor function, thereby contributing to IBS pathophysiology. Additionally, hormonal changes may underlie symptom flares. Post-prandial exacerbation of IBS symptoms has been linked to secretion of the incretin hormone, glucagon-like peptide-1 (GLP-1), which can also influence colonic secreto-motor activity. This study aimed to ascertain if the effects of GLP-1 on colonic secretory and contractile activity was impacted by elevated IL-6 levels and if sensory signals regarding such changes were reflected in altered vagal afferent activity. METHODS Colonic secretory currents and circular muscle contractile activity was investigated in Sprague Dawley rats using Ussing chamber and organ bath electrophysiology. Regional afferent signaling was assessed using extracellular electrophysiological recordings from colonic vagal afferents. KEY RESULTS Application of the GLP-1 receptor agonist, exendin-4 (Ex-4) in the presence of IL-6 potentiated colonic secretory currents and transepithelial resistance. Vagal afferent fibers originating in the submucosal layer exhibited larger responses to Ex-4 when IL-6 was also present. In contrast, co-application of Ex-4 and IL-6 to gut-bath chambers suppressed circular muscle contractile activity. The activity in extrinsic afferents originating in the colonic myenteric layer was similarly suppressed. CONCLUSIONS & INFERENCES Application of Ex-4 in the presence of IL-6 had divergent modulatory effects on colonic secretion and contractile activity. Similar patterns were observed in vagal afferent signaling originating in the submucosal and myenteric neuronal layers, indicating regional afferent activity reflected immune- and endocrine-mediated changes in colonic function.
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Affiliation(s)
- Rebecca O'Brien
- Department of Physiology, University College Cork, Cork, Ireland
| | - Maria M Buckley
- Department of Physiology, University College Cork, Cork, Ireland
| | - Dervla O'Malley
- Department of Physiology, University College Cork, Cork, Ireland.,APC Microbiome Ireland, University College Cork, Cork, Ireland
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7
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Borgmann D, Ciglieri E, Biglari N, Brandt C, Cremer AL, Backes H, Tittgemeyer M, Wunderlich FT, Brüning JC, Fenselau H. Gut-brain communication by distinct sensory neurons differently controls feeding and glucose metabolism. Cell Metab 2021; 33:1466-1482.e7. [PMID: 34043943 PMCID: PMC8280952 DOI: 10.1016/j.cmet.2021.05.002] [Citation(s) in RCA: 76] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Revised: 02/23/2021] [Accepted: 05/03/2021] [Indexed: 01/26/2023]
Abstract
Sensory neurons relay gut-derived signals to the brain, yet the molecular and functional organization of distinct populations remains unclear. Here, we employed intersectional genetic manipulations to probe the feeding and glucoregulatory function of distinct sensory neurons. We reconstruct the gut innervation patterns of numerous molecularly defined vagal and spinal afferents and identify their downstream brain targets. Bidirectional chemogenetic manipulations, coupled with behavioral and circuit mapping analysis, demonstrated that gut-innervating, glucagon-like peptide 1 receptor (GLP1R)-expressing vagal afferents relay anorexigenic signals to parabrachial nucleus neurons that control meal termination. Moreover, GLP1R vagal afferent activation improves glucose tolerance, and their inhibition elevates blood glucose levels independent of food intake. In contrast, gut-innervating, GPR65-expressing vagal afferent stimulation increases hepatic glucose production and activates parabrachial neurons that control normoglycemia, but they are dispensable for feeding regulation. Thus, distinct gut-innervating sensory neurons differentially control feeding and glucoregulatory neurocircuits and may provide specific targets for metabolic control.
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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; Translational Neurocircuitry Group, Max Planck Institute for Metabolism Research, Gleueler Strasse 50, 50931 Cologne, Germany; Center for Anatomy II, Neuroanatomy, University Hospital Cologne, Joseph-Stelzmann Str. 9, 50937 Cologne, Germany
| | - Elisa Ciglieri
- 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
| | - Nasim Biglari
- Max Planck Institute for Metabolism Research, Department of Neuronal Control of Metabolism, Gleueler Strasse 50, 50931 Cologne, Germany
| | - Claus Brandt
- Max Planck Institute for Metabolism Research, Department of Neuronal Control of Metabolism, Gleueler Strasse 50, 50931 Cologne, Germany
| | - Anna Lena Cremer
- Max Planck Institute for Metabolism Research, Department of Neuronal Control of Metabolism, Gleueler Strasse 50, 50931 Cologne, Germany
| | - Heiko Backes
- Max Planck Institute for Metabolism Research, Department of Neuronal Control of Metabolism, Gleueler Strasse 50, 50931 Cologne, Germany
| | - Marc Tittgemeyer
- Translational Neurocircuitry Group, Max Planck Institute for Metabolism Research, Gleueler Strasse 50, 50931 Cologne, Germany; Excellence Cluster on Cellular Stress Responses in Aging Associated Diseases (CECAD), University of Cologne, Joseph-Stelzmann-Straße 26, Cologne 50931, Germany
| | - F Thomas Wunderlich
- Center for Endocrinology, Diabetes and Preventive Medicine (CEDP), University Hospital Cologne, Kerpener Strasse 26, 50937 Cologne, Germany; Max Planck Institute for Metabolism Research, Department of Neuronal Control of Metabolism, Gleueler Strasse 50, 50931 Cologne, Germany; Excellence Cluster on Cellular Stress Responses in Aging Associated Diseases (CECAD), University of Cologne, Joseph-Stelzmann-Straße 26, Cologne 50931, Germany; Center of Molecular Medicine Cologne (CMMC), University of Cologne, Robert-Koch-Straße 21, 50931 Cologne, Germany
| | - Jens C Brüning
- Center for Endocrinology, Diabetes and Preventive Medicine (CEDP), University Hospital Cologne, Kerpener Strasse 26, 50937 Cologne, Germany; Max Planck Institute for Metabolism Research, Department of Neuronal Control of Metabolism, Gleueler Strasse 50, 50931 Cologne, Germany; Excellence Cluster on Cellular Stress Responses in Aging Associated Diseases (CECAD), University of Cologne, Joseph-Stelzmann-Straße 26, Cologne 50931, Germany; Center of Molecular Medicine Cologne (CMMC), University of Cologne, Robert-Koch-Straße 21, 50931 Cologne, Germany
| | - 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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8
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Biddinger JE, Lazarenko RM, Scott MM, Simerly R. Leptin suppresses development of GLP-1 inputs to the paraventricular nucleus of the hypothalamus. eLife 2020; 9:59857. [PMID: 33206596 PMCID: PMC7673779 DOI: 10.7554/elife.59857] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Accepted: 11/06/2020] [Indexed: 02/06/2023] Open
Abstract
The nucleus of the solitary tract (NTS) is critical for the central integration of signals from visceral organs and contains preproglucagon (PPG) neurons, which express leptin receptors in the mouse and send direct projections to the paraventricular nucleus of the hypothalamus (PVH). Here, we visualized projections of PPG neurons in leptin-deficient Lepob/ob mice and found that projections from PPG neurons are elevated compared with controls, and PPG projections were normalized by targeted rescue of leptin receptors in LepRbTB/TB mice, which lack functional neuronal leptin receptors. Moreover, Lepob/ob and LepRbTB/TB mice displayed increased levels of neuronal activation in the PVH following vagal stimulation, and whole-cell patch recordings of GLP-1 receptor-expressing PVH neurons revealed enhanced excitatory neurotransmission, suggesting that leptin acts cell autonomously to suppress representation of excitatory afferents from PPG neurons, thereby diminishing the impact of visceral sensory information on GLP-1 receptor-expressing neurons in the PVH.
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Affiliation(s)
- Jessica E Biddinger
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, United States
| | - Roman M Lazarenko
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, United States
| | - Michael M Scott
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, United States
| | - Richard Simerly
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, United States
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9
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West CL, Mao YK, Delungahawatta T, Amin JY, Farhin S, McQuade RM, Diwakarla S, Pustovit R, Stanisz AM, Bienenstock J, Barbut D, Zasloff M, Furness JB, Kunze WA. Squalamine Restores the Function of the Enteric Nervous System in Mouse Models of Parkinson's Disease. JOURNAL OF PARKINSONS DISEASE 2020; 10:1477-1491. [PMID: 32925094 DOI: 10.3233/jpd-202076] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
BACKGROUND Parkinson's disease (PD) is a progressive neurodegenerative disorder thought to be caused by accumulation of α-synuclein (α-syn) within the brain, autonomic nerves, and the enteric nervous system (ENS). Involvement of the ENS in PD often precedes the onset of the classic motor signs of PD by many years at a time when severe constipation represents a major morbidity. Studies conducted in vitro and in vivo, have shown that squalamine, a zwitterionic amphipathic aminosterol, originally isolated from the liver of the dogfish shark, effectively displaces membrane-bound α-syn. OBJECTIVE Here we explore the electrophysiological effect of squalamine on the gastrointestinal (GI) tract of mouse models of PD engineered to express the highly aggregating A53T human α-syn mutant. METHODS GI motility and in vivo response to oral squalamine in PD model mice and controls were assessed using an in vitro tissue motility protocol and via fecal pellet output. Vagal afferent response to squalamine was measured using extracellular mesenteric nerve recordings from the jejunum. Whole cell patch clamp was performed to measure response to squalamine in the myenteric plexus. RESULTS Squalamine effectively restores disordered colonic motility in vivo and within minutes of local application to the bowel. We show that topical squalamine exposure to intrinsic primary afferent neurons (IPANs) of the ENS rapidly restores excitability. CONCLUSION These observations may help to explain how squalamine may promote gut propulsive activity through local effects on IPANs in the ENS, and further support its possible utility in the treatment of constipation in patients with PD.
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Affiliation(s)
- Christine L West
- Brain-Body Institute, St. Joseph's Healthcare, Hamilton, ON, Canada.,Department of Biology, McMaster University, Hamilton, ON, Canada
| | - Yu-Kang Mao
- Brain-Body Institute, St. Joseph's Healthcare, Hamilton, ON, Canada
| | | | - Jessica Y Amin
- Brain-Body Institute, St. Joseph's Healthcare, Hamilton, ON, Canada
| | - Sohana Farhin
- Brain-Body Institute, St. Joseph's Healthcare, Hamilton, ON, Canada
| | - Rachel M McQuade
- Department of Anatomy and Neuroscience, University of Melbourne, and the Florey Institute of Neuroscience and Mental Health, Parkville, VIC, Australia
| | - Shanti Diwakarla
- Department of Anatomy and Neuroscience, University of Melbourne, and the Florey Institute of Neuroscience and Mental Health, Parkville, VIC, Australia
| | - Ruslan Pustovit
- Department of Anatomy and Neuroscience, University of Melbourne, and the Florey Institute of Neuroscience and Mental Health, Parkville, VIC, Australia
| | - Andrew M Stanisz
- Brain-Body Institute, St. Joseph's Healthcare, Hamilton, ON, Canada
| | - John Bienenstock
- Brain-Body Institute, St. Joseph's Healthcare, Hamilton, ON, Canada.,Department of Pathology and Molecular Medicine, McMaster University, Hamilton, ON, Canada.,Department of Medicine, McMaster University, Hamilton, ON, Canada
| | | | - Michael Zasloff
- Enterin, Inc., Philadelphia, PA, USA.,MedStar-Georgetown Transplant Institute, Georgetown University School of Medicine, Washington, DC, USA
| | - John B Furness
- Department of Anatomy and Neuroscience, University of Melbourne, and the Florey Institute of Neuroscience and Mental Health, Parkville, VIC, Australia
| | - Wolfgang A Kunze
- Brain-Body Institute, St. Joseph's Healthcare, Hamilton, ON, Canada.,Department of Biology, McMaster University, Hamilton, ON, Canada.,Department of Psychiatry and Behavioural Neurosciences, McMaster University, Hamilton, ON, Canada
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10
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Buckley MM, O'Brien R, Brosnan E, Ross RP, Stanton C, Buckley JM, O'Malley D. Glucagon-Like Peptide-1 Secreting L-Cells Coupled to Sensory Nerves Translate Microbial Signals to the Host Rat Nervous System. Front Cell Neurosci 2020; 14:95. [PMID: 32425756 PMCID: PMC7203556 DOI: 10.3389/fncel.2020.00095] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Accepted: 03/30/2020] [Indexed: 02/06/2023] Open
Abstract
An intact gut epithelium preserves the immunological exclusion of “non-self” entities in the external environment of the gut lumen. Nonetheless, information flows continuously across this interface, with the host immune, endocrine, and neural systems all involved in monitoring the luminal environment of the gut. Both pathogenic and commensal gastrointestinal (GI) bacteria can modulate centrally-regulated behaviors and brain neurochemistry and, although the vagus nerve has been implicated in the microbiota-gut-brain signaling axis, the cellular and molecular machinery that facilitates this communication is unclear. Studies were carried out in healthy Sprague–Dawley rats to understand cross-barrier communication in the absence of disease. A novel colonic-nerve electrophysiological technique was used to examine gut-to-brain vagal signaling by bacterial products. Calcium imaging and immunofluorescent labeling were used to explore the activation of colonic submucosal neurons by bacterial products. The findings demonstrate that the neuromodulatory molecule, glucagon-like peptide-1 (GLP-1), secreted by colonic enteroendocrine L-cells in response to the bacterial metabolite, indole, stimulated colonic vagal afferent activity. At a local level indole modified the sensitivity of submucosal neurons to GLP-1. These findings elucidate a cellular mechanism by which sensory L-cells act as cross-barrier signal transducers between microbial products in the gut lumen and the host peripheral nervous system.
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Affiliation(s)
- Maria M Buckley
- Department of Physiology, University College Cork, Cork, Ireland.,APC Microbiome Ireland, University College Cork, Cork, Ireland
| | - Rebecca O'Brien
- Department of Physiology, University College Cork, Cork, Ireland
| | - Eilish Brosnan
- Department of Physiology, University College Cork, Cork, Ireland
| | - R Paul Ross
- APC Microbiome Ireland, University College Cork, Cork, Ireland.,College of Science, Engineering and Food Science, University College Cork, Cork, Ireland.,Teagasc Food Research Centre, Cork, Ireland
| | - Catherine Stanton
- APC Microbiome Ireland, University College Cork, Cork, Ireland.,Teagasc Food Research Centre, Cork, Ireland
| | - Julliette M Buckley
- Department of Surgery, University College Cork, Cork, Ireland.,Mater Private Hospital, Cork, Ireland
| | - Dervla O'Malley
- Department of Physiology, University College Cork, Cork, Ireland.,APC Microbiome Ireland, University College Cork, Cork, Ireland
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11
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West CL, Amin JY, Farhin S, Stanisz AM, Mao YK, Kunze WA. Colonic Motility and Jejunal Vagal Afferent Firing Rates Are Decreased in Aged Adult Male Mice and Can Be Restored by an Aminosterol. Front Neurosci 2019; 13:955. [PMID: 31551703 PMCID: PMC6746984 DOI: 10.3389/fnins.2019.00955] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Accepted: 08/23/2019] [Indexed: 12/19/2022] Open
Abstract
There is a general decline in gastrointestinal function in old age including decreased intestinal motility, sensory signaling, and afferent sensitivity. There is also increased prevalence of significant constipation in aged populations. We hypothesized this may be linked to reduced colonic motility and alterations in vagal-gut-brain sensory signaling. Using in vitro preparations from young (3 months) and old (18–24 months) male CD1 mice we report functional age-related differences in colonic motility and jejunal mesenteric afferent firing. Furthermore, we tested the effect of the aminosterol squalamine on colonic motility and jejunal vagal firing rate. Old mice had significantly reduced velocity of colonic migrating motor complexes (MMC) by 27% compared to young mice (p = 0.0161). Intraluminal squalamine increased colonic MMC velocity by 31% in old mice (p = 0.0150), which also had significantly reduced mesenteric afferent single-unit firing rates from the jejunum by 51% (p < 0.0001). The jejunal vagal afferent firing rate was reduced in aged mice by 62% (p = 0.0004). While the time to peak response to squalamine was longer in old mice compared to young mice (18.82 ± 1.37 min vs. 12.95 ± 0.99 min; p = 0.0182), it significantly increased vagal afferent firing rate by 36 and 56% in young and old mice, respectively (p = 0.0006, p = 0.0013). Our results show for the first time that the jejunal vagal afferent firing rate is reduced in aged-mice. They also suggest that there is translational potential for the therapeutic use of squalamine in the treatment of age-related constipation and dysmotility.
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Affiliation(s)
- Christine L West
- St. Joseph's Healthcare, The Brain-Body Institute, McMaster University, Hamilton, ON, Canada.,Department of Biology, McMaster University, Hamilton, ON, Canada
| | - Jessica Y Amin
- St. Joseph's Healthcare, The Brain-Body Institute, McMaster University, Hamilton, ON, Canada
| | - Sohana Farhin
- St. Joseph's Healthcare, The Brain-Body Institute, McMaster University, Hamilton, ON, Canada
| | - Andrew M Stanisz
- St. Joseph's Healthcare, The Brain-Body Institute, McMaster University, Hamilton, ON, Canada
| | - Yu-Kang Mao
- St. Joseph's Healthcare, The Brain-Body Institute, McMaster University, Hamilton, ON, Canada
| | - Wolfgang A Kunze
- St. Joseph's Healthcare, The Brain-Body Institute, McMaster University, Hamilton, ON, Canada.,Department of Biology, McMaster University, Hamilton, ON, Canada.,Department of Psychiatry and Behavioural Neurosciences, McMaster University, Hamilton, ON, Canada
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12
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Adenosine triphosphate is co-secreted with glucagon-like peptide-1 to modulate intestinal enterocytes and afferent neurons. Nat Commun 2019; 10:1029. [PMID: 30833673 PMCID: PMC6399286 DOI: 10.1038/s41467-019-09045-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2018] [Accepted: 02/01/2019] [Indexed: 02/02/2023] Open
Abstract
Enteroendocrine cells are specialised sensory cells located in the intestinal epithelium and generate signals in response to food ingestion. Whilst traditionally considered hormone-producing cells, there is evidence that they also initiate activity in the afferent vagus nerve and thereby signal directly to the brainstem. We investigate whether enteroendocrine L-cells, well known for their production of the incretin hormone glucagon-like peptide-1 (GLP-1), also release other neuro-transmitters/modulators. We demonstrate regulated ATP release by ATP measurements in cell supernatants and by using sniffer patches that generate electrical currents upon ATP exposure. Employing purinergic receptor antagonists, we demonstrate that evoked ATP release from L-cells triggers electrical responses in neighbouring enterocytes through P2Y2 and nodose ganglion neurones in co-cultures through P2X2/3-receptors. We conclude that L-cells co-secrete ATP together with GLP-1 and PYY, and that ATP acts as an additional signal triggering vagal activation and potentially synergising with the actions of locally elevated peptide hormone concentrations.
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13
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Yu Y, Park SJ, Beyak MJ. Inducible nitric oxide synthase-derived nitric oxide reduces vagal satiety signalling in obese mice. J Physiol 2018; 597:1487-1502. [PMID: 30565225 DOI: 10.1113/jp276894] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Accepted: 11/19/2018] [Indexed: 12/22/2022] Open
Abstract
KEY POINTS Obesity is associated with disrupted satiety regulation. Mice with diet-induced obesity have reduced vagal afferent neuronal excitability and a decreased afferent response to satiety signals. A low grade inflammation occurs in obesity with increased expression of inducible nitric oxide synthase (iNOS). Inhibition of iNOS in diet-induced obese mice restored vagal afferent neuronal excitability, increased the afferent response to satiety mediators and distention of the gut, and reduced short-term energy intake. A prolonged inhibition of iNOS reduced energy intake and body weight gain during the first week, and reduced amounts of epididymal fat after 3 weeks. We identified a novel pathway underlying disrupted satiety regulation in obesity. Blocking of this pathway might be clinically useful for the management of obesity. ABSTRACT Vagal afferents regulate feeding by transmitting satiety signals to the brain. Mice with diet-induced obesity have reduced vagal afferent sensitivity to satiety signals. We investigated whether inducible nitric oxide synthase (iNOS)-derived NO contributed to this reduction. C57BL/6J mice were fed a high- or low-fat diet for 6-8 weeks. Nodose ganglia and jejunum were analysed by immunoblotting for iNOS expression; NO production was measured using a fluorometric assay. Nodose neuron excitability and intestinal afferent sensitivity were evaluated by whole-cell patch clamp and in vitro afferent recording, respectively. Expression of iNOS and production of NO were increased in nodose ganglia and the small intestine in obese mice. Inhibition of iNOS in obese mice by pre-treatment with an iNOS inhibitor increased nodose neuron excitability via 2-pore-domain K+ channel leak currents, restored afferent sensitivity to satiety signals and reduced short-term energy intake. Obese mice given the iNOS inhibitor daily for 3 weeks had reduced energy intake and decreased body weight gain during the first week, compared to mice given saline, and lower amounts of epididymal fat at the end of 3 weeks. Inhibition of iNOS or blocking the action of iNOS-derived NO on vagal afferent pathways might comprise therapeutic strategies for hyperphagia and obesity.
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Affiliation(s)
- Yang Yu
- Gastrointestinal Disease Research Unit, Kingston General Hospital, Queen's University, Kingston, ON, Canada
| | - Sung Jin Park
- Gastrointestinal Disease Research Unit, Kingston General Hospital, Queen's University, Kingston, ON, Canada
| | - Michael J Beyak
- Gastrointestinal Disease Research Unit, Kingston General Hospital, Queen's University, Kingston, ON, Canada
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14
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Brierley SM, Hibberd TJ, Spencer NJ. Spinal Afferent Innervation of the Colon and Rectum. Front Cell Neurosci 2018; 12:467. [PMID: 30564102 PMCID: PMC6288476 DOI: 10.3389/fncel.2018.00467] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2018] [Accepted: 11/16/2018] [Indexed: 12/12/2022] Open
Abstract
Despite their seemingly elementary roles, the colon and rectum undertake a variety of key processes to ensure our overall wellbeing. Such processes are coordinated by the transmission of sensory signals from the periphery to the central nervous system, allowing communication from the gut to the brain via the "gut-brain axis". These signals are transmitted from the peripheral terminals of extrinsic sensory nerve fibers, located within the wall of the colon or rectum, and via their axons within the spinal splanchnic and pelvic nerves to the spinal cord. Recent studies utilizing electrophysiological, anatomical and gene expression techniques indicate a surprisingly diverse set of distinct afferent subclasses, which innervate all layers of the colon and rectum. Combined these afferent sub-types allow the detection of luminal contents, low- and high-intensity stretch or contraction, in addition to the detection of inflammatory, immune, and microbial mediators. To add further complexity, the proportions of these afferents vary within splanchnic and pelvic pathways, whilst the density of the splanchnic and pelvic innervation also varies along the colon and rectum. In this review we traverse this complicated landscape to elucidate afferent function, structure, and nomenclature to provide insights into how the extrinsic sensory afferent innervation of the colon and rectum gives rise to physiological defecatory reflexes and sensations of discomfort, bloating, urgency, and pain.
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Affiliation(s)
- Stuart M Brierley
- Visceral Pain Research Group, Centre for Neuroscience, College of Medicine and Public Health, Flinders University, Bedford Park, SA, Australia.,Centre for Nutrition and Gastrointestinal Diseases, Discipline of Medicine, South Australian Health and Medical Research Institute (SAHMRI), University of Adelaide, Adelaide, SA, Australia
| | - Timothy J Hibberd
- Visceral Neurophysiology Laboratory, Centre for Neuroscience, College of Medicine and Public Health, Flinders University, Bedford Park, SA, Australia
| | - Nick J Spencer
- Visceral Neurophysiology Laboratory, Centre for Neuroscience, College of Medicine and Public Health, Flinders University, Bedford Park, SA, Australia
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15
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Egerod KL, Petersen N, Timshel PN, Rekling JC, Wang Y, Liu Q, Schwartz TW, Gautron L. Profiling of G protein-coupled receptors in vagal afferents reveals novel gut-to-brain sensing mechanisms. Mol Metab 2018; 12:62-75. [PMID: 29673577 PMCID: PMC6001940 DOI: 10.1016/j.molmet.2018.03.016] [Citation(s) in RCA: 112] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Revised: 03/24/2018] [Accepted: 03/29/2018] [Indexed: 12/13/2022] Open
Abstract
OBJECTIVES G protein-coupled receptors (GPCRs) act as transmembrane molecular sensors of neurotransmitters, hormones, nutrients, and metabolites. Because unmyelinated vagal afferents richly innervate the gastrointestinal mucosa, gut-derived molecules may directly modulate the activity of vagal afferents through GPCRs. However, the types of GPCRs expressed in vagal afferents are largely unknown. Here, we determined the expression profile of all GPCRs expressed in vagal afferents of the mouse, with a special emphasis on those innervating the gastrointestinal tract. METHODS Using a combination of high-throughput quantitative PCR, RNA sequencing, and in situ hybridization, we systematically quantified GPCRs expressed in vagal unmyelinated Nav1.8-expressing afferents. RESULTS GPCRs for gut hormones that were the most enriched in Nav1.8-expressing vagal unmyelinated afferents included NTSR1, NPY2R, CCK1R, and to a lesser extent, GLP1R, but not GHSR and GIPR. Interestingly, both GLP1R and NPY2R were coexpressed with CCK1R. In contrast, NTSR1 was coexpressed with GPR65, a marker preferentially enriched in intestinal mucosal afferents. Only few microbiome-derived metabolite sensors such as GPR35 and, to a lesser extent, GPR119 and CaSR were identified in the Nav1.8-expressing vagal afferents. GPCRs involved in lipid sensing and inflammation (e.g. CB1R, CYSLTR2, PTGER4), and neurotransmitters signaling (CHRM4, DRD2, CRHR2) were also highly enriched in Nav1.8-expressing neurons. Finally, we identified 21 orphan GPCRs with unknown functions in vagal afferents. CONCLUSION Overall, this study provides a comprehensive description of GPCR-dependent sensing mechanisms in vagal afferents, including novel coexpression patterns, and conceivably coaction of key receptors for gut-derived molecules involved in gut-brain communication.
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Affiliation(s)
- Kristoffer L Egerod
- Laboratory for Molecular Pharmacology, Department of Biomedical Sciences, and Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Nørre Allé 14, 2200, Copenhagen, Denmark.
| | - Natalia Petersen
- Laboratory for Molecular Pharmacology, Department of Biomedical Sciences, and Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Nørre Allé 14, 2200, Copenhagen, Denmark
| | - Pascal N Timshel
- Nordisk Foundation Center for Basic Metabolic Research, Section of Metabolic Genomics, Faculty of Health and Medical Sciences, University of Copenhagen, Nørre Allé 14, 2200, Copenhagen, Denmark
| | - Jens C Rekling
- Department of Neuroscience, University of Copenhagen, Nørre Allé 14, 2200, Copenhagen, Denmark
| | - Yibing Wang
- Department of Biochemistry, UT Southwestern Medical Center at Dallas, The University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX 75390, USA
| | - Qinghua Liu
- Department of Biochemistry, UT Southwestern Medical Center at Dallas, The University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX 75390, USA
| | - Thue W Schwartz
- Laboratory for Molecular Pharmacology, Department of Biomedical Sciences, and Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Nørre Allé 14, 2200, Copenhagen, Denmark
| | - Laurent Gautron
- Division of Hypothalamic Research and Department of Internal Medicine, The University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX 75390, USA.
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16
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Han T, Tang Y, Li J, Xue B, Gong L, Li J, Yu X, Liu C. Nitric oxide donor protects against acetic acid-induced gastric ulcer in rats via S-nitrosylation of TRPV1 on vagus nerve. Sci Rep 2017; 7:2063. [PMID: 28522805 PMCID: PMC5437002 DOI: 10.1038/s41598-017-02275-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Accepted: 04/10/2017] [Indexed: 12/19/2022] Open
Abstract
This study was conducted to investigate the effects of nitric oxide (NO) in acetic acid-induced gastric ulcer of rats and the underlying mechanisms. We found that peritoneal injection of sodium nitroprusside (SNP), a NO donor, decreased the ulcer area, inflammatory cell infiltration and MPO degree in acetic acid-induced gastric ulcer in rats. This effect was abolished by a transient receptor potential vanilloid 1 (TRPV1) antagonist or prior subdiaphragmatic vagotomy. SNP increased the jejunal mesenteric afferent discharge in a dose-depended manner, which was largely diminished by pretreatment of S-nitrosylation blocker N-ethylmaleimide, TRPV1 antagonist capsazepine, genetic deletion of TRPV1, or vagotomy. Whole-cell patch clamp recording showed that SNP depolarized the resting membrane potential of NG neurons, and enhanced capsaicin-induced inward current, which were both blocked by N-ethylmaleimide. Our results suggest that NO donor SNP alleviates acetic acid-induced gastric ulcer in rats via vagus nerve, while S-nitrosylation of TRPV1 may participate in this route. Our findings reveal a new mechanism for vagal afferent activation, and a new potential anti-inflammatory target.
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Affiliation(s)
- Ting Han
- Department of Physiology, School of Basic Medical Sciences, Shandong University Cheeloo Medical College, Shandong, China
| | - Yan Tang
- Department of Physiology, School of Basic Medical Sciences, Shandong University Cheeloo Medical College, Shandong, China
| | - Jing Li
- Department of Physiology, School of Basic Medical Sciences, Shandong University Cheeloo Medical College, Shandong, China
| | - Bing Xue
- Department of Physiology, School of Basic Medical Sciences, Shandong University Cheeloo Medical College, Shandong, China
| | - Liping Gong
- Department of Physiology, School of Basic Medical Sciences, Shandong University Cheeloo Medical College, Shandong, China
| | - Jingxin Li
- Department of Physiology, School of Basic Medical Sciences, Shandong University Cheeloo Medical College, Shandong, China
| | - Xiao Yu
- Department of Physiology, School of Basic Medical Sciences, Shandong University Cheeloo Medical College, Shandong, China
| | - Chuanyong Liu
- Department of Physiology, School of Basic Medical Sciences, Shandong University Cheeloo Medical College, Shandong, China. .,Provincial Key Lab of Mental Disorder, School of Basic Medical Sciences, Shandong University Cheeloo Medical College, Shandong, China.
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17
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Williams EK, Chang RB, Strochlic DE, Umans BD, Lowell BB, Liberles SD. Sensory Neurons that Detect Stretch and Nutrients in the Digestive System. Cell 2016; 166:209-21. [PMID: 27238020 DOI: 10.1016/j.cell.2016.05.011] [Citation(s) in RCA: 371] [Impact Index Per Article: 46.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2016] [Revised: 04/11/2016] [Accepted: 04/22/2016] [Indexed: 12/25/2022]
Abstract
Neural inputs from internal organs are essential for normal autonomic function. The vagus nerve is a key body-brain connection that monitors the digestive, cardiovascular, and respiratory systems. Within the gastrointestinal tract, vagal sensory neurons detect gut hormones and organ distension. Here, we investigate the molecular diversity of vagal sensory neurons and their roles in sensing gastrointestinal inputs. Genetic approaches allowed targeted investigation of gut-to-brain afferents involved in homeostatic responses to ingested nutrients (GPR65 neurons) and mechanical distension of the stomach and intestine (GLP1R neurons). Optogenetics, in vivo ganglion imaging, and genetically guided anatomical mapping provide direct links between neuron identity, peripheral anatomy, central anatomy, conduction velocity, response properties in vitro and in vivo, and physiological function. These studies clarify the roles of vagal afferents in mediating particular gut hormone responses. Moreover, genetic control over gut-to-brain neurons provides a molecular framework for understanding neural control of gastrointestinal physiology.
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Affiliation(s)
- Erika K Williams
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Rui B Chang
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
| | - David E Strochlic
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Benjamin D Umans
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Bradford B Lowell
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02115, USA
| | - Stephen D Liberles
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA.
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18
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19
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Wu W, Bates MA, Bursian SJ, Flannery B, Zhou HR, Link JE, Zhang H, Pestka JJ. Peptide YY3-36 and 5-hydroxytryptamine mediate emesis induction by trichothecene deoxynivalenol (vomitoxin). Toxicol Sci 2013; 133:186-95. [PMID: 23457120 DOI: 10.1093/toxsci/kft033] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Deoxynivalenol (DON, vomitoxin), a trichothecene mycotoxin produced by Fusarium sp. that frequently occurs in cereal grains, has been associated with human and animal food poisoning. Although a common hallmark of DON-induced toxicity is the rapid onset of emesis, the mechanisms for this adverse effect are not fully understood. Recently, our laboratory has demonstrated that the mink (Neovison vison) is a suitable small animal model for investigating trichothecene-induced emesis. The goal of this study was to use this model to determine the roles of two gut satiety hormones, peptide YY3-36 (PYY3-36) and cholecystokinin (CCK), and the neurotransmitter 5-hydroxytryptamine (5-HT) in DON-induced emesis. Following ip exposure to DON at 0.1 and 0.25mg/kg bw, emesis induction ensued within 15-30min and then persisted up to 120min. Plasma DON measurement revealed that this emesis period correlated with the rapid distribution and clearance of the toxin. Significant elevations in both plasma PYY3-36 (30-60min) and 5-HT (60min) but not CCK were observed during emesis. Pretreatment with the neuropeptide Y2 receptor antagonist JNJ-31020028 attenuated DON- and PYY-induced emesis, whereas the CCK1 receptor antagonist devezapide did not alter DON's emetic effects. The 5-HT3 receptor antagonist granisetron completely suppressed induction of vomiting by DON and the 5-HT inducer cisplatin. Granisetron pretreatment also partially blocked PYY3-36-induced emesis, suggesting a potential upstream role for this gut satiety hormone in 5-HT release. Taken together, the results suggest that both PYY3-36 and 5-HT play contributory roles in DON-induced emesis.
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Affiliation(s)
- Wenda Wu
- College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, P.R. China
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20
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Perez-Burgos A, Wang B, Mao YK, Mistry B, McVey Neufeld KA, Bienenstock J, Kunze W. Psychoactive bacteria Lactobacillus rhamnosus (JB-1) elicits rapid frequency facilitation in vagal afferents. Am J Physiol Gastrointest Liver Physiol 2013; 304:G211-20. [PMID: 23139216 DOI: 10.1152/ajpgi.00128.2012] [Citation(s) in RCA: 150] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Mounting evidence supports the influence of the gut microbiome on the local enteric nervous system and its effects on brain chemistry and relevant behavior. Vagal afferents are involved in some of these effects. We previously showed that ingestion of the probiotic bacterium Lactobacillus rhamnosus (JB-1) caused extensive neurochemical changes in the brain and behavior that were abrogated by prior vagotomy. Because information can be transmitted to the brain via primary afferents encoded as neuronal spike trains, our goal was to record those induced by JB-1 in vagal afferents in the mesenteric nerve bundle and thus determine the nature of the signals sent to the brain. Male Swiss Webster mice jejunal segments were cannulated ex vivo, and serosal and luminal compartments were perfused separately. Bacteria were added intraluminally. We found no evidence for translocation of labeled bacteria across the epithelium during the experiment. We recorded extracellular multi- and single-unit neuronal activity with glass suction pipettes. Within minutes of application, JB-1 increased the constitutive single- and multiunit firing rate of the mesenteric nerve bundle, but Lactobacillus salivarius (a negative control) or media alone were ineffective. JB-1 significantly augmented multiunit discharge responses to an intraluminal distension pressure of 31 hPa. Prior subdiaphragmatic vagotomy abolished all of the JB-1-evoked effects. This detailed exploration of the neuronal spike firing that encodes behavioral signaling to the brain may be useful to identify effective psychoactive bacteria and thereby offer an alternative new perspective in the field of psychiatry and comorbid conditions.
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Affiliation(s)
- Azucena Perez-Burgos
- McMaster Brain-Body Institute, St. Joseph's Healthcare, Hamilton, Ontario, Canada.
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21
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How JMY, Pumpa TJ, Sartor DM. Renal sympathoinhibitory and regional vasodilator responses to cholecystokinin are altered in obesity-related hypertension. Exp Physiol 2013. [DOI: 10.1113/expphysiol.2012.070151] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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22
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The Role of Cholecystokinin Receptors in the Short-Term Control of Food Intake. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2013; 114:277-316. [DOI: 10.1016/b978-0-12-386933-3.00008-x] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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23
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Metcalf SA, Washington MC, Brown TAL, Williams CS, Strader AD, Sayegh AI. Ileal interposition attenuates the satiety responses evoked by cholecystokinin-8 and -33. Peptides 2011; 32:1296-302. [PMID: 21557974 DOI: 10.1016/j.peptides.2011.04.023] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/04/2011] [Revised: 04/23/2011] [Accepted: 04/24/2011] [Indexed: 02/07/2023]
Abstract
One of the possible mechanisms by which the weight-reducing surgical procedure ileal interposition (II) works is by increasing circulating levels of lower gut peptides that reduce food intake, such as glucagon like peptide-1 and peptide YY. However, since this surgery involves both lower and upper gut segments, we tested the hypothesis that II alters the satiety responses evoked by the classic upper gut peptide cholecystokinin (CCK). To test this hypothesis, we determined meal size (MS), intermeal interval (IMI) and satiety ratio (SR) evoked by CCK-8 and -33 (0, 1, 3, 5nmol/kg, i.p.) in two groups of rats, II and sham-operated. CCK-8 and -33 reduced MS more in the sham group than in the II group; CCK-33 prolonged IMI in the sham group and increased SR in both groups. Reduction of cumulative food intake by CCK-8 in II rats was blocked by devazepide, a CCK(1) receptor antagonist. In addition, as previously reported, we found that II resulted in a slight reduction in body weight compared to sham-operated rats. Based on these observations, we conclude that ileal interposition attenuates the satiety responses of CCK. Therefore, it is unlikely that this peptide plays a significant role in reduction of body weight by this surgery.
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Affiliation(s)
- Shannon A Metcalf
- Gastroenterology Laboratory, Department of Biomedical Sciences, College of Veterinary Medicine, Tuskegee University, Tuskegee, AL 36088, USA
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24
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Powley TL, Spaulding RA, Haglof SA. Vagal afferent innervation of the proximal gastrointestinal tract mucosa: chemoreceptor and mechanoreceptor architecture. J Comp Neurol 2011; 519:644-60. [PMID: 21246548 DOI: 10.1002/cne.22541] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The vagus nerve supplies low-threshold chemo- and mechanosensitive afferents to the mucosa of the proximal gastrointestinal (GI) tract. The absence of a full characterization of the morphology and distributions of these projections has hampered comprehensive functional analyses. In the present experiment, dextran (10K) conjugated with tetramethylrhodamine and biotin was injected into the nodose ganglion and used to label the terminal arbors of individual vagal afferents of both rats and mice. Series of serial 100-μm thick sections of the initial segment of the duodenum as well as the pyloric antrum were collected and processed with diaminobenzidine for permanent tracer labeling. Examination of over 400 isolated afferent fibers, more than 200 from each species, indicated that three vagal afferent specializations, each distinct in morphology and in targets, innervate the mucosa of the proximal GI tract. One population of fibers, the villus afferents, supplies plates of varicose endings to the apical tips of intestinal villi, immediately subjacent to the epithelial wall. A second type of afferent, the crypt afferent, forms subepithelial rings of varicose processes encircling the intestinal glands or crypts, immediately below the crypt-villus junction. Statistical assessment of the isolated fibers indicated that the villus arbors and the crypt endings are independent, issued by different vagal afferents. A third vagal afferent specialization, the antral gland afferent, arborizes along the gastric antral glands and forms terminal concentrations immediately below the luminal epithelial wall. The terminal locations, morphological features, and regional distributions of these three specializations provide inferences about the sensitivities of the afferents.
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Affiliation(s)
- Terry L Powley
- Purdue University Life Sciences Program and Department of Psychological Sciences, Purdue University, West Lafayette, Indiana 47907-2081, USA.
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Daly DM, Park SJ, Valinsky WC, Beyak MJ. Impaired intestinal afferent nerve satiety signalling and vagal afferent excitability in diet induced obesity in the mouse. J Physiol 2011; 589:2857-70. [PMID: 21486762 DOI: 10.1113/jphysiol.2010.204594] [Citation(s) in RCA: 129] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Gastrointestinal vagal afferents transmit satiety signals to the brain via both chemical and mechanical mechanisms. There is indirect evidence that these signals may be attenuated in obesity. We hypothesized that responses to satiety mediators and distension of the gut would be attenuated after induction of diet induced obesity. Obesity was induced by feeding a high fat diet (60% kcal from fat). Low fat fed mice (10% kcal from fat) served as a control. High fat fed mice were obese, with increased visceral fat, but were not hyperglycaemic. Recordings from jejunal afferents demonstrated attenuated responses to the satiety mediators cholecystokinin (CCK, 100 nm) and 5-hydroxytryptamine (5-HT, 10 μm), as was the response to low intensity jejunal distension, while responses to higher distension pressures were preserved. We performed whole cell patch clamp recordings on nodose ganglion neurons, both unlabelled, and those labelled by fast blue injection into the wall of the jejunum. The cell membrane of both labelled and unlabelled nodose ganglion neurons was less excitable in HFF mice, with an elevated rheobase and decreased number of action potentials at twice rheobase. Input resistance of HFF neurons was also significantly decreased. Calcium imaging experiments revealed reduced proportion of nodose ganglion neurons responding to CCK and 5-HT in obese mice. These results demonstrate a marked reduction in afferent sensitivity to satiety related stimuli after a chronic high fat diet. A major mechanism underlying this change is reduced excitability of the neuronal cell membrane. This may explain the development of hyperphagia when a high fat diet is consumed. Improving sensitivity of gastrointestinal afferent nerves may prove useful to limit food intake in obesity.
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Affiliation(s)
- Donna M Daly
- Departments of Medicine and Physiology, Gastrointestinal Diseases Research Unit (GIDRU) Wing, Kingston General Hospital, 76 Stuart Street, Kingston, Ontario, Canada K7L2V7
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Okano-Matsumoto S, McRoberts JA, Taché Y, Adelson DW. Electrophysiological evidence for distinct vagal pathways mediating CCK-evoked motor effects in the proximal versus distal stomach. J Physiol 2011; 589:371-93. [PMID: 21078593 PMCID: PMC3043539 DOI: 10.1113/jphysiol.2010.196832] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2010] [Accepted: 11/09/2010] [Indexed: 12/26/2022] Open
Abstract
Intravenous cholecystokinin octapeptide (CCK-8) elicits vago-vagal reflexes that inhibit phasic gastric contractions and reduce gastric tone in urethane-anaesthetized rats. A discrete proximal subdivision of the ventral gastric vagus nerve (pVGV) innervates the proximal stomach, but the fibre populations within it have not been characterized previously.We hypothesized that I.V. CCK-8 injection would excite inhibitory efferent outflow in the pVGV, in contrast to its inhibitory effect on excitatory efferent outflow in the distal subdivision (dVGV), which supplies the distal stomach. In each VGV subdivision, a dual-recording technique was used to record afferent and efferent activity simultaneously, while also monitoring intragastric pressure (IGP). CCK-8 dose dependently (100-1000 pmol kg(-1), I.V.) reduced gastric tone, gastric contractile activity and multi-unit dVGV efferent discharge, but increased pVGV efferent firing. Single-unit analysis revealed a minority of efferent fibres in each branch whose response differed in direction from the bulk response. Unexpectedly, efferent excitation in the pVGV was significantly shorter lived and had a significantly shorter decay half-time than did efferent inhibition in the dVGV, indicating that distinct pathways drive CCK-evoked outflow to the proximal vs. the distal stomach. Efferent inhibition in the dVGV began several seconds before, and persisted significantly longer than, simultaneously recorded dVGV afferent excitation.Thus, dVGV afferent excitation could not account for the pattern of dVGV efferent inhibition. However, the time course of dVGV afferent excitation paralleled that of pVGV efferent excitation. Similarly, the duration of CCK-8-evoked afferent responses recorded in the accessory celiac branch of the vagus (ACV) matched the duration of dVGV efferent responses. The observed temporal relationships suggest that postprandial effects on gastric complicance of CCK released from intestinal endocrine cells may require circulating concentrations to rise to levels capable of exciting distal gastric afferent fibres, in contrast to more immediate effects on distal gastric contractile activity mediated via vago-vagal reflexes initiated by paracrine excitation of intestinal afferents.
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Lipid-enriched enteral nutrition controls the inflammatory response in murine Gram-negative sepsis. Crit Care Med 2010; 38:1996-2002. [DOI: 10.1097/ccm.0b013e3181eb90d7] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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Abstract
Studies on the control of pancreatic secretion in humans of all ages have been a difficult task over the years because of patients' availability and ethic committee rules. Nevertheless, studies were performed and the objectives of this review are to summarize our knowledge on the development of secretory process in newborns, on the different phases of the pancreatic responses to a meal, on the pancreatic responses to the different components of the diet, on the mechanisms involved in the control of the pancreatic responses, and finally on the receptors involved in these controls.
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Abstract
The aim of the present review is to synthesise and summarise our recent knowledge on the involvement of cholecystokinin (CCK) and gastrin peptides and their receptors in the control of digestive functions and more generally their role in the field of nutrition in mammals. First, we examined the release of these peptides from the gut, focusing on their molecular forms, the factors regulating their release and the signalling pathways mediating their effects. Second, general physiological effects of CCK and gastrin peptides are described with regard to their specific receptors and the role of CCK on vagal mucosal afferent nerve activities. Local effects of CCK and gastrin in the gut are also reported, including gut development, gastrointestinal motility and control of pancreatic functions through vagal afferent pathways, including NO. Third, some examples of the intervention of the CCK and gastrin peptides are exposed in diseases, taking into account intervention of the classical receptor subtypes (CCK1 and CCK2 receptors) and their heterodimerisation as well as CCK-C receptor subtype. Finally, applications and future challenges are suggested in the nutritional field (performances) and in therapy with regards to the molecular forms or in relation with the type of receptor as well as new techniques to be utilised in detection or in therapy of disease. In conclusion, the present review underlines recent developments in this field: CCK and gastrin peptides and their receptors are the key factor of nutritional aspects; a better understanding of the mechanisms involved may increase the efficiency of the nutritional functions and the treatment of abnormalities under pathological conditions.
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Roles of gastro-oesophageal afferents in the mechanisms and symptoms of reflux disease. Handb Exp Pharmacol 2009:227-57. [PMID: 19655109 DOI: 10.1007/978-3-540-79090-7_7] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Oesophageal pain is one of the most common reasons for physician consultation and/or seeking medication. It is most often caused by acid reflux from the stomach, but can also result from contractions of the oesophageal muscle. Different forms of pain are evoked by oesophageal acid, including heartburn and non-cardiac chest pain, but the basic mechanisms and pathways by which these are generated remain to be elucidated. Both vagal and spinal afferent pathways are implicated by basic research. The sensitivity of afferent fibres within these pathways may become altered after acid-induced inflammation and damage, but the severity of symptoms in humans does not necessarily correlate with the degree of inflammation. Gastro-oesophageal reflux disease (GORD) is caused by transient relaxations of the lower oesophageal sphincter, which are triggered by activation of gastric vagal mechanoreceptors. Vagal afferents are therefore an emerging therapeutic target for GORD. Pain in the absence of excess acid reflux remains a major challenge for treatment.
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Chaikomin R, Jones KL, Feinle-Bisset C, Meyer JH, Horowitz M, Rayner CK. Effects of intraluminal local anesthetic on upper gastrointestinal motor, sensory, and peptide hormone responses to intraduodenal glucose. Eur J Gastroenterol Hepatol 2009; 21:258-65. [PMID: 19279470 DOI: 10.1097/meg.0b013e3283200073] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
OBJECTIVE Enterally administered glucose modifies gut sensation, diminishes hunger, and slows gastric emptying by suppressing antral motility and stimulating pyloric pressures. We aimed to clarify the mechanism of small intestinal glucose sensing. METHODS We studied eight healthy males twice, in random order. An antroduodenal manometry catheter was positioned with a sleeve sensor across the pylorus. Benzocaine, or vehicle alone, was given into the proximal duodenum as a bolus, followed by continuous infusion for 105 min (T=-15 to 90 min). Glucose was also infused into the proximal duodenum at 3 kcal/min for 90 min (T=0-90 min). Sensations of hunger, bloating, and nausea were assessed with visual analog questionnaires, blood was sampled at intervals, and energy intake at a buffet meal (T=90-120 min) was measured. RESULTS Perceptions of bloating and nausea were markedly less with benzocaine when compared with vehicle (P<0.05 for each), with no difference in hunger, or energy intake. In contrast, the suppression of antral waves and stimulation of phasic and tonic pyloric pressures, duodenal waves, and propagated duodenal wave sequences by intraduodenal glucose infusion did not differ between the 2 days. No difference in blood glucose, plasma insulin, or plasma glucagon-like peptide 1 between benzocaine and control was observed, whereas glucose-dependent insulinotropic polypeptide and cholecystokinin concentrations were slightly higher with benzocaine (P<0.05 for both). CONCLUSION Mucosal anesthesia ameliorates unpleasant sensations induced by enteral glucose, but does not inhibit the release of gut peptides that feed back on appetite and gastroduodenal motility.
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Affiliation(s)
- Reawika Chaikomin
- University of Adelaide Discipline of Medicine, Royal Adelaide Hospital, Adelaide, Australia
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Sullivan CN, Raboin SJ, Gulley S, Sinzobahamvya NT, Green GM, Reeve JR, Sayegh AI. Endogenous cholecystokinin reduces food intake and increases Fos-like immunoreactivity in the dorsal vagal complex but not in the myenteric plexus by CCK1 receptor in the adult rat. Am J Physiol Regul Integr Comp Physiol 2007; 292:R1071-80. [PMID: 17082351 DOI: 10.1152/ajpregu.00490.2006] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
We hypothesized that endogenous CCK reduces food intake by activating the dorsal vagal complex (DVC) and the myenteric neurons of the gut. To test this hypothesis, adult rats were given camostat mesilate; a nonnutrient releaser of endogenous CCK, by orogastric gavage, and Fos-like immunoreactivity (Fos-LI) was quantified in the DVC and the myenteric plexus. The results for endogenous CCK were compared with those for exogenous CCK-8. Exogenous CCK-8 reduced food intake and stimulated Fos-LI in the DVC and in myenteric neurons of the duodenum and jejunum. In comparison, endogenous CCK reduced food intake and increased DVC Fos-LI but did not increase Fos-LI in the myenteric plexus. Similar to CCK-8, devazepide, a specific CCK1 receptor antagonist, and not L365,260, a specific CCK2 receptor antagonist, attenuated the reduction of food intake by camostat. In addition, Fos-LI in the DVC in response to both exogenous CCK-8 and camostat administration was significantly attenuated by vagotomy, as well as by blocking CCK1 receptors. These results demonstrate for the first time that reduction of food intake in adult rats by endogenous CCK released by a nonnutrient mechanism requires CCK1 receptors, the vagus nerve, and activation of the DVC, but not the myenteric plexus.
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Affiliation(s)
- Cherese N Sullivan
- Department of Biomedical Sciences, College of Veterinary Medicine, Tuskegee University, Tuskegee, AL 36088, USA
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Lorenzo-Figueras M, Merritt AM. Role of cholecystokinin in the gastric motor response to a meal in horses. Am J Vet Res 2006; 67:1998-2005. [PMID: 17144800 DOI: 10.2460/ajvr.67.12.1998] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To measure plasma cholecystokinin (CCK) activity and the effect of a CCK-1 receptor antagonist on accommodation of the proximal portion of the stomach, and subsequent gastric emptying, in horses after ingestion of high-fat or high-carbohydrate meals. ANIMALS 6 healthy adult horses with gastric cannulas. PROCEDURES In the first study, horses were offered a high-fat (8% fat) or a high-carbohydrate (3% fat) pelleted meal of identical volume, caloric density, and protein content. Related plasma CCK-like activity was measured by radioimmunoassay (RIA). In a separate experiment, a horse was fed a grain meal with corn oil and phenylalanine, and plasma CCK activity was assessed by bioassay. A second study evaluated the effect of a CCK-1 receptor antagonist, devazepide (0.1 mg/kg, IV), on gastric accommodation and emptying following a meal of grain supplemented with either corn oil (12.3% fat) or an isocaloric amount of glucose (2.9% fat). Gastric tone was measured by a barostat and emptying by the (13)C-octanoic acid breath test. RESULTS No plasma CCK-like activity was detected by RIA or bioassay before or after ingestion of meals. Preprandial devazepide did not alter the gastric accommodation response but did significantly shorten the gastric half-emptying time and time to peak breath (13)CO(2) content with the glucose-enriched meal. CONCLUSIONS AND CLINICAL RELEVANCE In horses, CCK participates in regulating the gastric motor response to a meal. Compared with other species, horses may be more responsive to carbohydrate than fat. A vagovagal reflex most likely mediates this regulation, with CCK as a paracrine intermediary at the intestinal level.
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Affiliation(s)
- Mireia Lorenzo-Figueras
- Island Whirl Equine Colic Research Laboratory, Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL 32610-0136, USA
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Murray CDR, Booth CE, Bulmer DCE, Kamm MA, Emmanuel AV, Winchester WJ. Ghrelin augments afferent response to distension in rat isolated jejunum. Neurogastroenterol Motil 2006; 18:1112-20. [PMID: 17109695 DOI: 10.1111/j.1365-2982.2006.00848.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Ghrelin has been shown to decrease firing of gastric vagal afferents at doses comparable with circulating levels in the fasted state. This raises the possibility that ghrelin may have a hormonal action on other vagal afferent populations. The aim of this study was to determine the effects of ghrelin on jejunal afferent activity; including responses to distension, 2-methyl-5-hydroxytryptamine (2-methyl-5-HT) and cholecystokinin (CCK) in both naïve and vagotomized rats. Ghrelin significantly augmented the afferent response to distension. No effect was observed on baseline afferent discharge, or the response to 2-methyl-5-HT and CCK. The effect of ghrelin was more pronounced at lower ramp distending pressures (0-30 mmHg). Similarly, ghrelin augmented the jejunal afferent responses to phasic distension at 10-30 mmHg, but had no effect at higher pressures. Chronic subdiaphragmatic vagotomy and administration of the growth hormone secretagogue receptor (GHS-R) antagonist [D-Lys3]-GHRP-6 prevented the augmentation of the afferent responses to distension indicating ghrelin is acting through the GHS-R on vagal afferent fibres. Ghrelin augments the mechanosensation of jejunal vagal afferents and hence may lead to increased perception of hunger contractions.
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Abstract
Cholecystokinin and gastrin receptors (CCK1R and CCK2R) are G protein-coupled receptors that have been the subject of intensive research in the last 10 years with corresponding advances in the understanding of their functioning and physiology. In this review, we first describe general properties of the receptors, such as the different signaling pathways used to exert short- and long-term effects and the structural data that explain their binding properties, activation, and regulation. We then focus on peripheral cholecystokinin receptors by describing their tissue distribution and physiological actions. Finally, pathophysiological peripheral actions of cholecystokinin receptors and their relevance in clinical disorders are reviewed.
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Affiliation(s)
- Marlène Dufresne
- Institut National de la Santé et de la Recherche Médicale U. 531, Institut Louis Bugnard, Centre Hospitalier Universitaire Rangueil, France
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Peters JH, Simasko SM, Ritter RC. Modulation of vagal afferent excitation and reduction of food intake by leptin and cholecystokinin. Physiol Behav 2006; 89:477-85. [PMID: 16872644 DOI: 10.1016/j.physbeh.2006.06.017] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2006] [Revised: 06/08/2006] [Accepted: 06/19/2006] [Indexed: 12/24/2022]
Abstract
The gut-peptide, cholecystokinin (CCK), reduces food intake by acting at CCK-1 receptors on vagal afferent neurons, whereas the feeding effects of the adipokine hormone, leptin, are associated primarily with its action on receptors (ObRb) in the hypothalamus. Recently, however, ObRb mRNA has been reported in vagal afferent neurons, some of which also express CCK-1 receptor, suggesting that leptin, alone or in cooperation with CCK, might activate vagal afferent neurons, and influence food intake via a vagal route. To evaluate these possibilities we have been examining the cellular and behavioral effects of leptin and CCK on vagal afferent neurons. In cultured vagal afferent neurons leptin and CCK evoked short latency, transient depolarizations, often leading to action potentials, and increases in cytosolic calcium. There was a much higher prevalence of CCK and leptin sensitivity amongst cultured vagal afferent neurons that innervate stomach or duodenum than there was in the overall vagal afferent population. Furthermore, almost all leptin-responsive gastric and duodenal vagal afferents also were sensitive to CCK. Leptin, infused into the upper GI tract arterial supply, reduced meal size, and enhanced satiation evoked by CCK. These results indicate that vagal afferent neurons are activated by leptin, and that this activation is likely to participate in meal termination, perhaps by enhancing vagal sensitivity to CCK. Our findings are consistent with the view that leptin and CCK exert their influence on food intake by accessing multiple neural systems (viscerosensory, motivational, affective and motor) at multiple points along the neuroaxis.
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Affiliation(s)
- James H Peters
- Department of V.C.A.P.P., College of Veterinary Medicine, Washington State University, Pullman, WA 99164-6520, USA
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Covasa M. CCK- and leptin-induced vagal afferent activation: a model for organ-specific endocrine modulation of visceral sensory information. Am J Physiol Regul Integr Comp Physiol 2006; 290:R1542-3. [PMID: 16682468 DOI: 10.1152/ajpregu.00082.2006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Peters JH, Ritter RC, Simasko SM. Leptin and CCK selectively activate vagal afferent neurons innervating the stomach and duodenum. Am J Physiol Regul Integr Comp Physiol 2005; 290:R1544-9. [PMID: 16384857 DOI: 10.1152/ajpregu.00811.2005] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The hormone leptin and the gut peptide CCK synergistically interact to enhance the process of satiation. Although this interaction may occur at several levels of the neuroaxis, our previous results indicate that leptin can specifically enhance the satiation effect of CCK by acting on subdiaphragmatic vagal afferent neurons. Because of this localized action, we hypothesized that a high proportion of vagal afferent neurons innervating the stomach or duodenum would be responsive to leptin and/or CCK. To test this hypothesis, we measured changes in cytosolic calcium levels induced by leptin and CCK in cultured nodose ganglion neurons labeled with a retrograde neuronal tracer injected into either the stomach or the duodenum. In the neurons labeled from the stomach, CCK activated 74% (39 of 53) compared with only 35% (34 of 97) of nonlabeled cells. Of the CCK-responsive neurons 60% (18 of 30) were capsaicin-sensitive. Leptin activated 42% (22 of 53) of the stomach innervating neurons compared with 26% of nonlabeled neurons. All of the leptin-sensitive neurons labeled from the stomach also responded to CCK. In the neurons labeled from the duodenum, CCK activated 71% (20 of 28). Of these CCK-responsive neurons 80% (12 of 15) were capsaicin sensitive. Leptin activated 46% (13 of 28) of these duodenal innervating neurons, of which 89% (8 of 9) were capsaicin-sensitive. Among neurons labeled from the duodenum 43% (12 of 28) were responsive to both leptin and CCK, compared with only 15% (15 of 97) of unlabeled neurons. Our results support the hypothesis that vagal afferent sensitivity to CCK and leptin is concentrated in neurons that innervate the stomach and duodenum. These specific visceral afferent populations are likely to comprise a substrate through which acute leptin/CCK interactions enhance satiation.
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Affiliation(s)
- J H Peters
- Program in Neuroscience, Department of Veterinary and Comparative Anatomy, Pharmacology, and Physiology, College of Veterinary Medicine, Washington State University, Pullman, WA 99164-6520, USA.
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Miyasaka K, Kanai S, Ohta M, Hosoya H, Takano S, Sekime A, Sakurai C, Kaneko T, Tahara S, Funakoshi A. Overeating after restraint stress in cholecystokinin-a receptor-deficient mice. ACTA ACUST UNITED AC 2005; 55:285-91. [PMID: 16274526 DOI: 10.2170/jjphysiol.r2117] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2005] [Accepted: 11/07/2005] [Indexed: 11/05/2022]
Abstract
In mammals, including humans, a brain-gut hormone, cholecystokinin (CCK) mediates the satiety effect via CCK-A receptor (R). We generated CCK-AR gene-deficient (-/-) mice and found that the daily food intake, energy expenditure, and gastric emptying of a liquid meal did not change compared with those of wild-type mice. Because CCK-AR(-/-) mice show anxiolytic status, we examined the effects of restraint stress. Seven hours of restraint stress was found to significantly decrease both body weight and food intake during the subsequent 3 days in all tested animals. On the fourth day after restraint stress, the CCK-AR(-/-) mice showed a significantly higher level of daily food intake than prior to stress, and food intake recovered to prestress levels in the wild-type mice. Since peripheral CCK-AR has been known to mediate gastric emptying, both gastric emptying and gastric acid secretion were determined to examine the mechanism of overeating in CCK-AR(-/-) mice. Neither gastric emptying nor gastric acid secretion differed between CCK-AR(-/-) and wild-type mice on the fourth day after stress. In contrast, however, the contents of dopamine and its metabolites in the cerebral cortex of CCK-AR(-/-) mice were increased by stress, but were rather decreased in wild-type mice. Changes in 5-hydroxytryptamine (5-HT) and its metabolite 5HIAA did not differ between the genotypes. In conclusion, CCK-AR(-/-) mice showed overeating after restraint stress, and dopaminergic hyperfunction in the brain of these mice was observed. The present evidence suggests that the CCK-AR function, possibly via altering the dopaminergic function, might be involved in overeating after stress.
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Affiliation(s)
- Kyoko Miyasaka
- Department of Clinical Physiology, Tokyo Metropolitan Institute of Gerontology, 35-2 Sakaecho Itabashiku, Tokyo, 173-0015 Japan.
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Peters JH, Ritter RC, Simasko SM. Leptin and CCK modulate complementary background conductances to depolarize cultured nodose neurons. Am J Physiol Cell Physiol 2005; 290:C427-32. [PMID: 16192299 DOI: 10.1152/ajpcell.00439.2005] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
We have previously reported that intraceliac infusion of leptin induces a reduction of meal size that depends on intact vagal afferents. This effect of leptin is enhanced in the presence of cholecystokinin (CCK). The mechanisms by which leptin and CCK activate vagal afferent neurons are not known. In the present study, we have begun to address this question by using patch-clamp electrophysiological techniques to examine the mechanisms by which leptin and CCK activate cultured vagal afferents from adult rat nodose ganglia. We found that leptin depolarized 41 (60%) of 68 neurons. The magnitude of membrane depolarization was dependent on leptin concentration and occurred in both capsaicin-sensitive and capsaicin-insensitive neurons. We also found that a majority (16 of 22; 73%) of nodose neurons activated by leptin were also sensitive to CCK. CCK-induced depolarization was primarily associated with the increase of an inward current (11 of 12), whereas leptin induced multiple changes in background conductances through a decrease in an outward current (7 of 13), an increase in an inward current (3 of 13), or both (3 of 13). However, further isolation of background currents by recording in solutions that contained only sodium or only potassium revealed that both leptin and CCK were capable of increasing a sodium-dependent conductance or inhibiting a potassium-dependent conductance. Our results support the hypothesis that vagal afferents are a point of convergence and integration of leptin and CCK signaling for control of food intake and suggest multiple ionic mechanisms by which leptin and CCK activate vagal afferent neurons.
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Affiliation(s)
- J H Peters
- Program in Neuroscience, Department of Veterinary and Comparative Anatomy, Pharmacology, and Physiology, College of Veterinary Medicine, Washington State University, Pullman 99164-6520, USA.
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van de Wall EHEM, Duffy P, Ritter RC. CCK enhances response to gastric distension by acting on capsaicin-insensitive vagal afferents. Am J Physiol Regul Integr Comp Physiol 2005; 289:R695-703. [PMID: 15905220 DOI: 10.1152/ajpregu.00809.2004] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Capsaicin treatment destroys vagal afferent C fibers and markedly attenuates reduction of food intake and induction of hindbrain Fos expression by CCK. However, both anatomical and electrophysiological data indicate that some gastric vagal afferents are not destroyed by capsaicin. Because CCK enhances behavioral and electrophysiological responses to gastric distension in rats and people, we hypothesized that CCK might enhance the vagal afferent response to gastric distension via an action on capsaicin-insensitive vagal afferents. To test this hypothesis, we quantified expression of Fos-like immunoreactivity (Fos) in the dorsal vagal complex (DVC) of capsaicin-treated (Cap) and control rats (Veh), following gastric balloon distension alone and in combination with CCK injection. In Veh rats, intraperitoneal CCK significantly increased DVC Fos, especially in nucleus of the solitary tract (NTS), whereas in Cap rats, CCK did not significantly increase DVC Fos. In contrast to CCK, gastric distension did significantly increase Fos expression in the NTS of both Veh and Cap rats, although distension-induced Fos was attenuated in Cap rats. When CCK was administered during gastric distension, it significantly enhanced NTS Fos expression in response to distension in Cap rats. Furthermore, CCK's enhancement of distension-induced Fos in Cap rats was reversed by the selective CCK-A receptor antagonist lorglumide. We conclude that CCK directly activates capsaicin-sensitive C-type vagal afferents. However, in capsaicin-resistant A-type afferents, CCK's principal action may be facilitation of responses to gastric distension.
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Affiliation(s)
- E H E M van de Wall
- Dept. of Neuroendocrinology, University of Groningen, PO Box 14, 9750 AA Haren, The Netherlands
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Sayegh AI, Reeve JR, Lampley ST, Hart B, Gulley S, Esdaile AR, Sharma SK, Webb T, Williams CS, Pruitt F. Role for the enteric nervous system in the regulation of satiety via cholecystokinin-8. J Am Vet Med Assoc 2005; 226:1809-16. [PMID: 15938055 DOI: 10.2460/javma.2005.226.1809] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- Ayman I Sayegh
- Gastroenterology Laboratory, Department of Biomedical Sciences, College of Veterinary Medicine, Tuskegee University, Tuskegee, AL 36088, USA
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Bulmer DCE, Jiang W, Hicks GA, Davis JB, Winchester WJ, Grundy D. Vagal selective effects of ruthenium red on the jejunal afferent fibre response to ischaemia in the rat. Neurogastroenterol Motil 2005; 17:102-11. [PMID: 15670270 DOI: 10.1111/j.1365-2982.2004.00586.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
A variety of inflammatory mediators and local metabolites, have been implicated in the sensitivity of intestinal afferent fibres to brief periods of ischaemia and reperfusion. As yet, the contribution of the vanilloid transient receptor potential (TRPV)1 receptor to the response to intestinal ischaemia remains undetermined. In the present study, the effect of pretreatment with the competitive TRPV1 antagonist capsazepine and the non-selective TRPV channel antagonist ruthenium red, on the mesenteric afferent fibre response to ischaemia was examined. In control animals there was a reproducible biphasic increase in whole nerve afferent fibre activity during two brief periods of ischaemia. Treatment with ruthenium red significantly attenuated the early phase increase in afferent fibre activity during ischaemia. However, capsazepine treatment did not significantly alter the afferent fibre response to either ischaemia or reperfusion. Further experiments in chronically vagotomized animals indicated that the early phase response to ischaemia was mediated via vagal afferent fibres. The mechanism via which ruthenium red selectively inhibited vagal afferent fibres during ischaemia is unknown, but it does not appear to involve blockade of the TRPV1 receptor.
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Affiliation(s)
- D C E Bulmer
- Department of Biomedical Sciences, University of Sheffield, Sheffield, UK
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Grundy D, Booth CE, Winchester W, Hicks GA. Peripheral opiate action on afferent fibres supplying the rat intestine. Neurogastroenterol Motil 2004; 16 Suppl 2:29-37. [PMID: 15357849 DOI: 10.1111/j.1743-3150.2004.00557.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The aim of the present study was to examine the sensitivity of mesenteric afferents supplying the rat small intestine to mu-opioid receptor ligands. Mesenteric afferent discharge was recorded electrophysiologically in response to [D-ALA2, N-Me-Phe4, Gly5-ol]-enkephalin (DAMGO; 100 mug kg(-1) i.v.), before and after treatment with the mu-receptor antagonist alvimopan (1 mg kg(-1) i.v.). DAMGO markedly stimulated whole nerve mesenteric afferent discharge (P < 0.05), an effect completely blocked by alvimopan. The response of mesenteric afferents to 2-methyl-5-hydroxytryptamine (30 microg kg(-1) i.v.), bradykinin (0.1-1 microg kg(-1) i.a.) and both low- and high-threshold distension (0-60 mmHg) was unaffected by alvimopan. In chronically vagotomized animals, the low-threshold response to distension was attenuated while the remaining high-threshold response was unaffected by alvimopan. In conclusion, mesenteric afferent fibres are markedly stimulated by mu-opioid receptor agonists, an effect blocked by alvimopan, which may contribute to the gastrointestinal reflex and behavioural responses to opiate treatment or abuse. However, alvimopan did not influence the normal sensitivity of intestinal afferents to chemical and mechanical stimuli that activate different subpopulations of vagal and spinal afferents. Thus, alvimopan may be useful for the treatment of gastrointestinal sequelae following opiate treatment for postoperative or chronic pain.
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Affiliation(s)
- D Grundy
- Department of Biomedical Science, University of Sheffield, Sheffield, UK.
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Abstract
Satiation for food comprises the physiological processes that result in the termination of eating. Satiation is evoked by physical and chemical qualities of ingested food, which trigger afferent signals to the brain from multiple sites in the GI tract, including the stomach, the proximal small intestine, the distal small intestine and the colon. The physiological nature of each signal's contribution to satiation and overall control of food intake is likely to vary, depending on the level of the GI tract from which the signal arises. This article is a critical, though non-exhaustive, review of our current understanding of the mechanisms and adaptive value of satiation signals from the stomach and intestine.
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Affiliation(s)
- Robert C Ritter
- Department of Veterinary and Comparative Anatomy, Pharmacology and Physiology, and Programs in Neuroscience, College of Veterinary Medicine, Washington State University, Pullman, WA 99164-6520, USA.
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Li Y, Wu XY, Owyang C. Serotonin and cholecystokinin synergistically stimulate rat vagal primary afferent neurones. J Physiol 2004; 559:651-62. [PMID: 15235095 PMCID: PMC1665123 DOI: 10.1113/jphysiol.2004.064816] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Recent studies indicate that cholecystokinin (CCK) and serotonin (5-hydroxytryptamine, 5-HT) act via vagal afferent fibres to mediate gastrointestinal functions. In the present study, we characterized the interaction between CCK and 5-HT in the vagal primary afferent neurones. Single neuronal discharges of vagal primary afferent neurones innervating the duodenum were recorded from rat nodose ganglia. Two groups of nodose ganglia neurones were identified: group A neurones responded to intra-arterial injection of low doses of cholecystokinin octapeptide (CCK-8; 10-60 pmol); group B neurones responded only to high doses of CCK-8 (120-240 pmol), and were also activated by duodenal distention. CCK-JMV-180, which acts as an agonist in high-affinity states and as an antagonist in low-affinity states, dose dependently stimulated group A neurones, but inhibited the effect of the high doses of CCK-8 on group B neurones. Duodenal perfusion of 5-HT evoked dose-dependent increases in nodose neuronal discharges. Some neurones that responded to 5-HT showed no response to either high or low doses of CCK-8. A separate group of nodose neurones that possessed high-affinity CCK type A (CCK-A) receptors also responded to luminal infusion of 5-HT. Further, a subthreshold dose of CCK-8 (i.e. 5 pmol) produced no measurable electrophysiological effects but it augmented the neuronal responses to 5-HT. This potentiation effect of CCK-8 was eliminated by CR 1409. From these results we concluded that the vagal nodose ganglion contains neurones that may possess only high- or low-affinity CCK-A receptors or 5-HT3 receptors. Some neurones that express high-affinity CCK-A receptors also express 5-HT3 receptors. Pre-exposure to luminal 5-HT may augment the subsequent response to a subthreshold dose of CCK.
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Affiliation(s)
- Y Li
- Gastroenterology Research Unit, Department of Internal Medicine, University of Michigan Health System, Ann Arbor, MI 48109-0682, USA.
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Rong W, Hillsley K, Davis JB, Hicks G, Winchester WJ, Grundy D. Jejunal afferent nerve sensitivity in wild-type and TRPV1 knockout mice. J Physiol 2004; 560:867-81. [PMID: 15331673 PMCID: PMC1665286 DOI: 10.1113/jphysiol.2004.071746] [Citation(s) in RCA: 169] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The aim of this study was to investigate the contribution of the TRPV1 receptor to jejunal afferent sensitivity in the murine intestine. Multiunit activity was recorded in vitro from mesenteric afferents supplying segments of mouse jejunum taken from wild-type (WT) and TRPV1 knockout (TRPV1(-/-)) animals. In WT preparations, ramp distension of the gut (up to 60 mmHg) produced biphasic changes in afferent activity so the pressure-response curve had an initial rapid increase in afferent discharge followed by a second phase of slower increase in activity. Afferent response to distension was significantly lower in TRPV1(-/-) than in WT mice. Single-unit analysis revealed three functional types of afferent fibres: (1) low-threshold fibres (2) wide dynamic range fibres and (3) high-threshold fibres. There was a marked downward shift of the pressure-response curve for wide dynamic range fibres in the TRPV1(-/-) mice as compared to the WT controls. The afferent response to intraluminal hydrochloric acid (20 mM) was also attenuated in the TRPV1(-/-) mice. In contrast, the response to bath application of bradykinin (1 microm, 3 ml) was not significantly different between the two groups. The TRPV1 antagonist capsazepine (10 microm) significantly attenuated the nerve responses to distension, intraluminal acid and bradykinin, as well as the spontaneous discharge in WT mice. The WT jejunal afferents responded to capsaicin with rapid increases in afferent activity, whereas TRPV1(-/-) afferents were not at all sensitive to capsaicin. Previous evidence indicates that TRPV1 is not mechanosensitive, so the results of the present study suggest that activation of TRPV1 may sensitize small intestinal afferent neurones.
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Affiliation(s)
- Weifang Rong
- Department of Biomedical Science, University of Sheffield, Alfred Danny Building, Western Bank, Sheffield S10 2TN, UK
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Danzer M, Jocic M, Samberger C, Painsipp E, Bock E, Pabst MA, Crailsheim K, Schicho R, Lippe IT, Holzer P. Stomach-brain communication by vagal afferents in response to luminal acid backdiffusion, gastrin, and gastric acid secretion. Am J Physiol Gastrointest Liver Physiol 2004; 286:G403-11. [PMID: 14592947 DOI: 10.1152/ajpgi.00308.2003] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Vagal afferents play a role in gut-brain signaling of physiological and pathological stimuli. Here, we investigated how backdiffusion of luminal HCl or NH(4)OH and pentagastrin-stimulated acid secretion interact in the communication between rat stomach and brain stem. Rats were pretreated intraperitoneally with vehicle or appropriate doses of cimetidine, omeprazole, pentagastrin, dexloxiglumide (CCK(1) receptor antagonist), and itriglumide (CCK(2) receptor antagonist) before intragastric administration of saline or backdiffusing concentrations of HCl or NH(4)OH. Two hours later, neuronal activation in the nucleus of the solitary tract (NTS) and area postrema was visualized by c-Fos immunohistochemistry. Exposure of the rat gastric mucosa to HCl (0.15-0.5 M) or NH(4)OH (0.1-0.3 M) led to a concentration-dependent expression of c-Fos in the NTS, which was not related to gender, gastric mucosal injury, or gastropyloric motor alterations. The c-Fos response to HCl was diminished by cimetidine and omeprazole, enhanced by pentagastrin, and left unchanged by dexloxiglumide and itriglumide. Pentagastrin alone caused an omeprazole-resistant expression of c-fos, which in the NTS was attenuated by itriglumide and prevented by dexloxiglumide but in the area postrema was reduced by dexloxiglumide and abolished by itriglumide. We conclude that vagal afferents transmit physiological stimuli (gastrin) and pathological events (backdiffusion of luminal HCl or NH(4)OH) from the stomach to the brain stem. These communication modalities interact because, firstly, acid secretion enhances afferent signaling of gastric acid backdiffusion and, secondly, gastrin activates NTS neurons through stimulation of CCK(1) receptors on vagal afferents and of CCK(2) receptors on area postrema neurons projecting to the NTS.
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Affiliation(s)
- Marion Danzer
- Deartment of Experimental and Clinical Pharmacology, University of Graz, A-8010 Graz, Austria
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Randich A, Chandler PC, Mebane HC, Turnbach ME, Meller ST, Kelm GR, Cox JE. Jejunal administration of linoleic acid increases activity of neurons in the paraventricular nucleus of the hypothalamus. Am J Physiol Regul Integr Comp Physiol 2004; 286:R166-73. [PMID: 14660477 DOI: 10.1152/ajpregu.00431.2003] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The present experiment examined whether neurons located in the paraventricular nucleus of the hypothalamus (PVN) respond to intestinal infusions of long-chain fatty acids. Single-unit recordings were made of neurons located in and adjacent to the PVN during jejunal administration of linoleic acid. Jejunal administration of linoleic acid increased single-unit activity of neurons located in the PVN but did not affect activity of neurons located in adjacent tissue outside the PVN. The largest increases in neuronal activity were observed in the anterior PVN (0.9-1.3 mm posterior to bregma) compared with the posterior PVN (1.8-2.1 mm posterior to bregma). Jejunal administration of saline failed to affect activity of neurons located either inside or outside the PVN. When the same neurons were subsequently tested for their response to intravenous administration of 2 microg/kg of CCK-8, excitatory responses were more frequently observed than inhibitory responses, but both types of responses were observed regardless of whether neurons were located inside or outside the PVN. In addition, there was no strong correlation between the magnitude of the neuronal response evoked by jejunal administration of linoleic acid compared with intravenous CCK-8. These data suggest that neurons located in the anterior PVN may play a role in the mediation of suppression of food intake produced by intestinal administration of lipids.
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Affiliation(s)
- Alan Randich
- Department of Psychology, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
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