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Sun H, Li C, Shi Y, Wang Y, Li J, Fan L, Yu Y, Ji X, Gao X, Hou K, Li Y. Investigating the L-Glu-NMDA receptor-H 2S-NMDA receptor pathway that regulates gastric function in rats' nucleus ambiguus. Front Pharmacol 2024; 15:1389873. [PMID: 38751777 PMCID: PMC11094298 DOI: 10.3389/fphar.2024.1389873] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2024] [Accepted: 04/15/2024] [Indexed: 05/18/2024] Open
Abstract
Background In previous investigations, we explored the regulation of gastric function by hydrogen sulfide (H2S) and L-glutamate (L-Glu) injections in the nucleus ambiguus (NA). We also determined that both H2S and L-Glu have roles to play in the physiological activities of the body, and that NA is an important nucleus for receiving visceral sensations. The purpose of this study was to explore the potential pathway link between L-Glu and H2S, resulting in the regulation of gastric function. Methods Physiological saline (PS), L-glutamate (L-Glu, 2 nmol), NaHS (2 nmol), D-2-amino-5-phopho-novalerate (D-AP5, 2 nmol) + L-Glu (2 nmol), aminooxyacetic acid (AOAA, 2 nmol) + L-Glu (2 nmol), D-AP5 (2 nmol) + NaHS (2 nmol) were injected into the NA. A balloon was inserted into the stomach to observe gastric pressure and for recording the changes of gastric smooth muscle contraction curve. The gastric fluid was collected by esophageal perfusion and for recording the change of gastric pH value. Results Injecting L-Glu in NA was found to significantly inhibit gastric motility and promote gastric acid secretion in rats (p < 0.01). On the other hand, injecting the PS, pre-injection N-methyl-D-aspartate (NMDA) receptor blocker D-AP5, cystathionine beta-synthase (CBS) inhibitor AOAA and re-injection L-Glu did not result in significant changes (p > 0.05). The same injection NaHS significantly inhibit gastric motility and promote gastric acid secretion in rats (p < 0.01), but is eliminated by injection D-AP5 (p > 0.05). Conclusion The results indicate that both exogenous L-Glu and H2S injected in NA regulate gastric motility and gastric acid secretion through NMDA receptors. This suggests that NA has an L-Glu-NMDA receptor-CBS-H2S pathway that regulates gastric function.
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Clyburn C, Browning KN. Glutamatergic plasticity within neurocircuits of the dorsal vagal complex and the regulation of gastric functions. Am J Physiol Gastrointest Liver Physiol 2021; 320:G880-G887. [PMID: 33730858 PMCID: PMC8202199 DOI: 10.1152/ajpgi.00014.2021] [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] [Indexed: 01/31/2023]
Abstract
The meticulous regulation of the gastrointestinal (GI) tract is required for the coordination of gastric motility and emptying, intestinal secretion, absorption, and transit as well as for the overarching management of food intake and energy homeostasis. Disruption of GI functions is associated with the development of severe GI disorders and the alteration of food intake and caloric balance. Functional GI disorders as well as the dysregulation of energy balance and food intake are frequently associated with, or result from, alterations in the central regulation of GI control. The faithful and rapid transmission of information from the stomach and upper GI tract to second-order neurons of the nucleus of the tractus solitarius (NTS) relies on the delicate modulation of excitatory glutamatergic transmission, as does the relay of integrated signals from the NTS to parasympathetic efferent neurons of the dorsal motor nucleus of the vagus (DMV). Many studies have focused on understanding the physiological and pathophysiological modulation of these glutamatergic synapses, although their role in the control and regulation of GI functions has lagged behind that of cardiovascular and respiratory functions. The purpose of this review is to examine the current literature exploring the role of glutamatergic transmission in the DVC in the regulation of GI functions.
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Affiliation(s)
- Courtney Clyburn
- Department of Neural and Behavioral Sciences, Penn State University College of Medicine, Hershey, Pennsylvania
| | - Kirsteen N. Browning
- Department of Neural and Behavioral Sciences, Penn State University College of Medicine, Hershey, Pennsylvania
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Filpa V, Moro E, Protasoni M, Crema F, Frigo G, Giaroni C. Role of glutamatergic neurotransmission in the enteric nervous system and brain-gut axis in health and disease. Neuropharmacology 2016; 111:14-33. [PMID: 27561972 DOI: 10.1016/j.neuropharm.2016.08.024] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Revised: 07/18/2016] [Accepted: 08/18/2016] [Indexed: 02/07/2023]
Abstract
Several studies have been carried out in the last 30 years in the attempt to clarify the possible role of glutamate as a neurotransmitter/neuromodulator in the gastrointestinal tract. Such effort has provided immunohistochemical, biomolecular and functional data suggesting that the entire glutamatergic neurotransmitter machinery is present in the complex circuitries of the enteric nervous system (ENS), which participates to the local coordination of gastrointestinal functions. Glutamate is also involved in the regulation of the brain-gut axis, a bi-directional connection pathway between the central nervous system (CNS) and the gut. The neurotransmitter contributes to convey information, via afferent fibers, from the gut to the brain, and to send appropriate signals, via efferent fibers, from the brain to control gut secretion and motility. In analogy with the CNS, an increasing number of studies suggest that dysregulation of the enteric glutamatergic neurotransmitter machinery may lead to gastrointestinal dysfunctions. On the whole, this research field has opened the possibility to find new potential targets for development of drugs for the treatment of gastrointestinal diseases. The present review analyzes the more recent literature on enteric glutamatergic neurotransmission both in physiological and pathological conditions, such as gastroesophageal reflux, gastric acid hypersecretory diseases, inflammatory bowel disease, irritable bowel syndrome and intestinal ischemia/reperfusion injury.
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Affiliation(s)
- Viviana Filpa
- Department of Clinical and Experimental Medicine, University of Insubria, via H. Dunant 5, I-21100 Varese, Italy
| | - Elisabetta Moro
- Department of Internal Medicine and Therapeutics, Section of Pharmacology, via Ferrata 9, I-27100 Pavia, Italy
| | - Marina Protasoni
- Department of Surgical and Morphological Sciences, University of Insubria, via F. Guicciardini 9, I-21100 Varese, Italy
| | - Francesca Crema
- Department of Internal Medicine and Therapeutics, Section of Pharmacology, via Ferrata 9, I-27100 Pavia, Italy
| | - Gianmario Frigo
- Department of Internal Medicine and Therapeutics, Section of Pharmacology, via Ferrata 9, I-27100 Pavia, Italy
| | - Cristina Giaroni
- Department of Clinical and Experimental Medicine, University of Insubria, via H. Dunant 5, I-21100 Varese, Italy
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Finlay C, Duty S. Therapeutic potential of targeting glutamate receptors in Parkinson's disease. J Neural Transm (Vienna) 2014; 121:861-80. [PMID: 24557498 DOI: 10.1007/s00702-014-1176-4] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2013] [Accepted: 02/05/2014] [Indexed: 12/28/2022]
Abstract
Glutamate plays a complex role in many aspects of Parkinson's disease including the loss of dopaminergic neurons, the classical motor symptoms as well as associated non-motor symptoms and the treatment-related side effect, L-DOPA-induced dyskinesia. This widespread involvement opens up possibilities for glutamate-based therapies to provide a more rounded approach to treatment than is afforded by current dopamine replacement therapies. Beneficial effects of blocking postsynaptic glutamate transmission have already been noted in a range of preclinical studies using antagonists of NMDA receptors or negative allosteric modulators of metabotropic glutamate receptor 5 (mGlu5), while positive allosteric modulators of mGlu4 in particular, although at an earlier stage of investigation, also look promising. This review addresses each of the key features of Parkinson's disease in turn, summarising the contribution glutamate makes to that feature and presenting an up-to-date account of the potential for drugs acting at ionotropic or metabotropic glutamate receptors to provide relief. Whilst only a handful of these have progressed to clinical trials to date, notably NMDA and NR2B antagonists against motor symptoms and L-DOPA-induced dyskinesia, with mGlu5 negative allosteric modulators also against L-DOPA-induced dyskinesia, the mainly positive outcomes of these trials, coupled with supportive preclinical data for other strategies in animal models of Parkinson's disease and L-DOPA-induced dyskinesia, raise cautious optimism that a glutamate-based therapeutic approach will have significant impact on the treatment of Parkinson's disease.
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Affiliation(s)
- Clare Finlay
- Wolfson Centre for Age-Related Diseases, King's College London, WW1.28. Hodgkin Building, Guy's Campus, London, SE1 1UL, UK
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The neural pathway of reflex regulation of electroacupuncture at orofacial acupoints on gastric functions in rats. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE 2012; 2012:753264. [PMID: 23346213 PMCID: PMC3549401 DOI: 10.1155/2012/753264] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/21/2012] [Revised: 12/14/2012] [Accepted: 12/16/2012] [Indexed: 01/14/2023]
Abstract
Acupuncture has a reflex regulation in gastrointestinal functions, which is characterized with segment. In the present study, the neural pathway of electroacupuncture (EA) at orofacial acupoints (ST2) on gastric myoelectric activity (GMA) in rats was investigated. The results indicated that EA at ST2 facilitated spike bursts of GMA, which is similar to EA at limbs and opposite to EA at abdomen. The excitatory effect was abolished by the transaction of infraorbital nerves, dorsal vagal complex lesion, and vagotomy, respectively. In addition, microinjection of L-glutamate into the nucleus of the solitary tract (NTS) attenuated the excitatory effect. All these data suggest that the dorsal vagal complex is involved in the reflex regulation of EA at orofacial acupoints on gastric functions and NTS-dorsal motor nucleus of the vagus (DMV) inhibitory connections may be essential for it.
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NMDA Receptors of Gastric-Projecting Neurons in the Dorsal Motor Nucleus of the Vagus Mediate the Regulation of Gastric Emptying by EA at Weishu (BL21). EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE 2012; 2012:583479. [PMID: 22654955 PMCID: PMC3359673 DOI: 10.1155/2012/583479] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/11/2012] [Accepted: 02/24/2012] [Indexed: 01/26/2023]
Abstract
A large number of studies have been conducted to explore the efficacy of electroacupuncture (EA) for the treatment of gastrointestinal motility. While several lines of evidence addressed the basic mechanism of EA on gastrointestinal motility regarding effects of limb and abdomen points, the mechanism for effects of the back points on gastric motility still remains unclear. Here we report that the NMDA receptor (NMDAR) antagonist kynurenic acid inhibited the gastric emptying increase induced by high-intensity EA at BL21 and agonist NMDA enhanced the effect of the same treatment. EA at BL21 enhanced NMDAR, but not AMPA receptor (AMPAR) component of miniature excitatory postsynaptic current (mEPSC) in gastric-projecting neurons of the dorsal motor nucleus of the vagus (DMV). In sum, our data demonstrate an important role of NMDAR-mediated synaptic transmission of gastric-projecting DMV neurons in mediating EA at BL21-induced enhancement of gastric emptying.
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Central regulation of the pharyngeal and upper esophageal reflexes during swallowing in the Japanese eel. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2009; 196:111-22. [PMID: 20035336 DOI: 10.1007/s00359-009-0498-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2009] [Revised: 11/24/2009] [Accepted: 12/08/2009] [Indexed: 10/20/2022]
Abstract
We investigated the regulation of the pharyngeal and upper esophageal reflexes during swallowing in eel. By retrograde tracing from the muscles, the motoneurons of the upper esophageal sphincter (UES) were located caudally within the mid-region of the glossopharyngeal-vagal motor complex (mGVC). In contrast, the motoneurons innervating the pharyngeal wall were localized medially within mGVC. Sensory pharyngeal fibers in the vagal nerve terminated in the caudal region of the viscerosensory column (cVSC). Using the isolated brain, we recorded 51 spontaneously active neurons within mGVC. These neurons could be divided into rhythmically (n = 8) and continuously (n = 43) firing units. The rhythmically firing neurons seemed to be restricted medially, whereas the continuously firing neurons were found caudally within mGVC. The rhythmically firing neurons were activated by the stimulation of the cVSC. In contrast, the stimulation of the cVSC inhibited firing of most, but not all the continuously firing neurons. The inhibitory effect was blocked by prazosin in 17 out of 38 neurons. Yohimbine also blocked the cVSC-induced inhibition in five of prazosin-sensitive neurons. We suggest that the neurons in cVSC inhibit the continuously firing motoneurons to relax the UES and stimulate the rhythmically firing neurons to constrict the pharynx simultaneously.
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Depolarization-induced release of endocannabinoids by murine dorsal motor nucleus of the vagus nerve neurons differentially regulates inhibitory and excitatory neurotransmission. Neuropharmacology 2009; 56:1106-15. [DOI: 10.1016/j.neuropharm.2009.03.009] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2008] [Revised: 02/26/2009] [Accepted: 03/18/2009] [Indexed: 11/17/2022]
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Zhou SY, Lu YX, Yao H, Owyang C. Spatial organization of neurons in the dorsal motor nucleus of the vagus synapsing with intragastric cholinergic and nitric oxide/VIP neurons in the rat. Am J Physiol Gastrointest Liver Physiol 2008; 294:G1201-9. [PMID: 18460697 PMCID: PMC3221413 DOI: 10.1152/ajpgi.00309.2006] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The dorsal motor nucleus of the vagus (DMV) contains preganglionic neurons that control gastric motility and secretion. Stimulation of different parts of the DMV results in a decrease or an increase in gastric motor activities, suggesting a spatial organization of vagal preganglionic neurons in the DMV. Little is known about how these preganglionic neurons in the DMV synapse with different groups of intragastric motor neurons to mediate contraction or relaxation of the stomach. We used pharmacological and immunohistochemical methods to characterize intragastric neural pathways involved in mediating gastric contraction and relaxation in rats. Microinjections of L-glutamate (L-Glu) into the rostral or caudal DMV produced gastric contraction and relaxation, respectively, in a dose-related manner. Intravenous infusion of hexamethonium blocked these actions, suggesting mediation via preganglionic cholinergic pathways. Atropine inhibited gastric contraction by 85.5 +/- 4.5%. Gastric relaxation was reduced by intravenous administration of N(G)-nitro-L-arginine methyl ester (L-NAME; 52.5 +/- 11.9%) or VIP antagonist (56.3 +/- 14.9%). Combined administration of L-NAME and VIP antagonist inhibited gastric relaxation evoked by L-Glu (87.8 +/- 4.3%). Immunohistochemical studies demonstrated choline acetyltransferase immunoreactivity in response to L-Glu microinjection into the rostral DMV in 88% of c-Fos-positive intragastric myenteric neurons. Microinjection of L-Glu into the caudal DMV evoked expression of nitric oxide (NO) synthase and VIP immunoreactivity in 81 and 39%, respectively, of all c-Fos-positive intragastric myenteric neurons. These data indicate spatial organization of the DMV. Depending on the location, microinjection of L-Glu into the DMV may stimulate intragastric myenteric cholinergic neurons or NO/VIP neurons to mediate gastric contraction and relaxation.
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Mizuta Y, Shikuwa S, Isomoto H, Mishima R, Akazawa Y, Masuda JI, Omagari K, Takeshima F, Kohno S. Recent insights into digestive motility in functional dyspepsia. J Gastroenterol 2006; 41:1025-40. [PMID: 17160514 DOI: 10.1007/s00535-006-1966-z] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/06/2006] [Accepted: 10/02/2006] [Indexed: 02/04/2023]
Abstract
Functional gastrointestinal disorders, such as functional dyspepsia (FD) and irritable bowel syndrome, are common pathologies of the gut. FD is a clinical syndrome defined as chronic or recurrent pain or discomfort of unknown origin in the upper abdomen. The pathophysiological mechanisms responsible for FD have not been fully elucidated, but new ideas regarding its pathophysiology and the significance of the pathophysiology with respect to the symptom pattern of FD have emerged. In particular, there is growing interest in alterations in gastric motility, such as accommodation to a meal or gastric emptying, and visceral sensation in FD. The mechanisms underlying impaired gastroduodenal motor function are unclear, but possible factors include abnormal neurohormonal function, autonomic dysfunction, visceral hypersensitivity to acid or mechanical distention, Helicobacter pylori infection, acute gastrointestinal infection, psychosocial comorbidity, and stress. Although the optimum treatment for FD is not yet clearly established, acid-suppressive drugs, prokinetic agents, eradication of H. pylori, and antidepressants have been widely used in the management of patients with FD. The therapeutic efficacy of prokinetics such as itopride hydrochloride and mosapride citrate in the treatment of FD is supported by the results of relatively large and well-controlled studies. In addition, recent research has yielded new therapeutic agents and modalities for dysmotility in FD, including agonists/antagonists of various sensorimotor receptors, activation of the nitrergic pathway, kampo medicine, acupuncture, and gastric electric stimulation. This review discusses recent research on the pathophysiology of and treatment options for FD, with special attention given to digestive dysmotility.
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Affiliation(s)
- Yohei Mizuta
- Second Department of Internal Medicine, Nagasaki University School of Medicine, 1-7-1 Sakamoto, Nagasaki 852-8501, Japan
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Iwa M, Nakade Y, Pappas TN, Takahashi T. Electroacupuncture elicits dual effects: stimulation of delayed gastric emptying and inhibition of accelerated colonic transit induced by restraint stress in rats. Dig Dis Sci 2006; 51:1493-500. [PMID: 16868821 DOI: 10.1007/s10620-006-9083-7] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/27/2005] [Accepted: 10/07/2005] [Indexed: 12/11/2022]
Abstract
Acupuncture has been used for treating functional gastrointestinal (GI) disorders. Animal studies have demonstrated that acupuncture antagonized various stress-induced responses. We investigated the effects of electroacupuncture (EA) at ST-36 (Zusanli; lower limb) on stress-induced alteration of GI motor activities. Solid gastric emptying was significantly delayed by restraint stress (29.6+/-2.4%; n=7) compared to that of controls (60.0+/-2.5%; n=8). Delayed gastric emptying was significantly improved by EA at ST-36 (47.2+/-1.8%). Intracisternal (IC) injection of corticotropin releasing factor (CRF; 1 microg) delayed gastric emptying to 25.4+/-3.1%, which was also improved by EA at ST-36, to 53.0+/-7.1% (n=8). The stimulatory effect of EA on stress-induced delayed gastric emptying was abolished by atropine (17.6+/-1.9%) but not by guanethidine (42.2+/-2.3%). Colonic transit was significantly accelerated by restraint stress (GC=7.2+/-0.3; n=8) compared to that of controls (GC=5.2+/-0.2; n=8). Accelerated colonic transit was significantly reduced by EA at ST-36 (GC=4.9+/-0.3). IC injection of CRF accelerated colonic transit (GC=6.9+/-0.2), which was also normalized by EA at ST-36 (GC=4.7+/-0.2). The inhibitory effect of EA on stress-induced acceleration of colonic transit was not affected by guanethidine (GC=4.6+/-0.3). In conclusion, EA at ST-36 showed dual effects: stimulation of stress-induced delayed gastric emptying and inhibition of stress-induced acceleration of colonic transit. The stimulatory effect of EA on stress-induced delayed gastric emptying is mediated via cholinergic pathways. The inhibitory effect of EA on stress-induced acceleration of colonic transit is independent of the sympathetic pathway.
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Affiliation(s)
- Masahiro Iwa
- Department of Surgery, Duke University and Durham Veterans Affairs Medical Center, Durham, North Carolina 27705, USA
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12
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Abstract
Brainstem parasympathetic circuits that modulate digestive functions of the stomach are comprised of afferent vagal fibers, neurons of the nucleus tractus solitarius (NTS), and the efferent fibers originating in the dorsal motor nucleus of the vagus (DMV). A large body of evidence has shown that neuronal communications between the NTS and the DMV are plastic and are regulated by the presence of a variety of neurotransmitters and circulating hormones as well as the presence, or absence, of afferent input to the NTS. These data suggest that descending central nervous system inputs as well as hormonal and afferent feedback resulting from the digestive process can powerfully regulate vago-vagal reflex sensitivity. This paper first reviews the essential "static" organization and function of vago-vagal gastric control neurocircuitry. We then present data on the opioidergic modulation of NTS connections with the DMV as an example of the "gating" of these reflexes, i.e., how neurotransmitters, hormones, and vagal afferent traffic can make an otherwise static autonomic reflex highly plastic.
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Iwa M, Nakade Y, Pappas TN, Takahashi T. Electroacupuncture improves restraint stress-induced delay of gastric emptying via central glutaminergic pathways in conscious rats. Neurosci Lett 2006; 399:6-10. [PMID: 16406343 DOI: 10.1016/j.neulet.2005.11.069] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2005] [Revised: 11/19/2005] [Accepted: 11/30/2005] [Indexed: 02/07/2023]
Abstract
Acupuncture has been used for treating functional gastrointestinal (GI) disorders. Animal studies demonstrated that acupuncture improves various stress-induced physiological responses. We investigated the effects of electroacupuncture (EA) at ST-36 (Zusanli; lower limb) on stress-induced delay of gastric emptying. Solid food gastric emptying in 90 min was significantly delayed by restraint stress (27.3 +/- 2.1%, n = 8), compared to that of controls (64 +/- 2.1%, n = 8). Restraint stress-induced delay of gastric emptying was significantly restored by the intracisternal (IC)-injection of GABA(A) receptor antagonist, bicuculline methiodide (46.5 +/- 3.1%; n = 6) and GABA(B) receptor antagonist, phaclofen (48 +/- 3.3%; n = 6). Delayed gastric emptying induced by restraint stress was significantly improved by EA at ST-36 (49.7 +/- 1.4%). The stimulatory effect of EA on stress-induced delay of gastric emptying was prevented by pretreatment with IC-injection of glutamate receptor antagonist, kynurenic acid (30.1 +/- 2.1%). In conclusion, restraint stress-induced delay of gastric emptying is mediated via central GABA(A) and GABA(B) receptors. EA at ST-36 stimulates glutaminergic neurons in the brainstem resulting in improvement of stress-induced delay of gastric emptying.
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Affiliation(s)
- Masahiro Iwa
- Department of Surgery, Duke University and Durham Veterans Affairs Medical Center, Surgical Service 112, 508 Fulton Street, NC 27705, USA
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Liao Z, Li ZS, Lu Y, Wang WZ. Glutamate receptors within the nucleus of solitary tract contribute to pancreatic secretion stimulated by intraduodenal hypertonic saline. Auton Neurosci 2005; 120:62-7. [PMID: 15897013 DOI: 10.1016/j.autneu.2005.04.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2005] [Revised: 04/13/2005] [Accepted: 04/14/2005] [Indexed: 02/05/2023]
Abstract
It is well known that central transmission of vago-vagal reflex within the nucleus of solitary tract (NST) plays an important role in the regulation of gastrointestinal functions. The present study was designed to assess the role of NST glutamate receptor mechanism in pancreatic secretion evoked by intraduodenal hypertonic saline (HS) in anesthetized rats. Intraduodenal infusion of HS significantly (P<0.01) stimulated pancreatic protein output (from 2.60+/-0.09 to 4.18+/-0.24 mg/15 min). Bilaterally microinjected L-glutamate (5 nmol) into the medial nucleus of solitary tract (mNST) produced a significant increase of pancreatic protein secretion (from 2.65+/-0.12 to 4.80+/-0.34 mg/15 min, P<0.01). Bilateral injection of glutamate receptor antagonist kynurenic acid (KYN, 5 nmol) into the mNST completely abolished the increase of pancreatic protein output stimulated by intraduodenal HS (from 4.28+/-0.21 to 2.83+/-0.19 mg/15 min). Either NMDA receptor antagonist dl-2-amino-5-phosphonopentanoic acid (AP5, 1.5 nmol) or AMPA/Kainate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX, 1.5 nmol) injected into the mNST markedly attenuated (P<0.05) the pancreatic protein secretion stimulated by intraduodenal HS. In conclusion, these findings showed that blockade of the NST glutamate receptors, including NMDA and AMPA/Kainate receptors antagonized pancreatic secretion evoked by intraduodenal osmolality factor, and suggested that glutamate receptor mechanism within the NST contributed to the central regulation of pancreatic secretion.
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Affiliation(s)
- Zhuan Liao
- Department of Gastroenterology, Changhai Hospital, Second Military Medical University, 174 Chang-Hai Road, Shanghai 200433, PR China.
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Kuiken SD, van den Berg SJT, Tytgat GNJ, Boeckxstaens GEE. Oral S(+)-ketamine does not change visceral perception in health. Dig Dis Sci 2004; 49:1745-51. [PMID: 15628696 DOI: 10.1007/s10620-004-9563-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/09/2022]
Abstract
Application of N-methyl-D-aspartate (NMDA)-receptor antagonists may hold promise for the treatment of visceral pain. In this study we evaluated the effect of oral S(+)-ketamine (sKET), a non-competitive NMDA-receptor antagonist, on visceral sensitivity in healthy volunteers. Eight healthy volunteers (five male, three female) underwent a gastric barostat study following oral administration of placebo, 25 mg sKET, and 50 mg sKET. Studies were performed in a double-blind randomized crossover fashion. Sensations evoked by stepwise isobaric distension (2 mm Hg/2 min) were scored on a 100-mm visual analogue scale. In addition, fasting and postprandial fundic volume were measured at a fixed pressure level (MDP + 2 mm Hg). During gastric distension, sKET did not alter sensation scores for bloating, nausea, satiation, and pain compared to placebo. sKET had also no effects on the thresholds for pain/discomfort, fundic wall compliance, fundic tone, or meal-induced fundic relaxation. sKET does not reduce visceral perception or gastric motility in healthy volunteers. The role of sKET in conditions characterized by visceral hypersensitivity needs to be studied further.
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Affiliation(s)
- Sjoerd D Kuiken
- Department of Gastroenterology and Hepatology, Academic Medical Center, Amsterdam, the Netherlands
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Grabauskas G, Zhou SY, Das S, Lu Y, Owyang C, Moises HC. Prolactin-releasing peptide affects gastric motor function in rat by modulating synaptic transmission in the dorsal vagal complex. J Physiol 2004; 561:821-39. [PMID: 15486017 PMCID: PMC1665377 DOI: 10.1113/jphysiol.2004.072736] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Prolactin-releasing peptide (PrRP) is a recently discovered neuropeptide implicated in the central control of feeding behaviour and autonomic homeostasis. PrRP-containing neurones and PrRP receptor mRNA are found in abundance in the caudal portion of the nucleus tractus solitarius (NTS), an area which together with the dorsal motor nucleus of the vagus (DMV) comprises an integrated structure, the dorsal vagal complex (DVC) that processes visceral afferent signals from and provides parasympathetic motor innervation to the gastrointestinal tract. In this study, microinjection experiments were conducted in vivo in combination with whole-cell recording from neurones in rat medullary slices to test the hypothesis that PrRP plays a role in the central control of gastric motor function, acting within the DVC to modulate the activity of preganglionic vagal motor neurones that supply the stomach. Microinjection of PrRP (0.2 pmol (20 nl)(-1)) into the DMV at the level of the area postrema (+0.2 to +0.6 mm from the calamus scriptorius, CS) markedly stimulated gastric contractions and increased intragastric pressure (IGP). Conversely, administration of peptide into the DMV at sites caudal to the obex (0.0 to -0.3 mm from the CS) decreased IGP and reduced phasic contractions. These effects occurred without change in mean arterial pressure and were abolished by ipsilateral vagotomy, indicating mediation via a vagal-dependent mechanism(s). The pattern of gastric motor responses evoked by PrRP mimicked that produced by administration of L-glutamate at the same sites, and both the effects of L-glutamate and PrRP were abolished following local administration of NMDA and non-NMDA-type glutamate receptor antagonists. On the other hand, microinjection of PrRP into the medial or comissural nucleus of the solitary tract (mNTS and comNTS, respectively) resulted in less robust changes in IGP in a smaller percentage of animals, accompanied by marked alterations in arterial pressure. Superfusion of brain slices with PrRP (100-300 nm) produced a small depolarization and increased spontaneous firing in 10 of 30 retrogradely labelled gastric-projecting DMV neurones. The excitatory effects were blocked by administration of TTX (2 mum) or specific glutamate receptor antagonists, indicating that they resulted from interactions of PrRP at a presynaptic site. Congruent with this, PrRP increased the amplitude of excitatory postsynaptic currents (EPSCs, 154 +/- 33%, 12 of 25 neurones) evoked by electrical stimulation in mNTS or comNTS. In addition, administration of PrRP decreased the paired-pulse ratio of EPSCs evoked by two identical stimuli delivered 100 ms apart (from 0.95 +/- 0.08 to 0.71 +/- 0.11, P < 0.05), whereas it did not affect the amplitude of inward currents evoked by exogenous application of L-glutamate to the slice. The frequency, but not amplitude of spontaneous EPSCs and action potential-independent miniature EPSCs was also increased by administration of PrRP, suggesting that the peptide was acting at least in part at receptors on presynaptic nerve terminals to enhance glutamatergic transmission. In recordings obtained from a separate group of slices, we did not observe any direct effects of PrRP on spontaneous discharge or postsynaptic excitability in either mNTS or comNTS neurones (n = 31). These data indicate that PrRP may act within the DVC to regulate gastric motor function by modulating the efficacy of conventional excitatory synaptic inputs from the NTS onto gastric-projecting vagal motor neurones.
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Affiliation(s)
- Gintautas Grabauskas
- GI Division, Department of Internal Medicine, University of Michigan Medical School, 1150 West Medical Center Drive, Ann Arbor, MI 48109-0622, USA
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Covasa M, Hung CY, Ritter RC, Burns GA. Intracerebroventricular administration of MK-801 increases food intake through mechanisms independent of gastric emptying. Am J Physiol Regul Integr Comp Physiol 2004; 287:R1462-7. [PMID: 15358605 DOI: 10.1152/ajpregu.00471.2004] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Systemic or hindbrain administration of MK-801, a noncompetitive N-methyl-D-aspartate receptor antagonist, increases meal size. To examine whether MK-801 enhances intake by increasing gastric emptying, we administered MK-801 (2.0 microg/3.0 microl) into the fourth ventricle [intracerebroventricular (ICV)] and measured feeding and gastric emptying of 5-ml NaCl or 15% sucrose loads. In a parallel experiment, we examined food intake and gastric emptying following intraperitoneal (IP) injection of MK-801 (100 microg/kg). MK-801, either IP or ICV, increased 30-min sucrose intake compared with control (12.3 +/- 0.7 vs. 9.8 +/- 0.5 and 16.6 +/- 2.0 vs. 10.7 +/- 0.7 ml, for IP and ICV administration, respectively). Also, IP MK-801 increased 5-min gastric emptying of NaCl (4.13 +/- 0.1 ml emptied) and sucrose (3.11 +/- 0.1 ml emptied) compared with control (3.75 +/- 0.2 and 2.28 +/- 0.1 ml emptied for NaCl and sucrose loads, respectively). In contrast, ICV MK-801 did not alter NaCl emptying (3.82 +/- 0.1 ml emptied) compared with control (3.82 +/- 0.3 ml emptied) and actually reduced gastric emptying of sucrose (2.1 +/- 0.2 and 2.94 +/- 0.1 ml emptied, for MK and vehicle, respectively). These data confirm previous results that systemic as well as hindbrain injection of MK-801 increases food intake. However, because ICV MK-801 failed to increase gastric emptying, these results indicate that MK-801 increases food intake through mechanisms independent of altered gastric emptying.
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Affiliation(s)
- M Covasa
- Department of Nutritional Sciences, College of Health and Human Development, The Pennsylvania State University, 126 South Henderson, University Park, PA 16802, USA.
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18
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Tsai LH, Lee YJ, Wu JY. Role of N-methyl-D-aspartate receptors in gastric mucosal blood flow induced by histamine. J Neurosci Res 2004; 77:730-8. [PMID: 15352220 DOI: 10.1002/jnr.20202] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Ionotropic N-methyl-D-aspartate (NMDA) receptor agonists, L-aspartic acid (L-Asp) and NMDA, have been shown to inhibit histamine-stimulated acid secretion, but their effect on gastric mucosal blood flow (GMBF) is largely unknown. The aim of this study was to investigate whether L-Asp and NMDA inhibit histamine-stimulated GMBF and to examine the expression patterns of NMDA receptor subunits NR1, NR2A, and NR2B in rat stomach. Laser Doppler flowmetry was used to measure gastric blood flow in anesthetized rats. The GMBF was assessed during an intravenous infusion of histamine in the presence of tripelennamine. The effects of L-Asp and NMDA on histamine-induced gastric blood flow were examined. In addition, the distribution patterns of NR1-, NR2A-, and NR2B-contaning NMDA receptors in rat stomach were determined immunohistochemically by using specific antibodies against NR1, NR2A, and NR2B. Histamine-induced enhancement of GMBF depended on acid secretion and the activation of H(2)-receptors. Neither L-Asp nor NMDA had an effect on the spontaneous GMBF. However, L-Asp and NMDA reduced the histamine-induced increase in GMBF. DL-2-amino-5-phosphonopentanoic acid (AP-5), an NMDA receptor antagonist; and prazosin, an alpha(1)-receptor antagonist; but not propanolol, a beta(2)-receptor antagonist; or yohimbine, a alpha(2)-receptor antagonist; reversed the inhibitory effect of L-Asp and NMDA on the histamine-induced increase in GMBF. Therefore, L-Asp and NMDA inhibit histamine-induced GMBF via a mechanism involving the activation of NMDA receptors and alpha(1)- adrenoceptors. The fact that NMDA receptor subunits NR1, NR2A, and NR2B were found to be localized in the rat stomach as visualized immunohistochemically with specific antibodies against NR1, NR2A, and NR2B is consistent with this hypothesis.
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Affiliation(s)
- Li Hsueh Tsai
- Department of Physiology, School of Medicine, Taipei Medical University, Taipei, Taiwan.
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Corbett EKA, Saha S, Deuchars J, McWilliam PN, Batten TFC. Ionotropic glutamate receptor subunit immunoreactivity of vagal preganglionic neurones projecting to the rat heart. Auton Neurosci 2003; 105:105-17. [PMID: 12798207 DOI: 10.1016/s1566-0702(03)00047-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The ionotropic glutamate receptor subunits expressed by vagal preganglionic neurones in the rat medulla oblongata were examined by using fluorescence immunolabelling combined with retrograde neuronal tracing. The general population of these neurones in the medulla was identified by intraperitoneal injections of Fluorogold and also with choline acetyltransferase antibodies. Cardiac projecting neurones were specifically identified by applying the fluorescent tracer 1,1'-dioctadecyl-3,3,3',3'-tetramethyl-indocarbocyanine (DiI) to the heart or by injecting cholera toxin B-subunit into the pericardium. Both tracers labelled populations of neurones lying in the dorsal vagal nucleus, intermediate reticular formation and nucleus ambiguus, and when both tracers were applied simultaneously, approximately 50% of cells were dual-labelled. Control experiments established that the labelling was specific for neurones projecting to the heart. Most vagal preganglionic neurones, including those projecting to the heart, irrespective of their location in the medulla, had a similar profile of glutamate receptor immunoreactivity. Labelling of somata for the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic (AMPA) subunit GluR1 was weak or absent, while labelling with antibodies directed to GluR2, a common sequence of GluR2 and GluR3, and GluR4 was moderate or intense. All neurones studied appeared to express the N-methyl-D-aspartate (NMDA) receptor subunit NR1, and while antibodies recognising the NR2A and NR2B splice variants gave strong labelling, immunoreactivity with a NR2B specific antibody was weaker. Weak to moderate labelling was seen in some neurones using antibodies to the kainate receptor subunits KA2 and GluR5-7. These results are consistent with neurophysiological data indicating the presence of AMPA, NMDA and kainate responses in cardiac vagal preganglionic neurones, and suggest that these neurones are similar to other vagal parasympathetic preganglionic neurones in expressing mainly AMPA receptor subunits GluR2-4.
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Affiliation(s)
- Eric K A Corbett
- Institute for Cardiovascular Research, School of Medicine, Worsley Building, University of Leeds, LS2 9JT, Leeds, UK
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20
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Zhang X, Fogel R. Involvement of glutamate in gastrointestinal vago-vagal reflexes initiated by gastrointestinal distention in the rat. Auton Neurosci 2003; 103:19-37. [PMID: 12531396 DOI: 10.1016/s1566-0702(02)00145-5] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Vago-vagal reflexes play an integral role in the regulation of gastrointestinal function. Although there have been a number of reports describing the effects of various stimuli on the firing rates of vagal afferent fibers and vagal motor neurons, little is known regarding the neurotransmitters that mediate the vago-vagal reflexes. In the present work, we investigated the role of glutamate in the vago-vagal reflex induced by gastrointestinal distention. Using single-cell recording techniques, we determined the effects of gastric and duodenal distention on the firing rates of gut-related neurons in the dorsal vagal complex, in the absence and presence of glutamate antagonists. Kynurenic acid, a competitive glutamate receptor antagonist, injected into the dorsal vagal complex, blocked the neuronal response of neurons in the dorsal motor nucleus of the vagus and the nucleus of the solitary tract to gastrointestinal distention. Injection of glutamate into the nucleus of the solitary tract produced inhibition of dorsal motor nucleus of the vagus neurons that were also inhibited by gastric and/or duodenal distention. Thus, the distention-induced inhibition of dorsal motor nucleus of the vagus neurons may be mediated by glutamate-induced excitation of gut-related nucleus of the solitary tract neurons. To investigate the role of the various glutamate receptor subtypes in the distention-induced events, we studied the effects of 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), a selective non-NMDA receptor antagonist, and DL-2-amino-5-phosphonopentanoic acid (DL-AP5), a selective NMDA receptor antagonist. CNQX injected into the dorsal vagal complex either blocked or attenuated the inhibitory response of the neurons in the dorsal motor nucleus of the vagus and nucleus of the solitary tract neurons to gastric and duodenal distention. In contrast, DL-AP5 had less effect, especially in the vago-vagal reflex elicited by gastric distention. The results suggest (1) distention activates vagal afferents in the gastrointestinal tract; (2) the central branches of the vagal afferents from the gut terminate in the nucleus of the solitary tract and release glutamate that mainly act on non-NMDA receptors; (3) glutamate activates the inhibitory neurons in the nucleus of the solitary tract that project to the dorsal motor nucleus of the vagus; and (4) the inhibitory neurotransmitter suppresses the activity of the dorsal motor nucleus of the vagus neurons. For the excitatory neuronal responses of the dorsal motor nucleus of the vagus neurons to gastrointestinal distention, the possible circuit is that the vagal afferents containing glutamate directly activate the receptors on the dendrites of the dorsal motor nucleus of the vagus.
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Affiliation(s)
- Xueguo Zhang
- Laboratory of Neurogastroenterology Research, Division of Gastroenterology, Henry Ford Health System, One Ford Place 2D, 6071 Second Avenue, Detroit, MI 48202, USA.
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21
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Huang J, Pickel VM. Ultrastructural localization of serotonin 2A and N-methyl-D-aspartate receptors in somata and dendrites of single neurons within rat dorsal motor nucleus of the vagus. J Comp Neurol 2003; 455:270-80. [PMID: 12454991 DOI: 10.1002/cne.10497] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Both glutamate and serotonin are potent modulators of autonomic functions involving the nucleus of the solitary tract (NTS) and the dorsal motor nucleus of the vagus (DMNV) at the level of the area postrema. Moreover, many of the dendrites in this NTS region express both N-methyl-D-aspartate (NMDA) and serotonin (5HT) 2A receptors, and some of these dendrites may arise from the adjacent DMNV. Thus, single neurons in DMNV may also express both receptors. To test this hypothesis, we used electron microscopic immunocytochemistry for dual localization of the essential R1 subunit of the NMDA receptor (NR1) and the 5HT2A receptor in rat intermediate DMNV, a region serving mainly gastrointestinal functions. Gold particles representing NR1 and peroxidase reaction product for 5HT2A receptors were seen in the cytoplasm, as well as on distinct segments of the plasma membrane of many dendrites. Of the NR1-labeled dendrites, 31% (254/814) also contained 5HT2A immunoreactivity; among the 5HT2A-labeled dendrites, 52% (254/485) expressed NR1. The 5HT2A labeling was also present in numerous small unmyelinated axons, axon terminals, and glial processes. These profiles were largely without NR1 immunoreactivity, although NR1 was detected in some of the dendrites postsynaptic to 5HT2A-labeled terminals. Our results suggest that calcium entry through NMDA channels and 5HT2A receptor activation may dramatically affect postsynaptic excitability of single neurons in the DMNV. In addition, the findings also indicate that the 5HT2A receptor is strategically positioned for involvement in modulation of the presynaptic release of neurotransmitters affecting the postsynaptic activity of DMNV neurons responsive to NMDA activation.
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Affiliation(s)
- Jie Huang
- Department of Neurology and Neuroscience, Weill Medical College of Cornell University, New York, New York, 10021, USA.
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22
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Kuiken SD, Lei A, Tytgat GNJ, Holman R, Boeckxstaens GEE. Effect of the low-affinity, noncompetitive N-methyl-d-aspartate receptor antagonist dextromethorphan on visceral perception in healthy volunteers. Aliment Pharmacol Ther 2002; 16:1955-62. [PMID: 12390105 DOI: 10.1046/j.1365-2036.2002.01358.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
BACKGROUND The use of N-methyl-d-aspartate (NMDA) receptor antagonists may hold promise for the treatment of pain of visceral origin, in particular in conditions characterized by visceral hypersensitivity. AIM To study the effect of dextromethorphan, a low affinity, non-competitive NMDA receptor antagonist, on visceral perception in healthy volunteers. METHODS Nine healthy volunteers (5 female, median age 22 years) underwent a gastric barostat study after oral administration of placebo, dextromethorphan 10 mg or dextromethorphan 30 mg, on three separate days in a double-blind, randomised order. Sensations induced by step-wise isobaric gastric distension (2 mmHg/2 min) were studied during fasting and 30 min after a meal. In addition, proximal gastric tone was measured during fasting and postprandially. RESULTS Compared to placebo, dextromethorphan 30 mg significantly increased the distension-evoked sensation scores for nausea (P=0.004) and satiation (P=0.004) during fasting; and for bloating (P= 0.001), nausea (P=0.000) and satiation (P=0.01) 30 min postprandially. Dextromethorphan did not alter pain scores, proximal gastric tone or gastric compliance. CONCLUSIONS Dextromethorphan increases the perception of non-painful sensations during gastric distension, without altering the perception of pain. Therefore, application of dextromethorphan as a visceral analgesic is questionable. Future studies with more specific NMDA receptor antagonist are warranted.
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Affiliation(s)
- S D Kuiken
- Department of Gastroenterology and Heptalogy, Academic Medical Centre, Amsterdam, the Netherlands
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23
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Zhang X, Sun X, Renehan W, Fogel R. GRP mediates an inhibitory response of gut-related vagal motor neurons to PVN stimulation. Peptides 2002; 23:1649-61. [PMID: 12217426 DOI: 10.1016/s0196-9781(02)00107-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We previously characterized neurons in the dorsal motor nucleus of the vagus (DMNV) that were modulated by electrical stimulation of the PVN and by gastrointestinal distention. Bombesin has been identified in a subset of PVN neurons projecting to the DMNV. It is currently unknown whether this neurotransmitter is involved in descending communication from PVN to DMNV neurons. In this study we determined whether the specific bombesin antagonist, N-acetyl-GRP(20-26), influenced (1) the basal firing rate of DMNV neurons and (2) the response to electrical current stimulation of the PVN. Our results indicate that N-acetyl-GRP(20-26), significantly attenuated the inhibitory response of DMNV neurons to PVN stimulation. These results provide a possible mechanism by which bombesin regulates gastrointestinal function, body temperature homeostasis, and feeding behaviors.
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Affiliation(s)
- Xueguo Zhang
- Laboratory of Neurogastroenterology Research, Division of Gastroenterology, Henry Ford Health System, One Ford Place 2D, 6071 Second Avenue, Detroit, MI 48202, USA.
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24
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Emch GS, Hermann GE, Rogers RC. TNF-alpha-induced c-Fos generation in the nucleus of the solitary tract is blocked by NBQX and MK-801. Am J Physiol Regul Integr Comp Physiol 2001; 281:R1394-400. [PMID: 11641108 DOI: 10.1152/ajpregu.2001.281.5.r1394] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Previous studies have shown that identified neurons of the nucleus of the solitary tract (NST) are excited by the cytokine tumor necrosis factor-alpha (TNF-alpha). Vagal afferent connections with the NST are predominantly glutaminergic. Therefore, we hypothesized that TNF-alpha effects on NST neurons may be via modulation of glutamate neurotransmission. The present study used activation of the immediate early gene product c-Fos as a marker for neuronal activation in the NST. c-Fos expression was evaluated after microinjections of TNF-alpha in the presence or absence of either the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor antagonist 1,2,3,4-tetrahydro-6-nitro-2,3-dioxo-benzo[f]quinoxaline-7-sulfonamide disodium (NBQX) or the N-methyl-D- aspartate (NMDA) antagonist MK-801. To assess the specificity of the interaction between TNF-alpha and glutamate, c-Fos expression was also evaluated after injection of oxytocin (OT) (which has a direct excitatory effect in this area of the brain stem) in the presence and absence of NBQX or MK-801. c-Fos labeling was significantly increased in the NST after TNF-alpha exposure. Coinjection of either NBQX or MK-801 with TNF-alpha prevented significant c-Fos induction in the NST. Microinjections of OT also induced significant NST c-Fos elevation, but this expression was unaffected by coinjection of either antagonist with OT. These data lead us to conclude that TNF-alpha activation of NST neurons depends on glutamate and such an interaction is not generalized to all agonists that act on the NST.
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Affiliation(s)
- G S Emch
- Department of Neuroscience, The Ohio State University, Columbus, Ohio 43210, USA
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25
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Tsuchiya S, Horie S, Yano S, Watanabe K. Stimulatory effects of centrally injected kainate and N-methyl-D-aspartate on gastric acid secretion in anesthetized rats. Brain Res 2001; 914:115-22. [PMID: 11578604 DOI: 10.1016/s0006-8993(01)02784-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The effects of N-methyl-D-aspartate (NMDA), kainate and (+/-)-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA), ionotropic glutamate agonists, on gastric acid secretion were investigated in the continuously perfused stomach of anesthetized rats. The lateral ventricular (LV) injection of kainate (0.01-1 microg) or NMDA (0.3-3 microg) dose-dependently stimulated gastric acid secretion. AMPA (3-10 microg) also stimulated gastric acid secretion but the effect was very weak. Repeated injections of kainate (0.1 microg) or NMDA (1 microg), at least twice, stimulated gastric acid secretion to a similar degree. The effect of kainate (0.1 microg) was blocked by the kainate receptor antagonists, 6-cyano-7-nitroquinoxaline-2,3-dione disodium (3 microg, LV) and D-gamma-glutamylaminomethanesulfonic acid (30 microg, LV), but not by NMDA receptor antagonists. The effect of NMDA (10 microg) was blocked by (+/-)-3-(2-carboxypiperazin-4-yl)-1-propylphosphonic acid (10 microg, LV), a competitive NMDA receptor antagonist, and (+)-5-methyl-10,11-dihydro-5H-dibenzocyclo-hepten-5,10-imine hydrogen maleate (10 microg, LV), a non-competitive NMDA receptor antagonist, but not by kainate receptor antagonists. Moreover, the gastric acid secretion stimulated by kainate and NMDA were completely blocked by systemic atropine injection (1 mg/kg, i.v.) and vagotomy. These findings suggest that kainate and NMDA receptor mechanisms are independently involved in the central nervous system to control gastric acid secretion through vagus cholinergic activation.
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Affiliation(s)
- S Tsuchiya
- Laboratory of Chemical Pharmacology, Faculty of Pharmaceutical Sciences, Chiba University, 263-8522, Chiba, Japan.
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26
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Tebbe JJ, Dietze T, Grote C, Mönnikes H. Excitatory stimulation of neurons in the arcuate nucleus inhibits gastric acid secretion via vagal pathways in anesthetized rats. Brain Res 2001; 913:10-7. [PMID: 11532242 DOI: 10.1016/s0006-8993(01)02746-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
It is well established that autonomic control of gastrointestinal function is modulated by central autonomic neurotransmission. In this context it has been shown that gastrointestinal motility and secretion can be modulated by exogenous neuropeptides microinjected into the paraventricular nucleus of the hypothalamus (PVN). Furthermore, there is considerable evidence suggesting that neurons projecting from the arcuate nucleus (Arc) to the PVN may be the source of endogenous neuropeptide release in the PVN. This poses the question whether stimulation of neurons in the arcuate nucleus, e.g. by an excitatory amino acid, alters gastrointestinal function. In the present study, we investigated the effect of an excitatory amino acid, kainate, microinjected into the arcuate nucleus on gastric acid secretion in urethane-anesthetized rats. Kainate (140 pmol/rat) bilaterally microinjected into the Arc induced an significant inhibition of pentagastrin (PG) stimulated (16 mg/kg per h) gastric acid secretion throughout an observation period of 120 min after microinjection. Microinjection of kainate into hypothalamic areas outside the arcuate nucleus did not modify gastric secretion. Bilateral cervical vagotomy blocked the effect of kainate injected into the Arc on PG-stimulated gastric acid secretion. These data show that gastric secretory function can be modulated by stimulation of neuronal activity in the Arc via efferent vagal pathways. The results suggest that the arcuate nucleus is a forebrain area involved in the CNS regulation of gastrointestinal function.
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Affiliation(s)
- J J Tebbe
- Department of Anatomy and Cell Biology, Philipps-Universität zu Marburg, Marburg, Germany
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27
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Hermann GE, Rogers RC, Bresnahan JC, Beattie MS. Tumor necrosis factor-alpha induces cFOS and strongly potentiates glutamate-mediated cell death in the rat spinal cord. Neurobiol Dis 2001; 8:590-9. [PMID: 11493024 DOI: 10.1006/nbdi.2001.0414] [Citation(s) in RCA: 155] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Excitotoxic cell death due to glutamate release is important in the secondary injury following CNS trauma or ischemia. Proinflammatory cytokines also play a role. Both glutamate and tumor necrosis factor-alpha (TNF(alpha)) are released immediately after spinal cord injury. Neurophysiological studies show that TNF(alpha) can potentiate the effects of glutamatergic afferent input to produce hyperactivation of brain-stem sensory neurons. Therefore, we hypothesized that TNF(alpha) might act cooperatively with glutamate to affect cell death in the spinal cord as well. Nanoinjections of either TNF(alpha) (60 pg) or kainate (KA; 32 ng) alone into the thoracic gray resulted in almost no tissue damage or cell death 90 min after injection. However, the combination of TNF(alpha) plus KA at these same doses produced a large area of tissue necrosis and neuronal cell death, an effect which was blocked by the AMPA receptor antagonist CNQX (17 ng). These results suggest that secondary injury may involve potentiation of AMPA receptor-mediated excitatory cell death by TNF(alpha).
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Affiliation(s)
- G E Hermann
- Laboratory of Autonomic Neuroscience, Department of Neuroscience, The Ohio State University Medical Center, 333 W. 10th Avenue, Columbus, Ohio 43210, USA.
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28
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Hornby PJ. Receptors and transmission in the brain-gut axis. II. Excitatory amino acid receptors in the brain-gut axis. Am J Physiol Gastrointest Liver Physiol 2001; 280:G1055-60. [PMID: 11352796 DOI: 10.1152/ajpgi.2001.280.6.g1055] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
In the last decade, there has been a dramatic increase in academic and pharmaceutical interest in central integration of vago-vagal reflexes controlling the gastrointestinal tract. Associated with this, there have been substantial efforts to determine the receptor-mediated events in the dorsal vagal complex that underlie the physiological responses to distension or variations in the composition of the gut contents. Strong evidence supports the idea that glutamate is a transmitter in afferent vagal fibers conveying information from the gut to the brain, and the implications of this are discussed in this themes article. Furthermore, both ionotropic and metabotropic glutamate receptors mediate pre- and postsynaptic control of glutamate transmission related to several reflexes, including swallowing motor pattern generation, gastric accommodation, and emesis. The emphasis of this themes article is on the potential therapeutic benefits afforded by modulation of these receptors at the site of the dorsal vagal complex.
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Affiliation(s)
- P J Hornby
- Department of Pharmacology and Neuroscience Center of Excellence, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112, USA.
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29
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Quigley EM. Gastroduodenal motility. Curr Opin Gastroenterol 1999; 15:481-91. [PMID: 17023994 DOI: 10.1097/00001574-199911000-00005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Abstract
Several major themes emerged over the past year in the area of gastroduodenal motility. Mostly, these themes represented extensions of research areas discussed in prior reviews in this series rather than the emergence of completely new concepts. Thus, for example, considerable emphasis has again been placed on regional gastric motor function in dyspepsia and on the role of fundic relaxation and accommodation, in particular. Not surprisingly, basic physiologic research has also shown a keen interest in the regulation of fundic relaxation. One new and exciting development is the recognition of the stomach's role in satiety. The spectrum of gastric motor dysfunction in diabetes mellitus continues to be explored, and the important role of hyperglycemia in regulating gastric function has been further emphasized. More data have been provided on noninvasive alternatives to gastric motor function testing, and several studies have looked at factors that may influence variability in these various tests. There have been few innovations over the past year in the therapeutic arena; rather, the indications and limitations of current therapies have been further developed.
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Affiliation(s)
- E M Quigley
- Department of Medicine, National University of Ireland, Cork, Ireland.
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Krowicki Z, Sivarao D, Abrahams T, Hornby P. Excitation of dorsal motor vagal neurons evokes non-nicotinic receptor-mediated gastric relaxation. ACTA ACUST UNITED AC 1999. [DOI: 10.1016/s0165-1838(99)00033-8] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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