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Fuder H, Muscholl E. Heteroreceptor-mediated modulation of noradrenaline and acetylcholine release from peripheral nerves. Rev Physiol Biochem Pharmacol 2006; 126:265-412. [PMID: 7886380 DOI: 10.1007/bfb0049778] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- H Fuder
- IKP-AKP, Professo Lücker GmbH, Grünstadt, Germany
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2
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Tsai LH. Function of GABAergic and glutamatergic neurons in the stomach. J Biomed Sci 2005; 12:255-66. [PMID: 15917994 DOI: 10.1007/s11373-005-1357-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2004] [Accepted: 11/18/2004] [Indexed: 11/26/2022] Open
Abstract
Gamma-aminobutyric acid (GABA) and L-glutamic acid (L-Glu) are transmitters of GABAergic and glutamatergic neurons in the enteric interneurons, targeting excitatory or inhibitory GABA receptors or glutamate receptors that modulate gastric motility and mucosal function. GABAergic and glutamatergic neuron immunoreactivity have been found in cholinergic enteric neurons in the stomach. GABA and L-Glu may also subserve hormonal and paracrine signaling. Disruption in gastrointestinal function following perturbation of enteric GABA receptors and glutamate receptors presents potential new target sites for drug development.
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Affiliation(s)
- Li Hsueh Tsai
- Department of Physiology, School of Medicine, Taipei Medical University, Taipei, 11014, Taiwan.
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3
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Nagahama M, Ma N, Semba R. L-aspartate-immunoreactive neurons in the rat enteric nervous system. Cell Tissue Res 2004; 318:483-92. [PMID: 15578269 DOI: 10.1007/s00441-004-0961-z] [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: 04/19/2004] [Accepted: 07/12/2004] [Indexed: 10/26/2022]
Abstract
L-aspartate (L-Asp) is an excitatory neurotransmitter in the central nervous system. In the present study, we demonstrate, for the first time, the presence of L-Asp in a particular neuronal cell class in the enteric nervous system (ENS). Scattered L-Asp-immunoreactive neuronal cell bodies and nerve fibers were found extensively in both the myenteric and submucosal plexus throughout the small and large intestines. Many L-Asp-immunoreactive nerve fibers, which originated from intrinsic nerve cell bodies, were found in the ganglia and interconnecting nerve bundles. Electron microscopy revealed that L-Asp-immunoreactive terminals frequently formed synaptic contacts with intrinsic nerve cells, suggesting that some L-Asp-immunoreactive neurons might function as interneurons. These results suggest that L-Asp-immunoreactive neurons play a significant role within the ENS to control intestinal functions. The presence of enteric L-Asp-immunoreactive neurons provides strong support for the proposal that L-Asp is a neuromodulator in the rat ENS.
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Affiliation(s)
- Masato Nagahama
- Department of Anatomy II, Mie University School of Medicine, 2-174 Edobashi, 514-0001, Tsu, Mie, Japan.
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4
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Piqueras L, Martinez V. Peripheral GABAB agonists stimulate gastric acid secretion in mice. Br J Pharmacol 2004; 142:1038-48. [PMID: 15210585 PMCID: PMC1575121 DOI: 10.1038/sj.bjp.0705876] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1 We characterized the effects of intravenous GABA and preferential GABAA (muscimol), GABAB (R-baclofen and SKF-97541) and GABAC agonists (imidazole-4-acetic acid) on gastric acid secretion in urethane-anesthetized mice implanted with a gastric cannula, and determined the role of vagal cholinergic mechanisms, and gastrin and somatostatin by using peptide immunoneutralization, the SSTR2 antagonist, PRL-2903, and SSTR2 knockout mice. 2 The selective GABA(B) agonists R-baclofen (0.1-3 mg kg(-1), i.v.) and SKF-97541 (0.01-0.3 mg kg(-1), i.v.) induced a dose-related stimulation of gastric acid secretion. SKF-97541 was about 10 times more potent than R-baclofen stimulating gastric acid secretion. Neither GABA (0.1-100 mg kg(-1), i.v.) nor muscimol (0.1-3 mg kg(-1)) nor imidazole-4-acetic acid (0.1-10 mg kg(-1)) affected basal gastric acid secretion. 3 Stimulatory effects of SKF-97541 (0.1 mg kg(-1), i.v.) were blocked by the selective GABAB antagonist, 2-hydroxysaclofen, cholinergic blockade with atropine, subdiaphragmatic vagotomy or gastrin immunoneutralization. 4 Somatostatin immunoneutralization or SSTR2 blockade with PRL-2903 enhanced the secretory response to SKF-97541 (0.1 mg kg(-1), i.v.) by 78 and 105%, respectively. 5 In SSTR2 knockout mice, SKF-97541 (0.1 mg kg(-1), i.v.) increased basal gastric acid secretion by 48%. Neither GABA nor muscimol nor imidazole-4-acetic acid modified basal gastric acid secretion in SSTR2 knockout mice. 6 These results indicate that, in mice, stimulation of GABAB receptors increases gastric acid secretion through vagal- and gastrin-dependent mechanisms. Somatostatin implication might be secondary to the release of gastrin and the increase in gastric luminal acidity.
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MESH Headings
- Animals
- Antibodies, Monoclonal/pharmacology
- Atropine/pharmacology
- Baclofen/analogs & derivatives
- Baclofen/pharmacology
- Deoxyglucose/pharmacology
- Dose-Response Relationship, Drug
- GABA Agonists/pharmacology
- GABA Antagonists/pharmacology
- GABA-A Receptor Agonists
- GABA-B Receptor Agonists
- Gastric Acid/metabolism
- Gastrins/immunology
- Imidazoles/pharmacology
- Injections, Intravenous
- Male
- Mice
- Mice, Knockout
- Muscimol/pharmacology
- Organophosphorus Compounds/pharmacology
- Pentagastrin/pharmacology
- Peptides, Cyclic/pharmacology
- Receptors, GABA/drug effects
- Receptors, GABA/physiology
- Receptors, GABA-A/physiology
- Receptors, GABA-B/physiology
- Receptors, Somatostatin/antagonists & inhibitors
- Receptors, Somatostatin/genetics
- Receptors, Somatostatin/physiology
- Somatostatin/immunology
- Time Factors
- Vagotomy
- gamma-Aminobutyric Acid/pharmacology
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Affiliation(s)
- Laura Piqueras
- Department of Physiology, Pharmacology and Toxicology, Cardenal Herrera CEU University, Valencia, Spain
| | - Vicente Martinez
- Department of Physiology, Pharmacology and Toxicology, Cardenal Herrera CEU University, Valencia, Spain
- Author for correspondence:
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5
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Minowa S, Ishihara S, Tsuchiya S, Horie S, Watanabe K, Murayama T. Involvement of glutamate and gamma-amino-butyric acid receptor systems on gastric acid secretion induced by activation of kappa-opioid receptors in the central nervous system in rats. Br J Pharmacol 2003; 138:1049-58. [PMID: 12684260 PMCID: PMC1573744 DOI: 10.1038/sj.bjp.0705082] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
1. Various neurotransmitters in the brain regulate gastric acid secretion. Previously, we reported that the central injection of kappa-opioid receptor agonists stimulated this secretion in rats. Although the existence of kappa(1)-kappa(3)-opioid receptor subtypes has been proposed, the character is not defined. We investigated the interactions between kappa-opioid receptor subtypes and glutamate, gamma-amino-butyric acid (GABA) or 5-hydroxy tryptamine (5-HT) receptors in the rat brain. 2. Gastric acid secretion induced by the injection of U69593 (8.41 nmol, a putative kappa(1)-opioid receptor agonist) into the lateral cerebroventricle was completely inhibited by the central injection of 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX, 10.9 nmol, an antagonist for non-N-methyl-D-aspartate (non-NMDA) receptors) and by bicuculline infusion (222 micro g kg(-1) per 10 min, i.v., GABA(A) receptor antagonist). The secretion induced by bremazocine (8.52 nmol, a putative kappa(2)-opioid receptor agonist) was inhibited by bicuculline infusion, but not by CNQX. The secretion induced by naloxone benzoylhydrazone (224 nmol, a putative kappa(3)-opioid receptor agonist) was slightly and partially inhibited by CNQX and bicuculline. 3. Treatment with CNQX and bicuculline inhibited gastric acid secretion induced by the injection of dynorphin A-(1-17) into the lateral, but not the fourth, cerebroventricle. Antagonists for NMDA, GABA(B) and 5-HT(2/1C) receptors did not inhibit the secretions by kappa-opioid receptor agonists. 4. In rat brain regions close to the lateral cerebroventricle, kappa-opioid receptor systems (kappa(1)>kappa(3)>>kappa(2)) are regulated by the non-NMDA type of glutamate receptor system, and kappa(1)- and kappa(2)-opioid receptor systems are regulated by the GABA(A) receptor system. The present findings show pharmacological evidence for kappa-opioid receptor subtypes that regulate gastric acid secretion in the rat brain.
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MESH Headings
- 6-Cyano-7-nitroquinoxaline-2,3-dione/pharmacology
- Animals
- Baclofen/analogs & derivatives
- Baclofen/pharmacology
- Benzeneacetamides/pharmacology
- Benzomorphans/pharmacology
- Bicuculline/pharmacology
- Brain/physiology
- Dynorphins/pharmacology
- Gastric Acid/metabolism
- Gastric Acid/physiology
- Injections, Intraventricular
- Ketanserin/pharmacology
- Male
- Perfusion/methods
- Piperazines/pharmacology
- Pyrrolidines/pharmacology
- Rats
- Rats, Wistar
- Receptors, GABA-A
- Receptors, Glutamate/drug effects
- Receptors, Kainic Acid/drug effects
- Receptors, N-Methyl-D-Aspartate
- Receptors, Opioid, kappa/administration & dosage
- Receptors, Opioid, kappa/agonists
- Receptors, Opioid, kappa/physiology
- Receptors, Serotonin
- Stomach/drug effects
- Stomach/physiopathology
- gamma-Aminobutyric Acid
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Affiliation(s)
- Sachie Minowa
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, Chiba University, Chiba 263-8522, Japan
| | - Satomi Ishihara
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, Chiba University, Chiba 263-8522, Japan
| | - Shizuko Tsuchiya
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, Chiba University, Chiba 263-8522, Japan
| | - Syunji Horie
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, Chiba University, Chiba 263-8522, Japan
| | - Kazuo Watanabe
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, Chiba University, Chiba 263-8522, Japan
| | - Toshihiko Murayama
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, Chiba University, Chiba 263-8522, Japan
- Author for correspondence:
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6
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Hardt J, Larsson LI, Hougaard DM. Immunocytochemical evidence suggesting that diamine oxidase catalyzes biosynthesis of gamma-aminobutyric acid in antropyloric gastrin cells. J Histochem Cytochem 2000; 48:839-46. [PMID: 10820157 DOI: 10.1177/002215540004800612] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
gamma-Aminobutyric acid (GABA) is a neurotransmitter that also occurs in a few non-neuronal cell types, where it may serve as a paracrine modulator. GABA is biosynthesized from glutamate by glutamate decarboxylase (GAD) and from putrescine via diamine oxidase (DAO). GAD is demonstrable in several GABA-positive cell types but is undetectable in the GABA-containing gastrin cells and somatostatin cells of the antropyloric mucosa of the stomach. Using two antisera raised against synthetic peptides corresponding to two different regions of rat DAO, we now demonstrate strong reactivity for DAO in gastrin-positive cells of the rat antropyloric mucosa, whereas somatostatin-positive cells as well as other structures of the antrum are unreactive. Western blotting analysis of antrum and colon demonstrate that both antisera react with a single band of 85 kD, consistent with the predicted molecular weight of DAO. Expression of DAO mRNA in the antrum is demonstrated by reverse transcriptase polymerase chain reaction (RT-PCR). Our results strongly indicate that gastrin cells produce GABA via DAO-catalyzed oxidation of putrescine, and experimental data moreover suggest that the biosynthesis of GABA is regulated by the prandial state. Because GABA modulates release of somatostatin, these results point to a new mechanism of paracrine interaction between gastrin cells and somatostatin cells.
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Affiliation(s)
- J Hardt
- Department of Clinical Biochemistry, Statens Serum Institut, Copenhagen, Denmark
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7
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Abstract
A plethora of neuronal messengers ("classical" transmitters, gaseous messengers, amino acid transmitters, and neuropeptides) are capable of mediating or modulating gastric functions. Accordingly, the stomach is richly innervated. Gastric nerves are either intrinsic to the gastric wall, i.e., they have their cell bodies in the intramural ganglia and thus belong to the enteric nervous system, or they reach the stomach from outside, originating in the brainstem, in sympathetic ganglia, or in sensory ganglia. Topographically, the nerve fibers in the stomach reach all layers from the most superficial portions of the gastric glands to the outer smooth muscle layer. This wide distribution implies that virtually all different cell types may be reached by neuronal messengers. Within the gastric mucosa endocrine and paracrine cells (e.g., gastrin cells, ECL cells, somatostatin cells), exocrine cells (parietal cells, chief cells, mucous cells), smooth muscle cells, and stromal cells are regulated by neuronal messengers. The sensory innervation, responding to capsaicin, plays an important role in mucosal protection, and in ulcer healing. Presumably also other nerves are involved and a plasticity in the neuropeptide expression has been demonstrated at the margin of gastric ulcers. Taken together, available data indicate a complex interplay between hormones, paracrine messengers and neuronal messengers, growth factors and cytokines in the regulation of gastric mucosal activities such as secretion, local blood flow, growth, and restitution after damage.
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Affiliation(s)
- E Ekblad
- Department of Physiological Sciences, Section for Neuroendocrine Cell Biology, Lund University, E-block, University Hospital, 221 85 Lund, Sweden
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8
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Poulter MO, Singhal R, Brown LA, Krantis A. GABA(A) receptor subunit messenger RNA expression in the enteric nervous system of the rat: implications for functional diversity of enteric GABA(A) receptors. Neuroscience 1999; 93:1159-65. [PMID: 10473280 DOI: 10.1016/s0306-4522(99)00174-8] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
GABAergic neurons occur in the myenteric plexus and submucosa and their innervations of the gut, where GABA stimulates motor neurons, and non-neural cells via "central type" GABA(A) receptors. These receptors occur on half of the neurons in the rat intestine. The GABA(A) receptor is a ligand-gated chloride channel constructed from different subunit families (alpha, beta, gamma, delta, epsilon). In rat these exist as subtypes, alpha1-6, beta1-3, gamma1-3 and delta, defining the clinically relevant pharmacological features of GABA(A) receptors. However, the identity, distribution, and abundance of enteric GABA(A) receptor subunits are unknown. To identify and map the regional expression of GABA(A) receptor subunit messenger RNAs in the enteric nervous system, we assayed enteric RNA from the ileum of Sprague-Dawley rats by reverse transcription-polymerase chain reaction for alpha1-6, beta 1-3, gamma1-3, and delta subunit messenger RNAs. Subunit messenger RNA localization, was probed by in situ hybridization. Reverse transcription-polymerase chain reaction analysis of RNA from myenteric and submucosal nerve layers revealed the expression alpha1, alpha3, beta2, beta3, gamma1 and gamma3 subunit messenger RNAs. Little alpha4 and alpha6 and no alpha2, beta1, gamma2 or delta subunit messenger RNA were detected. In situ hybridization revealed that transcripts for alpha1, alpha3, alpha5 and beta2 subunits occur in both myenteric and submucous ganglia. However, beta3 messenger RNA was found only in myenteric plexus. The gamma1 subunit messenger RNA was also restricted to the cells in the myenteric plexus while gamma3 was found in cells of both nerve layers. In this study of the subunit messenger RNA expression profile of GABA(A) receptors within the enteric nerve layers we show an abundant, diverse and widespread distribution that is unique in comparison to the CNS. The distinctive and heterogeneous distribution of enteric GABA(A) subunits may be important in the integration of neural control of gut function.
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Affiliation(s)
- M O Poulter
- Laboratory of Molecular Neuropharmacology, Institute for Biological Sciences, National Research Council of Canada, Ottawa, Ontario
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9
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Krantis A, Nichols K, Staines W. Neurochemical characterization and distribution of enteric GABAergic neurons and nerve fibres in the human colon. JOURNAL OF THE AUTONOMIC NERVOUS SYSTEM 1998; 68:33-42. [PMID: 9531443 DOI: 10.1016/s0165-1838(97)00113-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
GABA, somatostatin and enkephalin are neurotransmitters of enteric interneurons and comprise part of the intrinsic neural circuits regulating peristalsis. Within the relaxation phase of reflex peristalsis, nitric oxide (NO) is released by inhibitory motor neurons and perhaps enteric interneurons as well. Previously, we identified by GABA transaminase (GABA-T) immunohistochemistry, a subpopulation of GABAergic interneurons in the human colon which also contain NO synthase activity and hence produce NO. In this study, we have examined further the capacity for cotransmission within the GABAergic innervation in human colon. The expression of two important neuropeptides within GABAergic neurons was determined by combined double-labelled immunocytochemistry using antibodies for GABA-T, enkephalin and somatostatin, together with the demonstration of NO synthase-related NADPH diaphorase staining in cryosectioned colon. Both neuropeptides were found in GABAergic neurons of the colon. The evidence presented herein confirms the colocalization of NO synthase activity and GABA-T immunoreactivity in subpopulations of enteric neurons and further allows the neurochemical classification of GABAergic neurons of the human colon into three subsets: (i) neurons colocalizing somatostatin-like immunoreactivity representing about 40% of the GABAergic neurons, (ii) neurons colocalizing enkephalin-like immunoreactivity, about 9% of the GABAergic neurons and (iii) neurons colocalizing NO synthase activity, about 23% of the GABAergic neurons. This division of GABAergic interneurons into distinct subpopulations of neuropeptide or NO synthase containing cells is consistent with and provides an anatomical correlate for the pharmacology of these transmitters and the pattern of transmitter release during reflex peristalsis.
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Affiliation(s)
- A Krantis
- Department of Cellular and Molecular Medicine, University of Ottawa, Ont., Canada.
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10
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Abstract
Vigabatrin is a relatively new medication used in the treatment of epilepsia. The present report concerns the use of vigabatrin by a 19-year-old woman. The patient manifested marked gingival overgrowth compatible clinically and histologically with the overgrowth induced by phenytoin, cyclosporine and calcium channel blockers. This is the 1st report of vigabatrin-induced gingival overgrowth. Clinicians should be aware of similar lesions in patients using new anticonvulsants.
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Affiliation(s)
- J Katz
- Department of Oral Medicine, Sheba Medical Center, Tel Hashomer, Israel
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11
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Zeiter DK, Li X, Broussard DL. Identification of the GABAA receptor alpha-subunit mRNA in rat intestine. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 1996; 39:241-4. [PMID: 8804733 DOI: 10.1016/0169-328x(96)00077-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
We investigated the expression of gamma-aminobutyric acid type A (GABAA) receptor alpha 1-, alpha 2- and alpha 3-subunit mRNAs in the rat intestine using reverse transcription and polymerase chain reaction. alpha 1- and alpha 3-, but not alpha 2-, subunit mRNAs were amplified from the proximal intestine, ileum, and colon. In-situ hybridization studies demonstrated the expression of alpha 1-subunit mRNA by myenteric neurons. GABA may be active via the GABAA receptor in the enteric nervous system.
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Affiliation(s)
- D K Zeiter
- Division of Gastroenterology and Nutrition, Children's Hospital of Philadelphia, PA 19104, USA
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12
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Tillakaratne NJ, Medina-Kauwe L, Gibson KM. gamma-Aminobutyric acid (GABA) metabolism in mammalian neural and nonneural tissues. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. PART A, PHYSIOLOGY 1995; 112:247-63. [PMID: 7584821 DOI: 10.1016/0300-9629(95)00099-2] [Citation(s) in RCA: 134] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
4-Aminobutyric acid (GABA), a major inhibitory neurotransmitter of mammalian central nervous system, is found in a wide range of organisms, from prokaryotes to vertebrates. GABA is widely distributed in nonneural tissue including peripheral nervous and endocrine systems. GABA acts on GABAA and GABAB receptors. GABAA receptors are ligand-gated chloride channels modulated by a variety of drugs. GABAB receptors are essentially presynaptic, usually coupled to potassium or calcium channels, and they function via a GTP binding protein. In neural and nonneural tissues, GABA is metabolized by three enzymes--glutamic acid decarboxylase (GAD), which produces GABA from glutamic acid, and the catabolic enzymes GABA-transaminase (GABA-T) and succinic semialdehyde dehydrogenase (SSADH). Production of succinic acid by SSADH allows entry of the GABA carbon skeleton into the tricarboxylic acid cycle. Alternate sources of GABA include putrescine, spermine, spermidine and ornithine, which produce GABA via deamination and decarboxylation reactions, while L-glutamine is an additional source of glutamic acid via deamination. GAD from mammalian brain occurs in two molecular forms, GAD65 and GAD67 (referring to subunit relative molecular weight (Mr) in kilodaltons). These different forms of GAD are the product of different genes, differing in nucleotide sequence, immunoreactivity and subcellular localization. The presence and characteristics of GAD have been investigated in a wide variety of nonneural tissues including liver, kidney, pancreas, testis, ova, oviduct, adrenal, sympathetic ganglia, gastrointestinal tract and circulating erythrocytes. In some tissues, one form (GAD65 or GAD67) predominates. GABA-T has been located in most of the same tissues, primarily through histochemical and/or immunochemical methods; GABA-T is also present in a variety of circulating cells, including platelets and lymphocytes. SSADH, the final enzyme GABA catabolism, has been detected in some of the tissues in which GAD and GABA-T have been identified, although the presence of this enzyme has not been in mammalian pancreas, ova, oviduct, testis or sympathetic ganglia.
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Affiliation(s)
- N J Tillakaratne
- Department of Biology, University of California, Los Angeles, USA
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13
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Lin WC. Stimulatory effect of muscimol on gastric acid secretion stimulated by secretagogues in vagotomized rats under anesthesia. Eur J Pharmacol 1995; 279:43-50. [PMID: 7556381 DOI: 10.1016/0014-2999(95)00137-a] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The effect of intravenous administration of muscimol, a GABAA receptor agonist, on gastric acid secretion from perfused stomach was studied in vagotomized rats anesthetized with urethane. Muscimol did not stimulate acid secretion by itself. In contrast, muscimol dose dependently potentiated acid secretion induced by pentagastrin, bethanechol and direct vagal stimulation, but not histamine. Muscimol-potentiated acid secretion induced by pentagastrin and bethanechol was not influenced by pretreatment with atropine or cimetidine, respectively. Muscimol-potentiated acid secretion evoked by direct vagal stimulation was prevented by pretreatment with proglumide, a gastrin receptor antagonist. Muscimol-potentiated acid secretion evoked by bethanechol was dose dependently prevented by bicuculline methiodide, suggesting an involvement of peripheral GABAA receptors. These results suggest that muscimol stimulates acid secretion under certain conditions, and that two mechanisms are involved in this effect. The effects of muscimol on acid secretion may be mediated by increasing the release of histamine by pentagastrin, bethanechol and direct vagal stimulation. In addition, muscimol would also be effective if muscarinic agents were already occupying muscarinic acetylcholine receptors on parietal cells.
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Affiliation(s)
- W C Lin
- Department of Pharmacology, China Medical College, Taichung, Taiwan
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14
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Davanger S, Hjelle OP, Babaie E, Larsson LI, Hougaard D, Storm-Mathisen J, Ottersen OP. Colocalization of gamma-aminobutyrate and gastrin in the rat antrum: an immunocytochemical and in situ hybridization study. Gastroenterology 1994; 107:137-48. [PMID: 8020656 DOI: 10.1016/0016-5085(94)90071-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
BACKGROUND/AIMS The inhibitory neurotransmitter gamma-aminobutyrate (GABA) has been shown to coexist with insulin in pancreatic beta-cells. We have presently investigated whether GABA also colocalizes with gastrin in G cells in rat antral mucosa. METHODS Three alternative approaches were used: (1) gastrin in situ hybridization and GABA immunocytochemistry on consecutive cryostat sections; (2) GABA immunocytochemistry and gastrin immunocytochemistry on adjacent semithin and ultrathin sections; and (3) double-immunogold labeling of GABA and gastrin in the same ultrathin section. RESULTS Colocalization of GABA and gastrin was observed with each of the three approaches. In the double-immunogold labeled cells, the G-cell granules displayed a high gold-particle density indicating gastrin and a low particle density indicating GABA, whereas the converse was true for the extragranular cytoplasmic matrix. The gold-particle ratios between these compartments were 11 (for gastrin) and 0.36 (for GABA), respectively. GABA labeling was also observed in two other antral endocrine cell types, classified by morphological criteria as somatostatin producing D cells and serotonin producing ECn cells. CONCLUSIONS This is the first direct demonstration of GABA in gastrointestinal G cells. Our findings suggest that GABA may have a paracrine function in the stomach mucosa, analogous to its presumed role in the pancreatic islets.
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Affiliation(s)
- S Davanger
- Department of Anatomy, University of Oslo, Norway
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15
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Ren J, Harty RF. Presynaptic muscarinic receptors modulate acetylcholine release from rat antral mucosal/submucosal nerves. Dig Dis Sci 1994; 39:1099-106. [PMID: 8174423 DOI: 10.1007/bf02087564] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The purpose of the present studies was to determine whether autoinhibition of acetylcholine release could be demonstrated in vitro from mucosal/submucosal neurons in rat antrum. Rat antral mucosal/submucosal tissues preloaded with [3H]choline were perifused and [3H]acetylcholine release measured under basal and stimulated conditions. Carbachol inhibited both spontaneous and evoked (electrical field stimulation, KCl) acetylcholine release from rat antral tissues: 1 x 10(-5) M carbachol inhibited basal [3H]ACh release maximally to -38.2 +/- 3.1% (P < 0.001 vs control). The nonselective muscarinic antagonist atropine enhanced both basal and stimulated acetylcholine release and abolished carbachol-induced inhibition of acetylcholine release. Pirenzepine, a muscarinic M1 receptor antagonist, inhibited acetylcholine release and did not alter carbachol-induced inhibition of acetylcholine release. In conclusion, acetylcholine release from rat antral mucosal/submucosal neurons is regulated negatively by a presynaptic feedback mechanism involving M2 and/or M3 receptors, while presynaptic M1 receptors facilitate release of neurotransmitter.
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Affiliation(s)
- J Ren
- Department of Internal Medicine, University of Oklahoma Health Sciences Center, Oklahoma City 73126
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Krantis A, Tufts K, Nichols K, Morris GP. [3H]GABA uptake and GABA localization in mucosal endocrine cells of the rat stomach and colon. JOURNAL OF THE AUTONOMIC NERVOUS SYSTEM 1994; 47:225-32. [PMID: 8014381 DOI: 10.1016/0165-1838(94)90183-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The aim of this study was to characterize the distribution of GABAergic cells in the rat gut mucosa. Thin and/or thick serial sections of segments of rat antrum and distal colon were treated for autoradiographic localization of sites of [3H]GABA (50 nM) high-affinity uptake, or GABA immunoreactivity. Dense accumulations of silver grains were localized to a discrete population of granulated mucosal cells. These appeared to be D-type endocrine cells. These gut regions also displayed strongly GABA-immunoreactive mucosal cells. These results confirm the presence of GABAergic cells in the rat antral mucosa, and reveal that [3H]GABA is accumulated by mucosal endocrine cells in the rat colon.
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Affiliation(s)
- A Krantis
- Department of Physiology, University of Ottawa, Ontario, Canada
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Manela FD, Dyer WS, Ren J, Harty RF. Validation of the antral mucosal/submucosal sleeve preparation: studies of gastrin and acetylcholine release in response to luminal stimulation. Life Sci 1992; 51:1363-72. [PMID: 1406054 DOI: 10.1016/0024-3205(92)90636-4] [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: 12/26/2022]
Abstract
In the present study we developed an experimental model for direct assessment of antral endocrine cell and cholinergic neural responses to luminal stimulation. A sleeve of antral mucosal/submucosal tissue was prepared from rat antrum, mounted in perfusion chamber, and perfused in both luminal and submucosal compartments. Morphological and functional integrity of the antral sleeve were confirmed by histological examination and measurement of protein synthesis. Antral gastrin release was assessed in response to luminal stimulation with acid, peptone and distension. Luminal acid (pH3) inhibited basal gastrin release by -70.4% and luminal peptone stimulated gastrin release to 210% above control (p < 0.02). Distention of the antral sleeve by hydrostatic pressure (3-25cm H2O) caused stepwise and significant increase in gastrin release that was reversible. 3H-acetylcholine was stimulated significantly by KCl (56mM) to values twice control. In summary, these results establish the integrity and responsiveness of the antral sleeve to pharmacological and luminal stimulation. The antral sleeve may be a useful model in assessing antral function in response to luminal stimulation.
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Affiliation(s)
- F D Manela
- University of Nebraska Medical Center, Omaha Veterans Administration Medical Center
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