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Qian X, Zhao X, Yu L, Yin Y, Zhang XD, Wang L, Li JX, Zhu Q, Luo JL. Current status of GABA receptor subtypes in analgesia. Biomed Pharmacother 2023; 168:115800. [PMID: 37935070 DOI: 10.1016/j.biopha.2023.115800] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Revised: 10/15/2023] [Accepted: 10/26/2023] [Indexed: 11/09/2023] Open
Abstract
Gamma-aminobutyric acid (GABA), a non-protein-producing amino acid synthesized from the excitatory amino acid glutamate via the enzyme glutamic acid decarboxylase, is extensively found in microorganisms, plants and vertebrates, and is abundantly expressed in the spinal cord and brain. It is the major inhibitory neurotransmitter in the mammalian nervous system. GABA plays crucial roles in the regulation of synaptic transmission, the promotion of neuronal development and relaxation, and the prevention of insomnia and depression. As the major inhibitory neurotransmitter, GABA plays pivotal roles in the regulation of pain sensation, which is initiated by the activation of peripheral nociceptors and transmitted to the spinal cord and brain along nerves. GABA exerts these roles by directly acting on three types of receptors: ionotropic GABAA and GABAC receptors and G protein-coupled GABAB receptor. The chloride-permeable ion channel receptors GABAA and GABAC mediate fast neurotransmission, while the metabotropic GABAB receptor mediates slow effect. Different GABA receptors regulate pain sensation via different signaling pathways. Here we highlight recent updates on the involvement of specific GABA receptors and their subtypes in the process of pain sensation. Further understanding of different GABA receptors and signaling pathways in pain sensation will benefit the development of novel analgesics for pain management by targeting specific GABA receptor subtypes and signaling pathways.
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Affiliation(s)
- Xunjia Qian
- School of Pharmacy, Nantong University, Nantong 226001, Jiangsu, China
| | - Xinyi Zhao
- School of Pharmacy, Nantong University, Nantong 226001, Jiangsu, China
| | - Lulu Yu
- School of Pharmacy, Nantong University, Nantong 226001, Jiangsu, China
| | - Yujian Yin
- School of Pharmacy, Nantong University, Nantong 226001, Jiangsu, China
| | - Xiao-Dan Zhang
- School of Pharmacy, Nantong University, Nantong 226001, Jiangsu, China
| | - Liyun Wang
- School of Pharmacy, Nantong University, Nantong 226001, Jiangsu, China
| | - Jun-Xu Li
- School of Pharmacy, Nantong University, Nantong 226001, Jiangsu, China; Provincial Key Laboratory of Inflammation and Molecular Drug Target, Nantong 226001, Jiangsu, China
| | - Qing Zhu
- School of Pharmacy, Nantong University, Nantong 226001, Jiangsu, China; Provincial Key Laboratory of Inflammation and Molecular Drug Target, Nantong 226001, Jiangsu, China.
| | - Jia-Lie Luo
- School of Pharmacy, Nantong University, Nantong 226001, Jiangsu, China.
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Gomes P, Laroute V, Beaufrand C, Daveran-Mingot ML, Aubry N, Liebgott C, Ballet N, Legrain-Raspaud S, Theodorou V, Mercier-Bonin M, Cocaign-Bousquet M, Eutamene H. Lactococcus lactis CNCM I-5388 versus NCDO2118 by its GABA hyperproduction ability, counteracts faster stress-induced intestinal hypersensitivity in rats. FASEB J 2023; 37:e23264. [PMID: 37850915 DOI: 10.1096/fj.202301588r] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2023] [Revised: 09/21/2023] [Accepted: 10/04/2023] [Indexed: 10/19/2023]
Abstract
Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder characterized by its main symptom, visceral hypersensitivity (VH), which is aggravated by stress. Gut-brain interactions and gut bacteria may alleviate IBS symptoms, including VH. γ-amino butyric acid (GABA), produced notably by lactic acid bacteria (LAB), shows promising result in IBS symptoms treatment. In bacteria, GABA is generated through glutamate decarboxylase (GAD) metabolism of L-glutamic acid, maintaining intracellular pH. In mammals, GABA acts as an inhibitory neurotransmitter, modulating pain, stress, and anxiety. Therefore, utilizing GABA-producing LAB as a therapeutic approach might be beneficial. Our previous work showed that a GABA-producing Lactococcus lactis strain, NCDO2118, reduced VH induced by acute stress in rats after a 10-day oral treatment. Here, we identified the strain CNCM I-5388, with a four-fold higher GABA production rate under the same conditions as NCDO2118. Both strains shared 99.1% identical GAD amino acid sequences and in vitro analyses revealed the same optimal pH for GAD activity; however, CNCM I-5388 exhibited 17 times higher intracellular GAD activity and increased resistance to acidic pH. Additionally, in vivo experiments have demonstrated that CNCM I-5388 has faster anti-VH properties in rats compared with NCDO2118, starting from the fifth day of treatment. Finally, CNCM I-5388 anti-VH effects partially persisted after 5-day treatment interruption and after a single oral treatment. These findings highlight CNCM I-5388 as a potential therapeutic agent for managing VH in IBS patients.
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Affiliation(s)
- Pedro Gomes
- Toulouse Biotechnology Institute (TBI), Université de Toulouse, CNRS, INRAE, INSA, Toulouse, France
- Toxalim (Research Centre in Food Toxicology), Université de Toulouse, INRAE, ENVT, INP-Purpan, UPS, Toulouse, France
| | - Valérie Laroute
- Toulouse Biotechnology Institute (TBI), Université de Toulouse, CNRS, INRAE, INSA, Toulouse, France
| | - Catherine Beaufrand
- Toxalim (Research Centre in Food Toxicology), Université de Toulouse, INRAE, ENVT, INP-Purpan, UPS, Toulouse, France
| | | | - Nathalie Aubry
- Toulouse Biotechnology Institute (TBI), Université de Toulouse, CNRS, INRAE, INSA, Toulouse, France
| | - Chloé Liebgott
- Toxalim (Research Centre in Food Toxicology), Université de Toulouse, INRAE, ENVT, INP-Purpan, UPS, Toulouse, France
| | | | | | - Vassilia Theodorou
- Toxalim (Research Centre in Food Toxicology), Université de Toulouse, INRAE, ENVT, INP-Purpan, UPS, Toulouse, France
| | - Muriel Mercier-Bonin
- Toxalim (Research Centre in Food Toxicology), Université de Toulouse, INRAE, ENVT, INP-Purpan, UPS, Toulouse, France
| | - Muriel Cocaign-Bousquet
- Toulouse Biotechnology Institute (TBI), Université de Toulouse, CNRS, INRAE, INSA, Toulouse, France
| | - Hélène Eutamene
- Toxalim (Research Centre in Food Toxicology), Université de Toulouse, INRAE, ENVT, INP-Purpan, UPS, Toulouse, France
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Alijanpour S, Jafaripour S, Ghasemzadeh Z, Khakpai F, Zarrindast MR. Harmaline potentiates morphine-induced antinociception via affecting the ventral hippocampal GABA-A receptors in mice. Eur J Pharmacol 2020; 893:173806. [PMID: 33345854 DOI: 10.1016/j.ejphar.2020.173806] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2019] [Revised: 12/06/2020] [Accepted: 12/10/2020] [Indexed: 11/13/2022]
Abstract
Morphine is one of the most effective medications for treatment of pain, but its side effects limit its use. Therefore, identification of new strategies that can enhance morphine-induced antinociception and/or reduce its side effects will help to develop therapeutic approaches for pain relief. Considering antinociceptive efficacy of harmaline and also highlighted the important role of GABA-A receptors in the pain perception, this research aimed to determine whether the ventral hippocampal (vHip) GABA-A receptors are involved in the possible harmaline-induced enhancement of morphine antinociception. To achieve this, vHip regions of adult male mice were bilaterally cannulated and pain sensitivity was measured in a tail-flick apparatus. Intraperitoneally administration of morphine (0, 2, 4 and 6 mg/kg) or harmaline (0, 1.25, 5 and 10 mg/kg) increased the percentage of maximal possible effect (%MPE) and induced antinociception. Interestingly, co-administration of sub-effective doses of harmaline (5 mg/kg) and morphine (2 mg/kg) induced antinociception. Intra-vHip microinjection of muscimol (0, 200 and 300 ng/mice), a GABA-A receptor agonist, enhanced the anti-nociceptive effects of harmaline (2.5 mg/kg)+morphine (2 mg/kg) combination. Microinjection of the same doses of muscimol into the vHip by itself did not alter tail-flick latency. Intra-vHip microinjection of bicuculline (100 ng/mouse), a GABA-A receptor antagonist, did not cause a significant change in MPE%. Bicuculline (60 and 100 ng/mouse, intra-vHip) was administered with the harmaline (5 mg/kg)+morphine (2 mg/kg), and inhibited the potentiating effect of harmaline on morphine response. These findings favor the notion that GABAergic mechanisms in the vHip facilitate harmaline-induced potentiation of morphine response in the tail-flick test in part through GABA-A receptors. These findings shall provide insights and strategies into the development of pain suppressing drugs.
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Affiliation(s)
- Sakineh Alijanpour
- Department of Biology, Faculty of Science, Gonbad Kavous University, Gonbad Kavous, Iran.
| | - Samira Jafaripour
- Department of Biology, North Tehran Branch, Islamic Azad University, Tehran, Iran
| | - Zahra Ghasemzadeh
- Department of Animal Biology, School of Biology, College of Science, University of Tehran, Tehran, Iran
| | - Fatemeh Khakpai
- Cognitive and Neuroscience Research Center (CNRC), Tehran Medical Sciences, Islamic Azad University, Tehran, Iran
| | - Mohammad-Reza Zarrindast
- Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran; Iranian National Center for Addiction Studies, Tehran University of Medical Sciences, Tehran, Iran; Endocrinology and Metabolism Research Center, Endocrinology and Metabolism Clinical Sciences Institute, Tehran University of Medical Sciences, Tehran, Iran
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Nissen TD, Brock C, Lykkesfeldt J, Lindström E, Hultin L. Pharmacological modulation of colorectal distension evoked potentials in conscious rats. Neuropharmacology 2018; 140:193-200. [PMID: 30059662 DOI: 10.1016/j.neuropharm.2018.07.028] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2018] [Revised: 07/02/2018] [Accepted: 07/24/2018] [Indexed: 12/30/2022]
Abstract
BACKGROUND Cerebral evoked potentials (CEP) induced by colorectal distension (CRD) in conscious rats provides a novel method in studies of visceral sensitivity. The aim of this study was to explore the pharmacological effect on CEP of compounds known to reduce the visceromotor response to CRD. METHODS Epidural electrodes were chronically implanted in eight female Sprague-Dawley rats. Evoked potentials were elicited by colorectal rapid balloon distensions (100 ms, 80 mmHg) and the effect of WIN55 (cannabinoid CB receptor agonist), clonidine (adrenergic α2 receptor agonist), MPEP (mGluR5 receptor antagonist), pregabalin (ligand of α2δ subunits in voltage-gated calcium channels) and baclofen (GABA-B receptor agonist) on amplitudes and latency of CEP were determined. RESULTS WIN55 (0.1 μmol kg-1), clonidine (0.05 μmol kg-1), MPEP (10 μmol kg-1) and pregabalin (200 μmol kg-1) caused a significant, p < 0.05, reduction of the N2 to P2 peak-to-peak amplitude by 23 ± 8%, 25 ± 8%, 39 ± 5%, and 47 ± 6% respectively. Baclofen (9 μmol kg-1) induced a prolongation of the N2 peak latency of 18 ± 4% but had no significant effect on the amplitudes. CONCLUSION The obtained results suggest that MPEP, WIN55, clonidine, and pregabalin reduce visceral nociceptive input to the brain, whereas the lack of effect of baclofen on CRD evoked CEP amplitudes suggest that the effect on VMR is not due to a direct analgesic effect. Brain responses to colorectal distension provide a useful tool to evaluate pharmacological effects in rats and may serve as a valuable preclinical model for understanding pharmacological mechanisms related to visceral sensitivity.
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Affiliation(s)
- Thomas Dahl Nissen
- Laboratory Animal Sciences, Drug Safety and Metabolism, IMED Biotech Unit, AstraZeneca, Gothenburg, Sweden; Mech-Sense, Department of Gastroenterology & Hepatology, Aalborg University Hospital, Aalborg, Denmark; Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Christina Brock
- Mech-Sense, Department of Gastroenterology & Hepatology, Aalborg University Hospital, Aalborg, Denmark
| | - Jens Lykkesfeldt
- Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | | | - Leif Hultin
- Laboratory Animal Sciences, Drug Safety and Metabolism, IMED Biotech Unit, AstraZeneca, Gothenburg, Sweden.
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Lyubashina O, Sivachenko I. The 5-HT 4 receptor-mediated inhibition of visceral nociceptive neurons in the rat caudal ventrolateral medulla. Neuroscience 2017; 359:277-288. [DOI: 10.1016/j.neuroscience.2017.07.039] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2016] [Revised: 03/26/2017] [Accepted: 07/17/2017] [Indexed: 12/23/2022]
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Synergistic antipruritic effects of gamma aminobutyric acid A and B agonists in a mouse model of atopic dermatitis. J Allergy Clin Immunol 2017; 140:454-464.e2. [PMID: 28232084 DOI: 10.1016/j.jaci.2017.02.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2016] [Revised: 01/25/2017] [Accepted: 02/01/2017] [Indexed: 11/21/2022]
Abstract
BACKGROUND Despite recent insights into the pathophysiology of acute and chronic itch, chronic itch remains an often intractable condition. Among major contributors to chronic itch is dysfunction of spinal cord gamma aminobutyric acidergic (GABAergic) inhibitory controls. OBJECTIVES We sought to test the hypothesis that selective GABA agonists as well as cell transplant-derived GABA are antipruritic against acute itch and in a transgenic mouse model of atopic dermatitis produced by overexpression of the TH2 cell-associated cytokine, IL-31 (IL-31Tg mice). METHODS We injected wild-type and IL-31Tg mice with combinations of GABA-A (muscimol) or GABA-B (baclofen) receptor agonists 15 to 20 minutes prior to injection of various pruritogens (histamine, chloroquine, or endothelin-1) and recorded spontaneous scratching before and after drug administration. We also tested the antipruritic properties of intraspinal transplantation of precursors of GABAergic interneurons in the IL-31Tg mice. RESULTS Systemic muscimol or baclofen are antipruritic against both histamine-dependent and -independent pruritogens, but the therapeutic window using either ligand alone was very small. In contrast, combined subthreshold doses of baclofen and muscimol produced a significant synergistic antipruritic effect, with no sedation. Finally, transplant-mediated long-term enhancement of GABAergic signaling not only reduced spontaneous scratching in the IL-31Tg mice but also dramatically resolved the associated skin lesions. CONCLUSIONS Although additional research is clearly needed, existing approved GABA agonists should be considered in the management of chronic itch, notably atopic dermatitis.
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Mazzoli R, Pessione E. The Neuro-endocrinological Role of Microbial Glutamate and GABA Signaling. Front Microbiol 2016; 7:1934. [PMID: 27965654 PMCID: PMC5127831 DOI: 10.3389/fmicb.2016.01934] [Citation(s) in RCA: 193] [Impact Index Per Article: 24.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2016] [Accepted: 11/17/2016] [Indexed: 12/11/2022] Open
Abstract
Gut microbiota provides the host with multiple functions (e.g., by contributing to food digestion, vitamin supplementation, and defense against pathogenic strains) and interacts with the host organism through both direct contact (e.g., through surface antigens) and soluble molecules, which are produced by the microbial metabolism. The existence of the so-called gut–brain axis of bi-directional communication between the gastrointestinal tract and the central nervous system (CNS) also supports a communication pathway between the gut microbiota and neural circuits of the host, including the CNS. An increasing body of evidence has shown that gut microbiota is able to modulate gut and brain functions, including the mood, cognitive functions, and behavior of humans. Nonetheless, given the extreme complexity of this communication network, its comprehension is still at its early stage. The present contribution will attempt to provide a state-of-the art description of the mechanisms by which gut microbiota can affect the gut–brain axis and the multiple cellular and molecular communication circuits (i.e., neural, immune, and humoral). In this context, special attention will be paid to the microbial strains that produce bioactive compounds and display ascertained or potential probiotic activity. Several neuroactive molecules (e.g., catecholamines, histamine, serotonin, and trace amines) will be considered, with special focus on Glu and GABA circuits, receptors, and signaling. From the basic science viewpoint, “microbial endocrinology” deals with those theories in which neurochemicals, produced by both multicellular organisms and prokaryotes (e.g., serotonin, GABA, glutamate), are considered as a common shared language that enables interkingdom communication. With regards to its application, research in this area opens the way toward the possibility of the future use of neuroactive molecule-producing probiotics as therapeutic agents for the treatment of neurogastroenteric and/or psychiatric disorders.
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Affiliation(s)
- Roberto Mazzoli
- Laboratory of Biochemistry, Proteomics and Metabolic Engineering of Prokaryotes, Department of Life Sciences and Systems Biology, University of Torino Torino, Italy
| | - Enrica Pessione
- Laboratory of Biochemistry, Proteomics and Metabolic Engineering of Prokaryotes, Department of Life Sciences and Systems Biology, University of Torino Torino, Italy
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8
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Sumathi T, Christinal J. Neuroprotective Effect of Portulaca oleraceae Ethanolic Extract Ameliorates Methylmercury Induced Cognitive Dysfunction and Oxidative Stress in Cerebellum and Cortex of Rat Brain. Biol Trace Elem Res 2016; 172:155-165. [PMID: 26563420 DOI: 10.1007/s12011-015-0546-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Accepted: 10/15/2015] [Indexed: 12/30/2022]
Abstract
Methylmercury (MeHg) is highly toxic, and its principal target tissue in human is the nervous system, which has made MeHg intoxication a public health concern for many decades. Portulaca oleraceae (purslane), a member of the Portulacaceae family, is widespread as a weed and has been ranked the eighth most common plant in the world. In this study, we sought for potential beneficial effects of Portulaca oleracea ethanolic extract (POEE) against the neurotoxicity induced by MeHg in cerebellum and cortex of rats. Male Wistar rats were administered with MeHg orally at a dose of 5 mg/kg b.w. for 21 days. Experimental rats were given MeHg and also administered with POEE (4 mg/kg, orally) 1 h prior to the administration of MeHg for 21 days. After MeHg exposure, we determine the mercury concentration by atomic absorption spectroscopy (AAS); mercury content was observed high in MeHg-induced group. POEE reduced the mercury content. We also observed that the activities of catalase, superoxide dismutase, glutathione peroxidase, and the level of glutathione were reduced. The levels of glutathione reductase and thiobarbituric acid reactive substance were found to be increased. The above biochemical changes were found to be reversed with POEE. Behavioral changes like decrease tail flick response, longer immobility time, and decreased motor activity were noted down during MeHg exposure. POEE pretreatment offered protection from these behavioral changes. MeHg intoxication also caused histopathological changes in cerebellum and cortex, which was found to be normalized by treatment with POEE. The present results indicate that POEE has protective effect against MeHg-induced neurotoxicity.
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Affiliation(s)
- Thangarajan Sumathi
- Department of Medical Biochemistry, Dr. ALM Post Graduate Institute of Basic Medical Sciences, University of Madras, Taramani Campus, Chennai, Tamil Nadu, 600 113, India.
| | - Johnson Christinal
- Department of Medical Biochemistry, Dr. ALM Post Graduate Institute of Basic Medical Sciences, University of Madras, Taramani Campus, Chennai, Tamil Nadu, 600 113, India
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9
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Hyland NP, Golubeva AV. GABA B receptors in the bladder and bowel: therapeutic potential for positive allosteric modulators?: Commentary on Kalinichev et al., Br J Pharmacol 171: 995-1006. Br J Pharmacol 2015; 172:4588-4590. [PMID: 24641323 DOI: 10.1111/bph.12617] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2013] [Revised: 01/16/2014] [Accepted: 01/30/2014] [Indexed: 02/01/2023] Open
Abstract
LINKED ARTICLE This article is a Commentary on Kalinichev M, Palea S, Haddouk H, Royer-Urios I, Guilloteau V, Lluel P, Schneider M, Saporito M and Poli S (2014). ADX71441, a novel, potent and selective positive allosteric modulator of the GABAB receptor, shows efficacy in rodent models of overactive bladder. Br J Pharmacol 171: 995-1006. doi: 10.1111/bph.12517.
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Affiliation(s)
- Niall P Hyland
- Alimentary Pharmabiotic Centre, University College Cork, Cork, Ireland.,Department of Pharmacology & Therapeutics, University College Cork, Cork, Ireland
| | - Anna V Golubeva
- Alimentary Pharmabiotic Centre, University College Cork, Cork, Ireland
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10
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Moloney RD, O'Mahony SM, Dinan TG, Cryan JF. Stress-induced visceral pain: toward animal models of irritable-bowel syndrome and associated comorbidities. Front Psychiatry 2015; 6:15. [PMID: 25762939 PMCID: PMC4329736 DOI: 10.3389/fpsyt.2015.00015] [Citation(s) in RCA: 102] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Accepted: 01/28/2015] [Indexed: 12/12/2022] Open
Abstract
Visceral pain is a global term used to describe pain originating from the internal organs, which is distinct from somatic pain. It is a hallmark of functional gastrointestinal disorders such as irritable-bowel syndrome (IBS). Currently, the treatment strategies targeting visceral pain are unsatisfactory, with development of novel therapeutics hindered by a lack of detailed knowledge of the underlying mechanisms. Stress has long been implicated in the pathophysiology of visceral pain in both preclinical and clinical studies. Here, we discuss the complex etiology of visceral pain reviewing our current understanding in the context of the role of stress, gender, gut microbiota alterations, and immune functioning. Furthermore, we review the role of glutamate, GABA, and epigenetic mechanisms as possible therapeutic strategies for the treatment of visceral pain for which there is an unmet medical need. Moreover, we discuss the most widely described rodent models used to model visceral pain in the preclinical setting. The theory behind, and application of, animal models is key for both the understanding of underlying mechanisms and design of future therapeutic interventions. Taken together, it is apparent that stress-induced visceral pain and its psychiatric comorbidities, as typified by IBS, has a multifaceted etiology. Moreover, treatment strategies still lag far behind when compared to other pain modalities. The development of novel, effective, and specific therapeutics for the treatment of visceral pain has never been more pertinent.
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Affiliation(s)
- Rachel D Moloney
- Laboratory of Neurogastroenterology, Alimentary Pharmabiotic Centre, Biosciences Institute, University College Cork , Cork , Ireland
| | - Siobhain M O'Mahony
- Laboratory of Neurogastroenterology, Alimentary Pharmabiotic Centre, Biosciences Institute, University College Cork , Cork , Ireland ; Department of Anatomy and Neuroscience, University College Cork , Cork , Ireland
| | - Timothy G Dinan
- Laboratory of Neurogastroenterology, Alimentary Pharmabiotic Centre, Biosciences Institute, University College Cork , Cork , Ireland ; Department of Psychiatry, University College Cork , Cork , Ireland
| | - John F Cryan
- Laboratory of Neurogastroenterology, Alimentary Pharmabiotic Centre, Biosciences Institute, University College Cork , Cork , Ireland ; Department of Anatomy and Neuroscience, University College Cork , Cork , Ireland
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11
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Pregabalin role in inhibition of morphine analgesic tolerance and physical dependency in rats. Eur J Pharmacol 2014; 742:113-7. [DOI: 10.1016/j.ejphar.2014.08.030] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2014] [Revised: 08/25/2014] [Accepted: 08/26/2014] [Indexed: 12/11/2022]
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12
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Hasanein P, Parviz M. Role of GABAA receptor in modulation of acute thermal pain using a rat model of cholestasis. Pharmacol Biochem Behav 2014; 124:226-30. [DOI: 10.1016/j.pbb.2014.06.014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/09/2014] [Revised: 06/07/2014] [Accepted: 06/15/2014] [Indexed: 10/25/2022]
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13
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Rashvand M, Khajavai A, Parviz M, Hasanein P, Keshavarz M. GABAAreceptors are involved in the analgesic effects of morphine microinjected into the central nucleus of the amygdala. Clin Exp Pharmacol Physiol 2014; 41:338-44. [DOI: 10.1111/1440-1681.12223] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2013] [Revised: 02/19/2014] [Accepted: 02/21/2014] [Indexed: 12/12/2022]
Affiliation(s)
- Mina Rashvand
- Department of Physiology; School of Medicine; Tehran University of Medical Sciences; Tehran Iran
| | - Ali Khajavai
- Department of Physiology; School of Medicine; Tehran University of Medical Sciences; Tehran Iran
| | - Mohsen Parviz
- Department of Physiology; School of Medicine; Tehran University of Medical Sciences; Tehran Iran
| | - Parisa Hasanein
- Department of Biology; School of Basic Sciences; Bu-Ali Sina University; Hamedan Iran
| | - Mansoor Keshavarz
- Department of Physiology; School of Medicine; Tehran University of Medical Sciences; Tehran Iran
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Abstract
In the last decade, preclinical investigations of electroacupuncture mechanisms on persistent tissue injury (inflammatory), nerve injury (neuropathic), cancer, and visceral pain have increased. These studies show that electroacupuncture activates the nervous system differently in health than in pain conditions, alleviates both sensory and affective inflammatory pain, and inhibits inflammatory and neuropathic pain more effectively at 2 to 10 Hz than at 100 Hz. Electroacupuncture blocks pain by activating a variety of bioactive chemicals through peripheral, spinal, and supraspinal mechanisms. These include opioids, which desensitize peripheral nociceptors and reduce proinflammatory cytokines peripherally and in the spinal cord, and serotonin and norepinephrine, which decrease spinal N-methyl-D-aspartate receptor subunit GluN1 phosphorylation. Additional studies suggest that electroacupuncture, when combined with low dosages of conventional analgesics, provides effective pain management which can forestall the side effects of often-debilitating pharmaceuticals.
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Affiliation(s)
- Ruixin Zhang
- Assistant Professor, Center for Integrative Medicine, School of Medicine, University of Maryland, Baltimore, Maryland
| | - Lixing Lao
- Professor, Center for Integrative Medicine, School of Medicine, University of Maryland, Baltimore, Maryland
| | - Ke Ren
- Professor, Department of Neural and Pain Sciences, Dental School, University of Maryland, Baltimore, Maryland
| | - Brian M. Berman
- Professor, Center for Integrative Medicine, School of Medicine, University of Maryland, Baltimore, Maryland
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Christinal J, Sumathi T. Effect of Bacopa monniera extract on methylmercury-induced behavioral and histopathological changes in rats. Biol Trace Elem Res 2013; 155:56-64. [PMID: 23872736 DOI: 10.1007/s12011-013-9756-y] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Accepted: 07/04/2013] [Indexed: 11/28/2022]
Abstract
Methylmercury (MeHg) is a well-recognized environmental contaminant with established health risk to human beings by fish and marine mammal consumption. Bacopa monniera (BM) is a perennial herb and is used as a nerve tonic in Ayurveda, a traditional medicine system in India. This study was aimed to evaluate the effect of B. monniera extract (BME) on MeHg-induced toxicity in rat cerebellum. Male Wistar rats were administered with MeHg orally at a dose of 5 mg/kg b.w. for 21 days. Experimental rats were given MeHg and also administered with BME (40 mg/kg, orally) 1 h prior to the administration of MeHg for 21 days. After treatment period, MeHg exposure significantly decreases the body weight and also caused the following behavioral changes. Decrease tail flick response, longer immobility time, significant decrease in motor activity, and spatial short-term memory. BME pretreatment reverted the behavioral changes to normal. MeHg exposure decreases the DNA and RNA content in cerebellum and also caused some pathological changes in cerebellum. Pretreatment with BME restored all the changes to near normal. These findings suggest that BME has a potent efficacy to alleviate MeHg-induced toxicity in rat cerebellum.
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Affiliation(s)
- Johnson Christinal
- Department of Medical Biochemistry, Dr. ALM Post Graduate Institute of Basic Medical Sciences, University of Madras, Taramani Campus, Chennai, Tamil Nadu, India
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Tsakova A, Surcheva S, Vlaskovska M. Ex Situ-En Blockand In VitroAnimal Models of Mechanosensory and Motor Equivalents of Pelvic and Urogenital Pain. BIOTECHNOL BIOTEC EQ 2013. [DOI: 10.5504/bbeq.2013.0049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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Ishida R, Nikai T, Saito Y. In Response. Anesth Analg 2012. [DOI: 10.1213/ane.0b013e318263caa7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Huang CF, Yang RS, Liu SH, Hsieh PC, Lin-Shiau SY. Evidence for Improved Neuropharmacological Efficacy and Decreased Neurotoxicity in Mice with Traditional Processing of Rhizoma Arisaematis. THE AMERICAN JOURNAL OF CHINESE MEDICINE 2012; 39:981-98. [DOI: 10.1142/s0192415x11009354] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Rhizoma Arisaematis (RA, the rhizome of Pinellia pedatisecta Schott) is a traditional Chinese medicine commonly used in the treatment of convulsions, inflammation, and cancer. Despite the fact that it has been used for more than 2000 years, the pharmacological and toxic effects of traditionally processed products of RA are still unclear. In this study, we attempted to investigate the effects exerted by untreated crude RA and different preparations of RA treated with alumen in combination with ginger juice (Zhinanxing) or bile juice (Dannanxing) in ICR mice. The results showed that both the Zhinanxing and Dannanxing water extracts exerted significantly increased sedative effects, as indicated by the inhibitory effects on ambulatory distances, jumps, vertical-plane entries, and prolonged pentobarbital-induced sleeping time. The extracts also exerted significantly increased analgesic effects (increase of tail flick latency in nociceptive testing) in mice than did the unprocessed crude RA after oral administration for one to three days, and effects persisted 18 days after the cessation of treatment. By contrast, the toxic effects, such as an increase in stereotype-1 episodes of locomotor activities and reduction of the retention time on a rotating rod (motor equilibrium dysfunction), were observed only in mice treated with the unprocessed crude RA for three consecutive days, and effects persisted for 18 days after the cessation of treatment. These neurotoxic effects were accompanied by an increase in plasma lipid peroxidation (LPO), decrease in whole blood nitric oxide (NOx) levels, and inhibition of Na +/ K +-ATPase activities in membrane fractions of erythrocytes and in the cerebral cortex. In conclusion, these findings provide scientific evidence that the processed RA indeed possesses not only enhanced neuropharmacological efficacy but also reduced neurotoxic effects as compared to the unprocessed crude RA. The signaling of NO x/oxidative stress/ Na +- K +- ATPase activities played a role, at least in part, in the underlying mechanisms of neurotoxic effects induced by the crude RA.
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Affiliation(s)
- Chun-Fa Huang
- School of Chinese Medicine, College of Chinese Medicine, China Medical University, Taichung, Taiwan
- Institute of Toxicology, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Rong-Sen Yang
- Department of Orthopedics, National Taiwan University Hospital, Taipei, Taiwan
| | - Shing-Hwa Liu
- Institute of Toxicology, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Po-Chow Hsieh
- Division of Chinese Pharmacy, Committee on Chinese Medicine and Pharmacy, Department of Health, Executive Yuan, Taipei, Taiwan
| | - Shoei-Yn Lin-Shiau
- Institute of Pharmacology, College of Medicine, National Taiwan University, Taipei, Taiwan
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Lindström E, Brusberg M, Ravnefjord A, Kakol-Palm D, Påhlman I, Novén A, Larsson H, Martinez V. Oral baclofen reduces visceral pain-related pseudo-affective responses to colorectal distension in rats: relation between plasma exposure and efficacy. Scand J Gastroenterol 2011; 46:652-62. [PMID: 21443414 DOI: 10.3109/00365521.2011.560677] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
OBJECTIVE We previously showed that activation of GABA(B) receptors by intravenous baclofen reduces pseudo-affective responses to colorectal distension in rats. Here we evaluate the potential clinical significance of these observations. MATERIAL AND METHODS Clinically relevant colorectal distension protocols were used to assess the effects of oral baclofen on visceromotor and autonomic cardiovascular responses in conscious rats. Plasma levels of baclofen were monitored to provide clinical relevance to the doses used. Conscious female Sprague-Dawley rats were subjected to repeated noxious colorectal distension (12 × 80 mmHg), ascending-phasic colorectal distension (10-80 mmHg, 10 mmHg increments) or ramp colorectal distension (10 min ramp at 8 mmHg/min). Visceromotor and cardiovascular responses (mean arterial blood pressure and heart rate) were monitored. Pain-related response thresholds were assessed using ascending-phasic and ramp colorectal distension. RESULTS Baclofen (1-10 μmol/kg, p.o.) reduced the visceromotor response to colorectal distension, reaching a 40% maximal inhibition (p < 0.05). The highest dose (10 μmol/kg, p.o.) also inhibited pain-related cardiovascular responses in telemetrized rats (50-55% reduction in colorectal distension-evoked hypertensive and tachycardic responses; p < 0.05). Similar thresholds for pain-related visceromotor responses were determined during ramp or ascending-phasic colorectal distension (34.1 ± 1.9 and 31.7 ± 3.2 mmHg, respectively). Baclofen (10 μmol/kg, p.o.) increased thresholds to 71.1 ± 3.7 and 77.5 ± 1.8 mmHg during ramp and ascending-phasic colorectal distension, respectively (p < 0.001). Plasma levels of baclofen were 3.3 ± 0.2 μmol/l at 90 min post-dosing, corresponding to the end of the colorectal distension procedure. CONCLUSIONS Oral baclofen, at plasma levels similar to those reported safe and within a therapeutic range in humans, produced significant visceral anti-nociceptive effects in rats.
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Liu LS, Shenoy M, Pasricha PJ. The analgesic effects of the GABAB receptor agonist, baclofen, in a rodent model of functional dyspepsia. Neurogastroenterol Motil 2011; 23:356-61, e160-1. [PMID: 21199535 DOI: 10.1111/j.1365-2982.2010.01649.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
BACKGROUND The amino acid γ-aminobutyric acid (GABA) is an important modulator of pain but its role in visceral pain syndromes is just beginning to be studied. Our aims were to investigate the effect and mechanism of action of the GABA(B) receptor agonist, baclofen, on gastric hypersensitivity in a validated rat model of functional dyspepsia (FD). METHODS 10-day-old male rats received 0.2 mL of 0.1% iodoacetamide in 2% sucrose daily by oral gavages for 6 days. Control group received 2% sucrose. At 8-10 weeks rats treated with baclofen (0.3, 1, and 3 mg kg(-1) bw) or saline were tested for behavioral and electromyographic (EMG) visceromotor responses; gastric spinal afferent nerve activity to graded gastric distention and Fos protein expression in dorsal horn of spinal cord segments T8-T10 to noxious gastric distention. KEY RESULTS Baclofen administration was associated with a significant attenuation of the behavioral and EMG responses (at 1 and 3 mg kg(-1)) and expression of Fos in T8 and T9 segments in neonatal iodoacetamide sensitized rats. However, baclofen administration did not significantly affect splanchnic nerve activity to gastric distention. Baclofen (3 mg kg(-1)) also significantly reduced the expression of spinal Fos in response to gastric distention in control rats to a lesser extent than sensitized rats. CONCLUSIONS & INFERENCES Baclofen is effective in attenuating pain associated responses in an experimental model of FD and appears to act by central mechanisms. These results provide a basis for clinical trials of this drug in FD patients.
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Affiliation(s)
- L S Liu
- Division of Gastroenterology and Hepatology, Stanford University Medical Center, Stanford, CA 94305-5187, USA
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Sanders JC, Gerstein N, Torgeson E, Abram S. Intrathecal baclofen for postoperative analgesia after total knee arthroplasty. J Clin Anesth 2010; 21:486-92. [PMID: 20006256 DOI: 10.1016/j.jclinane.2008.12.019] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2007] [Revised: 11/29/2008] [Accepted: 12/01/2008] [Indexed: 12/14/2022]
Abstract
STUDY OBJECTIVE To determine whether intrathecal baclofen is an effective adjunctive agent to decrease acute and chronic postoperative pain after total knee arthroplasty. DESIGN Prospective, randomized, double-blind controlled trial. SETTING Operating room and inpatient units of a university hospital. PATIENTS 60 adult, ASA physical status I, II, and III patients presenting for total knee arthroplasty. INTERVENTIONS Anesthesia was provided by spinal injection of 15 mg of 0.75% hyperbaric bupivacaine combined with either 100 mcg baclofen or saline. Sedation was provided with intravenous midazolam and propofol. MEASUREMENTS Data were collected on adverse effects, opioid usage, and verbal pain scale (VPS) from 0 to 10. The study period was divided into six discrete time intervals that included the 1(st) 72-hour postoperative period and a three-month post-discharge follow-up telephone call. MAIN RESULTS The baclofen group used less morphine in the PACU than the control group (5 mg vs. 9.3 mg; P = 0.04). VPS were lower in the baclofen group than the treatment group, but significant differences could be demonstrated only in the time periods 48-72 hours and three months postoperatively. At three months, fewer patients in the baclofen group reported pain than the control group (8/27 vs. 19/29; P = 0.009). Regression analysis showed that the baclofen group was 4.5 times less likely to report pain at three months (95% CI: 1.5-16.6). CONCLUSIONS IT baclofen used as an adjuvant to spinal anesthesia for total knee arthroplasty allows for less postoperative opioid usage and less chronic pain at three months.
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Affiliation(s)
- John C Sanders
- Department of Anesthesiology and Critical Care, University of New Mexico - School of Medicine, Albuquerque, NM, USA.
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Abstract
The mechanism of visceral pain is still less understood compared with that of somatic pain. This is primarily due to the diverse nature of visceral pain compounded by multiple factors such as sexual dimorphism, psychological stress, genetic trait, and the nature of predisposed disease. Due to multiple contributing factors there is an enormous challenge to develop animal models that ideally mimic the exact disease condition. In spite of that, it is well recognized that visceral hypersensitivity can occur due to (1) sensitization of primary sensory afferents innervating the viscera, (2) hyperexcitability of spinal ascending neurons (central sensitization) receiving synaptic input from the viscera, and (3) dysregulation of descending pathways that modulate spinal nociceptive transmission. Depending on the type of stimulus condition, different neural pathways are involved in chronic pain. In early-life psychological stress such as maternal separation, chronic pain occurs later in life due to dysregulation of the hypothalamic-pituitary-adrenal axis and significant increase in corticotrophin releasing factor (CRF) secretion. In contrast, in early-life inflammatory conditions such as colitis and cystitis, there is dysregulation of the descending opioidergic system that results excessive pain perception (i.e., visceral hyperalgesia). Functional bowel disorders and chronic pelvic pain represent unexplained pain that is not associated with identifiable organic diseases. Often pain overlaps between two organs and approximately 35% of patients with chronic pelvic pain showed significant improvement when treated for functional bowel disorders. Animal studies have documented that two main components such as (1) dichotomy of primary afferent fibers innervating two pelvic organs and (2) common convergence of two afferent fibers onto a spinal dorsal horn are contributing factors for organ-to-organ pain overlap. With reports emerging about the varieties of peptide molecules involved in the pathological conditions of visceral pain, it is expected that better therapy will be achieved relatively soon to manage chronic visceral pain.
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Brusberg M, Ravnefjord A, Martinsson R, Larsson H, Martinez V, Lindström E. The GABAB receptor agonist, baclofen, and the positive allosteric modulator, CGP7930, inhibit visceral pain-related responses to colorectal distension in rats. Neuropharmacology 2009; 56:362-7. [DOI: 10.1016/j.neuropharm.2008.09.006] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2008] [Revised: 07/23/2008] [Accepted: 09/09/2008] [Indexed: 10/21/2022]
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Supraspinal and spinal cord opioid receptors are responsible for antinociception following intrathecal morphine injections. Eur J Anaesthesiol 2004. [DOI: 10.1097/00003643-200403000-00003] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Sengupta JN, Medda BK, Shaker R. Effect of GABA(B) receptor agonist on distension-sensitive pelvic nerve afferent fibers innervating rat colon. Am J Physiol Gastrointest Liver Physiol 2002; 283:G1343-51. [PMID: 12388205 DOI: 10.1152/ajpgi.00124.2002] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Spinal afferents innervating the gastrointestinal tract are the major pathways for visceral nociception. Many centrally acting analgesic drugs attenuate responses of visceral primary afferent fibers by acting at the peripheral site. Gamma-amino butyric acid (GABA), a major inhibitory neurotransmitter, acts via metobotropic GABA(B) and ionotropic GABA(A)/GABA(C) receptors. The aim of this study was to test the peripheral effect of selective GABA(B) receptor agonist baclofen on responses of the pelvic nerve afferent fibers innervating the colon of the rat. Distension-sensitive pelvic nerve afferent fibers were recorded from the S(1) sacral dorsal root in anesthetized rats. The effect of baclofen (1-300 micromol/kg) was tested on responses of these fibers to colorectal distension (CRD; 60 mmHg, 30 s). A total of 21 pelvic nerve afferent fibers was recorded. Mechanosensitive properties of four fibers were also recorded before and after bilateral transections of T(12)-S(3) ventral roots (VR). Effect of baclofen was tested on 15 fibers (7 in intact rats, 4 in rats with transected VR, and 4 in rats pretreated with CGP 54626). In nine fibers (5/7 in intact and 4/4 in VR transected rats), baclofen produced dose-dependent inhibition of response to CRD. Pretreatment with selective GABA(B) receptor antagonist CGP 54626 (1 micromol/kg) reversed the inhibitory effect of baclofen. Results suggest a peripheral role of GABA(B) receptors in the inhibition of mechanotransduction property of distension-sensitive pelvic nerve afferent fibers.
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Affiliation(s)
- Jyoti N Sengupta
- Division of Gastroenterology and Hepatology, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA.
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Walker SM, Goudas LC, Cousins MJ, Carr DB. Combination Spinal Analgesic Chemotherapy: A Systematic Review. Anesth Analg 2002. [DOI: 10.1213/00000539-200209000-00033] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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Mahmoudi M, Zarrindast MR. Effect of intracerebroventricular injection of GABA receptor agents on morphine-induced antinociception in the formalin test. J Psychopharmacol 2002; 16:85-91. [PMID: 11949777 DOI: 10.1177/026988110201600108] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In the present study, the effects of gamma-aminobutyric acid (GABA) receptor agonists and antagonists on antinociception induced by morphine in the formalin test were investigated in rats. Intraperitoneal (i.p.) injection of different doses of morphine (1, 3, 6 and 9 mg/kg) and intracerebroventricular (i.c.v.) injection of different doses of muscimol (0.5, 1 and 2 microg per rat) or baclofen (0.25, 0.5 and 1 microg per rat) induced a dose-related antinociception in the both first and second phases of the formalin test. The responses induced by muscimol or baclofen in both phases were reduced by bicuculline or CGP35348 [p-(3-aminopropyl)-p-diethoxymethyl-phosphinic acid], respectively. Bicuculline alone has produced antinociception in the second phase and CGP35348 alone has had antinociception in both phases of the formalin test. Morphine in combination with different doses of muscimol or baclofen did not elicit potentiation. The opioid receptor antagonist naloxone reduced the response induced by muscimol in the second phase and baclofen in both phases of the formalin test. It may be concluded that central GABA(A) and GABA(B) receptor stimulation induces antinociception in the formalin test. However, the antinociception induced by GABA receptor agonists may be mediated partly through supraspinal opioid receptor mechanisms and, for the GABA(B) receptor agonist, through spinal and supraspinal opioid receptor mechanisms.
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Affiliation(s)
- Mitra Mahmoudi
- Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Iran
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