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Hannan SB, Penzinger R, Mickute G, Smart TG. CGP7930 - An allosteric modulator of GABA BRs, GABA ARs and inwardly-rectifying potassium channels. Neuropharmacology 2023; 238:109644. [PMID: 37422181 PMCID: PMC10951960 DOI: 10.1016/j.neuropharm.2023.109644] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Revised: 06/01/2023] [Accepted: 06/22/2023] [Indexed: 07/10/2023]
Abstract
Type-A and -B GABA receptors (GABAARs/GABABRs) control brain function and behaviour by fine tuning neurotransmission. Over-time these receptors have become important therapeutic targets for treating neurodevelopmental and neuropsychiatric disorders. Several positive allosteric modulators (PAMs) of GABARs have reached the clinic and selective targeting of receptor subtypes is crucial. For GABABRs, CGP7930 is a widely used PAM for in vivo studies, but its full pharmacological profile has not yet been established. Here, we reveal that CGP7930 has multiple effects not only on GABABRs but also GABAARs, which for the latter involves potentiation of GABA currents, direct receptor activation, and also inhibition. Furthermore, at higher concentrations, CGP7930 also blocks G protein-coupled inwardly-rectifying K+ (GIRK) channels diminishing GABABR signalling in HEK 293 cells. In male and female rat hippocampal neuron cultures, CGP7930 allosteric effects on GABAARs caused prolonged rise and decay times and reduced the frequency of inhibitory postsynaptic currents and potentiated GABAAR-mediated tonic inhibition. Additional comparison between predominant synaptic- and extrasynaptic-isoforms of GABAAR indicated no evident subtype selectivity for CGP7930. In conclusion, our study of CGP7930 modulation of GABAARs, GABABRs and GIRK channels, indicates this compound is unsuitable for use as a specific GABABR PAM.
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Affiliation(s)
- Saad B Hannan
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK.
| | - Reka Penzinger
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Ginte Mickute
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Trevor G Smart
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK.
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2
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Abstract
A substantial fraction of the human population suffers from chronic pain states, which often cannot be sufficiently treated with existing drugs. This calls for alternative targets and strategies for the development of novel analgesics. There is substantial evidence that the G protein-coupled GABAB receptor is involved in the processing of pain signals and thus has long been considered a valuable target for the generation of analgesics to treat chronic pain. In this review, the contribution of GABAB receptors to the generation and modulation of pain signals, their involvement in chronic pain states as well as their target suitability for the development of novel analgesics is discussed.
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Affiliation(s)
- Dietmar Benke
- Institute of Pharmacology and Toxicology, University of Zurich, Zurich, Switzerland.
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3
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Song Y, Meng QX, Wu K, Hua R, Song ZJ, Song Y, Qin X, Cao JL, Zhang YM. Disinhibition of PVN-projecting GABAergic neurons in AV region in BNST participates in visceral hypersensitivity in rats. Psychoneuroendocrinology 2020; 117:104690. [PMID: 32417623 DOI: 10.1016/j.psyneuen.2020.104690] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Revised: 04/09/2020] [Accepted: 04/13/2020] [Indexed: 02/08/2023]
Abstract
Ample evidence suggests that early life stress (ELS) is a high-risk factor for the development of visceral pain disorders, whereas the mechanism underlying neuronal circuit remains elusive. Herein, we employed neonatal colorectal distension (CRD) to induce visceral hypersensitivity in rats. A combination of electrophysiology, pharmacology, behavioral test, molecular biology, chemogenetics and optogenetics confirmed that CRD in neonatal rats could predispose the elevated firing frequency of the parvocellular corticotropin-releasing hormone (CRH) neurons in the paraventricular nucleus of hypothalamus (PVN) in adulthood, with the CRH neurons activated and the frequency of spontaneous inhibitory postsynaptic currents (sIPSC) diminished, both contributing to chronic visceral hypersensitivity. Moreover, following administration of exogenous GABA (300 mM/0.5 μL) and GABAA receptor agonist muscimol (3 mM/0.5 μL) in PVN, visceral hyperalgesia was abrogated. In addition, the PVN-projecting GABAergic neurons were mainly distributed in the anterior ventral (AV) region in the bed nucleus of stria terminalis (BNST), and the excitability of these GABAergic neurons was weakened in visceral hypersensitivity. Specific depletion of the GABAergic neurons in AV region precipitated visceral hyperalgesia. Moreover, chemogenetic activation of the PVN-projecting neurons alleviated the visceral hypersensitivity. Photoactivation of PVN-projecting GABAergic neurons abated the visceral hypersensitivity in neonatal-CRD rats, whereas photoinhibition evoked visceral hyperalgesia in naïve rats. Our findings demonstrated that disinhibition of the PVN-projecting GABAergic neurons in AV region contributed to the excitation of CRH neurons, thereby mediating visceral hypersensitivity. Our study might provide a novel insight into the neuronal circuits involved in the ELS-induced visceral hypersensitivity.
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Affiliation(s)
- Yu Song
- Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical University, Xuzhou, Jiangsu Province 221004, China; Department of Anesthesiology, The Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu Province 221002, China; Jiangsu Province Key Laboratory of Anesthesia and Analgesia Application Technology, Xuzhou Medical University, Xuzhou, Jiangsu Province 221004, China
| | - Qing-Xiang Meng
- Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical University, Xuzhou, Jiangsu Province 221004, China; Jiangsu Province Key Laboratory of Anesthesia and Analgesia Application Technology, Xuzhou Medical University, Xuzhou, Jiangsu Province 221004, China
| | - Ke Wu
- Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical University, Xuzhou, Jiangsu Province 221004, China; Jiangsu Province Key Laboratory of Anesthesia and Analgesia Application Technology, Xuzhou Medical University, Xuzhou, Jiangsu Province 221004, China
| | - Rong Hua
- Department of Emergency, The Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu Province 221002, China
| | - Zhi-Jing Song
- Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical University, Xuzhou, Jiangsu Province 221004, China; Jiangsu Province Key Laboratory of Anesthesia and Analgesia Application Technology, Xuzhou Medical University, Xuzhou, Jiangsu Province 221004, China
| | - Ying Song
- Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical University, Xuzhou, Jiangsu Province 221004, China; Jiangsu Province Key Laboratory of Anesthesia and Analgesia Application Technology, Xuzhou Medical University, Xuzhou, Jiangsu Province 221004, China
| | - Xia Qin
- Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical University, Xuzhou, Jiangsu Province 221004, China; Jiangsu Province Key Laboratory of Anesthesia and Analgesia Application Technology, Xuzhou Medical University, Xuzhou, Jiangsu Province 221004, China
| | - Jun-Li Cao
- Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical University, Xuzhou, Jiangsu Province 221004, China; Jiangsu Province Key Laboratory of Anesthesia and Analgesia Application Technology, Xuzhou Medical University, Xuzhou, Jiangsu Province 221004, China.
| | - Yong-Mei Zhang
- Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical University, Xuzhou, Jiangsu Province 221004, China; Jiangsu Province Key Laboratory of Anesthesia and Analgesia Application Technology, Xuzhou Medical University, Xuzhou, Jiangsu Province 221004, China.
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van Thiel IAM, Botschuijver S, de Jonge WJ, Seppen J. Painful interactions: Microbial compounds and visceral pain. Biochim Biophys Acta Mol Basis Dis 2019; 1866:165534. [PMID: 31634534 DOI: 10.1016/j.bbadis.2019.165534] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Revised: 08/12/2019] [Accepted: 08/13/2019] [Indexed: 12/18/2022]
Abstract
Visceral pain, characterized by abdominal discomfort, originates from organs in the abdominal cavity and is a characteristic symptom in patients suffering from irritable bowel syndrome, vulvodynia or interstitial cystitis. Most organs in which visceral pain originates are in contact with the external milieu and continuously exposed to microbes. In order to maintain homeostasis and prevent infections, the immune- and nervous system in these organs cooperate to sense and eliminate (harmful) microbes. Recognition of microbial components or products by receptors expressed on cells from the immune and nervous system can activate immune responses but may also cause pain. We review the microbial compounds and their receptors that could be involved in visceral pain development.
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Affiliation(s)
- I A M van Thiel
- Tytgat Institute for Liver and Intestinal Research, Amsterdam UMC, location AMC, Meibergdreef 69, 1105 BK Amsterdam, the Netherlands
| | - S Botschuijver
- Tytgat Institute for Liver and Intestinal Research, Amsterdam UMC, location AMC, Meibergdreef 69, 1105 BK Amsterdam, the Netherlands
| | - W J de Jonge
- Tytgat Institute for Liver and Intestinal Research, Amsterdam UMC, location AMC, Meibergdreef 69, 1105 BK Amsterdam, the Netherlands
| | - J Seppen
- Tytgat Institute for Liver and Intestinal Research, Amsterdam UMC, location AMC, Meibergdreef 69, 1105 BK Amsterdam, the Netherlands.
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Marine Toxins and Nociception: Potential Therapeutic Use in the Treatment of Visceral Pain Associated with Gastrointestinal Disorders. Toxins (Basel) 2019; 11:toxins11080449. [PMID: 31370176 PMCID: PMC6723473 DOI: 10.3390/toxins11080449] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Revised: 07/24/2019] [Accepted: 07/26/2019] [Indexed: 12/12/2022] Open
Abstract
Visceral pain, of which the pathogenic basis is currently largely unknown, is a hallmark symptom of both functional disorders, such as irritable bowel syndrome, and inflammatory bowel disease. Intrinsic sensory neurons in the enteric nervous system and afferent sensory neurons of the dorsal root ganglia, connecting with the central nervous system, represent the primary neuronal pathways transducing gut visceral pain. Current pharmacological therapies have several limitations, owing to their partial efficacy and the generation of severe adverse effects. Numerous cellular targets of visceral nociception have been recognized, including, among others, channels (i.e., voltage-gated sodium channels, VGSCs, voltage-gated calcium channels, VGCCs, Transient Receptor Potential, TRP, and Acid-sensing ion channels, ASICs) and neurotransmitter pathways (i.e., GABAergic pathways), which represent attractive targets for the discovery of novel drugs. Natural biologically active compounds, such as marine toxins, able to bind with high affinity and selectivity to different visceral pain molecular mediators, may represent a useful tool (1) to improve our knowledge of the physiological and pathological relevance of each nociceptive target, and (2) to discover therapeutically valuable molecules. In this review we report the most recent literature describing the effects of marine toxin on gastrointestinal visceral pain pathways and the possible clinical implications in the treatment of chronic pain associated with gut diseases.
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Aggarwal S, Ahuja V, Paul J. Dysregulation of GABAergic Signalling Contributes in the Pathogenesis of Diarrhea-predominant Irritable Bowel Syndrome. J Neurogastroenterol Motil 2018; 24:422-430. [PMID: 29852727 PMCID: PMC6034664 DOI: 10.5056/jnm17100] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/28/2017] [Revised: 01/22/2018] [Accepted: 02/09/2018] [Indexed: 01/10/2023] Open
Abstract
Background/Aims Diarrhea-predominant irritable bowel syndrome (IBS-D) is a prevalent functional bowel disorder. Abdominal pain, discomfort and altered intestinal habits are the salient features of IBS-D. Low grade inflammation and altered neurotransmitters are the 2 recently identified factors contributing to the pathogenesis of IBS-D, but their role and interactions has not been elucidated in detail. Here we investigate the potential role of γ-aminobutyric acid (GABA) in regulating gut inflammation during IBS-D. Methods Blood samples and colonic mucosal biopsies from clinically diagnosed IBS-D patients and controls were collected. Levels of GABA were measured in serum samples through enzyme-linked immunosorbent assay (ELISA). Expression of GABAergic system and proinflammatory cytokines were analyzed in biopsy samples by reverse transcriptase polymerase chain reaction (RT-PCR). Effect of GABA and its antagonist on the expression of proinflammatory cytokines in lipopolysaccharide (LPS)-stimulated HT-29 cells was examined through RT-PCR. Results ELISA data revealed diminished level of GABA in IBS-D patients as compared to controls. RT-PCR analysis showed altered GABAergic signal system in IBS-D patients as compared to controls. GABA reduced the expression of proinflammatory cytokines in LPS stimulated HT-29 cells, whereas bicuculline methiodide (GABA antagonist) upregulated the expression of same cytokines in LPS stimulated HT-29 cells. Conclusions Our sets of data indicate that diminished level of GABA and altered GABAergic signal system contributes to pathogenesis of IBS-D by regulating inflammatory processes. These results provide novel evidence for anti-inflammatory role of GABA in IBS-D patients by altering the expression of pro-inflammatory cytokines.
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Affiliation(s)
- Surbhi Aggarwal
- School of Life Sciences, Jawaharlal Nehru University, New Delhi, India
| | - Vineet Ahuja
- Department of Gastroenterology, All India Institute of Medical Sciences, New Delhi, India
| | - Jaishree Paul
- School of Life Sciences, Jawaharlal Nehru University, New Delhi, India
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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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Naik R, Valentine H, Dannals RF, Wong DF, Horti AG. Synthesis and Evaluation of a New 18F-Labeled Radiotracer for Studying the GABA B Receptor in the Mouse Brain. ACS Chem Neurosci 2018; 9:1453-1461. [PMID: 29498831 DOI: 10.1021/acschemneuro.8b00038] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
New GABAB agonists, fluoropyridyl ether analogues of baclofen, have been synthesized as potential PET radiotracers. The compound with highest inhibition binding affinity as well as greatest agonist response, ( R)-4-amino-3-(4-chloro-3-((2-fluoropyridin-4-yl)methoxy)phenyl)butanoic acid (1b), was radiolabeled with 18F with good radiochemical yield, high radiochemical purity, and high molar radioactivity. The regional brain distribution of the radiolabeled ( R)-4-amino-3-(4-chloro-3-((2-[18F]fluoropyridin-4-yl)methoxy)phenyl)butanoic acid, [18F]1b, was studied in CD-1 male mice. The study demonstrated that [18F]1b enters the mouse brain (1% ID/g tissue). The accumulation of [18F]1b in the mouse brain was inhibited (35%) by preinjection of GABAB agonist 1a, suggesting that the radiotracer brain uptake is partially mediated by GABAB receptors. The presented data demonstrate a feasibility of imaging of GABAB receptors in rodents and justify further development of GABAB PET tracers with improved specific binding and greater blood-brain barrier permeability.
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Affiliation(s)
- Ravi Naik
- Department of Radiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21287 United States
| | - Heather Valentine
- Department of Radiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21287 United States
| | - Robert F. Dannals
- Department of Radiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21287 United States
| | - Dean F. Wong
- Department of Radiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21287 United States
| | - Andrew G. Horti
- Department of Radiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21287 United States
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9
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Contribution of membrane receptor signalling to chronic visceral pain. Int J Biochem Cell Biol 2018; 98:10-23. [DOI: 10.1016/j.biocel.2018.02.017] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Revised: 02/15/2018] [Accepted: 02/19/2018] [Indexed: 12/18/2022]
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Gao L, Zhao H, Zhu T, Liu Y, Hu L, Liu Z, Huang H, Chen F, Deng Z, Chu D, Du D. The Regulatory Effects of Lateral Hypothalamus Area GABA B Receptor on Gastric Ischemia-Reperfusion Injury in Rats. Front Physiol 2017; 8:722. [PMID: 28983255 PMCID: PMC5613147 DOI: 10.3389/fphys.2017.00722] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Accepted: 09/06/2017] [Indexed: 12/16/2022] Open
Abstract
HIGHLIGHTSThe aim of the research was to determine the functional effects and molecular mechanisms of GABAB receptor on ischemia reperfusion-induced gastric injury in rats. The lateral hypothalamus area GABAB receptor attenuated the ischemia reperfusion-induced gastric injury by up-regulating the production of GABA, GABABR, and down-regulating P-GABABR in the brain. This work would provide a new therapeutic strategy for acute gastric injury.
Gastric ischemia-reperfusion (GI-R) injury progression is largely associated with excessive activation of the greater splanchnic nerve (GSN). This study aims to investigate the protective effects of GABAB receptor (GABABR) in the lateral hypothalamic area (LHA) on GI-R injury. A model of GI-R injury was established by clamping the celiac artery for 30 min and then reperfusion for 1 h. The coordinate of FN and LHA was identified in Stereotaxic Coordinates and then the L-Glu was microinjected into FN, GABAB receptor agonist baclofen, or GABAB receptor antagonist CGP35348 was microinjected into the LHA, finally the GI-R model was prepared. The expression of GABABR, P-GABABR, NOX2, NOX4, and SOD in the LHA was detected by western blot, PCR, and RT-PCR. The expression of IL-1β, NOX2, and NXO4 in gastric mucosa was detected by western blot. We found that microinjection of L-Glu into the FN or GABAB receptor agonist (baclofen) into the LHA attenuated GI-R injury. Pretreatment with GABAB receptor antagonist CGP35348 reversed the protective effects of FN stimulation or baclofen into the LHA. Microinjection of baclofen into the LHA obviously reduced the expression of inflammatory factor IL-1β, NOX2, and NOX4 in the gastric mucosa. Conclusion: The protective effects of microinjection of GABABR agonist into LHA on GI-R injury in rats could be mediated by up-regulating the production of GABA, GABABR, and down-regulating P-GABABR in the LHA.
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Affiliation(s)
- Lin Gao
- Neurology Center, The First Affiliated Hospital of Zhengzhou UniversityZhengzhou, China
| | - Huiru Zhao
- Shanghai Key Laboratory of Bio-Crops, College of Life Science, Shanghai UniversityShanghai, China
| | - Tao Zhu
- Department of Life Science, Heze UniversityHeze, China
| | - Yeliu Liu
- Department of General Surgery, Huai'an First People's Hospital, Nanjing Medical UniversityHuai'an, China
| | - Li Hu
- Shanghai Key Laboratory of Bio-Crops, College of Life Science, Shanghai UniversityShanghai, China
| | - Zhenguo Liu
- Shanghai Key Laboratory of Bio-Crops, College of Life Science, Shanghai UniversityShanghai, China
| | - Hai Huang
- Shanghai Key Laboratory of Bio-Crops, College of Life Science, Shanghai UniversityShanghai, China
| | - Fuxue Chen
- Shanghai Key Laboratory of Bio-Crops, College of Life Science, Shanghai UniversityShanghai, China
| | - Zhenxu Deng
- Department of Life Science, Heze UniversityHeze, China
| | - Dechang Chu
- Department of Life Science, Heze UniversityHeze, China
| | - Dongshu Du
- Neurology Center, The First Affiliated Hospital of Zhengzhou UniversityZhengzhou, China.,Shanghai Key Laboratory of Bio-Crops, College of Life Science, Shanghai UniversityShanghai, China
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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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Castro J, Harrington AM, Garcia-Caraballo S, Maddern J, Grundy L, Zhang J, Page G, Miller PE, Craik DJ, Adams DJ, Brierley SM. α-Conotoxin Vc1.1 inhibits human dorsal root ganglion neuroexcitability and mouse colonic nociception via GABA B receptors. Gut 2017; 66:1083-1094. [PMID: 26887818 PMCID: PMC5532460 DOI: 10.1136/gutjnl-2015-310971] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/27/2015] [Revised: 12/22/2015] [Accepted: 01/14/2016] [Indexed: 01/29/2023]
Abstract
OBJECTIVE α-Conotoxin Vc1.1 is a small disulfide-bonded peptide from the venom of the marine cone snail Conus victoriae. Vc1.1 has antinociceptive actions in animal models of neuropathic pain, but its applicability to inhibiting human dorsal root ganglion (DRG) neuroexcitability and reducing chronic visceral pain (CVP) is unknown. DESIGN We determined the inhibitory actions of Vc1.1 on human DRG neurons and on mouse colonic sensory afferents in healthy and chronic visceral hypersensitivity (CVH) states. In mice, visceral nociception was assessed by neuronal activation within the spinal cord in response to noxious colorectal distension (CRD). Quantitative-reverse-transcription-PCR, single-cell-reverse-transcription-PCR and immunohistochemistry determined γ-aminobutyric acid receptor B (GABABR) and voltage-gated calcium channel (CaV2.2, CaV2.3) expression in human and mouse DRG neurons. RESULTS Vc1.1 reduced the excitability of human DRG neurons, whereas a synthetic Vc1.1 analogue that is inactive at GABABR did not. Human DRG neurons expressed GABABR and its downstream effector channels CaV2.2 and CaV2.3. Mouse colonic DRG neurons exhibited high GABABR, CaV2.2 and CaV2.3 expression, with upregulation of the CaV2.2 exon-37a variant during CVH. Vc1.1 inhibited mouse colonic afferents ex vivo and nociceptive signalling of noxious CRD into the spinal cord in vivo, with greatest efficacy observed during CVH. A selective GABABR antagonist prevented Vc1.1-induced inhibition, whereas blocking both CaV2.2 and CaV2.3 caused inhibition comparable with Vc1.1 alone. CONCLUSIONS Vc1.1-mediated activation of GABABR is a novel mechanism for reducing the excitability of human DRG neurons. Vc1.1-induced activation of GABABR on the peripheral endings of colonic afferents reduces nociceptive signalling. The enhanced antinociceptive actions of Vc1.1 during CVH suggest it is a novel candidate for the treatment for CVP.
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Affiliation(s)
- Joel Castro
- Visceral Pain Group, Centre for Nutrition and Gastrointestinal Diseases, Discipline of Medicine, Faculty of Health Sciences, The University of Adelaide, South Australian Health and Medical Research Institute (SAHMRI), Adelaide, South Australia, Australia
| | - Andrea M Harrington
- Visceral Pain Group, Centre for Nutrition and Gastrointestinal Diseases, Discipline of Medicine, Faculty of Health Sciences, The University of Adelaide, South Australian Health and Medical Research Institute (SAHMRI), Adelaide, South Australia, Australia
| | - Sonia Garcia-Caraballo
- Visceral Pain Group, Centre for Nutrition and Gastrointestinal Diseases, Discipline of Medicine, Faculty of Health Sciences, The University of Adelaide, South Australian Health and Medical Research Institute (SAHMRI), Adelaide, South Australia, Australia
| | - Jessica Maddern
- Visceral Pain Group, Centre for Nutrition and Gastrointestinal Diseases, Discipline of Medicine, Faculty of Health Sciences, The University of Adelaide, South Australian Health and Medical Research Institute (SAHMRI), Adelaide, South Australia, Australia
| | - Luke Grundy
- Visceral Pain Group, Centre for Nutrition and Gastrointestinal Diseases, Discipline of Medicine, Faculty of Health Sciences, The University of Adelaide, South Australian Health and Medical Research Institute (SAHMRI), Adelaide, South Australia, Australia
| | | | - Guy Page
- Anabios, San Diego, California, USA
| | | | - David J Craik
- Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, University of Queensland, Brisbane, Queensland, Australia
| | - David J Adams
- Illawarra Health & Medical Research Institute (IHMRI), University of Wollongong, Wollongong, NSW, Australia
| | - Stuart M Brierley
- Visceral Pain Group, Centre for Nutrition and Gastrointestinal Diseases, Discipline of Medicine, Faculty of Health Sciences, The University of Adelaide, South Australian Health and Medical Research Institute (SAHMRI), Adelaide, South Australia, Australia
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Shapoval LM, Dmytrenko OV, Naumenko AM, Davydovska TL, Sagach VF. Effects of Stereotactic Introduction of Baclofen in the Medullary Cardiovascular Nuclei of Rats. NEUROPHYSIOLOGY+ 2017. [DOI: 10.1007/s11062-017-9626-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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14
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Yaksh TL, Fisher CJ, Hockman TM, Wiese AJ. Current and Future Issues in the Development of Spinal Agents for the Management of Pain. Curr Neuropharmacol 2017; 15:232-259. [PMID: 26861470 PMCID: PMC5412694 DOI: 10.2174/1570159x14666160307145542] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Revised: 12/02/2015] [Accepted: 02/05/2016] [Indexed: 11/22/2022] Open
Abstract
Targeting analgesic drugs for spinal delivery reflects the fact that while the conscious experience of pain is mediated supraspinally, input initiated by high intensity stimuli, tissue injury and/or nerve injury is encoded at the level of the spinal dorsal horn and this output informs the brain as to the peripheral environment. This encoding process is subject to strong upregulation resulting in hyperesthetic states and downregulation reducing the ongoing processing of nociceptive stimuli reversing the hyperesthesia and pain processing. The present review addresses the biology of spinal nociceptive processing as relevant to the effects of intrathecally-delivered drugs in altering pain processing following acute stimulation, tissue inflammation/injury and nerve injury. The review covers i) the major classes of spinal agents currently employed as intrathecal analgesics (opioid agonists, alpha 2 agonists; sodium channel blockers; calcium channel blockers; NMDA blockers; GABA A/B agonists; COX inhibitors; ii) ongoing developments in the pharmacology of spinal therapeutics focusing on less studied agents/targets (cholinesterase inhibition; Adenosine agonists; iii) novel intrathecal targeting methodologies including gene-based approaches (viral vectors, plasmids, interfering RNAs); antisense, and toxins (botulinum toxins; resniferatoxin, substance P Saporin); and iv) issues relevant to intrathecal drug delivery (neuraxial drug distribution), infusate delivery profile, drug dosing, formulation and principals involved in the preclinical evaluation of intrathecal drug safety.
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Affiliation(s)
- Tony L. Yaksh
- University of California, San Diego, Anesthesia Research Lab 0818, 9500 Gilman Dr. LaJolla, CA 92093, USA
| | - Casey J. Fisher
- University of California, San Diego, Anesthesia Research Lab 0818, 9500 Gilman Dr. LaJolla, CA 92093, USA
| | - Tyler M. Hockman
- University of California, San Diego, Anesthesia Research Lab 0818, 9500 Gilman Dr. LaJolla, CA 92093, USA
| | - Ashley J. Wiese
- University of California, San Diego, Anesthesia Research Lab 0818, 9500 Gilman Dr. LaJolla, CA 92093, USA
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Kalinichev M, Donovan-Rodriguez T, Girard F, Haddouk H, Royer-Urios I, Schneider M, Bate ST, Marker C, Pomonis JD, Poli S. ADX71943 and ADX71441, novel positive allosteric modulators of the GABA B receptor with distinct central/peripheral profiles, show efficacy in the monosodium iodoacetate model of chronic osteoarthritis pain in the rat. Eur J Pharmacol 2016; 795:43-49. [PMID: 27916555 DOI: 10.1016/j.ejphar.2016.11.056] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2015] [Revised: 11/30/2016] [Accepted: 11/30/2016] [Indexed: 12/31/2022]
Abstract
We tested novel positive allosteric modulators (PAMs) of the γ-aminobutyric acid receptor B (GABAB), ADX71943 and ADX71441in the monosodium iodoacetate model of chronic osteoarthritis pain in rats with the objective to delineate the role of peripheral versus central GABAB receptor populations in modulation of chronic pain. Anesthetized Sprague-Dawley rats received an injection of monosodium iodoacetate into the knee and were tested for hyperalgesia starting post-MIA day 14. Effects of compounds on ipsilateral joint compression threshold were evaluated on post-MIA day 14 (after acute treatment), as well as after repeated, daily treatment on days 21 and 28 (ADX71943 only) and were compared to those of celecoxib (30mg/kg, p.o.). The PAMs were also tested in the rat rotarod test for potential muscle-relaxant effects. Acutely, ADX71943 (1-30mg/kg, p.o.), the peripherally restricted PAM, resulted in similar increases in pain threshold across the doses on day 14, while showing reduced efficacy on day 21 and no efficacy on day 28. A clear reduction in the efficacy of celecoxib across testing was also noted in this experiment. Acutely ADX71441 (0.3-15mg/kg, p.o.), the central-peripheral PAM, resulted in over 2-fold increases in pain threshold at 15mg/kg (but not at lower doses) on day 14, while causing more modest effects on day 21. Celecoxib increased pain threshold after both acute and daily treatment, showing overall similar efficacy. Thus, early, presumably more inflammatory phase of osteoarthritis pain in more sensitive to GABAB PAMs with peripherally restricted profile, while later, presumably more neuropathic phase is more sensitive to PAMs with central-peripheral profile.
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Affiliation(s)
- Mikhail Kalinichev
- Addex Therapeutics SA, Chemin des Mines 9, CH-1202, Geneva, Switzerland.
| | | | - Françoise Girard
- Addex Therapeutics SA, Chemin des Mines 9, CH-1202, Geneva, Switzerland
| | - Hasnaá Haddouk
- Addex Therapeutics SA, Chemin des Mines 9, CH-1202, Geneva, Switzerland
| | | | - Manfred Schneider
- Addex Therapeutics SA, Chemin des Mines 9, CH-1202, Geneva, Switzerland
| | - Simon T Bate
- Huntingdon Life Sciences Ltd., Huntingdon Research Centre, Woolley Road Alconbury, Huntingdon PE28 4HS, UK
| | - Cheryl Marker
- Algos Preclinical Serves Inc., 2848 Patton Road, Roseville, MN 55113, USA
| | - James D Pomonis
- Algos Preclinical Serves Inc., 2848 Patton Road, Roseville, MN 55113, USA
| | - Sonia Poli
- Addex Therapeutics SA, Chemin des Mines 9, CH-1202, Geneva, Switzerland
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Zemoura K, Ralvenius WT, Malherbe P, Benke D. The positive allosteric GABAB receptor modulator rac-BHFF enhances baclofen-mediated analgesia in neuropathic mice. Neuropharmacology 2016; 108:172-8. [PMID: 27108932 DOI: 10.1016/j.neuropharm.2016.04.028] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Revised: 04/01/2016] [Accepted: 04/20/2016] [Indexed: 10/21/2022]
Abstract
Neuropathic pain is associated with impaired inhibitory control of spinal dorsal horn neurons, which are involved in processing pain signals. The metabotropic GABAB receptor is an important component of the inhibitory system and is highly expressed in primary nociceptors and intrinsic dorsal horn neurons to control their excitability. Activation of GABAB receptors with the orthosteric agonist baclofen effectively reliefs neuropathic pain but is associated with severe side effects that prevent its widespread application. The recently developed positive allosteric GABAB receptor modulators lack most of these side effects and are therefore promising drugs for the treatment of pain. Here we tested the high affinity positive allosteric modulator rac-BHFF for its ability to relief neuropathic pain induced by chronic constriction of the sciatic nerve in mice. rac-BHFF significantly increased the paw withdrawal threshold to mechanical stimulation in healthy mice, indicating an endogenous GABABergic tone regulating the sensitivity to mechanical stimuli. Surprisingly, rac-BHFF displayed no analgesic activity in neuropathic mice although GABAB receptor expression was not affected in the dorsal horn as shown by quantitative receptor autoradiography. However, activation of spinal GABAB receptors by intrathecal injection of baclofen reduced hyperalgesia and its analgesic effect was considerably potentiated by co-application of rac-BHFF. These results indicate that under conditions of neuropathic pain the GABAergic tone is too low to provide a basis for allosteric modulation of GABAB receptors. However, allosteric modulators would be well suited as an add-on to reduce the dose of baclofen required to achieve analgesia.
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Affiliation(s)
- Khaled Zemoura
- Institute of Pharmacology and Toxicology, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - William T Ralvenius
- Institute of Pharmacology and Toxicology, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Pari Malherbe
- Discovery Neuroscience, F. Hoffmann-La Roche AG, pRED, Pharma Research & Early Development, Grenzacherstrasse 124, CH4070 Basel, Switzerland
| | - Dietmar Benke
- Institute of Pharmacology and Toxicology, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland; Neuroscience Center Zurich (ZNZ), Winterthurerstrasse 190, CH-8057 Zurich, Switzerland; Drug Discovery Network Zurich (DDNZ), Winterthurerstrasse 190, CH-8057 Zurich, Switzerland.
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Wang H, Zhang W, Wang X. Elucidation of a CGP7930 in vitro metabolite by liquid chromatography/electrospray ionization quadrupole time-of-flight tandem mass spectrometry. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2016; 30:491-496. [PMID: 26777679 DOI: 10.1002/rcm.7465] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2015] [Revised: 11/15/2015] [Accepted: 11/17/2015] [Indexed: 06/05/2023]
Abstract
RATIONALE γ-Aminobutyric acid-B (GABAB ) receptors are widely expressed in the nervous system and have been implicated as targets for various neurological and psychiatric disorders. CGP7930 is a positive allosteric modulator of GABAB receptors. It has been demonstrated to reduce drug self-administration and has gained increased research as a potential psychotropic treatment. METHODS An in vitro metabolic system with liver microsomes of SD rats has been conducted and evaluated by probe drugs. The predominant in vitro metabolite of CGP7930 was identified and elucidated using liquid chromatography/electrospray ionization quadrupole time-of-flight tandem mass spectrometry (LC/ESI-QTOF-MS/MS). Its structure was determined by comparing the characteristic ions of CGP7930 and those of the metabolite, based on the accurate mass measurement by MS and the fragmentation pattern obtained by MS/MS. RESULTS We found that the main metabolic pathway of CGP7930 was via a monohydroxylation reaction and the hydroxylation site located at the terminal butyl-carbon. The collision-induced dissociation (CID) fragmentation of the hydroxylated metabolite underwent McLafferty rearrangement and α-cleavage. CONCLUSIONS This work provides an understanding of the in vitro metabolism of CGP7930, which is helpful for the further study of the development of potential drug candidates targeting GABAB receptors, for the treatment of depression. The work also demonstrates that the LC/ESI-QTOF-MS/MS method has the advantage of possibly determining the structures of drug metabolites without the use of standards.
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Affiliation(s)
- Haidong Wang
- Key Laboratory of Catalysis and Materials Science of the State Ethnic Affairs Commission and Ministry of Education, College of Chemistry and Materials Science, South-Central University for Nationalities, Wuhan, Hubei, 430074, P.R. China
| | - Wenxiang Zhang
- Key Laboratory of Catalysis and Materials Science of the State Ethnic Affairs Commission and Ministry of Education, College of Chemistry and Materials Science, South-Central University for Nationalities, Wuhan, Hubei, 430074, P.R. China
| | - Xian Wang
- Key Laboratory of Catalysis and Materials Science of the State Ethnic Affairs Commission and Ministry of Education, College of Chemistry and Materials Science, South-Central University for Nationalities, Wuhan, Hubei, 430074, P.R. China
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Johnson AC, Greenwood-Van Meerveld B. The Pharmacology of Visceral Pain. ADVANCES IN PHARMACOLOGY 2016; 75:273-301. [PMID: 26920016 DOI: 10.1016/bs.apha.2015.11.002] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Visceral pain describes pain emanating from the internal thoracic, pelvic, or abdominal organs. Unlike somatic pain, visceral pain is generally vague, poorly localized, and characterized by hypersensitivity to a stimulus such as organ distension. While current therapeutics provides some relief from somatic pain, drugs used for treatment of chronic visceral pain are typically less efficacious and limited by multiple adverse side effects. Thus, the treatment of visceral pain represents a major unmet medical need. Further, more basic research into the physiology and pathophysiology of visceral pain is needed to provide novel targets for future drug development. In concert with chronic visceral pain, there is a high comorbidity with stress-related psychiatric disorders including anxiety and depression. The mechanisms linking visceral pain with these overlapping comorbidities remain to be elucidated. However, persistent stress facilitates pain perception and sensitizes pain pathways, leading to a feed-forward cycle promoting chronic visceral pain disorders. We will focus on stress-induced exacerbation of chronic visceral pain and provide supporting evidence that centrally acting drugs targeting the pain and stress-responsive brain regions may represent a valid target for the development of novel and effective therapeutics.
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Affiliation(s)
- Anthony C Johnson
- Oklahoma Center for Neuroscience, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA
| | - Beverley Greenwood-Van Meerveld
- Oklahoma Center for Neuroscience, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA; Veterans Affairs Medical Center, Oklahoma City, Oklahoma, USA; Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA.
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19
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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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20
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Kannampalli P, Sengupta JN. Role of principal ionotropic and metabotropic receptors in visceral pain. J Neurogastroenterol Motil 2015; 21:147-58. [PMID: 25843070 PMCID: PMC4398235 DOI: 10.5056/jnm15026] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/17/2015] [Revised: 02/24/2015] [Accepted: 03/26/2015] [Indexed: 12/13/2022] Open
Abstract
Visceral pain is the most common form of pain caused by varied diseases and a major reason for patients to seek medical consultation. It also leads to a significant economic burden due to workdays lost and reduced productivity. Further, long-term use of non-specific medications is also associated with side effects affecting the quality of life. Despite years of extensive research and the availability of several therapeutic options, management of patients with chronic visceral pain is often inadequate, resulting in frustration for both patients and physicians. This is, most likely, because the mechanisms associated with chronic visceral pain are different from those of acute pain. Accumulating evidence from years of research implicates several receptors and ion channels in the induction and maintenance of central and peripheral sensitization during chronic pain states. Understanding the specific role of these receptors will facilitate to capitalize on their unique properties to augment the therapeutic efficacy while at the same time minimizing unwanted side effects. The aim of this review is to provide a concise review of the recent literature that reports on the role of principal ionotropic receptors and metabotropic receptors in the modulation visceral pain. We also include an overview of the possibility of these receptors as potential new targets for the treatment of chronic visceral pain conditions.
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Affiliation(s)
- Pradeep Kannampalli
- Division of Gastroenterology and Hepatology, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Jyoti N Sengupta
- Division of Gastroenterology and Hepatology, Medical College of Wisconsin, Milwaukee, WI, USA
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21
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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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22
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McCarson KE, Enna SJ. GABA pharmacology: the search for analgesics. Neurochem Res 2014; 39:1948-63. [PMID: 24532294 DOI: 10.1007/s11064-014-1254-x] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2013] [Revised: 01/28/2014] [Accepted: 01/31/2014] [Indexed: 12/28/2022]
Abstract
Decades of research have been devoted to defining the role of GABAergic transmission in nociceptive processing. Much of this work was performed using rigid, orthosteric GABA analogs created by Povl Krogsgaard-Larsen and his associates. A relationship between GABA and pain is suggested by the anatomical distribution of GABA receptors and the ability of some GABA agonists to alter nociceptive responsiveness. Outlined in this report are data supporting this proposition, with particular emphasis on the anatomical localization and function of GABA-containing neurons and the molecular and pharmacological properties of GABAA and GABAB receptor subtypes. Reference is made to changes in overall GABAergic tone, GABA receptor expression and activity as a function of the duration and intensity of a painful stimulus or exposure to GABAergic agents. Evidence is presented that the plasticity of this receptor system may be responsible for the variability in the antinociceptive effectiveness of compounds that influence GABA transmission. These findings demonstrate that at least some types of persistent pain are associated with a regionally selective decline in GABAergic tone, highlighting the need for agents that enhance GABA activity in the affected regions without compromising GABA function over the long-term. As subtype selective positive allosteric modulators may accomplish these goals, such compounds might represent a new class of analgesic drugs.
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Affiliation(s)
- Kenneth E McCarson
- Department of Pharmacology, Toxicology, and Therapeutics, University of Kansas Medical Center, 3901 Rainbow Boulevard, Mail Stop 1018, Kansas City, KS, 66160, USA
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Differential development of tolerance to the functional and behavioral effects of repeated baclofen treatment in rats. Pharmacol Biochem Behav 2013; 106:27-32. [PMID: 23500188 DOI: 10.1016/j.pbb.2013.03.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/18/2012] [Revised: 02/27/2013] [Accepted: 03/02/2013] [Indexed: 11/21/2022]
Abstract
Baclofen, a gamma-aminobutyric acid (GABA)B receptor agonist, has been used clinically to treat muscle spasticity, rigidity and pain. More recently, interest in the use of baclofen as an addiction medicine has grown, with promising preclinical cocaine and amphetamine data and demonstrated clinical benefit from alcohol and nicotine studies. Few preclinical investigations, however, have utilized chronic dosing of baclofen, which is important given that tolerance can occur to many of its effects. Thus the question of whether chronic treatment of baclofen maintains the efficacy of acute doses is imperative. The neural substrates that underlie the effects of baclofen, particularly those after chronic treatment, are also not known. In the present study, therefore, rats were treated with either a) vehicle, b) acute baclofen (5 mg/kg) or c) chronic baclofen (5 mg/kg, t.i.d. for 5 days). The effects of acute and chronic baclofen administration, compared to vehicle, were assessed using locomotor activity and changes in brain glucose metabolism (a measure of functional brain activity). Acute baclofen significantly reduced locomotor activity (horizontal and total distance traveled), while chronic baclofen failed to affect locomotor activity. Acute baclofen resulted in significantly lower rates of local cerebral glucose utilization throughout many areas of the brain, including the prefrontal cortex, caudate putamen, septum and hippocampus. The majority of these functional effects, with the exception of the caudate putamen and septum, were absent in animals chronically treated with baclofen. Despite the tolerance to the locomotor and functional effects of baclofen following repeated treatment, these persistent effects on functional activity in the caudate putamen and septum may provide insights into the way in which baclofen alters the reinforcing effects of abused substances such as cocaine, alcohol, and methamphetamine both in humans and animal models.
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Adams DJ, Berecki G. Mechanisms of conotoxin inhibition of N-type (Ca(v)2.2) calcium channels. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1828:1619-28. [PMID: 23380425 DOI: 10.1016/j.bbamem.2013.01.019] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2012] [Revised: 01/16/2013] [Accepted: 01/19/2013] [Indexed: 12/27/2022]
Abstract
N-type (Ca(v)2.2) voltage-gated calcium channels (VGCC) transduce electrical activity into other cellular functions, regulate calcium homeostasis and play a major role in processing pain information. Although the distribution and function of these channels vary widely among different classes of neurons, they are predominantly expressed in nerve terminals, where they control neurotransmitter release. To date, genetic and pharmacological studies have identified that high-threshold, N-type VGCCs are important for pain sensation in disease models. This suggests that N-type VGCC inhibitors or modulators could be developed into useful drugs to treat neuropathic pain. This review discusses the role of N-type (Ca(v)2.2) VGCCs in nociception and pain transmission through primary sensory dorsal root ganglion (DRG) neurons (nociceptors). It also outlines the potent and selective inhibition of N-type VGCCs by conotoxins, small disulfide-rich peptides isolated from the venom of marine cone snails. Of these conotoxins, ω-conotoxins are selective N-type VGCC antagonists that preferentially block nociception in inflammatory pain models, and allodynia and/or hyperalgesia in neuropathic pain models. Another conotoxin family, α-conotoxins, were initially proposed as competitive antagonists of muscle and neuronal nicotinic acetylcholine receptors (nAChR). Surprisingly, however, α-conotoxins Vc1.1 and RgIA, also potently inhibit N-type VGCC currents in the sensory DRG neurons of rodents and α9 nAChR knockout mice, via intracellular signaling mediated by G protein-coupled GABAB receptors. Understanding how conotoxins inhibit VGCCs is critical for developing these peptides into analgesics and may result in better pain management. This article is part of a Special Issue entitled: Calcium channels.
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Affiliation(s)
- David J Adams
- Health Innovations Research Institute, RMIT University, Melbourne, Victoria, Australia.
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25
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Lebovitz EE, Keller JM, Kominsky H, Kaszas K, Maric D, Iadarola MJ. Positive allosteric modulation of TRPV1 as a novel analgesic mechanism. Mol Pain 2012; 8:70. [PMID: 22998799 PMCID: PMC3556054 DOI: 10.1186/1744-8069-8-70] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Accepted: 09/11/2012] [Indexed: 12/21/2022] Open
Abstract
Background The prevalence of long-term opiate use in treating chronic non-cancer pain is increasing, and prescription opioid abuse and dependence are a major public health concern. To explore alternatives to opioid-based analgesia, the present study investigates a novel allosteric pharmacological approach operating through the cation channel TRPV1. This channel is highly expressed in subpopulations of primary afferent unmyelinated C- and lightly-myelinated Aδ-fibers that detect low and high rates of noxious heating, respectively, and it is also activated by vanilloid agonists and low pH. Sufficient doses of exogenous vanilloid agonists, such as capsaicin or resiniferatoxin, can inactivate/deactivate primary afferent endings due to calcium overload, and we hypothesized that positive allosteric modulation of agonist-activated TRPV1 could produce a selective, temporary inactivation of nociceptive nerve terminals in vivo. We previously identified MRS1477, a 1,4-dihydropyridine that potentiates vanilloid and pH activation of TRPV1 in vitro, but displays no detectable intrinsic agonist activity of its own. To study the in vivo effects of MRS1477, we injected the hind paws of rats with a non-deactivating dose of capsaicin, MRS1477, or the combination. An infrared diode laser was used to stimulate TRPV1-expressing nerve terminals and the latency and intensity of paw withdrawal responses were recorded. qRT-PCR and immunohistochemistry were performed on dorsal root ganglia to examine changes in gene expression and the cellular specificity of such changes following treatment. Results Withdrawal responses of the capsaicin-only or MRS1477-only treated paws were not significantly different from the untreated, contralateral paws. However, rats treated with the combination of capsaicin and MRS1477 exhibited increased withdrawal latency and decreased response intensity consistent with agonist potentiation and inactivation or lesion of TRPV1-containing nerve terminals. The loss of nerve endings was manifested by an increase in levels of axotomy markers assessed by qRT-PCR and colocalization of ATF3 in TRPV1+ cells visualized via immunohistochemistry. Conclusions The present observations suggest a novel, non-narcotic, selective, long-lasting TRPV1-based approach for analgesia that may be effective in acute, persistent, or chronic pain disorders.
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Affiliation(s)
- Evan E Lebovitz
- Neurobiology and Pain Therapeutics Section, Laboratory Of Sensory Biology, NIDCR, NIH, Bldg 49 Rm 1C2049 Convent Dr, Bethesda, MD 20892, USA
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Effects of intraperitoneal administration of the GABAB receptor positive allosteric modulator 2,6-di tert-butyl-4-(2-hydroxy-2,2-dimethyl-propyl)-phenol (CGP7930) on food intake in non-deprived rats. Eur J Pharmacol 2012; 690:115-8. [DOI: 10.1016/j.ejphar.2012.05.021] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2012] [Revised: 04/24/2012] [Accepted: 05/15/2012] [Indexed: 01/05/2023]
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Harrington AM, Brierley SM, Isaacs N, Hughes PA, Castro J, Blackshaw LA. Sprouting of colonic afferent central terminals and increased spinal mitogen-activated protein kinase expression in a mouse model of chronic visceral hypersensitivity. J Comp Neurol 2012; 520:2241-55. [PMID: 22237807 DOI: 10.1002/cne.23042] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Visceral pain following infection or inflammation is a major clinical problem. Although we have knowledge of how peripheral endings of colonic afferents change in disease, their central projections have been overlooked. With neuroanatomical tracing and colorectal distension (CRD), we sought to identify colonic afferent central terminals (CACTs), the dorsal horn (DH) neurons activated by colonic stimuli in the thoracolumbar (T10-L1) DH, and determine how they are altered by postinflammatory chronic colonic mechanical hypersensitivity. Retrograde tracing from the colon identified CACTs in the DH, whereas immunohistochemistry for phosphorylated MAP kinase ERK 1/2 (pERK) identified DH neurons activated by CRD (80 mmHg). In healthy mice, CACTs were located primarily in DH laminae I (LI) and V (LV) and projected down middle and lateral DH collateral pathways. CRD evoked pERK immunoreactivity in DH neurons, the majority of which were located in LI and LV, the same regions as CACTs. In postinflammatory mice, CACTs were significantly increased in T12-L1 compared with healthy mice. Although CACTs remained abundant in LI, they were more widespread and were now present in deeper laminae. After CRD, significantly more DH neurons were pERK-IR postinflammation (T12-L1), with abundant expression in LI and deeper laminae. In both healthy and postinflammatory mice, many pERK neurons were in close apposition to CACTs, suggesting that colonic afferents can stimulate specific DH neurons in response to noxious CRD. Overall, we demonstrate that CACT density and the number of responsive DH neurons in the spinal cord increase postinflammation, which may facilitate aberrant central representation of colonic nociceptive signaling following chronic peripheral hypersensitivity.
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Affiliation(s)
- Andrea M Harrington
- Nerve-Gut Research Laboratory, Discipline of Medicine, The University of Adelaide, Adelaide, South Australia, Australia 5000.
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Johnson AC, Tran L, Schulkin J, Greenwood-Van Meerveld B. Importance of stress receptor-mediated mechanisms in the amygdala on visceral pain perception in an intrinsically anxious rat. Neurogastroenterol Motil 2012; 24:479-86, e219. [PMID: 22364507 PMCID: PMC3461498 DOI: 10.1111/j.1365-2982.2012.01899.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
BACKGROUND Stress worsens abdominal pain experienced by patients with irritable bowel syndrome (IBS), a chronic disorder of unknown origin with comorbid anxiety. Previously, we have demonstrated colonic hypersensitivity in Wistar-Kyoto rats (WKYs), a high-anxiety strain, which models abdominal pain in IBS. In low-anxiety rats, we have demonstrated that the central nucleus of the amygdala (CeA) regulates colonic hypersensitivity and anxiety induced by selective activation of either glucocorticoid receptors (GR) or mineralocorticoid receptors (MR), which is also mediated by the corticotropin releasing factor (CRF) Type-1 receptor. The goal of the present study was to test the hypothesis that the CeA through GR, MR, and/or CRF-1R regulates colonic hypersensitivity in WKYs. METHODS One series of WKYs had micropellets of a GR antagonist, an MR antagonist or cholesterol (control) stereotaxically implanted onto the CeA. Another series were infused in the CeA with CRF-1R antagonist, or vehicle. Colonic sensitivity was measured as a visceromotor response (VMR) to graded colorectal distension (CRD). KEY RESULTS The exaggerated VMR to graded CRD in WKYs was unaffected by GR or MR antagonism in the CeA. In contrast, direct CeA infusion of CRF-1R antagonist significantly inhibited the VMR to CRD at noxious distension pressures. CONCLUSIONS & INFERENCES Stress hormones in the CeA regulate colonic hypersensitivity in the rat through strain-dependent parallel pathways. The colonic hypersensitivity in WKYs is mediated by a CRF-1R mechanism in the CeA, independent of GR and MR. These complementary pathways suggest multiple etiologies whereby stress hormones in the CeA may regulate abdominal pain in IBS patients.
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Affiliation(s)
- Anthony C. Johnson
- Oklahoma Center for Neuroscience, University of Oklahoma Health Science Center, Oklahoma City, OK, USA
| | - Lee Tran
- Oklahoma Center for Neuroscience, University of Oklahoma Health Science Center, Oklahoma City, OK, USA
| | - Jay Schulkin
- Department of Research, American College of Obstetricians and Gynecologists, Washington DC, USA
| | - Beverley Greenwood-Van Meerveld
- V.A. Medical Center and University of Oklahoma Health Science Center, Oklahoma City, OK, USA
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Oklahoma Center for Neuroscience, University of Oklahoma Health Science Center, Oklahoma City, OK, USA
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Department of Physiology, University of Oklahoma Health Science Center, Oklahoma City, OK, USA
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29
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Davis MP. Drug management of visceral pain: concepts from basic research. PAIN RESEARCH AND TREATMENT 2012; 2012:265605. [PMID: 22619712 PMCID: PMC3348642 DOI: 10.1155/2012/265605] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 12/12/2011] [Accepted: 02/13/2012] [Indexed: 12/24/2022]
Abstract
Visceral pain is experienced by 40% of the population, and 28% of cancer patients suffer from pain arising from intra- abdominal metastasis or from treatment. Neuroanatomy of visceral nociception and neurotransmitters, receptors, and ion channels that modulate visceral pain are qualitatively or quantitatively different from those that modulate somatic and neuropathic pain. Visceral pain should be recognized as distinct pain phenotype. TRPV1, Na 1.8, and ASIC3 ion channels and peripheral kappa opioid receptors are important mediators of visceral pain. Mu agonists, gabapentinoids, and GABAB agonists reduce pain by binding to central receptors and channels. Combinations of analgesics and adjuvants in animal models have supra-additive antinociception and should be considered in clinical trials. This paper will discuss the neuroanatomy, receptors, ion channels, and neurotransmitters important to visceral pain and provide a basic science rationale for analgesic trials and management.
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Affiliation(s)
- Mellar P. Davis
- Cleveland Clinic Lerner School of Medicine, Case Western Reserve University, Cleveland, OH 44195, USA
- Solid Tumor Division, Harry R. Horvitz Center for Palliative Medicine, Taussig Cancer Institute, USA
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Moloney RD, O'Leary OF, Felice D, Bettler B, Dinan TG, Cryan JF. Early-life stress induces visceral hypersensitivity in mice. Neurosci Lett 2012; 512:99-102. [PMID: 22326388 DOI: 10.1016/j.neulet.2012.01.066] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2011] [Revised: 01/26/2012] [Accepted: 01/27/2012] [Indexed: 12/23/2022]
Abstract
Early-life stress is a risk factor for irritable bowel syndrome (IBS), a common and debilitating functional gastrointestinal disorder that is often co-morbid with stress-related psychiatric disorders. In the rat, maternal separation (MS) stress has been shown to induce visceral hypersensitivity in adulthood and thus has become a useful model of IBS. However, development of mouse models of maternal separation has been difficult. Given the advent of transgenic mouse technology, such models would be useful to further our understanding of the pathophysiology of IBS and to develop new pharmacological treatments. Thus, the present study aimed to develop a mouse model of MS stress-induced visceral hyperalgesia as measured using manometric recordings of colorectal distension (CRD). Moreover, since the GABA(B) receptor has been reported to play a role in pain processes, we also assessed its role in visceral nociception using novel GABA(B(1b)) receptor subunit knockout mice. CRD was performed in adult male wildtype and GABA(B(1b)) receptor knockout mice that had undergone unpredictable MS combined with unpredictable maternal stress (MSUS) from postnatal day 1 through 14 (PND 1-14). MSUS induced visceral hypersensitivity in both wildtype and GABA(B(1b)) receptor knockout mice when compared with non-stressed mice. Wildtype and GABA(B(1b)) receptor knockout mice did not differ in baseline or stress-induced visceral sensitivity. To the best of our knowledge, this is the first study to show that early-life stress induces visceral hypersensitivity in a mouse model. These findings may provide a novel mouse model of visceral hypersensitivity which may aid our understanding of its underlying mechanisms in future studies.
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Affiliation(s)
- Rachel D Moloney
- Laboratory of Neurogastroenterology, Alimentary Pharmabiotic Centre, Biosciences Institute, University College Cork, Ireland
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31
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Melancon BJ, Hopkins CR, Wood MR, Emmitte KA, Niswender CM, Christopoulos A, Conn PJ, Lindsley CW. Allosteric modulation of seven transmembrane spanning receptors: theory, practice, and opportunities for central nervous system drug discovery. J Med Chem 2012; 55:1445-64. [PMID: 22148748 DOI: 10.1021/jm201139r] [Citation(s) in RCA: 180] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- Bruce J Melancon
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee 37232, United States
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32
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Larauche M, Mulak A, Taché Y. Stress and visceral pain: from animal models to clinical therapies. Exp Neurol 2012; 233:49-67. [PMID: 21575632 PMCID: PMC3224675 DOI: 10.1016/j.expneurol.2011.04.020] [Citation(s) in RCA: 126] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2011] [Revised: 04/07/2011] [Accepted: 04/28/2011] [Indexed: 02/07/2023]
Abstract
Epidemiological studies have implicated stress (psychosocial and physical) as a trigger of first onset or exacerbation of irritable bowel syndrome (IBS) symptoms of which visceral pain is an integrant landmark. A number of experimental acute or chronic exteroceptive or interoceptive stressors induce visceral hyperalgesia in rodents although recent evidence also points to stress-related visceral analgesia as established in the somatic pain field. Underlying mechanisms of stress-related visceral hypersensitivity may involve a combination of sensitization of primary afferents, central sensitization in response to input from the viscera and dysregulation of descending pathways that modulate spinal nociceptive transmission or analgesic response. Biochemical coding of stress involves the recruitment of corticotropin releasing factor (CRF) signaling pathways. Experimental studies established that activation of brain and peripheral CRF receptor subtype 1 plays a primary role in the development of stress-related delayed visceral hyperalgesia while subtype 2 activation induces analgesic response. In line with stress pathways playing a role in IBS, non-pharmacologic and pharmacologic treatment modalities aimed at reducing stress perception using a broad range of evidence-based mind-body interventions and centrally-targeted medications to reduce anxiety impact on brain patterns activated by visceral stimuli and dampen visceral pain.
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Affiliation(s)
- Muriel Larauche
- CURE/Digestive Diseases Research Center, Digestive Diseases Division, Department of Medicine, David Geffen School of Medicine, UCLA, Los Angeles, CA 90073, USA.
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33
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Salari P, Abdollahi M. Systematic review of modulators of benzodiazepine receptors in irritable bowel syndrome: Is there hope? World J Gastroenterol 2011; 17:4251-7. [PMID: 22090780 PMCID: PMC3214699 DOI: 10.3748/wjg.v17.i38.4251] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/23/2011] [Revised: 05/20/2011] [Accepted: 05/27/2011] [Indexed: 02/06/2023] Open
Abstract
Several drugs are used in the treatment of irritable bowel syndrome (IBS) but all have side effects and variable efficacy. Considering the role of the gut-brain axis, immune, neural, and endocrine pathways in the pathogenesis of IBS and possible beneficial effects of benzodiazepines (BZD) in this axis, the present systematic review focuses on the efficacy of BZD receptor modulators in human IBS. For the years 1966 to February 2011, all literature was searched for any articles on the use of BZD receptor modulators and IBS. After thorough evaluation and omission of duplicate data, 10 out of 69 articles were included. BZD receptor modulators can be helpful, especially in the diarrhea-dominant form of IBS, by affecting the inflammatory, neural, and psychologic pathways, however, controversies still exist. Recently, a new BZD receptor modulator, dextofisopam was synthesized and studied in human subjects, but the studies are limited to phase IIb clinical trials. None of the existing trials considered the neuroimmunomodulatory effect of BZDs in IBS, but bearing in mind the concentration-dependent effect of BZDs on cytokines and cell proliferation, future studies using pharmacodynamic and pharmacokinetic approaches are highly recommended.
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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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35
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Larauche M, Mulak A, Taché Y. Stress and visceral pain: from animal models to clinical therapies. Exp Neurol 2011. [PMID: 21575632 DOI: 10.1016/j.expneurol.2011.04.020.] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Epidemiological studies have implicated stress (psychosocial and physical) as a trigger of first onset or exacerbation of irritable bowel syndrome (IBS) symptoms of which visceral pain is an integrant landmark. A number of experimental acute or chronic exteroceptive or interoceptive stressors induce visceral hyperalgesia in rodents although recent evidence also points to stress-related visceral analgesia as established in the somatic pain field. Underlying mechanisms of stress-related visceral hypersensitivity may involve a combination of sensitization of primary afferents, central sensitization in response to input from the viscera and dysregulation of descending pathways that modulate spinal nociceptive transmission or analgesic response. Biochemical coding of stress involves the recruitment of corticotropin releasing factor (CRF) signaling pathways. Experimental studies established that activation of brain and peripheral CRF receptor subtype 1 plays a primary role in the development of stress-related delayed visceral hyperalgesia while subtype 2 activation induces analgesic response. In line with stress pathways playing a role in IBS, non-pharmacologic and pharmacologic treatment modalities aimed at reducing stress perception using a broad range of evidence-based mind-body interventions and centrally-targeted medications to reduce anxiety impact on brain patterns activated by visceral stimuli and dampen visceral pain.
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Affiliation(s)
- Muriel Larauche
- CURE/Digestive Diseases Research Center, Digestive Diseases Division, Department of Medicine, David Geffen School of Medicine, UCLA, Los Angeles, CA 90073, USA.
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36
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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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37
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Urwyler S. Allosteric modulation of family C G-protein-coupled receptors: from molecular insights to therapeutic perspectives. Pharmacol Rev 2011; 63:59-126. [PMID: 21228259 DOI: 10.1124/pr.109.002501] [Citation(s) in RCA: 164] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Allosteric receptor modulation is an attractive concept in drug targeting because it offers important potential advantages over conventional orthosteric agonism or antagonism. Allosteric ligands modulate receptor function by binding to a site distinct from the recognition site for the endogenous agonist. They often have no effect on their own and therefore act only in conjunction with physiological receptor activation. This article reviews the current status of allosteric modulation at family C G-protein coupled receptors in the light of their specific structural features on the one hand and current concepts in receptor theory on the other hand. Family C G-protein-coupled receptors are characterized by a large extracellular domain containing the orthosteric agonist binding site known as the "venus flytrap module" because of its bilobal structure and the dynamics of its activation mechanism. Mutational analysis and chimeric constructs have revealed that allosteric modulators of the calcium-sensing, metabotropic glutamate and GABA(B) receptors bind to the seven transmembrane domain, through which they modify signal transduction after receptor activation. This is in contrast to taste-enhancing molecules, which bind to different parts of sweet and umami receptors. The complexity of interactions between orthosteric and allosteric ligands is revealed by a number of adequate biochemical and electrophysiological assay systems. Many allosteric family C GPCR modulators show in vivo efficacy in behavioral models for a variety of clinical indications. The positive allosteric calcium sensing receptor modulator cinacalcet is the first drug of this type to enter the market and therefore provides proof of principle in humans.
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Affiliation(s)
- Stephan Urwyler
- Department of Chemistry and Biochemistry, University of Berne, P/A Weissensteinweg 3, CH-3303 Jegenstorf, Berne, Switzerland.
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38
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Hyland NP, Cryan JF. A Gut Feeling about GABA: Focus on GABA(B) Receptors. Front Pharmacol 2010; 1:124. [PMID: 21833169 PMCID: PMC3153004 DOI: 10.3389/fphar.2010.00124] [Citation(s) in RCA: 113] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2010] [Accepted: 09/07/2010] [Indexed: 12/15/2022] Open
Abstract
γ-Aminobutyric acid (GABA) is the main inhibitory neurotransmitter in the body and hence GABA-mediated neurotransmission regulates many physiological functions, including those in the gastrointestinal (GI) tract. GABA is located throughout the GI tract and is found in enteric nerves as well as in endocrine-like cells, implicating GABA as both a neurotransmitter and an endocrine mediator influencing GI function. GABA mediates its effects via GABA receptors which are either ionotropic GABA(A) or metabotropic GABA(B). The latter which respond to the agonist baclofen have been least characterized, however accumulating data suggest that they play a key role in GI function in health and disease. Like GABA, GABA(B) receptors have been detected throughout the gut of several species in the enteric nervous system, muscle, epithelial layers as well as on endocrine-like cells. Such widespread distribution of this metabotropic GABA receptor is consistent with its significant modulatory role over intestinal motility, gastric emptying, gastric acid secretion, transient lower esophageal sphincter relaxation and visceral sensation of painful colonic stimuli. More intriguing findings, the mechanisms underlying which have yet to be determined, suggest GABA(B) receptors inhibit GI carcinogenesis and tumor growth. Therefore, the diversity of GI functions regulated by GABA(B) receptors makes it a potentially useful target in the treatment of several GI disorders. In light of the development of novel compounds such as peripherally acting GABA(B) receptor agonists, positive allosteric modulators of the GABA(B) receptor and GABA producing enteric bacteria, we review and summarize current knowledge on the function of GABA(B) receptors within the GI tract.
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Affiliation(s)
- Niall P Hyland
- Alimentary Pharmabiotic Centre and Department of Pharmacology and Therapeutics, University College Cork Cork, Ireland
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Ohashi-Doi K, Gale JD, Kurebayashi Y. Pregabalin inhibits accelerated defecation and decreased colonic nociceptive threshold in sensitized rats. Eur J Pharmacol 2010; 643:107-12. [DOI: 10.1016/j.ejphar.2010.06.014] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2009] [Revised: 05/19/2010] [Accepted: 06/07/2010] [Indexed: 01/14/2023]
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Bowery N. Historical Perspective and Emergence of the GABAB Receptor. GABABRECEPTOR PHARMACOLOGY - A TRIBUTE TO NORMAN BOWERY 2010; 58:1-18. [DOI: 10.1016/s1054-3589(10)58001-3] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Froestl W. Chemistry and Pharmacology of GABAB Receptor Ligands. GABABRECEPTOR PHARMACOLOGY - A TRIBUTE TO NORMAN BOWERY 2010; 58:19-62. [DOI: 10.1016/s1054-3589(10)58002-5] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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Irritable bowel syndrome: towards biomarker identification. Trends Mol Med 2009; 15:478-89. [PMID: 19811951 DOI: 10.1016/j.molmed.2009.08.001] [Citation(s) in RCA: 147] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2009] [Revised: 08/02/2009] [Accepted: 08/05/2009] [Indexed: 02/06/2023]
Abstract
Irritable bowel syndrome (IBS), the most common functional gastrointestinal disorder referred to gastroenterologists, affects 7-10% of the general population worldwide. The lack of suitable disease-defining biological markers coupled with a poorly understood underlying pathophysiology complicates patient diagnosis and seriously hampers drug discovery efforts. Over the past few years, a number of potential biomarkers have emerged, and in this review we critically evaluate such candidates. In particular, we highlight the increasing number of studies supporting a low-grade immune activation in IBS and consider how the latest preclinical developments can contribute to the development of more robust and reliable biological markers of this disorder. The successful identification of biomarkers is critical to progressing our understanding of IBS and addressing the unmet therapeutic needs of this debilitating condition.
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Lindström E, Ravnefjord A, Brusberg M, Hjorth S, Larsson H, Martinez V. The Selective 5-Hydroxytryptamine 1A Antagonist, AZD7371 [3(R)-(N,N-Dicyclobutylamino)-8-fluoro-3,4-dihydro-2H-1-benzopyran-5-carboxamide (R,R)-tartrate Monohydrate] (Robalzotan Tartrate Monohydrate), Inhibits Visceral Pain-Related Visceromotor, but Not Autonomic Cardiovascular, Responses to Colorectal Distension in Rats. J Pharmacol Exp Ther 2009; 329:1048-55. [DOI: 10.1124/jpet.109.152330] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
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CB1 receptors mediate the analgesic effects of cannabinoids on colorectal distension-induced visceral pain in rodents. J Neurosci 2009; 29:1554-64. [PMID: 19193902 DOI: 10.1523/jneurosci.5166-08.2009] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Activation of cannabinoid receptors (CB(1), CB(2) and GPR(55)) produces analgesic effects in several experimental pain models, including visceral pain arising from the gastrointestinal tract. We assessed the role of CB(1), CB(2), and GPR(55) receptors and the endogenous cannabinoid system on basal pain responses and acute mechanical hyperalgesia during colorectal distension (CRD) in rodents. The effects of cannabinoid receptor agonists and antagonists on pain-related responses to CRD were assessed in rats and in wild-type and CB(1) receptor knock-out mice. The dual CB(1/2) agonist, WIN55,212-2, and the peripherally acting CB(1)-selective agonist, SAB-378, inhibited pain-related responses to repetitive noxious CRD (80 mmHg) in a dose-related manner in rats. The analgesic effects of WIN55,212-2 and SAB-378 were blocked by the selective CB(1) antagonist SR141716, but were not affected by the selective CB(2) antagonist SR144528. SR141716, per se, increased the responses to repetitive noxious CRD, indicative of hyperalgesia, and induced pain-related responses during non-noxious CRD (20 mmHg), indicative of allodynia. The cannabinoid receptor agonists anandamide, virodhamine and O-1602 had no effect. At analgesic doses, WIN55,212-2 did not affect colonic compliance. In accordance to the rat data, WIN55,212-2 produced analgesia, whereas SR141716 induced hyperalgesia, during noxious CRD (55 mmHg) in wild-type but not in CB(1)-knock-out mice. These data indicate that peripheral CB(1) receptors mediate the analgesic effects of cannabinoids on visceral pain from the gastrointestinal tract. The allodynic and hyperalgesic responses induced by SR141716 suggest the existence of an endogenous cannabinoid tone and the activation of CB(1) receptors during noxious CRD.
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