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Abstract
Gamma-aminobutyric acid (GABA), the main inhibitory neurotransmitter in the brain, acts at the ionotropic GABAA and GABAC receptors, and the metabotropic GABAB receptor. This chapter summarizes the studies that have investigated the role of the GABAB receptor in stress-related psychiatric disorders including anxiety and mood disorders. Overall, clinical and preclinical evidences strongly suggest that the GABAB receptor is a therapeutic candidate for depression and anxiety disorders. However, the clinical development of GABAB receptor-based drugs to treat these disorders has been hampered by their potential side-effects, particularly those of agonists. Nevertheless, the discovery of novel GABAB receptor allosteric modulators, and increasing understanding of the influence of specific intracellular GABAB receptor-associated proteins on GABAB receptor activity, may now pave the way towards GABAB receptor therapeutics in the treatment of mood and anxiety disorders.
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Affiliation(s)
- Daniela Felice
- Department of Anatomy and Neuroscience, University College Cork, Cork, Ireland
- APC Microbiome Ireland, University College Cork, Cork, Ireland
| | - John F Cryan
- Department of Anatomy and Neuroscience, University College Cork, Cork, Ireland.
- APC Microbiome Ireland, University College Cork, Cork, Ireland.
| | - Olivia F O'Leary
- Department of Anatomy and Neuroscience, University College Cork, Cork, Ireland.
- APC Microbiome Ireland, University College Cork, Cork, Ireland.
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2
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Porcu A, Mostallino R, Serra V, Melis M, Sogos V, Beggiato S, Ferraro L, Manetti F, Gianibbi B, Bettler B, Corelli F, Mugnaini C, Castelli MP. COR758, a negative allosteric modulator of GABA B receptors. Neuropharmacology 2021; 189:108537. [PMID: 33798546 DOI: 10.1016/j.neuropharm.2021.108537] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Revised: 03/20/2021] [Accepted: 03/22/2021] [Indexed: 10/21/2022]
Abstract
Allosteric modulators of G protein coupled receptors (GPCRs), including GABABRs (GABABRs), are promising therapeutic candidates. While several positive allosteric modulators (PAM) of GABABRs have been characterized, only recently the first negative allosteric modulator (NAM) has been described. In the present study, we report the characterization of COR758, which acts as GABABR NAM in rat cortical membranes and CHO cells stably expressing GABABRs (CHO-GABAB). COR758 failed to displace the antagonist [3H]CGP54626 from the orthosteric binding site of GABABRs showing that it acts through an allosteric binding site. Docking studies revealed a possible new allosteric binding site for COR758 in the intrahelical pocket of the GABAB1 monomer. COR758 inhibited basal and GABABR-stimulated O-(3-[35Sthio)-triphosphate ([35S]GTPγS) binding in brain membranes and blocked the enhancement of GABABR-stimulated [35S]GTPγS binding by the PAM GS39783. Bioluminescent resonance energy transfer (BRET) measurements in CHO-GABAB cells showed that COR758 inhibited G protein activation by GABA and altered GABABR subunit rearrangements. Additionally, the compound altered GABABR-mediated signaling such as baclofen-induced inhibition of cAMP production in transfected HEK293 cells, agonist-induced Ca2+ mobilization as well as baclofen and the ago-PAM CGP7930 induced phosphorylation of extracellular signal-regulated kinases (ERK1/2) in CHO-GABAB cells. COR758 also prevented baclofen-induced outward currents recorded from rat dopamine neurons, substantiating its property as a NAM for GABABRs. Altogether, these data indicate that COR758 inhibits G protein signaling by GABABRs, likely by interacting with an allosteric binding-site. Therefore, COR758 might serve as a scaffold to develop additional NAMs for therapeutic intervention.
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Affiliation(s)
- Alessandra Porcu
- Department of Biomedical Sciences, University of Cagliari, 09042, Monserrato, Italy; Department of Biomedicine, University of Basel, Klingelbergstrasse 50-70, CH-4056, Basel, Switzerland
| | - Rafaela Mostallino
- Department of Biomedical Sciences, University of Cagliari, 09042, Monserrato, Italy
| | - Valeria Serra
- Department of Biomedical Sciences, University of Cagliari, 09042, Monserrato, Italy
| | - Miriam Melis
- Department of Biomedical Sciences, University of Cagliari, 09042, Monserrato, Italy
| | - Valeria Sogos
- Department of Biomedical Sciences, University of Cagliari, 09042, Monserrato, Italy
| | - Sarah Beggiato
- Department of Life Sciences and Biotechnology, Section of Medicinal and Health Products, and LTTA Center, University of Ferrara, Ferrara, Italy; Department of Medical, Oral and Biotechnological Sciences, University of Chieti-Pescara, 66100, Chieti, Italy
| | - Luca Ferraro
- Department of Life Sciences and Biotechnology, Section of Medicinal and Health Products, and LTTA Center, University of Ferrara, Ferrara, Italy
| | - Fabrizio Manetti
- Department of Biotechnology, Chemistry, and Pharmacy, University of Siena, I-53100, Siena, SI, Italy
| | - Beatrice Gianibbi
- Department of Biotechnology, Chemistry, and Pharmacy, University of Siena, I-53100, Siena, SI, Italy
| | - Bernhard Bettler
- Department of Biomedicine, University of Basel, Klingelbergstrasse 50-70, CH-4056, Basel, Switzerland
| | - Federico Corelli
- Department of Biotechnology, Chemistry, and Pharmacy, University of Siena, I-53100, Siena, SI, Italy
| | - Claudia Mugnaini
- Department of Biotechnology, Chemistry, and Pharmacy, University of Siena, I-53100, Siena, SI, Italy
| | - M Paola Castelli
- Department of Biomedical Sciences, University of Cagliari, 09042, Monserrato, Italy; Guy Everett Laboratory, University of Cagliari, 09042, Monserrato, Italy; Center of Excellence "Neurobiology of Addiction", University of Cagliari, 09042, Monserrato, Italy.
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Xia S, He C, Zhu Y, Wang S, Li H, Zhang Z, Jiang X, Liu J. GABA BR-Induced EGFR Transactivation Promotes Migration of Human Prostate Cancer Cells. Mol Pharmacol 2017; 92:265-277. [PMID: 28424220 DOI: 10.1124/mol.116.107854] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Accepted: 04/14/2017] [Indexed: 12/11/2022] Open
Abstract
G protein-coupled receptors (GPCRs) and receptor tyrosine kinases (RTKs) act in concert to regulate cell growth, proliferation, survival, and migration. Metabotropic GABAB receptor (GABABR) is the GPCR for the main inhibitory neurotransmitter GABA in the central nervous system. Increased expression of GABABR has been detected in human cancer tissues and cancer cell lines, but the role of GABABR in these cells is controversial and the underlying mechanism remains poorly understood. Here, we investigated whether GABABR hijacks RTK signaling to modulate the fates of human prostate cancer cells. RTK array analysis revealed that the GABABR-specific agonist baclofen selectively induced the transactivation of EGFR in PC-3 cells. EGFR transactivation resulted in the activation of ERK1/2 by a mechanism that is dependent on Gi/o protein and that requires matrix metalloproteinase-mediated proligand shedding. Positive allosteric modulators (PAMs) of GABABR, such as CGP7930, rac-BHFF, and GS39783, can function as PAM agonists to induce EGFR transactivation and subsequent ERK1/2 activation. Moreover, both baclofen and CGP7930 promoted cell migration and invasion through EGFR signaling. In summary, our observations demonstrated that GABABR transactivated EGFR in a ligand-dependent mechanism to promote prostate cancer cell migration and invasion, thus providing new insights into developing a novel strategy for prostate cancer treatment by targeting neurotransmitter signaling.
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Affiliation(s)
- Shuai Xia
- Cell Signaling Laboratory, College of Life Science and Technology, Collaborative Innovation Center for Genetics and Development, and Key Laboratory of Molecular Biophysics of Ministry of Education, Huazhong University of Science and Technology, Wuhan, Hubei, People's Republic of China
| | - Cong He
- Cell Signaling Laboratory, College of Life Science and Technology, Collaborative Innovation Center for Genetics and Development, and Key Laboratory of Molecular Biophysics of Ministry of Education, Huazhong University of Science and Technology, Wuhan, Hubei, People's Republic of China
| | - Yini Zhu
- Cell Signaling Laboratory, College of Life Science and Technology, Collaborative Innovation Center for Genetics and Development, and Key Laboratory of Molecular Biophysics of Ministry of Education, Huazhong University of Science and Technology, Wuhan, Hubei, People's Republic of China
| | - Suyun Wang
- Cell Signaling Laboratory, College of Life Science and Technology, Collaborative Innovation Center for Genetics and Development, and Key Laboratory of Molecular Biophysics of Ministry of Education, Huazhong University of Science and Technology, Wuhan, Hubei, People's Republic of China
| | - Huiping Li
- Cell Signaling Laboratory, College of Life Science and Technology, Collaborative Innovation Center for Genetics and Development, and Key Laboratory of Molecular Biophysics of Ministry of Education, Huazhong University of Science and Technology, Wuhan, Hubei, People's Republic of China
| | - Zhongling Zhang
- Cell Signaling Laboratory, College of Life Science and Technology, Collaborative Innovation Center for Genetics and Development, and Key Laboratory of Molecular Biophysics of Ministry of Education, Huazhong University of Science and Technology, Wuhan, Hubei, People's Republic of China
| | - Xinnong Jiang
- Cell Signaling Laboratory, College of Life Science and Technology, Collaborative Innovation Center for Genetics and Development, and Key Laboratory of Molecular Biophysics of Ministry of Education, Huazhong University of Science and Technology, Wuhan, Hubei, People's Republic of China
| | - Jianfeng Liu
- Cell Signaling Laboratory, College of Life Science and Technology, Collaborative Innovation Center for Genetics and Development, and Key Laboratory of Molecular Biophysics of Ministry of Education, Huazhong University of Science and Technology, Wuhan, Hubei, People's Republic of China
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Kalinichev M, Girard F, Haddouk H, Rouillier M, Riguet E, Royer-Urios I, Mutel V, Lütjens R, Poli S. The drug candidate, ADX71441, is a novel, potent and selective positive allosteric modulator of the GABA B receptor with a potential for treatment of anxiety, pain and spasticity. Neuropharmacology 2016; 114:34-47. [PMID: 27889489 DOI: 10.1016/j.neuropharm.2016.11.016] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2014] [Revised: 11/13/2016] [Accepted: 11/21/2016] [Indexed: 11/17/2022]
Abstract
Positive allosteric modulation of the GABAB receptor is a promising alternative to direct activation of the receptor as a therapeutic approach for treatment of addiction, chronic pain, anxiety, epilepsy, autism, Fragile X syndrome, and psychosis. Here we describe in vitro and in vivo characterization of a novel, potent and selective GABAB positive allosteric modulator (PAM) N-(5-(4-(4-chloro-3-fluorobenzyl)-6-methoxy-3,5-dioxo-4,5-dihydro-1,2,4-triazin-2(3H)-yl)-2-fluorophenyl)acetamide (ADX71441). In vitro, Schild plot and reversibility tests at the target confirmed PAM properties of the compound. In mice and rats ADX71441 is bioavailable after oral administration and is brain penetrant. A single dose of ADX71441 had an anxiolytic-like profile in the mouse marble burying test (minimum effective dose; MED 3 mg/kg) as well as in the elevated plus maze test in mice and rats (both MED 3 mg/kg). Also, in mice, acute administration of ADX71441 reduced visceral pain-associated behaviors in the acetic acid-induced writhing test. ADX71441 dose-dependently reduced time on rotarod in rats (MED 10 mg/kg) indicative of muscle-relaxant qualities. ADX71441 reduced locomotor activity in mice (10 mg/kg) and rats (3 mg/kg) after single dose; however, following sub-chronic administration in mice, 30 mg/kg ADX71441 was associated with normal locomotor activity. While acute administration of ADX71441 reduced body temperature in rats and mice (both MED 10 mg/kg), the effect in the former was transient, rapidly returning to normal levels despite high concentrations of the compound remaining in plasma. Thus, the GABAB PAM ADX71441 represents a valid therapeutic approach for development of novel treatment of anxiety, pain and spasticity.
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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
| | - Hasnaà Haddouk
- Addex Therapeutics SA, Chemin des Mines 9, CH-1202, Geneva, Switzerland
| | - Mélanie Rouillier
- Addex Therapeutics SA, Chemin des Mines 9, CH-1202, Geneva, Switzerland
| | - Eric Riguet
- Addex Therapeutics SA, Chemin des Mines 9, CH-1202, Geneva, Switzerland
| | | | - Vincent Mutel
- Addex Therapeutics SA, Chemin des Mines 9, CH-1202, Geneva, Switzerland
| | - Robert Lütjens
- Addex Therapeutics SA, Chemin des Mines 9, CH-1202, Geneva, Switzerland
| | - Sonia Poli
- Addex Therapeutics SA, Chemin des Mines 9, CH-1202, Geneva, Switzerland
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Porcu A, Lobina C, Giunta D, Solinas M, Mugnaini C, Castelli MP. In vitro and in vivo pharmacological characterization of SSD114, a novel GABAB positive allosteric modulator. Eur J Pharmacol 2016; 791:115-123. [PMID: 27578262 DOI: 10.1016/j.ejphar.2016.08.032] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Revised: 08/25/2016] [Accepted: 08/26/2016] [Indexed: 12/18/2022]
Abstract
Positive allosteric modulators (PAMs) of the GABAB receptor have emerged as a novel approach to the pharmacological manipulation of the GABAB receptor, enhancing the effects of receptor agonists with few side effects. Here, we identified N-cyclohexyl-4-methoxy-6-(4-(trifluoromethyl)phenyl)pyrimidin-2-amine (SSD114) as a new compound with activity as a GABAB PAM in in vitro and in vivo assays. SSD114 potentiated GABA-stimulated [35S]GTPγS binding to native GABAB receptors, whereas it had no effect when used alone. Its effect on GTPγS stimulation was suppressed when GABA-induced activation was blocked with CGP54626, a competitive antagonist of the GABAB receptor. SSD114 failed to potentiate WIN55,212,2-, morphine- and quinpirole-induced [35S]GTPγS binding to cortical and striatal membranes, respectively, indicating that it is a selective GABAB PAM. Increasing SSD114 fixed concentrations induced a leftward shift of the GABA concentration-response curve, enhancing the potency of GABA rather than its efficacy. SSD114 concentration-response curves in the presence of fixed concentrations of GABA (1, 10, and 20μM) revealed a potentiating effect on GABA-stimulated binding of [35S]GTPγS to rat cortical membranes, with EC50 values in the low micromolar range. Bioluminescence resonance energy transfer (BRET) experiments in Chinese Hamster Ovary (CHO)-cells expressing GABAB receptors showed that SSD114 potentiates the GABA inhibition of adenylyl-cyclase mediated by GABAB receptors. Our compound is also effective in vivo potentiating baclofen-induced sedation/hypnosis in mice, with no effect when tested alone. These findings indicate that SSD114, a molecule with a different chemical structure compared to known GABAB PAMs, is a novel GABAB PAM with potential usefulness in the GABAB-receptor research field.
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Affiliation(s)
- Alessandra Porcu
- Department of Biomedical Sciences, Division of Neuroscience and Clinical Pharmacology, University of Cagliari, Cagliari, Italy
| | - Carla Lobina
- Neuroscience Institute, National Research Council of Italy, Section of Cagliari, Cagliari, Italy
| | - Daniela Giunta
- Biomolecular Chemistry Institute, National Research Council of Italy, Section of Sassari, Sassari, Italy
| | - Maurizio Solinas
- Biomolecular Chemistry Institute, National Research Council of Italy, Section of Sassari, Sassari, Italy
| | - Claudia Mugnaini
- Department of Biotechnology Chemistry and Pharmacy, University of Siena, Siena, Italy
| | - M Paola Castelli
- Department of Biomedical Sciences, Division of Neuroscience and Clinical Pharmacology, University of Cagliari, Cagliari, Italy.
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First asymmetric organocatalyzed domino Friedel–Crafts/lactonization reaction in the enantioselective synthesis of the GABAB receptor modulator (S)-BHFF. Tetrahedron Lett 2016. [DOI: 10.1016/j.tetlet.2016.01.015] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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Brown JW, Moeller A, Schmidt M, Turner SC, Nimmrich V, Ma J, Rueter LE, van der Kam E, Zhang M. Anticonvulsant effects of structurally diverse GABA(B) positive allosteric modulators in the DBA/2J audiogenic seizure test: Comparison to baclofen and utility as a pharmacodynamic screening model. Neuropharmacology 2015; 101:358-69. [PMID: 26471422 DOI: 10.1016/j.neuropharm.2015.10.009] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Revised: 07/31/2015] [Accepted: 10/04/2015] [Indexed: 02/02/2023]
Abstract
The GABA(B) receptor has been indicated as a promising target for multiple CNS-related disorders. Baclofen, a prototypical orthosteric agonist, is used clinically for the treatment of spastic movement disorders, but is associated with unwanted side-effects, such as sedation and motor impairment. Positive allosteric modulators (PAM), which bind to a topographically-distinct site apart from the orthosteric binding pocket, may provide an improved side-effect profile while maintaining baclofen-like efficacy. GABA, the major inhibitory neurotransmitter in the CNS, plays an important role in the etiology and treatment of seizure disorders. Baclofen is known to produce anticonvulsant effects in the DBA/2J mouse audiogenic seizure test (AGS), suggesting it may be a suitable assay for assessing pharmacodynamic effects. Little is known about the effects of GABA(B) PAMs, however. The studies presented here sought to investigate the AGS test as a pharmacodynamic (PD) screening model for GABA(B) PAMs by comparing the profile of structurally diverse PAMs to baclofen. GS39783, rac-BHFF, CMPPE, A-1295120 (N-(3-(4-(4-chloro-3-fluorobenzyl)-6-methoxy-3,5-dioxo-4,5-dihydro-1,2,4-triazin-2(3H)-yl)phenyl)acetamide), and A-1474713 (N-(3-(4-(4-chlorobenzyl)-3,5-dioxo-4,5-dihydro-1,2,4-triazin-2(3H)-yl)phenyl)acetamide) all produced robust, dose-dependent anticonvulsant effects; a similar profile was observed with baclofen. Pre-treatment with the GABA(B) antagonist SCH50911 completely blocked the anticonvulsant effects of baclofen and CMPPE in the AGS test, indicating such effects are likely mediated by the GABA(B) receptor. In addition to the standard anticonvulsant endpoint of the AGS test, video tracking software was employed to assess potential drug-induced motor side-effects during the acclimation period of the test. This analysis was sensitive to detecting drug-induced changes in total distance traveled, which was used to establish a therapeutic index (TI = hypoactivity/anticonvulsant effects). Calculated TIs for A-1295120, CMPPE, rac-BHFF, GS39783, and A-1474713 were 5.31x, 5.00x, 4.74x, 3.41x, and 1.83x, respectively, whereas baclofen was <1. The results presented here suggest the DBA/2J mouse AGS test is a potentially useful screening model for detecting PD effects of GABA(B) PAMs and can provide an initial read-out on target-related motor side-effects. Furthermore, an improved TI was observed for PAMs compared to baclofen, indicating the PAM approach may be a viable therapeutic alternative to baclofen.
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Affiliation(s)
- Jordan W Brown
- Neuroscience Discovery, AbbVie, Inc., 1 North Waukegan Rd., North Chicago, IL 60064, United States.
| | - Achim Moeller
- Neuroscience Discovery, AbbVie Deutschland GmbH & Co KG, Knollstrasse, Ludwigshafen 67061, Germany
| | - Martin Schmidt
- Neuroscience Discovery, AbbVie Deutschland GmbH & Co KG, Knollstrasse, Ludwigshafen 67061, Germany
| | - Sean C Turner
- Neuroscience Discovery, AbbVie Deutschland GmbH & Co KG, Knollstrasse, Ludwigshafen 67061, Germany
| | - Volker Nimmrich
- Neuroscience Discovery, AbbVie Deutschland GmbH & Co KG, Knollstrasse, Ludwigshafen 67061, Germany
| | - Junli Ma
- Drug Metabolism and Pharmacokinetics, AbbVie, Inc., North Chicago, IL 60064, United States
| | - Lynne E Rueter
- Neuroscience Discovery, AbbVie, Inc., 1 North Waukegan Rd., North Chicago, IL 60064, United States
| | - Elizabeth van der Kam
- Neuroscience Discovery, AbbVie Deutschland GmbH & Co KG, Knollstrasse, Ludwigshafen 67061, Germany
| | - Min Zhang
- Neuroscience Discovery, AbbVie, Inc., 1 North Waukegan Rd., North Chicago, IL 60064, United States
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Inhibition of alcohol self-administration by positive allosteric modulators of the GABAB receptor in rats: lack of tolerance and potentiation of baclofen. Psychopharmacology (Berl) 2015; 232:1831-41. [PMID: 25420609 DOI: 10.1007/s00213-014-3815-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/19/2014] [Accepted: 11/10/2014] [Indexed: 12/11/2022]
Abstract
RATIONALE Treatment with positive allosteric modulators (PAMs) of the GABAB receptor (GABAB PAMs) inhibits several alcohol-motivated behaviors in rodents, including operant, oral alcohol self-administration. OBJECTIVES The present study assessed the effects of (a) repeated administration of the GABAB PAMs, GS39783, and rac-BHFF and (b) a combination of an ineffective dose of either GS39783, or rac-BHFF, and an ineffective dose of the prototypic GABAB receptor agonist, baclofen, on operant, oral alcohol self-administration. METHODS Studies were conducted using selectively bred Sardinian alcohol-preferring (sP) rats exposed to a standard procedure of fixed ratio (FR) 4 (FR4) schedule of reinforcement for 15 % (v/v) alcohol. RESULTS Repeated treatment with GS39783 (50 mg/kg, i.g.) or rac-BHFF (50 mg/kg, i.g.) produced an initial 40 % reduction in number of lever responses for alcohol and amount of self-administered alcohol that was maintained unaltered throughout the 10-day period of the GS39783 treatment and increased throughout the 5-day period of the rac-BHFF treatment. Combination of per se ineffective doses of GS39783 (5 mg/kg, i.g.), or rac-BHFF (5 mg/kg, i.g.), and baclofen (1 mg/kg, i.p.) reduced, by 35-45 %, both number of lever responses for alcohol and amount of self-administered alcohol. CONCLUSIONS GS39783 and rac-BHFF (a) reduced alcohol reinforcing properties when given repeatedly, with no development of tolerance, and (b) potentiated baclofen effect. Both sets of data possess translational interest, as they suggest potential effectiveness of GABAB PAMs under chronic treatment and selective potentiation of baclofen effect.
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Filip M, Frankowska M, Sadakierska-Chudy A, Suder A, Szumiec Ł, Mierzejewski P, Bienkowski P, Przegaliński E, Cryan JF. GABAB receptors as a therapeutic strategy in substance use disorders: Focus on positive allosteric modulators. Neuropharmacology 2015; 88:36-47. [DOI: 10.1016/j.neuropharm.2014.06.016] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2014] [Revised: 06/10/2014] [Accepted: 06/15/2014] [Indexed: 12/16/2022]
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Kalinichev M, Donovan-Rodriguez T, Girard F, Riguet E, Rouillier M, Bournique B, Haddouk H, Mutel V, Poli S. Evaluation of peripheral versus central effects of GABA(B) receptor activation using a novel, positive allosteric modulator of the GABA(B) receptor ADX71943, a pharmacological tool compound with a fully peripheral activity profile. Br J Pharmacol 2014; 171:4941-54. [PMID: 24923436 DOI: 10.1111/bph.12812] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Revised: 05/27/2014] [Accepted: 06/06/2014] [Indexed: 01/14/2023] Open
Abstract
BACKGROUND AND PURPOSE The GABA(B) receptor agonist, baclofen, has shown promising effects in patients suffering from pain, post-traumatic stress disorder, alcoholism, overactive bladder and gastroesophageal reflux disease. However, baclofen's short duration of action and side effects limit its wider use. Here we characterized a novel, GABA(B) receptor positive allosteric modulator (PAM) ADX71943. EXPERIMENTAL APPROACH In vitro, ADX71943 was assessed for pharmacological activity and selectivity using recombinant and native GABA(B) receptors. In vivo ADX71943 was assessed in the acetic acid-induced writhing (AAW) test in mice and formalin tests (FTs) in mice and rats. Marble burying (MB) and elevated plus maze (EPM) tests, rotarod, spontaneous locomotor activity (sLMA) and body temperature (BT) tests in mice and rats were used to investigate centrally-mediated effects. KEY RESULTS In vitro, in the presence of GABA, ADX71943 increased the potency and efficacy of agonists and showed selectivity at the GABA(B) receptor. ADX71943 reduced pain-associated behaviours in AAW; an effect blocked by GABA(B) receptor antagonist CGP63360. ADX71943 reduced pain in the FT in mice and rats, but was inactive in the MB and EPM despite reaching high concentrations in plasma. ADX71943 had no effect on BT, rotarod and sLMA. CONCLUSIONS AND IMPLICATIONS ADX71943 showed consistent and target-related efficacy in tests of disorders that have a significant peripheral component (acute and chronic pain), while having no effect in those associated with centrally-mediated anxiety-like reactivity and side effects. Thus, ADX71943 is a useful pharmacological tool for delineation of peripherally- versus centrally-mediated effects of GABA(B) receptor activation.
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Frau R, Bini V, Pillolla G, Malherbe P, Pardu A, Thomas AW, Devoto P, Bortolato M. Positive allosteric modulation of GABAB receptors ameliorates sensorimotor gating in rodent models. CNS Neurosci Ther 2014; 20:679-84. [PMID: 24703381 DOI: 10.1111/cns.12261] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Revised: 03/07/2014] [Accepted: 03/08/2014] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND Converging evidence points to the involvement of γ-amino-butyric acid B receptors (GABABRs) in the regulation of information processing. We previously showed that GABABR agonists exhibit antipsychotic-like properties in rodent models of sensorimotor gating deficits, as measured by the prepulse inhibition (PPI) of the acoustic startle reflex. The therapeutic potential of these agents, however, is limited by their neuromuscular side effects; thus, in this study, we analyzed whether rac-BHFF, a potent GABABR-positive allosteric modulator (PAM), could counter spontaneous and pharmacologically induced PPI deficits across various rodent models. METHODS We tested the antipsychotic effects of rac-BHFF on the PPI deficits caused by the N-methyl-D-aspartate glutamate receptor antagonist dizocilpine, in Sprague-Dawley rats and C57BL/6 mice. Furthermore, we verified whether rac-BHFF ameliorated the spontaneous PPI impairments in DBA/2J mice. RESULTS rac-BHFF dose-dependently countered the PPI deficits across all three models, in a fashion akin to the GABABR agonist baclofen and the atypical antipsychotic clozapine; in contrast with these compounds, however, rac-BHFF did not affect startle magnitude. CONCLUSIONS The present data further support the implication of GABABRs in the modulation of sensorimotor gating and point to their PAMs as a novel promising tool for antipsychotic treatment, with fewer side effects than GABABR agonists.
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Affiliation(s)
- Roberto Frau
- "Guy Everett" Laboratory, Department of Biomedical Sciences, University of Cagliari, Cagliari, Italy; Tourette Syndrome Center, University of Cagliari, Cagliari, Italy
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Horváth C. Alterations in brain temperatures as a possible cause of migraine headache. Med Hypotheses 2014; 82:529-34. [PMID: 24581675 DOI: 10.1016/j.mehy.2014.02.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2013] [Revised: 01/24/2014] [Accepted: 02/03/2014] [Indexed: 12/12/2022]
Abstract
Migraine is a debilitating disease with a recurring generally unilateral headache and concomitant symptoms of nausea, vomiting and photo- and/or phonophobia that affects some 11-18% of the population. Most of the mechanisms previously put forward to explain the attacks have been questioned or give an explanation only some of the symptoms. Moreover, the best drugs for treatment are still the 20-year-old triptans, which have serious limitations as regards both efficacy and tolerability. As the dura and some cranial vessels are the only intracranial structures capable of pain sensations, a vascular theory of migraine emerged, but has been debated. Recent theories identified the hyperexcitability of structures involved in pain transmission, such as the trigeminal system or the cortex, or an abnormal modulatory function of the brainstem. However, there is ongoing scientific debate concerning these theories, neither of which is fully capable of explaining the occurrence of a migraine attack. The present article puts forward a hypothesis of the possibility of abnormal temperature regulation in certain regions or the overall brain in migraineurs, the attack being a defense mechanism to prevent neuronal damage. Few examinations have been made of temperature regulation in the human brain. It lacks the carotid rete, a vascular heat exchanger that serves in many animals to provide constant brain temperature. The human brain contains a high density of neurons with a considerable energy demand that is converted to heat. The human brain has a higher temperature than other parts of the body and needs continuous cooling. Recent studies revealed unexpectedly great variations in temperature of various structures of the brain and considerable changes in response to functional activation. There is various evidence in support of the hypothesis that accumulated heat in some structure or the overall brain may be behind the symptoms observed, such as a platelet abnormality, a decreased serotonin content, and dural "inflammation" including vasodilation and brainstem activation. The hypothesis postulates that a migraine attack serves to restore the brain temperature. Abnormally low temperatures in the brain can also result in headache. Surprisingly, no systematic examination of brain temperature changes in migraineurs has been published. Certain case reports support the present hypothesis. Various noninvasive technologies (e.g. MR) capable of monitoring brain temperature are available. If a systematic examination of local brain temperature revealed abnormalities in structures presumed to be involved in migraine, that would increase our understanding of the disease and trigger the development of improved treatment.
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Affiliation(s)
- Csilla Horváth
- Gedeon Richter Plc., 19-21 Gyömrői út, H-1103 Budapest, Hungary.
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Vetica F, Pelosi A, Gambacorta A, Loreto MA, Miceli M, Gasperi T. Catalytic Friedel-Crafts/Lactonization Domino Reaction: Facile Access to 3-Hydroxybenzofuran-2-one Scaffold. European J Org Chem 2014. [DOI: 10.1002/ejoc.201301686] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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14
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Therapeutic potential of GABA(B) receptor ligands in drug addiction, anxiety, depression and other CNS disorders. Pharmacol Biochem Behav 2013; 110:174-84. [PMID: 23872369 DOI: 10.1016/j.pbb.2013.07.003] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Revised: 06/27/2013] [Accepted: 07/05/2013] [Indexed: 01/06/2023]
Abstract
Glutamate and γ-aminobutyric acid (GABA) are the major excitatory and inhibitory neurotransmitter systems, respectively in the central nervous system (CNS). Dysregulation, in any of these or both, has been implicated in various CNS disorders. GABA acts via ionotropic (GABA(A) and GABA(C) receptor) and metabotropic (GABA(B)) receptor. Dysregulation of GABAergic signaling and alteration in GABA(B) receptor expression has been implicated in various CNS disorders. Clinically, baclofen-a GABA(B) receptor agonist is available for the treatment of spasticity, dystonia etc., associated with various neurological disorders. Moreover, GABAB receptor ligands has also been suggested to be beneficial in various neuropsychiatric and neurodegenerative disorders. The present review is aimed to discuss the role of GABA(B) receptors and the possible outcomes of GABA(B) receptor modulation in CNS disorders.
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Loi B, Maccioni P, Lobina C, Carai MA, Gessa GL, Thomas AW, Malherbe P, Colombo G. Reduction of alcohol intake by the positive allosteric modulator of the GABA(B) receptor, rac-BHFF, in alcohol-preferring rats. Alcohol 2013; 47:69-73. [PMID: 23218664 DOI: 10.1016/j.alcohol.2012.11.002] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2012] [Revised: 11/20/2012] [Accepted: 11/23/2012] [Indexed: 01/05/2023]
Abstract
Previous research has demonstrated that treatment with the positive allosteric modulator (PAM) of the GABA(B) receptor (GABA(B) PAM), rac-BHFF, suppressed lever-responding for alcohol and amount of self-administered alcohol in Sardinian alcohol-preferring (sP) rats. The present study was designed to extend the investigation on the anti-alcohol effects of rac-BHFF to alcohol drinking behavior. To this end, sP rats were exposed to the homecage, 2-bottle "alcohol (10%, v/v) vs water" choice regimen, with unlimited access for 24 h/day. rac-BHFF was administered once daily and for 7 consecutive days at the doses of 0, 50, 100, and 200 mg/kg (i.g.). Treatment with rac-BHFF resulted in an immediate, stable, and dose-related reduction in daily alcohol intake; the overall magnitude of reduction in alcohol intake averaged approximately 25%, 40%, and 65% in 50, 100, and 200 mg/kg rac-BHFF-treated rat groups, respectively. An increase in daily water intake fully compensated the reduction in alcohol intake, so that daily total fluid intake was unaffected by treatment with rac-BHFF. Daily food intake tended to be reduced only by the highest dose of rac-BHFF. These results complement closely with previous data indicating that (a) rac-BHFF suppressed operant, oral alcohol self-administration in sP rats and (b) the prototypic GABA(B) PAMs, CGP7930 and GS39783, reduced alcohol drinking in sP rats. However, while the reducing effect of CGP7930 and GS39783 on the daily alcohol intake tended to vanish after the first 2-3 days of treatment, the reducing effect of rac-BHFF on daily alcohol intake remained unchanged over the entire 7-day treatment period. These data strengthen the hypothesis that GABA(B) PAMs may represent a step forward in the search for GABA(B) receptor ligands with therapeutic potential for alcoholism.
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Koek W, Cheng K, Rice KC. Discriminative stimulus effects of the GABAB receptor-positive modulator rac-BHFF: comparison with GABAB receptor agonists and drugs of abuse. J Pharmacol Exp Ther 2012; 344:553-60. [PMID: 23275067 DOI: 10.1124/jpet.112.202226] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
GABA(B) receptor-positive modulators are thought to have advantages as potential medications for anxiety, depression, and drug addiction. They may have fewer side effects than GABA(B) receptor agonists, because selective enhancement of activated receptors could have effects different from nonselective activation of all receptors. To examine this, pigeons were trained to discriminate the GABA(B) receptor-positive modulator (R,S)-5,7-di-tert-butyl-3-hydroxy-3-trifluoromethyl-3H-benzofuran-2-one (rac-BHFF) from its vehicle. The discriminative stimulus effects of rac-BHFF were not mimicked by the GABA(B) receptor agonists baclofen and γ-hydroxybutyrate (GHB), not by diazepam, and not by alcohol, cocaine, and nicotine, whose self-administration has been reported to be attenuated by GABA(B) receptor-positive modulators. The discriminative stimulus effects of rac-BHFF were not antagonized by the GABA(B) receptor antagonist 3-aminopropyl (diethoxymethyl)phosphinic acid (CGP35348) but were attenuated by the less efficacious GABA(B) receptor-positive modulator 2,6-di-tert-butyl-4-(3-hydroxy-2,2-dimethylpropyl)phenol (CGP7930), suggesting the possibility that rac-BHFF produces its discriminative stimulus effects by directly activating GABA(B2) subunits of GABA(B) receptors. At a dose 10-fold lower than the training dose, rac-BHFF enhanced the discriminative stimulus effects of baclofen, but not of GHB. This study provides evidence that the effects of GABA(B) receptor-positive modulators are not identical to those of GABA(B) receptor agonists. In addition, the results suggest that positive modulation of GABA(B) receptors does not produce discriminative stimulus effects similar to those of benzodiazepines, alcohol, cocaine, and nicotine. Finally, the finding that rac-BHFF enhanced effects of baclofen but not of GHB is consistent with converging evidence that the populations of GABA(B) receptors mediating the effects of baclofen and GHB are not identical.
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Affiliation(s)
- Wouter Koek
- Department of Psychiatry and Pharmacology, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, Mail Code 7792, San Antonio, TX, USA.
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Rey AA, Purrio M, Viveros MP, Lutz B. Biphasic effects of cannabinoids in anxiety responses: CB1 and GABA(B) receptors in the balance of GABAergic and glutamatergic neurotransmission. Neuropsychopharmacology 2012; 37:2624-34. [PMID: 22850737 PMCID: PMC3473327 DOI: 10.1038/npp.2012.123] [Citation(s) in RCA: 233] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Biphasic effects of cannabinoids have been shown in processes such as feeding behavior, motor activity, motivational processes and anxiety responses. Using two different tests for the characterization of anxiety-related behavior (elevated plus-maze and holeboard), we first identified in wild-type C57BL/6N mice, two doses of the synthetic CB1 cannabinoid receptor agonist CP-55,940 with anxiolytic (1 μg/kg) and anxiogenic properties (50 μg/kg), respectively. To clarify the role of CB1 receptors in this biphasic effect, both doses were applied to two different conditional CB1 receptor knockout (KO) mouse lines, GABA-CB1-KO (CB1 receptor inactivation in forebrain GABAergic neurons) and Glu-CB1-KO (CB1 receptor inactivation in cortical glutamatergic neurons). We found that the anxiolytic-like effects of the low dose of cannabinoids are mediated via the CB1 receptor on cortical glutamatergic terminals, because this anxiolytic-like response was abrogated only in Glu-CB1-KO mice. On the contrary, the CB1 receptor on the GABAergic terminals is required to induce an anxiogenic-like effect under a high-dose treatment because of the fact that this effect was abolished specifically in GABA-CB1-KO mice. These experiments were carried out in both sexes, and no differences occurred with the doses tested in the mutant mice. Interestingly, the positive allosteric modulation of GABA(B) receptor with GS-39783 was found to largely abrogate the anxiogenic-like effect of the high dose of CP-55,940. Our results shed new light in further understanding the biphasic effects of cannabinoids at the molecular level and, importantly, pave the way for the development of novel anxiolytic cannabinoid drugs, which may have favorable effect profiles targeting the CB1 receptor on glutamatergic terminals.
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Affiliation(s)
- Alejandro Aparisi Rey
- Institute of Physiological Chemistry, University Medical Center of the Johannes Gutenberg University, Mainz, Germany
| | - Martin Purrio
- Institute of Physiological Chemistry, University Medical Center of the Johannes Gutenberg University, Mainz, Germany
| | - Maria-Paz Viveros
- Departamento de Fisiología (Fisiología Animal II), Facultad de Biología, Universidad Complutense, Jose Antonio Novais 2, Madrid, Spain,Departamento de Fisiología (Fisiología Animal II), Facultad de Biología, Universidad Complutense, Jose Antonio Novais 2, 28040 Madrid, Spain, Tel: +34 91 3944993, Fax: +34 91 3944935, E-mail:
| | - Beat Lutz
- Institute of Physiological Chemistry, University Medical Center of the Johannes Gutenberg University, Mainz, Germany,Institute of Physiological Chemistry, University Medical Center of the Johannes Gutenberg University, Duesbergweg 6, 55128 Mainz, Germany, Tel: +49 6131 39 25912, Fax: +49 6131 39 23536, E-mail:
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Koek W, France CP, Cheng K, Rice KC. Effects of the GABAB receptor-positive modulators CGP7930 and rac-BHFF in baclofen- and γ-hydroxybutyrate-discriminating pigeons. J Pharmacol Exp Ther 2012; 341:369-76. [PMID: 22319197 DOI: 10.1124/jpet.111.190975] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
In vivo effects of GABA(B) receptor-positive modulators suggest them to have therapeutic potential to treat central nervous system disorders such as anxiety and drug abuse. Although these effects are thought to be mediated by positive modulation of GABA(B) receptors, such modulation has been examined primarily in vitro. This study further examined the in vivo properties of the GABA(B) receptor-positive modulators 2,6-di-tert-butyl-4-(3-hydroxy-2,2-dimethylpropyl) phenol (CGP7930) and (R,S)-5,7-di-tert-butyl-3-hydroxy-3-trifluoromethyl-3H-benzofuran-2-one (rac-BHFF). In pigeons discriminating baclofen from saline, γ-hydroxybutyrate (GHB) produced 100% baclofen-appropriate responding, and the GABA(B) antagonist 3-aminopropyl(dimethoxymethyl) phosphinic acid (CGP35348) blocked the effects of both drugs. CGP7930 and rac-BHFF produced at most 41 and 74% baclofen-appropriate responding, respectively, and enhanced the discriminative stimulus effects of baclofen, but not of GHB. In pigeons discriminating GHB from saline, CGP7930 and rac-BHFF produced at most 1 and 49% GHB-appropriate responding, respectively, and enhanced the effects of baclofen, but not of GHB. Enhancement of the discriminative stimulus effects of baclofen by rac-BHFF and CGP7930 is further evidence of their effectiveness as GABA(B) receptor-positive modulators in vivo. Furthermore, lack of complete substitution of the positive modulators rac-BHFF and CGP7930 for baclofen and GHB suggests that their discriminative stimulus effects differ from those of GABA(B) receptor agonists. Finally, together with converging evidence that the GABA(B) receptor populations mediating the effects of baclofen and GHB are not identical, the present findings suggest that these populations differ in their susceptibility to positive modulatory effects. Such differences could allow for more selective therapeutic targeting of the GABA(B) system.
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Affiliation(s)
- Wouter Koek
- Departments of Psychiatry and Pharmacology, University of Texas Health Science Center, 7703 Floyd Curl Drive, Mail Code 7792, San Antonio, TX 78229-3900, USA.
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Castelli MP, Casu A, Casti P, Lobina C, Carai MAM, Colombo G, Solinas M, Giunta D, Mugnaini C, Pasquini S, Tafi A, Brogi S, Gessa GL, Corelli F. Characterization of COR627 and COR628, two novel positive allosteric modulators of the GABA(B) receptor. J Pharmacol Exp Ther 2011; 340:529-38. [PMID: 22129594 DOI: 10.1124/jpet.111.186460] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The potential efficacy of GABA(B) receptor agonists in the treatment of pain, drug addiction, epilepsy, cognitive dysfunctions, and anxiety disorders is supported by extensive preclinical and clinical evidence. However, the numerous side effects produced by the GABA(B) receptor agonist baclofen considerably limit the therapeutic use of this compound. The identification of positive allosteric modulators (PAMs) of the GABA(B) receptor may constitute a novel approach in the pharmacological manipulation of the GABA(B) receptor, leading to fewer side effects. The present study reports the identification of two novel compounds, methyl 2-(1-adamantanecarboxamido)-4-ethyl-5-methylthiophene-3-carboxylate (COR627) and methyl 2-(cyclohexanecarboxamido)-4-ethyl-5-methylthiophene-3-carboxylate (COR628), which act as GABA(B) PAMs in 1) rat cortical membranes and 2) in vivo assay. Both compounds potentiated GABA- and baclofen-stimulated guanosine 5'-O-(3-[(35)S]thio)-triphosphate binding to native GABA(B) receptors, while producing no effect when given alone. GABA concentration-response curves in the presence of fixed concentrations of COR627 and COR628 revealed an increase of potency of GABA rather than its maximal efficacy. In radioligand binding experiments [displacement of the GABA(B) receptor antagonist, 3-N-[1-((S)-3,4dichlorophenyl)-ethylaminol]-2-(S)hydroxypropyl cyclo-hexylmethyl phosphinic acid ([(3)H]CGP54626)], both COR627 and COR628 increased the affinity of high- and low-affinity binding sites for GABA, producing no effect when administered alone up to a concentration of 1 mM. In vivo experiments indicated that pretreatment with per se ineffective doses of COR627 and COR628 potentiated the sedative/hypnotic effect of baclofen. In conclusion, COR627 and COR628 may represent two additional tools for use in investigating the roles and functions of positive allosteric modulatory binding sites of the GABA(B) receptor.
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Affiliation(s)
- M Paola Castelli
- Department of Neuroscience Bernard B. Brodie, University of Cagliari, Cagliari, Italy.
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Perdona’ E, Costantini VJ, Tessari M, Martinelli P, Carignani C, Valerio E, Mok MS, Zonzini L, Visentini F, Gianotti M, Gordon L, Rocheville M, Corsi M, Capelli AM. In vitro and in vivo characterization of the novel GABAB receptor positive allosteric modulator, 2-{1-[2-(4-chlorophenyl)-5-methylpyrazolo[1,5-a]pyrimidin-7-yl]-2-piperidinyl}ethanol (CMPPE). Neuropharmacology 2011; 61:957-66. [DOI: 10.1016/j.neuropharm.2011.06.024] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2010] [Revised: 06/23/2011] [Accepted: 06/26/2011] [Indexed: 12/16/2022]
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Gannon RL, Millan MJ. Positive allosteric modulators at GABAB receptors exert intrinsic actions and enhance the influence of baclofen on light-induced phase shifts of hamster circadian activity rhythms. Pharmacol Biochem Behav 2011; 99:712-7. [DOI: 10.1016/j.pbb.2011.06.029] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/04/2011] [Revised: 06/20/2011] [Accepted: 06/24/2011] [Indexed: 11/28/2022]
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Hensler JG, Advani T, Burke TF, Cheng K, Rice KC, Koek W. GABAB receptor-positive modulators: brain region-dependent effects. J Pharmacol Exp Ther 2011; 340:19-26. [PMID: 21954301 DOI: 10.1124/jpet.111.186577] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
This study examined the positive modulatory properties of 2,6-di-tert-butyl-4-(3-hydroxy-2,2-dimethyl-propyl)-phenol (CGP7930) and (R,S)-5,7-di-tert-butyl-3-hydroxy-3-trifluoromethyl-3H-benzofuran-2-one (rac-BHFF) at γ-aminobutyric acid B (GABA(B)) receptors in different brain regions. Using quantitative autoradiography, we measured GABA(B) receptor-stimulated binding of guanosine 5'-O-(3-[³⁵S]thiotriphosphate) ([³⁵S]GTPγS) to G proteins in medial prefrontal cortex (mPFC), hippocampus, and cerebellum. CGP7930 and rac-BHFF enhanced baclofen-stimulated [³⁵S]GTPγS binding similarly in mPFC and hippocampus, but were more effective in cerebellum. CGP7930 (100 μM) increased [³⁵S]GTPγS binding stimulated by baclofen (30 μM) from 29 to 241% above basal in mPFC and from 13 to 1530% above basal in cerebellum. Likewise, rac-BHFF (10 μM) increased baclofen-stimulated [³⁵S]GTPγS binding more in cerebellum (from 13 to 1778% above basal) than in mPFC (from 29 to 514% above basal). rac-BHFF (10 μM) in combination with γ-hydroxybutyrate (20 mM) increased [³⁵S]GTPγS binding in cerebellum but not in mPFC. rac-BHFF also enhanced the effects of 3-aminopropyl(diethoxymethyl)phosphinic acid (CGP35348). Consistent with its partial agonist properties, CGP35348 stimulated [³⁵S]GTPγS binding in mPFC when given alone (to 18% above basal), but less extensively than baclofen (140% above basal), and antagonized baclofen when given together. CGP35348 (1 mM) in combination with rac-BHFF (100 μM) produced an increase in [³⁵S]GTPγS binding that was larger in cerebellum (from 61 to 1260% above basal) than in mPFC (from 18 to 118% above basal). Taken together, the results show that GABA(B) receptor-positive modulators enhance [³⁵S]GTPγS binding stimulated by GABA(B) receptor agonists in a brain region-dependent manner. This regionally selective enhancement is further evidence of pharmacologically distinct GABA(B) receptor populations, possibly allowing for more selective therapeutic targeting of the GABA(B) system.
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Affiliation(s)
- Julie G Hensler
- Department of Pharmacology, MC 7764, University of Texas Health Science Center, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA.
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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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