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Nikolic S, Gazdic-Jankovic M, Rosic G, Miletic-Kovacevic M, Jovicic N, Nestorovic N, Stojkovic P, Filipovic N, Milosevic-Djordjevic O, Selakovic D, Zivanovic M, Seklic D, Milivojević N, Markovic A, Seist R, Vasilijic S, Stankovic KM, Stojkovic M, Ljujic B. Orally administered fluorescent nanosized polystyrene particles affect cell viability, hormonal and inflammatory profile, and behavior in treated mice. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2022; 305:119206. [PMID: 35405220 DOI: 10.1016/j.envpol.2022.119206] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Revised: 03/12/2022] [Accepted: 03/22/2022] [Indexed: 06/14/2023]
Abstract
Commercially manufactured or generated through environmental degradation, microplastics (MPs) and nanoplastics (NPs) considerably contribute to environmental pollution. There is a knowledge gap in how exposure to MPs/NPs changes cellular function and affects animal and human health. Here, we demonstrate that after oral uptake, fluorescent polystyrene (PS) nanoparticles pass through the mouse digestive system, accumulate and aggregate in different organs, and induce functional changes in cells and organs. Using cochlear explant as a novel in vitro system, we confirmed the consequences of PS-MP/NP interaction with inner ear cells by detecting aggregates and hetero-aggregates of PS particles in hair cells. The testes of treated males accumulated MPs/NPs in the interstitial compartment surrounding the seminiferous tubules, which was associated with a statistically significant decrease in testosterone levels. Male mice showed increased secretion of interleukins (IL-12p35 and IL-23) by splenocytes while cyto- and genotoxicity tests indicated impaired cell viability and increased DNA damage in spleen tissue. Males also showed a broad range of anxiogenic responses to PS nanoparticles while hippocampal samples from treated females showed an increased expression of Bax and Nlrp3 genes, indicating a pro-apoptotic/proinflammatory effect of PS treatment. Taken together, induced PS effects are also gender-dependent, and therefore, strongly motivate future research to mitigate the deleterious effects of nanosized plastic particles.
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Affiliation(s)
- Sandra Nikolic
- Department of Genetics, Faculty of Medical Sciences, University of Kragujevac, Kragujevac, Serbia
| | - Marina Gazdic-Jankovic
- Department of Genetics, Faculty of Medical Sciences, University of Kragujevac, Kragujevac, Serbia
| | - Gvozden Rosic
- Department of Physiology, Faculty of Medical Sciences, University of Kragujevac, Kragujevac, Serbia
| | - Marina Miletic-Kovacevic
- Department of Histology and Embryology, University of Kragujevac, Faculty of Medical Sciences, Kragujevac, Serbia
| | - Nemanja Jovicic
- Department of Histology and Embryology, University of Kragujevac, Faculty of Medical Sciences, Kragujevac, Serbia
| | - Natasa Nestorovic
- Institute for Biological Research "Sinisa Stankovic", National Institute of Republic of Serbia, University of Belgrade, Serbia
| | | | - Nenad Filipovic
- Faculty of Engineering, University of Kragujevac, Kragujevac, Serbia
| | - Olivera Milosevic-Djordjevic
- Department of Genetics, Faculty of Medical Sciences, University of Kragujevac, Kragujevac, Serbia; Department of Biology and Ecology, Faculty of Science, University of Kragujevac, Kragujevac, Serbia
| | - Dragica Selakovic
- Department of Physiology, Faculty of Medical Sciences, University of Kragujevac, Kragujevac, Serbia
| | - Marko Zivanovic
- Laboratory for Bioengineering, Institute of Information Technologies Kragujevac, University of Kragujevac, Kragujevac, Serbia
| | - Dragana Seklic
- Laboratory for Bioengineering, Institute of Information Technologies Kragujevac, University of Kragujevac, Kragujevac, Serbia
| | - Nevena Milivojević
- Laboratory for Bioengineering, Institute of Information Technologies Kragujevac, University of Kragujevac, Kragujevac, Serbia
| | - Aleksandra Markovic
- Department of Biology and Ecology, Faculty of Science, University of Kragujevac, Kragujevac, Serbia
| | - Richard Seist
- Department of Otolaryngology - Head and Neck Surgery, Harvard Medical School and Massachusetts Eye and Ear, Boston, MA, United States; Program Department of Otorhinolaryngology-Head and Neck Surgery, Paracelsus Medical University, Salzburg, Austria
| | - Sasa Vasilijic
- Department of Otolaryngology - Head and Neck Surgery, Harvard Medical School and Massachusetts Eye and Ear, Boston, MA, United States
| | - Konstantina M Stankovic
- Department of Otolaryngology - Head and Neck Surgery, Harvard Medical School and Massachusetts Eye and Ear, Boston, MA, United States
| | - Miodrag Stojkovic
- Department of Genetics, Faculty of Medical Sciences, University of Kragujevac, Kragujevac, Serbia; SPEBO Medical, Fertility Clinic Leskovac, Serbia
| | - Biljana Ljujic
- Department of Genetics, Faculty of Medical Sciences, University of Kragujevac, Kragujevac, Serbia.
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Luquin E, Paternain B, Zugasti I, Santomá C, Mengual E. Stereological estimations and neurochemical characterization of neurons expressing GABAA and GABAB receptors in the rat pedunculopontine and laterodorsal tegmental nuclei. Brain Struct Funct 2022; 227:89-110. [PMID: 34510281 PMCID: PMC8741722 DOI: 10.1007/s00429-021-02375-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Accepted: 08/31/2021] [Indexed: 11/29/2022]
Abstract
To better understand GABAergic transmission at two targets of basal ganglia downstream projections, the pedunculopontine (PPN) and laterodorsal (LDT) tegmental nuclei, the anatomical localization of GABAA and GABAB receptors was investigated in both nuclei. Specifically, the total number of neurons expressing the GABAA receptor γ2 subunit (GABAAR γ2) and the GABAB receptor R2 subunit (GABAB R2) in PPN and LDT was estimated using stereological methods, and the neurochemical phenotype of cells expressing each subunit was also determined. The mean number of non-cholinergic cells expressing GABAAR γ2 was 9850 ± 1856 in the PPN and 8285 ± 962 in the LDT, whereas those expressing GABAB R2 were 7310 ± 1970 and 9170 ± 1900 in the PPN and LDT, respectively. In addition, all cholinergic neurons in both nuclei co-expressed GABAAR γ2 and 95-98% of them co-expressed GABAB R2. Triple labeling using in situ hybridization revealed that 77% of GAD67 mRNA-positive cells in the PPT and 49% in the LDT expressed GABAAR γ2, while 90% (PPN) and 65% (LDT) of Vglut2 mRNA-positive cells also expressed GABAAR γ2. In contrast, a similar proportion (~2/3) of glutamatergic and GABAergic cells co-expressed GABAB R2 in both nuclei. The heterogeneous distribution of GABAAR and GABABR among non-cholinergic cells in PPN and LDT may give rise to physiological differences within each neurochemical subpopulation. In addition, the dissimilar proportion of GABAAR γ2-expressing glutamatergic and GABAergic neurons in the PPN and LDT may contribute to some of the functional differences found between the two nuclei.
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Affiliation(s)
- Esther Luquin
- Department of Pathology, Anatomy, and Physiology, School of Medicine, University of Navarra, Ed. Los Castaños, Irunlarrea 1, 31008 Pamplona, Spain
- IdiSNA, Navarra Institute for Health Research, 31008 Pamplona, Spain
| | - Beatriz Paternain
- Department of Pathology, Anatomy, and Physiology, School of Medicine, University of Navarra, Ed. Los Castaños, Irunlarrea 1, 31008 Pamplona, Spain
- IdiSNA, Navarra Institute for Health Research, 31008 Pamplona, Spain
| | - Inés Zugasti
- Department of Pathology, Anatomy, and Physiology, School of Medicine, University of Navarra, Ed. Los Castaños, Irunlarrea 1, 31008 Pamplona, Spain
- IdiSNA, Navarra Institute for Health Research, 31008 Pamplona, Spain
| | - Carmen Santomá
- Department of Pathology, Anatomy, and Physiology, School of Medicine, University of Navarra, Ed. Los Castaños, Irunlarrea 1, 31008 Pamplona, Spain
- IdiSNA, Navarra Institute for Health Research, 31008 Pamplona, Spain
| | - Elisa Mengual
- Department of Pathology, Anatomy, and Physiology, School of Medicine, University of Navarra, Ed. Los Castaños, Irunlarrea 1, 31008 Pamplona, Spain
- IdiSNA, Navarra Institute for Health Research, 31008 Pamplona, Spain
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Targeting GABA C Receptors Improves Post-Stroke Motor Recovery. Brain Sci 2021; 11:brainsci11030315. [PMID: 33801560 PMCID: PMC8000079 DOI: 10.3390/brainsci11030315] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2021] [Revised: 02/25/2021] [Accepted: 02/26/2021] [Indexed: 11/16/2022] Open
Abstract
Ischemic stroke remains a leading cause of disability worldwide, with limited treatment options available. This study investigates GABAC receptors as novel pharmacological targets for stroke recovery. The expression of ρ1 and ρ2 mRNA in mice were determined in peri-infarct tissue following photothrombotic motor cortex stroke. (R)-4-amino-cyclopent-1-enyl butylphosphinic acid (R)-4-ACPBPA and (S)-4-ACPBPA were assessed using 2-elecotrode voltage electrophysiology in Xenopus laevis oocytes. Stroke mice were treated for 4 weeks with either vehicle, the α5-selective negative allosteric modulator, L655,708, or the ρ1/2 antagonists, (R)-4-ACPBPA and (S)-4-ACPBPA respectively from 3 days post-stroke. Infarct size and expression levels of GAT3 and reactive astrogliosis were determined using histochemistry and immunohistochemistry respectively, and motor function was assessed using both the grid-walking and cylinder tasks. After stroke, significant increases in ρ1 and ρ2 mRNAs were observed on day 3, with ρ2 showing a further increase on day 7. (R)- and (S)-4-ACPBPA are both potent antagonists at ρ2 and only weak inhibitors of α5β2γ2 receptors. Treatment with either L655,708, (S)-4-ACPBPA (ρ1/2 antagonist; 5 mM only), or (R)-4-ACPBPA (ρ2 antagonist; 2.5 and 5 mM) from 3 days after stroke resulted in a significant improvement in motor recovery on the grid-walking task, with L655,708 and (R)-4-ACPBPA also showing an improvement in the cylinder task. Infarct size was unaffected, and only (R)-4-ACPBPA significantly increased peri-infarct GAT3 expression and decreased the level of reactive astrogliosis. Importantly, inhibiting GABAC receptors affords significant improvement in motor function after stroke. Targeting the ρ-subunit could provide a novel delayed treatment option for stroke recovery.
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Viana MB, Martins RS, Silva MSCF, Xapelli S, Vaz SH, Sebastião AM. Deep Brain Stimulation of the dorsal raphe abolishes serotonin 1A facilitation of AMPA receptor-mediated synaptic currents in the ventral hippocampus. Behav Brain Res 2021; 403:113134. [PMID: 33476685 DOI: 10.1016/j.bbr.2021.113134] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2020] [Revised: 12/11/2020] [Accepted: 01/11/2021] [Indexed: 11/24/2022]
Abstract
In a previous study we showed that Deep Brain Stimulation (DBS) of the rat dorsal subregion of the dorsal raphe (DRD), which sends serotonergic projections to forebrain areas, such as the ventral hippocampus, induces anxiolytic-like effects. The purpose of the present study was to investigate neurobiological alterations which might underline these behavioral effects. For that, we tested the influence of DBS upon the neuromodulatory action of serotonin on excitatory post-synaptic currents (EPSCs) in the ventral hippocampus. Male Wistar rats were submitted to high-frequency stimulation (100 μA, 100 Hz) of the DRD for 1 h during three consecutive days. On the third day, immediately after the DBS procedure, animals were euthanized. Slices of the ventral hippocampus were processed for whole cell patch clamp recordings of AMPA-receptor (AMPAR) mediated EPSCs in the CA1 area. As reported by others, we confirmed that in pre-weaning rats a high affinity 5-HT1A receptor agonist (8-OH-PIPAT, 0.5-5nM) inhibits EPSCs. However, in adult rats (non-operated or sham-operated), 8-OH-PIPAT (0.5-5 nM) increased EPSC amplitude, an effect blocked by the 5-HT1A antagonist WAY-100,635 (200 nM). Importantly, in adult rats exposed to DBS, the 5-HT1A agonist was devoid of effect. Taken together these results show that: 1) changes in 5-HT1A receptor-mediated hippocampal synaptic transmission occur with age; 2) these changes lead to a facilitatory effect of 5-HT1A receptors; 3) DBS blocks this serotonergic facilitatory action. These observations suggest that an alteration in serotonin modulation of limbic areas may underlie the psychotherapeutic effects of DBS.
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Affiliation(s)
- M B Viana
- Departamento de Biociências, Universidade Federal de São Paulo (UNIFESP), Santos, Brazil.
| | - R S Martins
- Departamento de Farmacologia e Fisiologia, Universidade Federal Fluminense (UFF), Niterói, Brazil
| | - M S C F Silva
- Departamento de Biociências, Universidade Federal de São Paulo (UNIFESP), Santos, Brazil
| | - S Xapelli
- Instituto Farmacologia e Neurociências, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal; Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal
| | - S H Vaz
- Instituto Farmacologia e Neurociências, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal; Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal
| | - A M Sebastião
- Instituto Farmacologia e Neurociências, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal; Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal
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5
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Germann AL, Reichert DE, Burbridge AB, Pierce SR, Evers AS, Steinbach JH, Akk G. Analysis of Modulation of the ρ1 GABA A Receptor by Combinations of Inhibitory and Potentiating Neurosteroids Reveals Shared and Distinct Binding Sites. Mol Pharmacol 2020; 98:280-291. [PMID: 32675382 DOI: 10.1124/mol.120.119842] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Accepted: 07/07/2020] [Indexed: 11/22/2022] Open
Abstract
The ρ1 GABAA receptor is prominently expressed in the retina and is present at lower levels in several brain regions and other tissues. Although the ρ1 receptor is insensitive to many anesthetic drugs that modulate the heteromeric GABAA receptor, it maintains a rich and multifaceted steroid pharmacology. The receptor is negatively modulated by 5β-reduced steroids, sulfated or carboxylated steroids, and β-estradiol, whereas many 5α-reduced steroids potentiate the receptor. In this study, we analyzed modulation of the human ρ1 GABAA receptor by several neurosteroids, individually and in combination, in the framework of the coagonist concerted transition model. Experiments involving coapplication of two or more steroids revealed that the receptor contains at least three classes of distinct, nonoverlapping sites for steroids, one each for the inhibitory steroids pregnanolone (3α5βP), 3α5βP sulfate, and β-estradiol. The site for 3α5βP can accommodate the potentiating steroid 5αTHDOC. The findings are discussed with respect to receptor modulation by combinations of endogenous neurosteroids. SIGNIFICANCE STATEMENT: The study describes modulation of the ρ1 GABAA receptor by neurosteroids. The coagonist concerted transition model was used to determine overlap of binding sites for several inhibitory and potentiating steroids.
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Affiliation(s)
- Allison L Germann
- Departments of Anesthesiology (A.L.G., A.B.B., S.R.P., A.S.E., J.H.S., G.A.) and Radiology (D.E.R.) and the Taylor Family Institute for Innovative Psychiatric Research (D.E.R., A.S.E., J.H.S., G.A.), Washington University School of Medicine, St. Louis, Missouri
| | - David E Reichert
- Departments of Anesthesiology (A.L.G., A.B.B., S.R.P., A.S.E., J.H.S., G.A.) and Radiology (D.E.R.) and the Taylor Family Institute for Innovative Psychiatric Research (D.E.R., A.S.E., J.H.S., G.A.), Washington University School of Medicine, St. Louis, Missouri
| | - Ariel B Burbridge
- Departments of Anesthesiology (A.L.G., A.B.B., S.R.P., A.S.E., J.H.S., G.A.) and Radiology (D.E.R.) and the Taylor Family Institute for Innovative Psychiatric Research (D.E.R., A.S.E., J.H.S., G.A.), Washington University School of Medicine, St. Louis, Missouri
| | - Spencer R Pierce
- Departments of Anesthesiology (A.L.G., A.B.B., S.R.P., A.S.E., J.H.S., G.A.) and Radiology (D.E.R.) and the Taylor Family Institute for Innovative Psychiatric Research (D.E.R., A.S.E., J.H.S., G.A.), Washington University School of Medicine, St. Louis, Missouri
| | - Alex S Evers
- Departments of Anesthesiology (A.L.G., A.B.B., S.R.P., A.S.E., J.H.S., G.A.) and Radiology (D.E.R.) and the Taylor Family Institute for Innovative Psychiatric Research (D.E.R., A.S.E., J.H.S., G.A.), Washington University School of Medicine, St. Louis, Missouri
| | - Joe Henry Steinbach
- Departments of Anesthesiology (A.L.G., A.B.B., S.R.P., A.S.E., J.H.S., G.A.) and Radiology (D.E.R.) and the Taylor Family Institute for Innovative Psychiatric Research (D.E.R., A.S.E., J.H.S., G.A.), Washington University School of Medicine, St. Louis, Missouri
| | - Gustav Akk
- Departments of Anesthesiology (A.L.G., A.B.B., S.R.P., A.S.E., J.H.S., G.A.) and Radiology (D.E.R.) and the Taylor Family Institute for Innovative Psychiatric Research (D.E.R., A.S.E., J.H.S., G.A.), Washington University School of Medicine, St. Louis, Missouri
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6
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Stajic D, Selakovic D, Jovicic N, Joksimovic J, Arsenijevic N, Lukic ML, Rosic G. The role of galectin-3 in modulation of anxiety state level in mice. Brain Behav Immun 2019; 78:177-187. [PMID: 30682502 DOI: 10.1016/j.bbi.2019.01.019] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Revised: 01/16/2019] [Accepted: 01/19/2019] [Indexed: 01/19/2023] Open
Abstract
Galectin-3 (Gal-3), a member of lectin family that binds to oligosaccharides, is involved in several biological processes, including maturation and function of nervous system. It had been reported that Gal-3 regulates oligodendrocytes differentiation and that Gal-3/Toll-like receptor-4 (TLR4) axis is involved in neuroinflammation. As both, central nervous system (CNS) maturation and neuroinflammation may affect behavior, the principle aim of this study was to examine the effects of Gal-3 gene deletion on behavior. Here we provide the evidence that Gal-3 deficiency shows clear anxiogenic effect in mature untreated animals (basal conditions). This was accompanied with lower interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) relative gene expression and hippocampal content, with no effect on TLR4 expression. Gal-3 deficiency was also accompanied with lower brain-derived neurotrophic factor (BDNF) relative gene expression and immunoreactivity in hippocampus (predominantly in CA1 region). Besides, the Gal-3 gene deletion resulted in attenuation of the hippocampal relative gene expression of GABA-A receptor subunits 2 and 5 (GABA-AR2S and GABA-AR5S), On the other hand, Gal-3 deficiency attenuates LPS-induced neuroinflammation. The anxiogenic effect of acute neuroinflammation was accompanied with increased hippocampal IL-6, TNF-α and TLR4 gene expression, as well as decreased gene and immunohistochemical BDNF expression in hippocampus, with significant decline in GABA-AR2S in wild type (WT) mice in comparison to basal conditions. Gal-3 gene deletion prevented the increase in IL-6, the decline in BDNF gene expression and immunoreactivity, and reduction in hippocampal GABA-AR2S, and therefore attenuated the anxiogenic effect of neuroinflammation. In summary, our data demonstrate that apparently opposite effects of Gal-3 deficiency on anxiety levels (anxiogenic effect under basal conditions and anxiolytic action during neuroinflammation) seem to be related to the shift in IL-6, TNF-α and hippocampal BDNF.
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Affiliation(s)
- Dalibor Stajic
- Department of Hygiene and Ecology, Faculty of Medical Sciences, University of Kragujevac, Serbia; Center for Molecular Medicine and Stem Cell Research, Faculty of Medical Sciences, University of Kragujevac, Serbia
| | - Dragica Selakovic
- Department of Physiology, Faculty of Medical Sciences, University of Kragujevac, Serbia
| | - Nemanja Jovicic
- Department of Histology and Embryology, Faculty of Medical Sciences, University of Kragujevac, Serbia
| | - Jovana Joksimovic
- Department of Physiology, Faculty of Medical Sciences, University of Kragujevac, Serbia
| | - Nebojsa Arsenijevic
- Center for Molecular Medicine and Stem Cell Research, Faculty of Medical Sciences, University of Kragujevac, Serbia
| | - Miodrag L Lukic
- Center for Molecular Medicine and Stem Cell Research, Faculty of Medical Sciences, University of Kragujevac, Serbia.
| | - Gvozden Rosic
- Department of Physiology, Faculty of Medical Sciences, University of Kragujevac, Serbia.
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7
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Naffaa MM, Hung S, Chebib M, Johnston GAR, Hanrahan JR. GABA-ρ receptors: distinctive functions and molecular pharmacology. Br J Pharmacol 2017; 174:1881-1894. [PMID: 28258627 DOI: 10.1111/bph.13768] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Revised: 02/26/2017] [Accepted: 03/01/2017] [Indexed: 01/14/2023] Open
Abstract
The homomeric GABA-ρ ligand-gated ion channels (also known as GABAC or GABAA -ρ receptors) are similar to heteromeric GABAA receptors in structure, function and mechanism of action. However, their distinctive pharmacological properties and distribution make them of special interest. This review focuses on GABA-ρ ion channel structure, ligand selectivity toward ρ receptors over heteromeric GABAA receptor sub-types and selectivity between different homomeric ρ sub-type receptors. Several GABA analogues show selectivity at homomeric GABA-ρ receptors over heteromeric GABAA receptors. More recently, some synthetic ligands have been found to show selectivity at receptors formed from one ρ subtype over others. The unique pharmacological profiles of these agents are discussed in this review. The classical binding site of GABA within the orthosteric site of GABA-ρ homomeric receptors is discussed in detail regarding the loops and residues that constitute the binding site. The ligand-residue interactions in this classical binding and those of mutant receptors are discussed. The structure and conformations of GABA are discussed in regard to its flexibility and molecular properties. Although the binding mode of GABA is difficult to predict, several interactions between GABA and the receptor assist in predicting its potential conformation and mode of action. The structure-activity relationships of GABA and structurally key ligands at ρ receptors are described and discussed.
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Affiliation(s)
- Moawiah M Naffaa
- Faculty of Pharmacy, University of Sydney, Sydney, NSW, Australia
| | - Sandy Hung
- Faculty of Pharmacy, University of Sydney, Sydney, NSW, Australia
| | - Mary Chebib
- Faculty of Pharmacy, University of Sydney, Sydney, NSW, Australia
| | | | - Jane R Hanrahan
- Faculty of Pharmacy, University of Sydney, Sydney, NSW, Australia
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Furlong TM, Duncan JR, Corbit LH, Rae CD, Rowlands BD, Maher AD, Nasrallah FA, Milligan CJ, Petrou S, Lawrence AJ, Balleine BW. Toluene inhalation in adolescent rats reduces flexible behaviour in adulthood and alters glutamatergic and GABAergic signalling. J Neurochem 2016; 139:806-822. [PMID: 27696399 DOI: 10.1111/jnc.13858] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2016] [Revised: 09/15/2016] [Accepted: 09/18/2016] [Indexed: 12/24/2022]
Abstract
Toluene is a commonly abused inhalant that is easily accessible to adolescents. Despite the increasing incidence of use, our understanding of its long-term impact remains limited. Here, we used a range of techniques to examine the acute and chronic effects of toluene exposure on glutameteric and GABAergic function, and on indices of psychological function in adult rats after adolescent exposure. Metabolomics conducted on cortical tissue established that acute exposure to toluene produces alterations in cellular metabolism indicative of a glutamatergic and GABAergic profile. Similarly, in vitro electrophysiology in Xenopus oocytes found that acute toluene exposure reduced NMDA receptor signalling. Finally, in an adolescent rodent model of chronic intermittent exposure to toluene (10 000 ppm), we found that, while toluene exposure did not affect initial learning, it induced a deficit in updating that learning when response-outcome relationships were reversed or degraded in an instrumental conditioning paradigm. There were also group differences when more effort was required to obtain the reward; toluene-exposed animals were less sensitive to progressive ratio schedules and to delayed discounting. These behavioural deficits were accompanied by changes in subunit expression of both NMDA and GABA receptors in adulthood, up to 10 weeks after the final exposure to toluene in the hippocampus, prefrontal cortex and ventromedial striatum; regions with recognized roles in behavioural flexibility and decision-making. Collectively, our data suggest that exposure to toluene is sufficient to induce adaptive changes in glutamatergic and GABAergic systems and in adaptive behaviour that may underlie the deficits observed following adolescent inhalant abuse, including susceptibility to further drug-use.
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Affiliation(s)
- Teri M Furlong
- Brain & Mind Centre, University of Sydney, Sydney, New South Wales, Australia.,School of Psychology, University of Sydney, Sydney, New South Wales, Australia
| | - Jhodie R Duncan
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia.,Department of Anatomy and Neuroscience, University of Melbourne, Melbourne, Victoria, Australia
| | - Laura H Corbit
- School of Psychology, University of Sydney, Sydney, New South Wales, Australia
| | - Caroline D Rae
- Neuroscience Research Australia, Randwick, New South Wales, Australia.,School of Medical Sciences, University of NSW, Kensington, New South Wales, Australia
| | - Benjamin D Rowlands
- Neuroscience Research Australia, Randwick, New South Wales, Australia.,School of Medical Sciences, University of NSW, Kensington, New South Wales, Australia
| | - Anthony D Maher
- Neuroscience Research Australia, Randwick, New South Wales, Australia
| | | | - Carol J Milligan
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
| | - Steven Petrou
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
| | - Andrew J Lawrence
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
| | - Bernard W Balleine
- Brain & Mind Centre, University of Sydney, Sydney, New South Wales, Australia.,School of Psychology, University of NSW, Kensington, New South Wales, Australia
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9
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Ma Z, Niu B, Shi Z, Li J, Wang J, Zhang F, Gao X, Zhang K. Genetic Polymorphism of GABRR2 Modulates Individuals' General Cognitive Ability in Healthy Chinese Han People. Cell Mol Neurobiol 2016; 37:93-100. [PMID: 26922432 DOI: 10.1007/s10571-016-0347-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2015] [Accepted: 02/08/2016] [Indexed: 01/04/2023]
Abstract
Previous studies have indicated that the cognitive impairment or deficit is associated with GABAergic signaling in central nervous system. Inspired by the finding that receptor GABRR2 modulates concentration of GABA and phasic inhibitory GABAergic transmission in brain. This study investigated to what extent a genetic variant (c.1423C>T, rs282129) of GABRR2 gene modulates individuals' general cognitive ability in 987 Chinese Han people. Results showed a significant influence of GABRR2 gene polymorphism on individuals' Raven's Standard Progressive Matrices (RSPM) performance (F = 3.58, P = .028 by ANOVA and χ 2 = 9.35, P = .009 by K-W test, respectively), even if non-genetic factors were partialed out (gender, major, types of birthplace, and socioeconomic index) (B = -.67, SE = .26, t = 2.63, P = .009). The finding provided a strong evidence, to our knowledge, for the view that genetic variant of GABRR2 gene may contribute to the difference of individuals' general cognitive ability, independently.
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Affiliation(s)
- Zhe Ma
- Key Laboratory of Resource Biology and Biotechnology in Western China (Ministry of Education), Institute of Population and Health, College of Life Science, Northwest University, Xi'an, 710069, China
| | - Binbin Niu
- Key Laboratory of Resource Biology and Biotechnology in Western China (Ministry of Education), Institute of Population and Health, College of Life Science, Northwest University, Xi'an, 710069, China
| | - Zhangyan Shi
- Key Laboratory of Resource Biology and Biotechnology in Western China (Ministry of Education), Institute of Population and Health, College of Life Science, Northwest University, Xi'an, 710069, China
| | - Junlin Li
- Key Laboratory of Resource Biology and Biotechnology in Western China (Ministry of Education), Institute of Population and Health, College of Life Science, Northwest University, Xi'an, 710069, China
| | - Jian Wang
- Department of Applied Psychology, Institute of Applied Psychology, College of Public Management, Northwest University, Xi'an, 710069, China
| | - Fuchang Zhang
- Key Laboratory of Resource Biology and Biotechnology in Western China (Ministry of Education), Institute of Population and Health, College of Life Science, Northwest University, Xi'an, 710069, China.,Department of Applied Psychology, Institute of Applied Psychology, College of Public Management, Northwest University, Xi'an, 710069, China
| | - Xiaocai Gao
- Key Laboratory of Resource Biology and Biotechnology in Western China (Ministry of Education), Institute of Population and Health, College of Life Science, Northwest University, Xi'an, 710069, China. .,Department of Applied Psychology, Institute of Applied Psychology, College of Public Management, Northwest University, Xi'an, 710069, China. .,School of Public Management, Institute of Application Psychology, Institute of Population and Health, Northwest University, Xi'an, 710127, China.
| | - Kejin Zhang
- Key Laboratory of Resource Biology and Biotechnology in Western China (Ministry of Education), Institute of Population and Health, College of Life Science, Northwest University, Xi'an, 710069, China.
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10
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Abstract
This review centers on the discoveries made during more than six decades of neuroscience research on the role of gamma-amino-butyric acid (GABA) as neurotransmitter. In doing so, special emphasis is directed to the significant involvement of Canadian scientists in these advances. Starting with the early studies that established GABA as an inhibitory neurotransmitter at central synapses, we summarize the results pointing at the GABA receptor as a drug target as well as more recent evidence showing that GABAA receptor signaling plays a surprisingly active role in neuronal network synchronization, both during development and in the adult brain. Finally, we briefly address the involvement of GABA in neurological conditions that encompass epileptic disorders and mental retardation.
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Rae C, Nasrallah FA, Balcar VJ, Rowlands BD, Johnston GAR, Hanrahan JR. Metabolomic Approaches to Defining the Role(s) of GABAρ Receptors in the Brain. J Neuroimmune Pharmacol 2015; 10:445-56. [PMID: 25577264 DOI: 10.1007/s11481-014-9579-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2014] [Accepted: 12/26/2014] [Indexed: 10/24/2022]
Abstract
The inhibitory neurotransmitter γ-aminobutyric acid (GABA) acts through various types of receptors in the central nervous system. GABAρ receptors, defined by their characteristic pharmacology and presence of ρ subunits in the channel structure, are poorly understood and their role in the cortex is ill-defined. Here, we used a targeted pharmacological, NMR-based functional metabolomic approach in Guinea pig brain cortical tissue slices to identify a distinct role for these receptors. We compared metabolic fingerprints generated by a range of ligands active at GABAρ and included these in a principal components analysis with a library of other metabolic fingerprints obtained using ligands active at GABAA and GABAB, with inhibitors of GABA uptake and with compounds acting to inhibit enzymes active in the GABAergic system. This enabled us to generate a metabolic "footprint" of the GABAergic system which revealed classes of metabolic activity associated with GABAρ which are distinct from other GABA receptors. Antagonised GABAρ produce large metabolic effects at extrasynaptic sites suggesting they may be involved in tonic inhibition.
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Affiliation(s)
- Caroline Rae
- Neuroscience Research Australia, Barker St, Randwick, NSW, 2031, Australia,
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12
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Unsaturated Analogues of the Neurotransmitter GABA: trans-4-Aminocrotonic, cis-4-Aminocrotonic and 4-Aminotetrolic Acids. Neurochem Res 2015; 41:476-80. [DOI: 10.1007/s11064-015-1619-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2015] [Revised: 05/15/2015] [Accepted: 05/18/2015] [Indexed: 10/23/2022]
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13
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Eaton MM, Lim YB, Covey DF, Akk G. Modulation of the human ρ1 GABAA receptor by inhibitory steroids. Psychopharmacology (Berl) 2014; 231:3467-78. [PMID: 24317445 PMCID: PMC4048647 DOI: 10.1007/s00213-013-3379-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/16/2013] [Accepted: 11/25/2013] [Indexed: 11/28/2022]
Abstract
RATIONALE Modulators of the ρ1 GABAA receptor may be useful in the treatment of visual, sleep, and cognitive disorders. Neuroactive steroids and analogues have been shown to modulate ρ1 receptor function, but the molecular mechanisms are poorly understood. OBJECTIVES We employed electrophysiology and voltage-clamp fluorometry to compare the actions of several neuroactive steroids and analogues on the human ρ1 GABAA receptor. RESULTS Results confirmed that P294S and T298F mutations affect modulation by steroids. The P294S mutation abolished inhibition by (3α,5β)-3-hydroxypregnan-20-one (3α5βP) while the T298F mutation eliminated inhibition by 17β-estradiol. Voltage-clamp fluorometry demonstrated that steroids differing in the presence of a charged group on C3 or nature of substituent on C17 uniquely modified fluorescence changes elicited by GABA in the extracellular domain. The I307Q mutation reversed the inhibitory effect of 3α5βP but was without effect on modulation by (3α,5β)-3-hydroxypregnan-20-one sulfate or 17β-estradiol. The effect of 3α5βP on the fluorescence change generated at Y241C was dependent on whether the steroid acted as an inhibitor or a potentiator. Further, the effect was limited to uncharged 5β-reduced steroids containing an acetyl group on C17. CONCLUSIONS The data demonstrate that steroids and analogues differ with respect to conformational changes elicited by these drugs as well as sensitivity to the effects of mutations. Steroids and analogues could be provisionally divided into three major groups based on their actions on the ρ1 GABAA receptor: 5β-reduced uncharged steroids, sulfated and carboxylated steroids, and 17β-estradiol. Further division among 5β-reduced uncharged steroids was based on substituent at position C17.
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Affiliation(s)
- Megan M Eaton
- Department of Anesthesiology, Washington University School of Medicine, Campus Box 8054, 660 S. Euclid Ave, St. Louis, MO, 63110, USA
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14
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Kilb W, Kirischuk S, Luhmann HJ. Role of tonic GABAergic currents during pre- and early postnatal rodent development. Front Neural Circuits 2013; 7:139. [PMID: 24027498 PMCID: PMC3760143 DOI: 10.3389/fncir.2013.00139] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2013] [Accepted: 08/16/2013] [Indexed: 11/13/2022] Open
Abstract
In the last three decades it became evident that the GABAergic system plays an essential role for the development of the central nervous system, by influencing the proliferation of neuronal precursors, neuronal migration and differentiation, as well as by controlling early activity patterns and thus formation of neuronal networks. GABA controls neuronal development via depolarizing membrane responses upon activation of ionotropic GABA receptors. However, many of these effects occur before the onset of synaptic GABAergic activity and thus require the presence of extrasynaptic tonic currents in neuronal precursors and immature neurons. This review summarizes our current knowledge about the role of tonic GABAergic currents during early brain development. In this review we compare the temporal sequence of the expression and functional relevance of different GABA receptor subunits, GABA synthesizing enzymes and GABA transporters. We also refer to other possible endogenous agonists of GABAA receptors. In addition, we describe functional consequences mediated by the GABAergic system during early developmental periods and discuss current models about the origin of extrasynaptic GABA and/or other endogenous GABAergic agonists during early developmental states. Finally, we present evidence that tonic GABAergic activity is also critically involved in the generation of physiological as well as pathophysiological activity patterns before and after the establishment of functional GABAergic synaptic connections.
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Affiliation(s)
- Werner Kilb
- Institute of Physiology and Pathophysiology, University Medical Center, Johannes Gutenberg University Mainz, Germany
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15
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Rosas-Arellano A, Machuca-Parra AI, Reyes-Haro D, Miledi R, Martínez-Torres A. Expression of GABAρ receptors in the neostriatum: localization in aspiny, medium spiny neurons and GFAP-positive cells. J Neurochem 2012; 122:900-10. [PMID: 22168837 DOI: 10.1111/j.1471-4159.2011.07621.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
GABAergic transmission in the neostriatum plays a central role in motor coordination, in which a plethora of GABA-A receptor subunits combine to modulate neural inhibition. GABAρ receptors were originally described in the mammalian retina. These receptors possess special electrophysiological and pharmacological properties, forming a characteristic class of ionotropic receptors. In previous studies, we suggested that GABAρ receptors are expressed in the neostriatum, and in this report we show that they are indeed present in all the calretinin-positive interneurons of the neostriatum. In addition, they are located in calbindin-positive interneurons and projection neurons that express the dopamine D(2) receptor. GABAρ receptors were also located in 30% of the glial fibrillary acidic protein-positive cells, and may therefore also contribute to gliotransmission. Quantitative reverse transcription-PCR suggested that the mRNAs of this receptor do not express as much as in the retina, and that GABAρ2 is more abundant than GABAρ1. Electrophysiological recordings in brain slices provided evidence of neurons expressing a cis-4-aminocrotonic acid-activated, 1,2,5,6-tetrahydropyridine-4-yl methylphosphinic acid-sensitive ionotropic GABA receptor, indicating the presence of functional GABAρ receptors in the neostriatum. Finally, electron-microscopy and immunogold located the receptors mainly in perisynaptic as well as in extrasynaptic sites. All these observations reinforce the importance of GABAρ receptors in the neostriatum and contribute to the diversity of inhibitory regulation in this area.
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Affiliation(s)
- Abraham Rosas-Arellano
- Departamento de Neurobiología Celular y Molecular, Universidad Nacional Autónoma de México, Instituto de Neurobiología, Campus Juriquilla, Querétaro, Mexico
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16
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Avoli M, de Curtis M. GABAergic synchronization in the limbic system and its role in the generation of epileptiform activity. Prog Neurobiol 2011; 95:104-32. [PMID: 21802488 PMCID: PMC4878907 DOI: 10.1016/j.pneurobio.2011.07.003] [Citation(s) in RCA: 190] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2011] [Revised: 07/14/2011] [Accepted: 07/15/2011] [Indexed: 11/30/2022]
Abstract
GABA is the main inhibitory neurotransmitter in the adult forebrain, where it activates ionotropic type A and metabotropic type B receptors. Early studies have shown that GABA(A) receptor-mediated inhibition controls neuronal excitability and thus the occurrence of seizures. However, more complex, and at times unexpected, mechanisms of GABAergic signaling have been identified during epileptiform discharges over the last few years. Here, we will review experimental data that point at the paradoxical role played by GABA(A) receptor-mediated mechanisms in synchronizing neuronal networks, and in particular those of limbic structures such as the hippocampus, the entorhinal and perirhinal cortices, or the amygdala. After having summarized the fundamental characteristics of GABA(A) receptor-mediated mechanisms, we will analyze their role in the generation of network oscillations and their contribution to epileptiform synchronization. Whether and how GABA(A) receptors influence the interaction between limbic networks leading to ictogenesis will be also reviewed. Finally, we will consider the role of altered inhibition in the human epileptic brain along with the ability of GABA(A) receptor-mediated conductances to generate synchronous depolarizing events that may lead to ictogenesis in human epileptic disorders as well.
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Affiliation(s)
- Massimo Avoli
- Montreal Neurological Institute and Departments of Neurology & Neurosurgery, and of Physiology, McGill University, Montreal H3A 2B4 Quebec, Canada.
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17
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Martínez-Delgado G, Estrada-Mondragón A, Miledi R, Martínez-Torres A. An Update on GABAρ Receptors. Curr Neuropharmacol 2011; 8:422-33. [PMID: 21629448 PMCID: PMC3080597 DOI: 10.2174/157015910793358141] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2009] [Revised: 04/08/2010] [Accepted: 06/21/2010] [Indexed: 01/29/2023] Open
Abstract
The present review discusses the functional and molecular diversity of GABAρ receptors. These receptors were originally described in the mammalian retina, and their functional role in the visual pathway has been recently elucidated; however new studies on their distribution in the brain and spinal cord have revealed that they are more spread than originally thought, and thus it will be important to determine their physiological contribution to the GABAergic transmission in other areas of the central nervous system. In addition, molecular modeling has revealed peculiar traits of these receptors that have impacted on the interpretations of the latest pharmacolgical and biophysical findings. Finally, sequencing of several vertebrate genomes has permitted a comparative analysis of the organization of the GABAρ genes.
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Affiliation(s)
- Gustavo Martínez-Delgado
- Instituto de Neurbiología, Departamento de Neurobiología Celular y Molecular, Laboratorio D15, Campus UNAM Juriquilla. Querétaro 76230, México
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18
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Rosas-Arellano A, Parodi J, Machuca-Parra AI, Sánchez-Gutiérrez A, Inestrosa NC, Miledi R, Martínez-Torres A. The GABA(A)ρ receptors in hippocampal spontaneous activity and their distribution in hippocampus, amygdala and visual cortex. Neurosci Lett 2011; 500:20-5. [PMID: 21683123 DOI: 10.1016/j.neulet.2011.05.235] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2011] [Revised: 05/13/2011] [Accepted: 05/31/2011] [Indexed: 10/18/2022]
Abstract
A bicuculline-resistant and TPMPA-sensitive GABAergic component was identified in hippocampal neurons in culture and in acute isolated brain slices. In both preparations, total GABAergic activity showed two inactivation kinetics: fast and slow. RT-PCR, in situ hybridization (ISH) and immunohistochemistry detected expression of GABAρ subunits. Immunogold and electron microscopy indicated that the receptors are mostly extrasynaptic. In addition, by RT-PCR and immunofluorescence we found GABAρ present in amygdala and visual cortex.
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Affiliation(s)
- Abraham Rosas-Arellano
- Departamento de Neurobiología Celular y Molecular, Laboratorio de Neurobiología Molecular y Celular, Instituto de Neurobiología, Campus UNAM-Juriquilla, Querétaro, QRO 76230, Mexico
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19
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Abstract
The inhibitory neurotransmitter, GABA, is a low-molecular-weight molecule that can achieve many low-energy conformations, which are recognized by GABA receptors and transporters. In this article, we assess the structure–activity relationship profiles of GABA analogs at the ionotropic ρ GABAC receptor. Such studies have significantly contributed to the design and development of potent and selective agonists and antagonists for this subclass of GABA receptors. With these tools in hand, the role of ρ GABAC receptors is slowly being realized. Of particular interest is the development of selective phosphinic acid analogs of GABA and their potential use in sleep disorders, inhibiting the development of myopia, and in improving learning and memory.
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20
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Johnston GAR, Chebib M, Hanrahan JR, Mewett KN. Neurochemicals for the investigation of GABA(C) receptors. Neurochem Res 2010; 35:1970-7. [PMID: 20963487 DOI: 10.1007/s11064-010-0271-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/13/2010] [Indexed: 01/23/2023]
Abstract
GABA(C) receptors are being investigated for their role in many aspects of nervous system function including memory, myopia, pain and sleep. There is evidence for functional GABA(C) receptors in many tissues such as retina, hippocampus, spinal cord, superior colliculus, pituitary and the gut. This review describes a variety of neurochemicals that have been shown to be useful in distinguishing GABA(C) receptors from other receptors for the major inhibitory neurotransmitter GABA. Some selective agonists (including (+)-CAMP and 5-methyl-IAA), competitive antagonists (such as TPMPA, (±)-cis-3-ACPBPA and aza-THIP), positive (allopregnanolone) and negative modulators (epipregnanolone, loreclezole) are described. Neurochemicals that may assist in distinguishing between homomeric ρ1 and ρ2 GABA(C) receptors (2-methyl-TACA and cyclothiazide) are also covered. Given their less widespread distribution, lower abundance and relative structural simplicity compared to GABA(A) and GABA(B) receptors, GABA(C) receptors are attractive drug targets.
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Affiliation(s)
- Graham A R Johnston
- Adrien Albert Laboratory of Medicinal Chemistry, Department of Pharmacology D06, The University of Sydney, Sydney, NSW 2006, Australia.
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21
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Abstract
The activity of many receptors and ion channels in the nervous system can be regulated by redox-dependent mechanisms. Native and recombinant GABA(A) receptors are modulated by endogenous and pharmacological redox agents. However, the sensitivity of GABA(C) receptors to redox modulation has not been demonstrated. We studied the actions of different reducing and oxidizing agents on human homomeric GABArho(1) receptors expressed in Xenopus laevis oocytes. The reducing agents dithiothreitol (2 mM) and N-acetyl-L-cysteine (1 mM) potentiated GABA-evoked Cl(-) currents recorded by two-electrode voltage-clamp, while the oxidants 5-5'-dithiobis-2-nitrobenzoic acid (500 microM) and oxidized dithiothreitol (2 mM) caused inhibition. The endogenous antioxidant glutathione (5 mM) also enhanced GABArho(1) receptor-mediated currents while its oxidized form GSSG (3 mM) had inhibitory effects. All the effects were rapid and easily reversible. Redox modulation of GABArho(1) receptors was strongly dependent on the GABA concentration; dose-response curves for GABA were shifted to the left in the presence of reducing agents, whereas oxidizing agents produced the opposite effect, without changes in the maximal response to GABA and in the Hill coefficient. Our results demonstrate that, similarly to GABA(A) receptors and other members of the cys-loop receptor superfamily, GABA(C) receptors are subjected to redox modulation.
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Affiliation(s)
- Cecilia I Calero
- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Facultad de Ciencias Exactas y Naturales Universidad de Buenos Aires (UBA), Ciudad Autónoma de Buenos Aires, Argentina
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22
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Xu JY, Yang B, Sastry BR. The involvement of GABA-C receptors in paired-pulse depression of inhibitory postsynaptic currents in rat hippocampal CA1 pyramidal neurons. Exp Neurol 2008; 216:243-6. [PMID: 19100735 DOI: 10.1016/j.expneurol.2008.11.013] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2008] [Revised: 11/04/2008] [Accepted: 11/19/2008] [Indexed: 11/25/2022]
Abstract
In rat hippocampal CA1 pyramidal neurons, gamma-aminobutyric acid (GABA) A receptor-mediated inhibitory postsynaptic currents (IPSCs) undergo a paired-pulse depression (PPD) by the second of two pulses, with inter-pulse intervals of 100-2000 ms, applied to the stratum radiatum. While GABA-C receptors are described in the CA1 area, their functional significance is unknown. In this study, the involvement of GABA-C receptors in PPD was examined using an in vitro hippocampal slice preparation. IPSCs evoked by stimulations in stratum radiatum were recorded with patch pipettes from CA1 pyramidal cells. PPD, when induced in the above fashion, was blocked by the GABA-C receptor antagonist (1,2,5,6-Tetrahydropyridin-4-yl) methylphosphinic acid (TPMPA, 10 muM, applied in the superfusing medium). GABA-A and GABA-B receptor-mediated IPSCs, as well as the baclofen-induced suppression of the GABA-A receptor mediated IPSC, were not antagonized by TPMPA (10-20 muM). These results indicate that PPD of the IPSC is mediated by the activation of GABA-C receptors.
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Affiliation(s)
- J-Y Xu
- Neuroscience Research Laboratory, Department of Anesthesiology, Pharmacology and Therapeutics, Faculty of Medicine, The University of British Columbia, Vancouver, BC, Canada
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23
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Chebib M, Hinton T, Schmid KL, Brinkworth D, Qian H, Matos S, Kim HL, Abdel-Halim H, Kumar RJ, Johnston GAR, Hanrahan JR. Novel, potent, and selective GABAC antagonists inhibit myopia development and facilitate learning and memory. J Pharmacol Exp Ther 2008; 328:448-57. [PMID: 18984654 DOI: 10.1124/jpet.108.146464] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
This study reports pharmacological and physiological effects of cis- and trans-(3-aminocyclopentanyl)butylphosphinic acid (cis- and trans-3-ACPBPA). These compounds are conformationally restricted analogs of the orally active GABA(B/C) receptor antagonist (3-aminopropyl)-n-butylphosphinic acid (CGP36742 or SGS742). cis-[IC(50)(rho1) = 5.06 microM and IC(50)(rho2) = 11.08 microM; n = 4] and trans-3-ACPMPA [IC(50)(rho1) = 72.58 microM and IC(50)(rho2) = 189.7 microM; n = 4] seem competitive at GABA(C) receptors expressed in Xenopus laevis oocytes, having no effect as agonists (1 mM) but exerting weak antagonist (1 mM) effects on human GABA(A) and GABA(B) receptors. cis-3-ACPBPA was more potent and selective than the trans-compound, being more than 100 times more potent at GABA(C) than GABA(A) or GABA(B) receptors. cis-3-ACPBPA was further evaluated on dissociated rat retinal bipolar cells and dose-dependently inhibited the native GABA(C) receptor (IC(50) = 47 +/- 4.5 microM; n = 6). When applied to the eye as intravitreal injections, cis- and trans-3-ACPBPA prevented experimental myopia development and inhibited the associated vitreous chamber elongation, in a dose-dependent manner in the chick model. Doses only 10 times greater than required to inhibit recombinant GABA(C) receptors caused the antimyopia effects. Using intraperitoneal administration, cis- (30 mg/kg) and trans-3-ACPBPA (100 mg/kg) enhanced learning and memory in male Wistar rats; compared with vehicle there was a significant reduction in time for rats to find the platform in the Morris water maze task (p < 0.05; n = 10). As the physiological effects of cis- and trans-3-ACPBPA are similar to those reported for CGP36742, the memory and refractive effects of CGP36742 may be due in part to its GABA(C) activity.
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Affiliation(s)
- Mary Chebib
- Faculty of Pharmacy A15, The University of Sydney, Sydney, NSW 2006, Australia.
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24
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Inhibitory interaction between P2X4 and GABA(C) rho1 receptors. Biochem Biophys Res Commun 2008; 375:38-43. [PMID: 18675255 DOI: 10.1016/j.bbrc.2008.07.096] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2008] [Accepted: 07/18/2008] [Indexed: 01/16/2023]
Abstract
Reciprocal functional inhibition between P2X and GABA(A/C) receptors represents a novel mechanism fine-tuning neuronal excitability. However, the participating receptors and underlying mechanisms are not fully understood. P2X(4) receptor is widely found in neurons that express GABA(C) rho1 receptor. Thus, we co-expressed P2X(4) and rho1 receptors in HEK293 cells and, using patch-clamp recording, examined whether they have mutual functional inhibition. Currents evoked by simultaneous application of ATP and GABA (I(ATP+GABA)) were significantly smaller compared to the addition of I(ATP) and I(GABA). Furthermore, I(ATP) were strongly suppressed during rho1 receptor activation. Similarly, I(GABA) were greatly attenuated during P2X(4) receptor activation. Such mutual inhibition was absent in cells only expressing P2X(4) or rho1 receptor. Taken together, these functional data support negative cross-talk between P2X(4) and rho1 receptors.
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25
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Li W, Jin X, Covey DF, Steinbach JH. Neuroactive steroids and human recombinant rho1 GABAC receptors. J Pharmacol Exp Ther 2007; 323:236-47. [PMID: 17636008 DOI: 10.1124/jpet.107.127365] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The gamma-aminobutyric acid type C (GABAC) receptor is structurally related to the GABAA receptors, yet quite distinct physiologically and pharmacologically. Neuroactive steroids are known to be potent and efficacious modulators of the GABAA receptor, but they are less well characterized in their actions on the GABAC receptor. We have examined the actions of neuroactive steroids and analogs on rho1 (GABAC) receptors expressed in Xenopus laevis oocytes, with two goals in mind. First, we tested a larger number of endogenous steroids, to determine whether particularly potent steroids could be found. Second, we examined the structure-activity relationship for steroid actions, and some mechanistic features, to determine the possible numbers of steroid binding sites and mechanisms of action. In total, 41 compounds were examined. Estradiols are inhibitors, essentially equipotent with picrotoxinin. No endogenous steroid tested was highly efficacious at potentiation. The results of the structure-activity studies and the effects of two mutations to the second transmembrane region of the rho1 GABAC receptor indicate that there are several mechanisms by which steroids can inhibit the receptor. Surprisingly, estradiol shares some features with picrotoxin. Inhibition by negatively charged compounds was not sensitive to membrane potential, and inhibition by all compounds tested was reduced at higher concentrations of GABA. The data indicate that the binding sites mediating potentiation and inhibition differ from each other and that there are several (three or more) mechanisms for producing inhibition.
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Affiliation(s)
- Wenjun Li
- Department of Anesthesiology, Washington University School of Medicine, 660 S. Euclid Ave., St. Louis, MO, USA
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26
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Chebib M, Hanrahan JR, Kumar RJ, Mewett KN, Morriss G, Wooller S, Johnston GAR. (3-Aminocyclopentyl)methylphosphinic acids: Novel GABAC receptor antagonists. Neuropharmacology 2007; 52:779-87. [PMID: 17098260 DOI: 10.1016/j.neuropharm.2006.09.014] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2006] [Revised: 08/28/2006] [Accepted: 09/25/2006] [Indexed: 12/30/2022]
Abstract
Our understanding of the role GABA(C) receptors play in the central nervous system is limited due to a lack of specific ligands. Here we describe the pharmacological effects of (+/-)-cis-3- and (+/-)-trans-3-(aminocyclopentyl)methylphosphinic acids ((+/-)-cis- and (+/-)-trans-3-ACPMPA) as novel ligands for the GABA(C) receptor showing little activity at GABA(A) or GABA(B) receptors. (+/-)-cis-3-ACPMPA has similar potency to (1,2,5,6-tetrahydropyridin-4-yl)methylphosphinic acid (TPMPA) at human recombinant rho1 (K(B)=1.0+/-0.2microM) and rat rho3 (K(B)=5.4+/-0.8microM) but is 15 times more potent than TPMPA on human recombinant rho2 (K(B)=1.0+/-0.3microM) GABA(C) receptors expressed in Xenopus oocytes. (+/-)-cis- and (+/-)-trans-3-ACPMPA are novel lead compounds for developing into more potent and selective GABA(C) receptor antagonists with increased lipophilicity for in vivo studies.
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Affiliation(s)
- Mary Chebib
- Faculty of Pharmacy, Pharmacy Building A15, The University of Sydney, NSW 2006, Australia.
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Rosas-Arellano A, Ochoa-de la Paz LD, Miledi R, Martínez-Torres A. Brain distribution and molecular cloning of the bovine GABA rho1 receptor. Neurosci Res 2007; 57:347-53. [PMID: 17188384 DOI: 10.1016/j.neures.2006.11.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2006] [Revised: 10/06/2006] [Accepted: 11/06/2006] [Indexed: 10/23/2022]
Abstract
GABA(C) receptors were originally found in the mammalian retina and recent evidence shows that they are also expressed in several areas of the brain, including caudate nucleus, brain stem, pons and corpus callosum. In this study, plasma membranes from the caudate nucleus were microinjected into X. laevis oocytes. This led the oocyte plasma membrane to incorporate functional bicuculline-resistant, Cl(-) conducting bovine GABA receptors, similar to those of the retina. Immunolocalization of the GABA rho1 subunit revealed its expression in bovine neurons in the head of the caudate as well as in the olive, cuneiform and reticular nuclei of the brain stem. The same antibodies failed to show expression in the callosum and pons, where the GABA rho1 mRNA was previously detected. The cloned GABA rho1 sequence predicts a protein with 473 amino acids and 74-93% similarity to other GABA rho1 subunits. Oocytes injected with the cDNA express a non-desensitizing, homomeric receptor with a GABA EC(50)=6.0 microM and a Hill coefficient of 1.8. The results confirm the presence of GABA(C) receptor mRNAs in several areas of the mammalian brain and show that some of these areas express functional GABA rho1 receptors that have the classic GABA(C) receptor characteristics.
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Affiliation(s)
- Abraham Rosas-Arellano
- Instituto de Neurobiología, Laboratorio de Neurobiología Molecular y Celular II, Universidad Nacional Autónoma de México, Km 15.5 Carretera a San Luis Potosí 76001 Juriquilla, Querétaro, México
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