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Gonda X, Tarazi FI, Dome P. The emergence of antidepressant drugs targeting GABA A receptors: A concise review. Biochem Pharmacol 2024:116481. [PMID: 39147329 DOI: 10.1016/j.bcp.2024.116481] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2024] [Revised: 08/06/2024] [Accepted: 08/09/2024] [Indexed: 08/17/2024]
Abstract
Depression is among the most common psychiatric illnesses, which imposes a major socioeconomic burden on patients, caregivers, and the public health system. Treatment with classical antidepressants (e.g. tricyclic antidepressants and selective serotonine reuptake inhibitors), which primarily affect monoaminergic systems has several limitations, such as delayed onset of action and moderate efficacy in a relatively large proportion of depressed patients. Furthermore, depression is highly heterogeneus, and its different subtypes, including post-partum depression, involve distinct neurobiology, warranting a differential approach to pharmacotherapy. Given these shortcomings, the need for novel antidepressants that are superior in efficacy and faster in onset of action is fully justified. The development and market introduction of rapid-acting antidepressants has accelerated in recent years. Some of these new antidepressants act through the GABAergic system. In this review, we discuss the discovery, efficacy, and limitations of treatment with classic antidepressants. We provide a detailed discussion of GABAergic neurotransmission, with a special focus on GABAA receptors, and possible explanations for the mood-enhancing effects of GABAergic medications (in particular neurosteroids acting at GABAA receptors), and, ultimately, we present the most promising molecules belonging to this family which are currently used in clinical practice or are in late phases of clinical development.
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Affiliation(s)
- Xenia Gonda
- Department of Psychiatry and Psychotherapy, Semmelweis University, Budapest, Hungary; NAP3.0-SE Neuropsychopharmacology Research Group, Hungarian Brain Research Program, Semmelweis University, Budapest, Hungary.
| | - Frank I Tarazi
- Department of Psychiatry and Neurology, Harvard Medical School and McLean Hospital, Boston, MA, USA
| | - Peter Dome
- Department of Psychiatry and Psychotherapy, Semmelweis University, Budapest, Hungary; Nyiro Gyula National Institute of Psychiatry and Addictology, Budapest, Hungary
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2
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Smith SS, Benanni S, Jones Q, Kenney L, Evrard MR. Manipulation of α4βδ GABA A receptors alters synaptic pruning in layer 3 prelimbic prefrontal cortex and impairs temporal order recognition: Implications for schizophrenia and autism. Brain Res 2024; 1835:148929. [PMID: 38599510 DOI: 10.1016/j.brainres.2024.148929] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2024] [Revised: 04/04/2024] [Accepted: 04/06/2024] [Indexed: 04/12/2024]
Abstract
Temporal order memory is impaired in autism spectrum disorder (ASD) and schizophrenia (SCZ). These disorders, more prevalent in males, result in abnormal dendritic spine pruning during adolescence in layer 3 (L3) medial prefrontal cortex (mPFC), yielding either too many (ASD) or too few (SCZ) spines. Here we tested whether altering spine density in neural circuits including the mPFC could be associated with impaired temporal order memory in male mice. We have shown that α4βδ GABAA receptors (GABARs) emerge at puberty on spines of L5 prelimbic mPFC (PL) where they trigger pruning. We show here that α4βδ receptors also increase at puberty in L3 PL (P < 0.0001) and used these receptors as a target to manipulate spine density here. Pubertal injection (14 d) of the GABA agonist gaboxadol, at a dose (3 mg/kg) selective for α4βδ, reduced L3 spine density by half (P < 0.0001), while α4 knock-out increased spine density ∼ 40 % (P < 0.0001), mimicking spine densities in SCZ and ASD, respectively. In both cases, performance on the mPFC-dependent temporal order recognition task was impaired, resulting in decreases in the discrimination ratio which assesses preference for the novel object: -0.39 ± 0.15, gaboxadol versus 0.52 ± 0.09, vehicle; P = 0.0002; -0.048 ± 0.10, α4 KO versus 0.49 ± 0.04, wild-type; P < 0.0001. In contrast, the number of approaches was unaltered, reflecting unchanged locomotion. These data suggest that altering α4βδ GABAR expression/activity alters spine density in L3 mPFC and impairs temporal order memory to mimic changes in ASD and SCZ. These findings may provide insight into these disorders.
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Affiliation(s)
- Sheryl S Smith
- Department of Physiology and Pharmacology, SUNY Downstate Medical Center, 450 Clarkson Ave., Brooklyn, NY 11203, USA.
| | - Safae Benanni
- Department of Physiology and Pharmacology, SUNY Downstate Medical Center, 450 Clarkson Ave., Brooklyn, NY 11203, USA.
| | - Quiana Jones
- Department of Physiology and Pharmacology, SUNY Downstate Medical Center, 450 Clarkson Ave., Brooklyn, NY 11203, USA.
| | - Lindsay Kenney
- Department of Physiology and Pharmacology, SUNY Downstate Medical Center, 450 Clarkson Ave., Brooklyn, NY 11203, USA.
| | - Matthew R Evrard
- Department of Physiology and Pharmacology, SUNY Downstate Medical Center, 450 Clarkson Ave., Brooklyn, NY 11203, USA.
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3
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Meera P, Uusi-Oukari M, Wallner M, Lipshutz GS. Guanidinoacetate (GAA) is a potent GABA A receptor GABA mimetic: Implications for neurological disease pathology. J Neurochem 2023; 165:445-454. [PMID: 36726215 DOI: 10.1111/jnc.15774] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2022] [Revised: 01/24/2023] [Accepted: 01/28/2023] [Indexed: 02/03/2023]
Abstract
Impairment of excretion and enzymatic processing of nitrogen, for example, because of liver or kidney failure, or with urea cycle and creatine synthesis enzyme defects, surprisingly leads to primarily neurologic symptoms, yet the exact mechanisms remain largely mysterious. In guanidinoacetate N-methyltransferase (GAMT) deficiency, the guanidino compound guanidinoacetate (GAA) increases dramatically, including in the cerebrospinal fluid (CSF), and has been implicated in mediating the neurological symptoms in GAMT-deficient patients. GAA is synthesized by arginine-glycine amidinotransferase (AGAT), a promiscuous enzyme that not only transfers the amidino group from arginine to glycine, but also to primary amines in, for example, GABA and taurine to generate γ-guanidinobutyric acid (γ-GBA) and guanidinoethanesulfonic acid (GES), respectively. We show that GAA, γ-GBA, and GES share structural similarities with GABA, evoke GABAA receptor (GABAA R) mediated currents (whereas creatine [methylated GAA] and arginine failed to evoke discernible currents) in cerebellar granule cells in mouse brain slices and displace the high-affinity GABA-site radioligand [3 H]muscimol in total brain homogenate GABAA Rs. While γ-GBA and GES are GABA agonists and displace [3 H]muscimol (EC50 /IC50 between 10 and 40 μM), GAA stands out as particularly potent in both activating GABAA Rs (EC50 ~6 μM) and also displacing the GABAA R ligand [3 H]muscimol (IC50 ~3 μM) at pathophysiologically relevant concentrations. These findings stress the role of substantially elevated GAA as a primary neurotoxic agent in GAMT deficiency and we discuss the potential role of GAA in arginase (and creatine transporter) deficiency which show a much more modest increase in GAA concentrations yet share the unique hyperexcitability neuropathology with GAMT deficiency. We conclude that orthosteric activation of GABAA Rs by GAA, and potentially other GABAA R mimetic guanidino compounds (GCs) like γ-GBA and GES, interferes with normal inhibitory GABAergic neurotransmission which could mediate, and contribute to, neurotoxicity.
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Affiliation(s)
- Pratap Meera
- Department of Neurobiology, University of California, Los Angeles, California, USA
| | - Mikko Uusi-Oukari
- Integrative Physiology and Pharmacology, Institute of Biomedicine, University of Turku, Turku, Finland
| | - Martin Wallner
- Departments of Surgery, University of California, Los Angeles, California, USA
| | - Gerald S Lipshutz
- Departments of Surgery, University of California, Los Angeles, California, USA.,Molecular & Medical Pharmacology, University of California, Los Angeles, California, USA.,Intellectual and Developmental Disabilities Research Center, University of California, Los Angeles, California, USA.,Semel Institute for Neuroscience, University of California, Los Angeles, California, USA
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4
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Wollman LB, Flanigan EG, Fregosi RF. Chronic, episodic nicotine exposure alters GABAergic synaptic transmission to hypoglossal motor neurons and genioglossus muscle function at a critical developmental age. J Neurophysiol 2022; 128:1483-1500. [PMID: 36350047 PMCID: PMC9722256 DOI: 10.1152/jn.00397.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Revised: 11/02/2022] [Accepted: 11/03/2022] [Indexed: 11/11/2022] Open
Abstract
Regulation of GABAergic signaling through nicotinic acetylcholine receptor (nAChR) activation is critical for neuronal development. Here, we test the hypothesis that chronic episodic developmental nicotine exposure (eDNE) disrupts GABAergic signaling, leading to dysfunction of hypoglossal motor neurons (XIIMNs), which innervate the tongue muscles. We studied control and eDNE pups at two developmentally vulnerable age ranges: postnatal days (P)1-5 and P10-12. The amplitude and frequency of spontaneous and miniature inhibitory postsynaptic currents (sIPSCs, mIPSCs) at baseline were not altered by eDNE at either age. In contrast, eDNE increased GABAAR-α1 receptor expression on XIIMNs and, in the older group, the postsynaptic response to muscimol (GABAA receptor agonist). Activation of nAChRs with exogenous nicotine increased the frequency of GABAergic sIPSCs in control and eDNE neurons at P1-5. By P10-12, acute nicotine increased sIPSC frequency in eDNE but not control neurons. In vivo experiments showed that the breathing-related activation of tongue muscles, which are innervated by XIIMNs, is reduced at P10-12. This effect was partially mitigated by subcutaneous muscimol, but only in the eDNE pups. Taken together, these data indicate that eDNE alters GABAergic transmission to XIIMNs at a critical developmental age, and this is expressed as reduced breathing-related drive to XIIMNs in vivo.NEW & NOTEWORTHY Here, we provide a thorough assessment of the effects of nicotine exposure on GABAergic synaptic transmission, from the cellular to the systems level. This work makes significant advances in our understanding of the impact of nicotine exposure during development on GABAergic neurotransmission within the respiratory network and the potential role this plays in the excitatory/inhibitory imbalance that is thought to be an important mechanism underlying neonatal breathing disorders, including sudden infant death syndrome.
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Affiliation(s)
- Lila Buls Wollman
- Department of Physiology, The University of Arizona, Tucson, Arizona
| | | | - Ralph F Fregosi
- Department of Physiology, The University of Arizona, Tucson, Arizona
- Department of Neuroscience, The University of Arizona, Tucson, Arizona
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Acute mushroom poisoning of Amanita pseudosychnopyramis: A case report from Fujian, China with exact species identification and descriptive study. Toxicon 2022; 212:55-61. [DOI: 10.1016/j.toxicon.2022.04.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2022] [Revised: 04/02/2022] [Accepted: 04/02/2022] [Indexed: 11/24/2022]
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6
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Sikstus S, Benkherouf AY, Soini SL, Uusi-Oukari M. The Influence of AA29504 on GABA A Receptor Ligand Binding Properties and Its Implications on Subtype Selectivity. Neurochem Res 2022; 47:667-678. [PMID: 34727270 PMCID: PMC8847198 DOI: 10.1007/s11064-021-03475-y] [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: 06/04/2021] [Revised: 09/03/2021] [Accepted: 10/27/2021] [Indexed: 10/26/2022]
Abstract
The unique pharmacological properties of δ-containing γ-aminobutyric acid type A receptors (δ-GABAARs) make them an attractive target for selective and persistent modulation of neuronal excitability. However, the availability of selective modulators targeting δ-GABAARs remains limited. AA29504 ([2-amino-4-(2,4,6-trimethylbenzylamino)-phenyl]-carbamic acid ethyl ester), an analog of K+ channel opener retigabine, acts as an agonist and a positive allosteric modulator (Ago-PAM) of δ-GABAARs. Based on electrophysiological studies using recombinant receptors, AA29504 was found to be a more potent and effective agonist in δ-GABAARs than in γ2-GABAARs. In comparison, AA29504 positively modulated the activity of recombinant δ-GABAARs more effectively than γ2-GABAARs, with no significant differences in potency. The impact of AA29504's efficacy- and potency-associated GABAAR subtype selectivity on radioligand binding properties remain unexplored. Using [3H]4'-ethynyl-4-n-propylbicycloorthobenzoate ([3H]EBOB) binding assay, we found no difference in the modulatory potency of AA29504 on GABA- and THIP (4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol)-induced responses between native forebrain GABAARs of wild type and δ knock-out mice. In recombinant receptors expressed in HEK293 cells, AA29504 showed higher efficacy on δ- than γ2-GABAARs in the GABA-independent displacement of [3H]EBOB binding. Interestingly, AA29504 showed a concentration-dependent stimulation of [3H]muscimol binding to γ2-GABAARs, which was absent in δ-GABAARs. This was explained by AA29504 shifting the low-affinity γ2-GABAAR towards a higher affinity desensitized state, thereby rising new sites capable of binding GABAAR agonists with low nanomolar affinity. Hence, the potential of AA29504 to act as a desensitization-modifying allosteric modulator of γ2-GABAARs deserves further investigation for its promising influence on shaping efficacy, duration and plasticity of GABAAR synaptic responses.
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Affiliation(s)
- Sylvia Sikstus
- Integrative Physiology and Pharmacology, Institute of Biomedicine, University of Turku, Kiinamyllynkatu 10, 20014, Turku, Finland
| | - Ali Y Benkherouf
- Integrative Physiology and Pharmacology, Institute of Biomedicine, University of Turku, Kiinamyllynkatu 10, 20014, Turku, Finland
| | - Sanna L Soini
- Integrative Physiology and Pharmacology, Institute of Biomedicine, University of Turku, Kiinamyllynkatu 10, 20014, Turku, Finland
| | - Mikko Uusi-Oukari
- Integrative Physiology and Pharmacology, Institute of Biomedicine, University of Turku, Kiinamyllynkatu 10, 20014, Turku, Finland.
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Yorgason JT, Wadsworth HA, Anderson EJ, Williams BM, Brundage JN, Hedges DM, Stockard AL, Jones ST, Arthur SB, Hansen DM, Schilaty ND, Jang EY, Lee AM, Wallner M, Steffensen SC. Modulation of dopamine release by ethanol is mediated by atypical GABA A receptors on cholinergic interneurons in the nucleus accumbens. Addict Biol 2022; 27:e13108. [PMID: 34713509 DOI: 10.1111/adb.13108] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Revised: 08/31/2021] [Accepted: 09/24/2021] [Indexed: 12/18/2022]
Abstract
Previous studies indicate that moderate-to-high ethanol (EtOH) concentrations enhance dopamine (DA) neurotransmission in the mesolimbic DA system from the ventral tegmental area (VTA) and projecting to the nucleus accumbens core (NAc). However, voltammetry studies demonstrate that moderate-to-high EtOH concentrations decrease evoked DA release at NAc terminals. The involvement of γ-aminobutyric acid (GABA) receptors (GABAA Rs), glycine (GLY) receptors (GLYRs) and cholinergic interneurons (CINs) in mediating EtOH inhibition of evoked NAc DA release were examined. Fast scan cyclic voltammetry, electrophysiology, optogenetics and immunohistochemistry techniques were used to evaluate the effects of acute and chronic EtOH exposure on DA release and CIN activity in C57/BL6, CD-1, transgenic mice and δ-subunit knockout (KO) mice (δ-/-). Ethanol decreased DA release in mice with an IC50 of 80 mM ex vivo and 2.0 g/kg in vivo. GABA and GLY decreased evoked DA release at 1-10 mM. Typical GABAA R agonists inhibited DA release at high concentrations. Typical GABAA R antagonists had minimal effects on EtOH inhibition of evoked DA release. However, EtOH inhibition of DA release was blocked by the α4 β3 δ GABAA R antagonist Ro15-4513, the GLYR antagonist strychnine and by the GABA ρ1 (Rho-1) antagonist TPMPA (10 μM) and reduced significantly in GABAA R δ-/- mice. Rho-1 expression was observed in CINs. Ethanol inhibited GABAergic synaptic input to CINs from the VTA and enhanced firing rate, both of which were blocked by TPMPA. Results herein suggest that EtOH inhibition of DA release in the NAc is modulated by GLYRs and atypical GABAA Rs on CINs containing δ- and Rho-subunits.
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Affiliation(s)
- Jordan T Yorgason
- Department of Cellular Biology and Physiology, Brigham Young University, Provo, Utah, USA
| | - Hillary A Wadsworth
- Department of Psychology and Center for Neuroscience, Brigham Young University, Provo, Utah, USA
| | - Elizabeth J Anderson
- Department of Psychology and Center for Neuroscience, Brigham Young University, Provo, Utah, USA
| | - Benjamin M Williams
- Department of Psychology and Center for Neuroscience, Brigham Young University, Provo, Utah, USA
| | - James N Brundage
- Department of Psychology and Center for Neuroscience, Brigham Young University, Provo, Utah, USA
| | - David M Hedges
- Enterprise Information Management, Billings Clinic, Billings, Montana, USA
| | - Alyssa L Stockard
- Department of Psychology and Center for Neuroscience, Brigham Young University, Provo, Utah, USA
| | - Stephen T Jones
- Department of Psychology and Center for Neuroscience, Brigham Young University, Provo, Utah, USA
| | - Summer B Arthur
- Department of Psychology and Center for Neuroscience, Brigham Young University, Provo, Utah, USA
| | - David Micah Hansen
- Department of Psychology and Center for Neuroscience, Brigham Young University, Provo, Utah, USA
| | - Nathan D Schilaty
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, United States
| | - Eun Young Jang
- Research Center for Convergence Toxicology, Korea Institute of Toxicology, Daejeon, South Korea
| | - Anna M Lee
- Department of Pharmacology, University of Minnesota, Minneapolis, Minnesota, USA
| | - Martin Wallner
- Department of Molecular and Medical Pharmacology, University of California Los Angeles, Los Angeles, California, USA
| | - Scott C Steffensen
- Department of Psychology and Center for Neuroscience, Brigham Young University, Provo, Utah, USA
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Soualah Z, Taly A, Crespin L, Saulais O, Henrion D, Legendre C, Tricoire-Leignel H, Legros C, Mattei C. GABA A Receptor Subunit Composition Drives Its Sensitivity to the Insecticide Fipronil. Front Neurosci 2021; 15:768466. [PMID: 34912189 PMCID: PMC8668240 DOI: 10.3389/fnins.2021.768466] [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: 08/31/2021] [Accepted: 10/19/2021] [Indexed: 11/13/2022] Open
Abstract
Fipronil (FPN) is a worldwide-used neurotoxic insecticide, targeting, and blocking GABAA receptors (GABAARs). Beyond its efficiency on insect GABAARs, FPN causes neurotoxic effects in humans and mammals. Here, we investigated the mode of action of FPN on mammalian α6-containing GABAARs to understand its inhibitory effects on GABA-induced currents, as a function of the synaptic or extrasynaptic localization of GABAARs. We characterized the effects of FPN by electrophysiology using Xenopus oocytes which were microtransplanted with cerebellum membranes or injected with α6β3, α6β3γ2S (synaptic), and α6β3δ (extrasynaptic) cDNAs. At micromolar concentrations, FPN dose-dependently inhibited cerebellar GABA currents. FPN acts as a non-competitive antagonist on ternary receptors. Surprisingly, the inhibition of GABA-induced currents was partial for extra-synaptic (α6β3δ) and binary (α6β3) receptors, while synaptic α6β3γ2S receptors were fully blocked, indicating that the complementary γ or δ subunit participates in FPN-GABAAR interaction. FPN unexpectedly behaved as a positive modulator on β3 homopentamers. These data show that FPN action is driven by the subunit composition of GABAARs-highlighting the role of the complementary subunit-and thus their localization within a physiological synapse. We built a docking model of FPN on GABAARs, which reveals two putative binding sites. This is consistent with a double binding mode of FPN on GABAARs, possibly one being of high affinity and the other of low affinity. Physiologically, the γ/δ subunit incorporation drives its inhibitory level and has important significance for its toxicity on the mammalian nervous system, especially in acute exposure.
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Affiliation(s)
- Zineb Soualah
- Univ Angers, INSERM, CNRS, MITOVASC, Equipe CarMe, SFR ICAT, Angers, France
| | - Antoine Taly
- Laboratoire de Biochimie Théorique, CNRS, Université de Paris, UPR 9080, Paris, France.,Institut de Biologie Physico-Chimique, Fondation Edmond de Rothschild, PSL Research University, Paris, France
| | - Lucille Crespin
- Univ Angers, INSERM, CNRS, MITOVASC, Equipe CarMe, SFR ICAT, Angers, France
| | - Ophélie Saulais
- Univ Angers, INSERM, CNRS, MITOVASC, Equipe CarMe, SFR ICAT, Angers, France
| | - Daniel Henrion
- Univ Angers, INSERM, CNRS, MITOVASC, Equipe CarMe, SFR ICAT, Angers, France
| | - Claire Legendre
- Univ Angers, INSERM, CNRS, MITOVASC, Equipe CarMe, SFR ICAT, Angers, France
| | | | - Christian Legros
- Univ Angers, INSERM, CNRS, MITOVASC, Equipe CarMe, SFR ICAT, Angers, France
| | - César Mattei
- Univ Angers, INSERM, CNRS, MITOVASC, Equipe CarMe, SFR ICAT, Angers, France
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Muscimol Directly Activates the TREK-2 Channel Expressed in GABAergic Neurons through Its N-Terminus. Int J Mol Sci 2021; 22:ijms22179320. [PMID: 34502229 PMCID: PMC8431218 DOI: 10.3390/ijms22179320] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Revised: 08/25/2021] [Accepted: 08/25/2021] [Indexed: 11/23/2022] Open
Abstract
The two-pore domain K+ (K2P) channel, which is involved in setting the resting membrane potential in neurons, is an essential target for receptor agonists. Activation of the γ-aminobutyric acid (GABA) receptors (GABAAR and GABABR) reduces cellular excitability through Cl- influx and K+ efflux in neurons. Relatively little is known about the link between GABAAR and the K+ channel. The present study was performed to identify the effect of GABAR agonists on K2P channel expression and activity in the neuroblastic B35 cells that maintain glutamic acid decarboxylase (GAD) activity and express GABA. TASK and TREK/TRAAK mRNA were expressed in B35 cells with a high level of TREK-2 and TRAAK. In addition, TREK/TRAAK proteins were detected in the GABAergic neurons obtained from GABA transgenic mice. Furthermore, TREK-2 mRNA and protein expression levels were markedly upregulated in B35 cells by GABAAR and GABABR agonists. In particular, muscimol, a GABAAR agonist, significantly increased TREK-2 expression and activity, but the effect was reduced in the presence of the GABAAR antagonist bicuculine or TREK-2 inhibitor norfluoxetine. In the whole-cell and single-channel patch configurations, muscimol increased TREK-2 activity, but the muscimol effect disappeared in the N-terminal deletion mutant. These results indicate that muscimol directly induces TREK-2 activation through the N-terminus and suggest that muscimol can reduce cellular excitability by activating the TREK-2 channel and by inducing Cl- influx in GABAergic neurons.
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10
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Grotell M, Abdurakhmanova S, Elsilä LV, Korpi ER. Mice Lacking GABA A Receptor δ Subunit Have Altered Pharmaco-EEG Responses to Multiple Drugs. Front Pharmacol 2021; 12:706894. [PMID: 34234684 PMCID: PMC8255781 DOI: 10.3389/fphar.2021.706894] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2021] [Accepted: 06/11/2021] [Indexed: 11/13/2022] Open
Abstract
In the brain, extrasynaptically expressed ionotropic, δ subunit-containing γ-aminobutyric acid A-type receptors (δ-GABAARs) have been implicated in drug effects at both neuronal and behavioral levels. These alterations are supposed to be caused via drug-induced modulation of receptor ionophores affecting chloride ion-mediated inhibitory tonic currents. Often, a transgenic mouse model genetically lacking the δ-GABAARs (δ-KO) has been used to study the roles of δ-GABAARs in brain functions, because a specific antagonist of the δ-GABAARs is still lacking. We have previously observed with these δ-KO mice that activation of δ-GABAARs is needed for morphine-induced conditioning of place preference, and others have suggested that δ-GABAARs act as targets selectively for low doses of ethanol. Furthermore, activation of these receptors via drug-mediated agonism induces a robust increase in the slow-wave frequency bands of electroencephalography (EEG). Here, we tested δ-KO mice (compared to littermate wild-type controls) for the pharmaco-EEG responses of a broad spectrum of pharmacologically different drug classes, including alcohol, opioids, stimulants, and psychedelics. Gaboxadol (THIP), a known superagonist of δ-GABAARs, was included as the positive control, and as expected, δ-KO mice produced a blunted pharmaco-EEG response to 6 mg/kg THIP. Pharmaco-EEGs showed notable differences between treatments but also differences between δ-KO mice and their wild-type littermates. Interestingly mephedrone (4-MMC, 5 mg/kg), an amphetamine-like stimulant, had reduced effects in the δ-KO mice. The responses to ethanol (1 g/kg), LSD (0.2 mg/kg), and morphine (20 mg/kg) were similar in δ-KO and wild-type mice. Since stimulants are not known to act on δ-GABAARs, our findings on pharmaco-EEG effects of 4-MMC suggest that δ-GABAARs are involved in the secondary indirect regulation of the brain rhythms after 4-MMC.
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Affiliation(s)
- Milo Grotell
- Department of Pharmacology, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | | | - Lauri V Elsilä
- Department of Pharmacology, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Esa R Korpi
- Department of Pharmacology, Faculty of Medicine, University of Helsinki, Helsinki, Finland
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11
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GABAergic Mechanisms Can Redress the Tilted Balance between Excitation and Inhibition in Damaged Spinal Networks. Mol Neurobiol 2021; 58:3769-3786. [PMID: 33826070 PMCID: PMC8279998 DOI: 10.1007/s12035-021-02370-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2020] [Accepted: 03/22/2021] [Indexed: 12/19/2022]
Abstract
Correct operation of neuronal networks depends on the interplay between synaptic excitation and inhibition processes leading to a dynamic state termed balanced network. In the spinal cord, balanced network activity is fundamental for the expression of locomotor patterns necessary for rhythmic activation of limb extensor and flexor muscles. After spinal cord lesion, paralysis ensues often followed by spasticity. These conditions imply that, below the damaged site, the state of balanced networks has been disrupted and that restoration might be attempted by modulating the excitability of sublesional spinal neurons. Because of the widespread expression of inhibitory GABAergic neurons in the spinal cord, their role in the early and late phases of spinal cord injury deserves full attention. Thus, an early surge in extracellular GABA might be involved in the onset of spinal shock while a relative deficit of GABAergic mechanisms may be a contributor to spasticity. We discuss the role of GABA A receptors at synaptic and extrasynaptic level to modulate network excitability and to offer a pharmacological target for symptom control. In particular, it is proposed that activation of GABA A receptors with synthetic GABA agonists may downregulate motoneuron hyperexcitability (due to enhanced persistent ionic currents) and, therefore, diminish spasticity. This approach might constitute a complementary strategy to regulate network excitability after injury so that reconstruction of damaged spinal networks with new materials or cell transplants might proceed more successfully.
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Akk G, Germann AL, Sugasawa Y, Pierce SR, Evers AS, Steinbach JH. Enhancement of Muscimol Binding and Gating by Allosteric Modulators of the GABA A Receptor: Relating Occupancy to State Functions. Mol Pharmacol 2020; 98:303-313. [PMID: 32873746 PMCID: PMC7472144 DOI: 10.1124/molpharm.120.000066] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2020] [Accepted: 07/17/2020] [Indexed: 01/08/2023] Open
Abstract
Muscimol is a psychoactive isoxazole derived from the mushroom Amanita muscaria and a potent orthosteric agonist of the GABAA receptor. The binding of [3H]muscimol has been used to evaluate the distribution of GABAA receptors in the brain, and studies of modulation of [3H]muscimol binding by allosteric GABAergic modulators such as barbiturates and steroid anesthetics have provided insight into the modes of action of these drugs on the GABAA receptor. It has, however, not been feasible to directly apply interaction parameters derived from functional studies to describe the binding of muscimol to the receptor. Here, we employed the Monod-Wyman-Changeux concerted transition model to analyze muscimol binding isotherms. We show that the binding isotherms from recombinant α1β3 GABAA receptors can be qualitatively predicted using electrophysiological data pertaining to properties of receptor activation and desensitization in the presence of muscimol. The model predicts enhancement of [3H]muscimol binding in the presence of the steroids allopregnanolone and pregnenolone sulfate, although the steroids interact with distinct sites and either enhance (allopregnanolone) or reduce (pregnenolone sulfate) receptor function. We infer that the concerted transition model can be used to link radioligand binding and electrophysiological data. SIGNIFICANCE STATEMENT: The study employs a three-state resting-active-desensitized model to link radioligand binding and electrophysiological data. We show that the binding isotherms can be qualitatively predicted using parameters estimated in electrophysiological experiments and that the model accurately predicts the enhancement of [3H]muscimol binding in the presence of the potentiating steroid allopregnanolone and the inhibitory steroid pregnenolone sulfate.
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Affiliation(s)
- Gustav Akk
- Department of Anesthesiology (G.A., A.L.G., Y.S., S.R.P., A.S.E., J.H.S.) and the Taylor Family Institute for Innovative Psychiatric Research (G.A., A.S.E., J.H.S.), Washington University School of Medicine, St. Louis, Missouri
| | - Allison L Germann
- Department of Anesthesiology (G.A., A.L.G., Y.S., S.R.P., A.S.E., J.H.S.) and the Taylor Family Institute for Innovative Psychiatric Research (G.A., A.S.E., J.H.S.), Washington University School of Medicine, St. Louis, Missouri
| | - Yusuke Sugasawa
- Department of Anesthesiology (G.A., A.L.G., Y.S., S.R.P., A.S.E., J.H.S.) and the Taylor Family Institute for Innovative Psychiatric Research (G.A., A.S.E., J.H.S.), Washington University School of Medicine, St. Louis, Missouri
| | - Spencer R Pierce
- Department of Anesthesiology (G.A., A.L.G., Y.S., S.R.P., A.S.E., J.H.S.) and the Taylor Family Institute for Innovative Psychiatric Research (G.A., A.S.E., J.H.S.), Washington University School of Medicine, St. Louis, Missouri
| | - Alex S Evers
- Department of Anesthesiology (G.A., A.L.G., Y.S., S.R.P., A.S.E., J.H.S.) and the Taylor Family Institute for Innovative Psychiatric Research (G.A., A.S.E., J.H.S.), Washington University School of Medicine, St. Louis, Missouri
| | - Joe Henry Steinbach
- Department of Anesthesiology (G.A., A.L.G., Y.S., S.R.P., A.S.E., J.H.S.) and the Taylor Family Institute for Innovative Psychiatric Research (G.A., A.S.E., J.H.S.), Washington University School of Medicine, St. Louis, Missouri
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Neonatal Clonazepam Administration Induced Long-Lasting Changes in GABA A and GABA B Receptors. Int J Mol Sci 2020; 21:ijms21093184. [PMID: 32366006 PMCID: PMC7246485 DOI: 10.3390/ijms21093184] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 04/24/2020] [Accepted: 04/28/2020] [Indexed: 11/17/2022] Open
Abstract
Benzodiazepines (BZDs) are widely used in patients of all ages. Unlike adults, neonatal animals treated with BZDs exhibit a variety of behavioral deficits later in life; however, the mechanisms underlying these deficits are poorly understood. This study aims to examine whether administration of clonazepam (CZP; 1 mg/kg/day) in 7-11-day-old rats affects Gama aminobutyric acid (GABA)ergic receptors in both the short and long terms. Using RT-PCR and quantitative autoradiography, we examined the expression of the selected GABAA receptor subunits (α1, α2, α4, γ2, and δ) and the GABAB B2 subunit, and GABAA, benzodiazepine, and GABAB receptor binding 48 h, 1 week, and 2 months after treatment discontinuation. Within one week after CZP cessation, the expression of the α2 subunit was upregulated, whereas that of the δ subunit was downregulated in both the hippocampus and cortex. In the hippocampus, the α4 subunit was downregulated after the 2-month interval. Changes in receptor binding were highly dependent on the receptor type, the interval after treatment cessation, and the brain structure. GABAA receptor binding was increased in almost all of the brain structures after the 48-h interval. BZD-binding was decreased in many brain structures involved in the neuronal networks associated with emotional behavior, anxiety, and cognitive functions after the 2-month interval. Binding of the GABAB receptors changed depending on the interval and brain structure. Overall, the described changes may affect both synaptic development and functioning and may potentially cause behavioral impairment.
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Vega Alanis BA, Iorio MT, Silva LL, Bampali K, Ernst M, Schnürch M, Mihovilovic MD. Allosteric GABA A Receptor Modulators-A Review on the Most Recent Heterocyclic Chemotypes and Their Synthetic Accessibility. Molecules 2020; 25:E999. [PMID: 32102309 PMCID: PMC7070463 DOI: 10.3390/molecules25040999] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Revised: 02/18/2020] [Accepted: 02/19/2020] [Indexed: 11/17/2022] Open
Abstract
GABAA receptor modulators are structurally almost as diverse as their target protein. A plethora of heterocyclic scaffolds has been described as modulating this extremely important receptor family. Some made it into clinical trials and, even on the market, some were dismissed. This review focuses on the synthetic accessibility and potential for library synthesis of GABAA receptor modulators containing at least one heterocyclic scaffold, which were disclosed within the last 10 years.
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Affiliation(s)
- Blanca Angelica Vega Alanis
- Institute of Applied Synthetic Chemistry, TU Wien, Getreidemarkt 9/193, 1060 Vienna, Austria; (B.A.V.A.); (M.T.I.); (M.D.M.)
| | - Maria Teresa Iorio
- Institute of Applied Synthetic Chemistry, TU Wien, Getreidemarkt 9/193, 1060 Vienna, Austria; (B.A.V.A.); (M.T.I.); (M.D.M.)
| | - Luca L. Silva
- Department of Anesthesiology and Intensive Care Medicine, Charité–Universitätsmedizin, Charitéplatz 1, 10117 Berlin, Germany;
| | - Konstantina Bampali
- Department of Molecular Neurosciences, Center for Brain Research, Medical University of Vienna, Spitalgasse 4, 1090 Vienna, Austria;
| | - Margot Ernst
- Department of Molecular Neurosciences, Center for Brain Research, Medical University of Vienna, Spitalgasse 4, 1090 Vienna, Austria;
| | - Michael Schnürch
- Institute of Applied Synthetic Chemistry, TU Wien, Getreidemarkt 9/193, 1060 Vienna, Austria; (B.A.V.A.); (M.T.I.); (M.D.M.)
| | - Marko D. Mihovilovic
- Institute of Applied Synthetic Chemistry, TU Wien, Getreidemarkt 9/193, 1060 Vienna, Austria; (B.A.V.A.); (M.T.I.); (M.D.M.)
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Mechanisms of GABA B receptor enhancement of extrasynaptic GABA A receptor currents in cerebellar granule cells. Sci Rep 2019; 9:16683. [PMID: 31723152 PMCID: PMC6853962 DOI: 10.1038/s41598-019-53087-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Accepted: 10/26/2019] [Indexed: 12/31/2022] Open
Abstract
Many neurons, including cerebellar granule cells, exhibit a tonic GABA current mediated by extrasynaptic GABAA receptors. This current is a critical regulator of firing and the target of many clinically relevant compounds. Using a combination of patch clamp electrophysiology and photolytic uncaging of RuBi-GABA we show that GABAB receptors are tonically active and enhance extrasynaptic GABAA receptor currents in cerebellar granule cells. This enhancement is not associated with meaningful changes in GABAA receptor potency, mean channel open-time, open probability, or single-channel current. However, there was a significant (~40%) decrease in the number of channels participating in the GABA uncaging current and an increase in receptor desensitization. Furthermore, we find that adenylate cyclase, PKA, CaMKII, and release of Ca2+ from intracellular stores are necessary for modulation of GABAA receptors. Overall, this work reveals crosstalk between postsynaptic GABAA and GABAB receptors and identifies the signaling pathways and mechanisms involved.
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Olsen RW, Lindemeyer AK, Wallner M, Li X, Huynh KW, Zhou ZH. Cryo-electron microscopy reveals informative details of GABA A receptor structural pharmacology: implications for drug discovery. ANNALS OF TRANSLATIONAL MEDICINE 2019; 7:S144. [PMID: 31576351 DOI: 10.21037/atm.2019.06.23] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Richard W Olsen
- Department of Molecular and Medical Pharmacology, Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - A Kerstin Lindemeyer
- Department of Molecular and Medical Pharmacology, Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - Martin Wallner
- Department of Molecular and Medical Pharmacology, Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - Xiaorun Li
- California NanoSystems Institute, University of California, Los Angeles, CA, USA
| | - Kevin W Huynh
- California NanoSystems Institute, University of California, Los Angeles, CA, USA
| | - Z Hong Zhou
- California NanoSystems Institute, University of California, Los Angeles, CA, USA
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