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Richardson RJ, Petrou S, Bryson A. Established and emerging GABA A receptor pharmacotherapy for epilepsy. Front Pharmacol 2024; 15:1341472. [PMID: 38449810 PMCID: PMC10915249 DOI: 10.3389/fphar.2024.1341472] [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: 11/20/2023] [Accepted: 02/07/2024] [Indexed: 03/08/2024] Open
Abstract
Drugs that modulate the GABAA receptor are widely used in clinical practice for both the long-term management of epilepsy and emergency seizure control. In addition to older medications that have well-defined roles for the treatment of epilepsy, recent discoveries into the structure and function of the GABAA receptor have led to the development of newer compounds designed to maximise therapeutic benefit whilst minimising adverse effects, and whose position within the epilepsy pharmacologic armamentarium is still emerging. Drugs that modulate the GABAA receptor will remain a cornerstone of epilepsy management for the foreseeable future and, in this article, we provide an overview of the mechanisms and clinical efficacy of both established and emerging pharmacotherapies.
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Affiliation(s)
- Robert J. Richardson
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, VIC, Australia
- Department of Neurology, Austin Health, Heidelberg, VIC, Australia
| | - Steven Petrou
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, VIC, Australia
- Praxis Precision Medicines, Boston, MA, United States
| | - Alexander Bryson
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, VIC, Australia
- Department of Neurology, Austin Health, Heidelberg, VIC, Australia
- Department of Neurology, Eastern Health, Melbourne, VIC, Australia
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Liddiard GT, Suryavanshi PS, Glykys J. Enhancing GABAergic Tonic Inhibition Reduces Seizure-Like Activity in the Neonatal Mouse Hippocampus and Neocortex. J Neurosci 2024; 44:e1342232023. [PMID: 38176909 PMCID: PMC10869160 DOI: 10.1523/jneurosci.1342-23.2023] [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: 07/17/2023] [Revised: 11/27/2023] [Accepted: 12/21/2023] [Indexed: 01/06/2024] Open
Abstract
Approximately one-third of neonatal seizures do not respond to first-line anticonvulsants, including phenobarbital, which enhances phasic inhibition. Whether enhancing tonic inhibition decreases seizure-like activity in the neonate when GABA is mainly depolarizing at this age is unknown. We evaluated if increasing tonic inhibition using THIP [4,5,6,7-tetrahydroisoxazolo(5,4-c)pyridin-3-ol, gaboxadol], a δ-subunit-selective GABAA receptor agonist, decreases seizure-like activity in neonatal C57BL/6J mice (postnatal day P5-8, both sexes) using acute brain slices. Whole-cell patch-clamp recordings showed that THIP enhanced GABAergic tonic inhibitory conductances in layer V neocortical and CA1 pyramidal neurons and increased their rheobase without altering sEPSC characteristics. Two-photon calcium imaging demonstrated that enhancing the activity of extrasynaptic GABAARs decreased neuronal firing in both brain regions. In the 4-aminopyridine and the low-Mg2+ model of pharmacoresistant seizures, THIP reduced epileptiform activity in the neocortex and CA1 hippocampal region of neonatal and adult brain slices in a dose-dependent manner. We conclude that neocortical layer V and CA1 pyramidal neurons have tonic inhibitory conductances, and when enhanced, they reduce neuronal firing and decrease seizure-like activity. Therefore, augmenting tonic inhibition could be a viable approach for treating neonatal seizures.
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Affiliation(s)
- G T Liddiard
- Stead Family Department of Pediatrics, Iowa Neuroscience Institute, The University of Iowa, Iowa City 52242, Iowa
- Interdisciplinary Graduate Program in Neuroscience, The University of Iowa, Iowa City 52242, Iowa
| | - P S Suryavanshi
- Stead Family Department of Pediatrics, Iowa Neuroscience Institute, The University of Iowa, Iowa City 52242, Iowa
| | - J Glykys
- Stead Family Department of Pediatrics, Iowa Neuroscience Institute, The University of Iowa, Iowa City 52242, Iowa
- Interdisciplinary Graduate Program in Neuroscience, The University of Iowa, Iowa City 52242, Iowa
- Department of Neurology, The University of Iowa, Iowa City 52242, Iowa
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Shin H, Sharma R, Neupane C, Pham TL, Park SE, Lee SY, Kim HW, Bae YM, Stern JE, Park JB. Tonic NMDAR Currents of NR2A-Containing NMDARs Represent Altered Ambient Glutamate Concentration in the Supraoptic Nucleus. eNeuro 2024; 11:ENEURO.0279-23.2023. [PMID: 38176904 PMCID: PMC10863629 DOI: 10.1523/eneuro.0279-23.2023] [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: 07/26/2023] [Revised: 12/03/2023] [Accepted: 12/21/2023] [Indexed: 01/06/2024] Open
Abstract
NMDA receptors (NMDARs) modulate glutamatergic excitatory tone in the brain via two complementary modalities: a phasic excitatory postsynaptic current and a tonic extrasynaptic modality. Here, we demonstrated that the tonic NMDAR-current (I NMDA) mediated by NR2A-containing NMDARs is an efficient biosensor detecting the altered ambient glutamate level in the supraoptic nucleus (SON). I NMDA of magnocellular neurosecretory cells (MNCs) measured by nonselective NMDARs antagonist, AP5, at holding potential (V holding) -70 mV in low concentration of ECF Mg2+ ([Mg2+]o) was transiently but significantly increased 1-week post induction of a DOCA salt hypertensive model rat which was compatible with that induced by a NR2A-selective antagonist, PEAQX (I PEAQX) in both DOCA-H2O and DOCA-salt groups. In agreement, NR2B antagonist, ifenprodil, or NR2C/D antagonist, PPDA, did not affect the holding current (I holding) at V holding -70 mV. Increased ambient glutamate by exogenous glutamate (10 mM) or excitatory amino acid transporters (EAATs) antagonist (TBOA, 50 mM) abolished the I PEAQX difference between two groups, suggesting that attenuated EAATs activity increased ambient glutamate concentration, leading to the larger I PEAQX in DOCA-salt rats. In contrast, only ifenprodil but not PEAQX and PPDA uncovered I NMDA at V holding +40 mV under 1.2 mM [Mg2+]o condition. I ifenprodil was not different in DOCA-H2O and DOCA-salt groups. Finally, NR2A, NR2B, and NR2D protein expression were not different in the SON of the two groups. Taken together, NR2A-containing NMDARs efficiently detected the increased ambient glutamate concentration in the SON of DOCA-salt hypertensive rats due to attenuated EAATs activity.
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Affiliation(s)
- Hyunjin Shin
- Department of Physiology & Medical Science, College of Medicine & Brain Research Institute, Chungnam National University, Daejeon 35015, South Korea
| | - Ramesh Sharma
- Department of Physiology & Medical Science, College of Medicine & Brain Research Institute, Chungnam National University, Daejeon 35015, South Korea
- Laboratory of Veterinary Pharmacology, College of Veterinary Medicine and Research Institute for Veterinary Science, Seoul National University, Seoul 08826, Republic of Korea
| | - Chiranjivi Neupane
- Laboratory of Veterinary Pharmacology, College of Veterinary Medicine and Research Institute for Veterinary Science, Seoul National University, Seoul 08826, Republic of Korea
| | - Thuy Linh Pham
- Department of Physiology & Medical Science, College of Medicine & Brain Research Institute, Chungnam National University, Daejeon 35015, South Korea
| | - Su Eun Park
- Department of Physiology & Medical Science, College of Medicine & Brain Research Institute, Chungnam National University, Daejeon 35015, South Korea
| | - So Yeong Lee
- Laboratory of Veterinary Pharmacology, College of Veterinary Medicine and Research Institute for Veterinary Science, Seoul National University, Seoul 08826, Republic of Korea
| | - Hyun-Woo Kim
- Department of Physiology & Medical Science, College of Medicine & Brain Research Institute, Chungnam National University, Daejeon 35015, South Korea
| | - Young Min Bae
- Department of Physiology, Konkuk University School of Medicine, Chungju 27478, Republic of Korea
| | - Javier E Stern
- Neuroscience Institute and Center for Neuroinflammation and Cardiometabolic Diseases, Georgia State University, Atlanta, Georgia 30302
| | - Jin Bong Park
- Laboratory of Veterinary Pharmacology, College of Veterinary Medicine and Research Institute for Veterinary Science, Seoul National University, Seoul 08826, Republic of Korea
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Bogaj K, Kaplon R, Urban-Ciecko J. GABAAR-mediated tonic inhibition differentially modulates intrinsic excitability of VIP- and SST- expressing interneurons in layers 2/3 of the somatosensory cortex. Front Cell Neurosci 2023; 17:1270219. [PMID: 37900589 PMCID: PMC10602639 DOI: 10.3389/fncel.2023.1270219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Accepted: 09/25/2023] [Indexed: 10/31/2023] Open
Abstract
Extrasynaptic GABAA receptors (GABAARs) mediating tonic inhibition are thought to play an important role in the regulation of neuronal excitability. However, little is known about a cell type-specific tonic inhibition in molecularly distinctive types of GABAergic interneurons in the mammalian neocortex. Here, we used whole-cell patch-clamp techniques in brain slices prepared from transgenic mice expressing red fluorescent protein (TdTomato) in vasoactive intestinal polypeptide- or somatostatin- positive interneurons (VIP-INs and SST-INs, respectively) to investigate tonic and phasic GABAAR-mediated inhibition as well as effects of GABAA inhibition on intrinsic excitability of these interneurons in layers 2/3 (L2/3) of the somatosensory (barrel) cortex. We found that tonic inhibition was stronger in VIP-INs compared to SST-INs. Contrary to the literature data, tonic inhibition in SST-INs was comparable to pyramidal (Pyr) neurons. Next, tonic inhibition in both interneuron types was dependent on the activity of delta subunit-containing GABAARs. Finally, the GABAAR activity decreased intrinsic excitability of VIP-INs but not SST-INs. Altogether, our data indicate that GABAAR-mediated inhibition modulates neocortical interneurons in a type-specific manner. In contrast to L2/3 VIP-INs, intrinsic excitability of L2/3 SST-INs is immune to the GABAAR-mediated inhibition.
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Affiliation(s)
| | | | - Joanna Urban-Ciecko
- Laboratory of Electrophysiology, Nencki Institute of Experimental Biology, Warsaw, Poland
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Fogarty MJ. Inhibitory Synaptic Influences on Developmental Motor Disorders. Int J Mol Sci 2023; 24:ijms24086962. [PMID: 37108127 PMCID: PMC10138861 DOI: 10.3390/ijms24086962] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2023] [Revised: 04/05/2023] [Accepted: 04/06/2023] [Indexed: 04/29/2023] Open
Abstract
During development, GABA and glycine play major trophic and synaptic roles in the establishment of the neuromotor system. In this review, we summarise the formation, function and maturation of GABAergic and glycinergic synapses within neuromotor circuits during development. We take special care to discuss the differences in limb and respiratory neuromotor control. We then investigate the influences that GABAergic and glycinergic neurotransmission has on two major developmental neuromotor disorders: Rett syndrome and spastic cerebral palsy. We present these two syndromes in order to contrast the approaches to disease mechanism and therapy. While both conditions have motor dysfunctions at their core, one condition Rett syndrome, despite having myriad symptoms, has scientists focused on the breathing abnormalities and their alleviation-to great clinical advances. By contrast, cerebral palsy remains a scientific quagmire or poor definitions, no widely adopted model and a lack of therapeutic focus. We conclude that the sheer abundance of diversity of inhibitory neurotransmitter targets should provide hope for intractable conditions, particularly those that exhibit broad spectra of dysfunction-such as spastic cerebral palsy and Rett syndrome.
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Affiliation(s)
- Matthew J Fogarty
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, MN 55902, USA
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Function of the GABAergic System in Diabetic Encephalopathy. Cell Mol Neurobiol 2023; 43:605-619. [PMID: 35460435 DOI: 10.1007/s10571-022-01214-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Accepted: 03/17/2022] [Indexed: 11/03/2022]
Abstract
Diabetes is a common metabolic disease characterized by loss of blood sugar control and a high rate of complications. γ-Aminobutyric acid (GABA) functions as the primary inhibitory neurotransmitter in the adult mammalian brain. The normal function of the GABAergic system is affected in diabetes. Herein, we summarize the role of the GABAergic system in diabetic cognitive dysfunction, diabetic blood sugar control disorders, diabetes-induced peripheral neuropathy, diabetic central nervous system damage, maintaining diabetic brain energy homeostasis, helping central control of blood sugar and attenuating neuronal oxidative stress damage. We show the key regulatory role of the GABAergic system in multiple comorbidities in patients with diabetes and hope that further studies elucidating the role of the GABAergic system will yield benefits for the treatment and prevention of comorbidities in patients with diabetes.
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Bryson A, Reid C, Petrou S. Fundamental Neurochemistry Review: GABA A receptor neurotransmission and epilepsy: Principles, disease mechanisms and pharmacotherapy. J Neurochem 2023; 165:6-28. [PMID: 36681890 DOI: 10.1111/jnc.15769] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2022] [Revised: 12/12/2022] [Accepted: 01/04/2023] [Indexed: 01/23/2023]
Abstract
Epilepsy is a common neurological disorder associated with alterations of excitation-inhibition balance within brain neuronal networks. GABAA receptor neurotransmission is the most prevalent form of inhibitory neurotransmission and is strongly implicated in both the pathophysiology and treatment of epilepsy, serving as a primary target for antiseizure medications for over a century. It is now established that GABA exerts a multifaceted influence through an array of GABAA receptor subtypes that extends far beyond simply negating excitatory activity. As the role of GABAA neurotransmission within inhibitory circuits is elaborated, this will enable the development of precision therapies that correct the network dysfunction underlying epileptic pathology.
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Affiliation(s)
- Alexander Bryson
- The Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, Victoria, Australia.,Department of Neurology, Austin Health, Heidelberg, Victoria, Australia
| | - Christopher Reid
- The Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, Victoria, Australia
| | - Steven Petrou
- The Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, Victoria, Australia.,Praxis Precision Medicines, Inc., Cambridge, Massachusetts, USA
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The GABA and GABA-Receptor System in Inflammation, Anti-Tumor Immune Responses, and COVID-19. Biomedicines 2023; 11:biomedicines11020254. [PMID: 36830790 PMCID: PMC9953446 DOI: 10.3390/biomedicines11020254] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Revised: 01/16/2023] [Accepted: 01/16/2023] [Indexed: 01/20/2023] Open
Abstract
GABA and GABAA-receptors (GABAA-Rs) play major roles in neurodevelopment and neurotransmission in the central nervous system (CNS). There has been a growing appreciation that GABAA-Rs are also present on most immune cells. Studies in the fields of autoimmune disease, cancer, parasitology, and virology have observed that GABA-R ligands have anti-inflammatory actions on T cells and antigen-presenting cells (APCs), while also enhancing regulatory T cell (Treg) responses and shifting APCs toward anti-inflammatory phenotypes. These actions have enabled GABAA-R ligands to ameliorate autoimmune diseases, such as type 1 diabetes (T1D), multiple sclerosis (MS), and rheumatoid arthritis, as well as type 2 diabetes (T2D)-associated inflammation in preclinical models. Conversely, antagonism of GABAA-R activity promotes the pro-inflammatory responses of T cells and APCs, enhancing anti-tumor responses and reducing tumor burden in models of solid tumors. Lung epithelial cells also express GABA-Rs, whose activation helps maintain fluid homeostasis and promote recovery from injury. The ability of GABAA-R agonists to limit both excessive immune responses and lung epithelial cell injury may underlie recent findings that GABAA-R agonists reduce the severity of disease in mice infected with highly lethal coronaviruses (SARS-CoV-2 and MHV-1). These observations suggest that GABAA-R agonists may provide off-the-shelf therapies for COVID-19 caused by new SARS-CoV-2 variants, as well as novel beta-coronaviruses, which evade vaccine-induced immune responses and antiviral medications. We review these findings and further advance the notions that (1) immune cells possess GABAA-Rs to limit inflammation in the CNS, and (2) this natural "braking system" on inflammatory responses may be pharmacologically engaged to slow the progression of autoimmune diseases, reduce the severity of COVID-19, and perhaps limit neuroinflammation associated with long COVID.
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Germinated brown rice protects against glutamate toxicity in HT22 hippocampal neurons through the jnk-mediated apoptotic pathway via the GABA A receptor. IBRO Neurosci Rep 2022; 14:38-49. [PMID: 36590249 PMCID: PMC9800259 DOI: 10.1016/j.ibneur.2022.12.004] [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: 07/23/2022] [Revised: 12/07/2022] [Accepted: 12/08/2022] [Indexed: 12/14/2022] Open
Abstract
The anti-apoptosis effect of germinated brown rice (GBR) focusing on differentiated HT22 cells results in improved nutritional values after the germination process of GBR which contains total phenolic compounds and γ-aminobutyric acid (GABA). Cell death induced by 5 mM glutamate was investigated for 24 h to determine whether GBR mediates cell death through GABA receptors by using antagonists. The results showed that GBR (100 µg/ml) suppressed glutamate-induced cytotoxicity and caused arrest at the G1/S phase of the cell cycle in differentiated HT22 cells. Furthermore, GBR significantly decreased the expression level of c-Jun, while its active form, p-c-Jun, is the downstream product of the JNK-mediated apoptotic pathway and causes subsequent cell death. In addition, bicuculline (12.5 nM), a GABAA antagonist, could eliminate GBR effects, but phaclofen (1 mM), a GABAB antagonist, could not. Surprisingly, GBR exhibited a better neuroprotective effect than a pure commercial GABA compound (0.115 µM). These results indicated that GBR possessed high anti-apoptotic activity and inhibited cell death in differentiated HT22 cells by perturbing re-entry of the cell cycle and apoptosis via the GABAA receptor. Hence, GBR could be further used as a valuable nutritional compound to prevent apoptosis-induced neurodegenerative diseases.
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Key Words
- AMPA, α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid
- Apoptosis
- Bic, bicuculline
- Cell cycle
- Differentiated HT22 cells
- GABA, gamma-aminobutyric acid
- GABAA receptor
- GABRG2, GABAA receptor (γ2 subunit)
- GBR
- GBR, germinated brown rice
- Glu, glutamate
- HT22, mouse hippocampal neuronal cell line
- JNKs
- JNKs, c-Jun N-terminal kinases
- MAPKs, mitogen-activated protein kinase
- NMDA, N-methyl-D-aspartate receptors
- Pha, phaclofen
- ROS, reactive oxygen species
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Nimitvilai-Roberts S, Woodward JJ. The ethanol inhibition of basolateral amygdala neuron spiking is mediated by a γ-aminobutyric acid type A-mediated tonic current. Alcohol Clin Exp Res 2022; 46:1665-1676. [PMID: 35915568 PMCID: PMC9509443 DOI: 10.1111/acer.14918] [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: 05/12/2022] [Revised: 07/19/2022] [Accepted: 07/28/2022] [Indexed: 01/31/2023]
Abstract
BACKGROUND The basolateral nucleus of the amygdala (BLA) plays an important role in the development of fear and anxiety-related behaviors. The BLA receives inputs from all sensory stimuli. After processing those stimuli, BLA neurons signal neurons within the central amygdala and other brain regions, including the ventral and dorsal striatum and frontal cortex. Studies suggest that the BLA is involved in drug dependence and in the reinforcing actions of ethanol. For example, acute exposure to ethanol reduces anxiety, while withdrawal from chronic ethanol exposure alters BLA synaptic transmission, which increases anxiety, a common underlying cause of relapse. Exposure to and withdrawal from chronic alcohol also disrupts many brain areas that connect with the BLA. Despite these important findings, the acute actions of alcohol on the intrinsic excitability of BLA neurons have not been fully characterized. METHODS Brain slices containing the BLA were prepared from adult C57BL/6J male mice. Whole-cell and sharp electrode electrophysiological recordings were performed to characterize the effects of acute ethanol on BLA neuronal and astrocyte function, respectively. RESULTS Ethanol inhibited action potential (AP) firing of BLA neurons but had no effect on BLA astrocyte resting membrane potential. The ethanol-induced inhibition of firing was concentration-dependent (11 to 66 mM) and accompanied by a reduction in the input resistance and an increase in the rheobase of BLA neurons. The inhibitory effect of ethanol was suppressed by picrotoxin, which blocks both γ-aminobutyric acid type A (GABAA ) and glycine receptors, but not by the selective glycine receptor antagonist strychnine, which suggests an involvement of GABAA receptors. Ethanol did not affect spontaneous inhibitory postsynaptic currents suggesting that the inhibition of BLA neuronal excitability by ethanol was not due to an increase in GABAA -mediated synaptic transmission. However, acute ethanol enhanced the amplitude of the holding current of BLA neurons, an effect that was prevented by picrotoxin, which by itself reduced the holding current. CONCLUSIONS These results suggest that BLA neurons express a GABA-mediated tonic current that is enhanced by acute ethanol, which leads to reduced excitability of BLA neurons.
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Affiliation(s)
| | - John J. Woodward
- Department of Neuroscience, Medical University of South Carolina, Charleston, SC 29425
- Department of Psychiatry and Behavioral Sciences, Addiction Sciences Division, Medical University of South Carolina, Charleston, SC 29425
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Sun Y, Peng Z, Wei X, Zhang N, Huang CS, Wallner M, Mody I, Houser CR. Virally-induced expression of GABAA receptor δ subunits following their pathological loss reveals their role in regulating GABAA receptor assembly. Prog Neurobiol 2022; 218:102337. [PMID: 35934131 PMCID: PMC10091858 DOI: 10.1016/j.pneurobio.2022.102337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2022] [Revised: 07/26/2022] [Accepted: 08/03/2022] [Indexed: 10/31/2022]
Abstract
Decreased expression of the δ subunit of the GABAA receptor (GABAAR) has been found in the dentate gyrus in several animal models of epilepsy and other disorders with increased excitability and is associated with altered modulation of tonic inhibition in dentate granule cells (GCs). In contrast, other GABAAR subunits, including α4 and γ2 subunits, are increased, but the relationship between these changes is unclear. The goals of this study were to determine if viral transfection of δ subunits in dentate GCs could increase δ subunit expression, alter expression of potentially-related GABAAR subunits, and restore more normal network excitability in the dentate gyrus in a mouse model of epilepsy. Pilocarpine-induced seizures were elicited in DOCK10-Cre mice that express Cre selectively in dentate GCs, and two weeks later the mice were injected unilaterally with a Cre-dependent δ-GABAAR viral vector. At 4-6 weeks following transfection, δ subunit immunolabeling was substantially increased in dentate GCs on the transfected side compared to the nontransfected side. Importantly, α4 and γ2 subunit labeling was downregulated on the transfected side. Electrophysiological studies revealed enhanced tonic inhibition, decreased network excitability, and increased neurosteroid sensitivity in slices from the δ subunit-transfected side compared to those from the nontransfected side of the same pilocarpine-treated animal, consistent with the formation of δ subunit-containing GABAARs. No differences were observed between sides of eYFP-transfected animals. These findings are consistent with the idea that altering expression of key subunits, such as the δ subunit, regulates GABAAR subunit assemblies, resulting in substantial effects on network excitability.
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Boychuk JA, Butler CR, Smith KC, Halmos MB, Smith BN. Zolpidem Profoundly Augments Spared Tonic GABAAR Signaling in Dentate Granule Cells Ipsilateral to Controlled Cortical Impact Brain Injury in Mice. Front Syst Neurosci 2022; 16:867323. [PMID: 35694044 PMCID: PMC9178240 DOI: 10.3389/fnsys.2022.867323] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Accepted: 05/05/2022] [Indexed: 11/18/2022] Open
Abstract
Type A GABA receptors (GABAARs) are pentameric combinations of protein subunits that give rise to tonic (ITonicGABA) and phasic (i.e., synaptic; ISynapticGABA) forms of inhibitory GABAAR signaling in the central nervous system. Remodeling and regulation of GABAAR protein subunits are implicated in a wide variety of healthy and injury-dependent states, including epilepsy. The present study undertook a detailed analysis of GABAAR signaling using whole-cell patch clamp recordings from mouse dentate granule cells (DGCs) in coronal slices containing dorsal hippocampus at 1–2 or 8–13 weeks after a focal, controlled cortical impact (CCI) or sham brain injury. Zolpidem, a benzodiazepine-like positive modulator of GABAARs, was used to test for changes in GABAAR signaling of DGCs due to its selectivity for α1 subunit-containing GABAARs. Electric charge transfer and statistical percent change were analyzed in order to directly compare tonic and phasic GABAAR signaling and to account for zolpidem’s ability to modify multiple parameters of GABAAR kinetics. We observed that baseline ITonicGABA is preserved at both time-points tested in DGCs ipsilateral to injury (Ipsi-DGCs) compared to DGCs contralateral to injury (Contra-DGCs) or after sham injury (Sham-DGCs). Interestingly, application of zolpidem resulted in modulation of ITonicGABA across groups, with Ipsi-DGCs exhibiting the greatest responsiveness to zolpidem. We also report that the combination of CCI and acute application of zolpidem profoundly augments the proportion of GABAAR charge transfer mediated by tonic vs. synaptic currents at both time-points tested, whereas gene expression of GABAAR α1, α2, α3, and γ2 subunits is unchanged at 8–13 weeks post-injury. Overall, this work highlights the shift toward elevated influence of tonic inhibition in Ipsi-DGCs, the impact of zolpidem on all components of inhibitory control of DGCs, and the sustained nature of these changes in inhibitory tone after CCI injury.
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Affiliation(s)
- Jeffery A Boychuk
- Department of Physiology, University of Kentucky, Lexington, KY, United States
- Department of Cellular and Integrative Physiology, UT Health San Antonio, San Antonio, TX, United States
| | - Corwin R Butler
- Department of Physiology, University of Kentucky, Lexington, KY, United States
- Department of Anesthesiology and Perioperative Medicine, Oregon Health and Science University, Portland, OR, United States
| | - Katalin Cs Smith
- Department of Physiology, University of Kentucky, Lexington, KY, United States
- Department of Neuroscience, University of Kentucky, Lexington, KY, United States
| | - Miklos B Halmos
- Department of Psychology, Georgia State University, Atlanta, GA, United States
| | - Bret N Smith
- Department of Physiology, University of Kentucky, Lexington, KY, United States
- Department of Neuroscience, University of Kentucky, Lexington, KY, United States
- Spinal Cord and Brain Injury Research Center (SCoBIRC), University of Kentucky, Lexington, KY, United States
- Department of Biomedical Sciences, Colorado State University, Fort Collins, CO, United States
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Defining and overcoming the therapeutic obstacles in canine refractory status epilepticus. Vet J 2022; 283-284:105828. [DOI: 10.1016/j.tvjl.2022.105828] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Revised: 04/08/2022] [Accepted: 04/09/2022] [Indexed: 11/20/2022]
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Michalettos G, Ruscher K. Crosstalk Between GABAergic Neurotransmission and Inflammatory Cascades in the Post-ischemic Brain: Relevance for Stroke Recovery. Front Cell Neurosci 2022; 16:807911. [PMID: 35401118 PMCID: PMC8983863 DOI: 10.3389/fncel.2022.807911] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Accepted: 02/28/2022] [Indexed: 11/28/2022] Open
Abstract
Adaptive plasticity processes are required involving neurons as well as non-neuronal cells to recover lost brain functions after an ischemic stroke. Recent studies show that gamma-Aminobutyric acid (GABA) has profound effects on glial and immune cell functions in addition to its inhibitory actions on neuronal circuits in the post-ischemic brain. Here, we provide an overview of how GABAergic neurotransmission changes during the first weeks after stroke and how GABA affects functions of astroglial and microglial cells as well as peripheral immune cell populations accumulating in the ischemic territory and brain regions remote to the lesion. Moreover, we will summarize recent studies providing data on the immunomodulatory actions of GABA of relevance for stroke recovery. Interestingly, the activation of GABA receptors on immune cells exerts a downregulation of detrimental anti-inflammatory cascades. Conversely, we will discuss studies addressing how specific inflammatory cascades affect GABAergic neurotransmission on the level of GABA receptor composition, GABA synthesis, and release. In particular, the chemokines CXCR4 and CX3CR1 pathways have been demonstrated to modulate receptor composition and synthesis. Together, the actual view on the interactions between GABAergic neurotransmission and inflammatory cascades points towards a specific crosstalk in the post-ischemic brain. Similar to what has been shown in experimental models, specific therapeutic modulation of GABAergic neurotransmission and inflammatory pathways may synergistically promote neuronal plasticity to enhance stroke recovery.
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Affiliation(s)
- Georgios Michalettos
- Laboratory for Experimental Brain Research, Division of Neurosurgery, Department of Clinical Sciences, Wallenberg Neuroscience Center, Lund University, Lund, Sweden
| | - Karsten Ruscher
- Laboratory for Experimental Brain Research, Division of Neurosurgery, Department of Clinical Sciences, Wallenberg Neuroscience Center, Lund University, Lund, Sweden
- LUBIN Lab—Lunds Laboratorium för Neurokirurgisk Hjärnskadeforskning, Division of Neurosurgery, Department of Clinical Sciences, Lund University, Lund, Sweden
- *Correspondence: Karsten Ruscher
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15
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Field M, Lukacs IP, Hunter E, Stacey R, Plaha P, Livermore L, Ansorge O, Somogyi P. Tonic GABA A Receptor-Mediated Currents of Human Cortical GABAergic Interneurons Vary Amongst Cell Types. J Neurosci 2021; 41:9702-9719. [PMID: 34667071 PMCID: PMC8612645 DOI: 10.1523/jneurosci.0175-21.2021] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Revised: 09/08/2021] [Accepted: 09/10/2021] [Indexed: 12/03/2022] Open
Abstract
Persistent anion conductances through GABAA receptors (GABAARs) are important modulators of neuronal excitability. However, it is currently unknown how the amplitudes of these currents vary among different cell types in the human neocortex, particularly among diverse GABAergic interneurons. We have recorded 101 interneurons in and near layer 1 from cortical tissue surgically resected from both male and female patients, visualized 84 of them and measured tonic GABAAR currents in 48 cells with an intracellular [Cl-] of 65 mm and in the presence of 5 μm GABA. We compare these tonic currents among five groups of interneurons divided by firing properties and four types of interneuron defined by axonal distributions; rosehip, neurogliaform, stalked-bouton, layer 2-3 innervating and a pool of other cells. Interestingly, the rosehip cell, a type of interneuron only described thus far in human tissue, and layer 2-3 innervating cells exhibit larger tonic currents than other layer 1 interneurons, such as neurogliaform and stalked-bouton cells; the latter two groups showing no difference. The positive allosteric modulators of GABAARs allopregnanolone and DS2 also induced larger current shifts in the rosehip and layer 2-3 innervating cells, consistent with higher expression of the δ subunit of the GABAAR in these neurons. We have also examined how patient parameters, such as age, seizures, type of cancer and anticonvulsant treatment may alter tonic inhibitory currents in human neurons. The cell type-specific differences in tonic inhibitory currents could potentially be used to selectively modulate cortical circuitry.SIGNIFICANCE STATEMENT Tonic currents through GABAA receptors (GABAARs) are a potential therapeutic target for a number of neurologic and psychiatric conditions. Here, we show that these currents in human cerebral cortical GABAergic neurons display cell type-specific differences in their amplitudes which implies differential modulation of their excitability. Additionally, we examine whether the amplitudes of the tonic currents measured in our study show any differences between patient populations, finding some evidence that age, seizures, type of cancer, and anticonvulsant treatment may alter tonic inhibition in human tissue. These results advance our understanding of how pathology affects neuronal excitability and could potentially be used to selectively modulate cortical circuitry.
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Affiliation(s)
- Martin Field
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, United Kingdom
| | - Istvan P Lukacs
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, United Kingdom
| | - Emily Hunter
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, United Kingdom
| | - Richard Stacey
- Department of Neurosurgery, John Radcliffe Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford OX3 9DU, United Kingdom
| | - Puneet Plaha
- Department of Neurosurgery, John Radcliffe Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford OX3 9DU, United Kingdom
| | - Laurent Livermore
- Department of Neurosurgery, John Radcliffe Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford OX3 9DU, United Kingdom
| | - Olaf Ansorge
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford OX3 9DU, United Kingdom
| | - Peter Somogyi
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, United Kingdom
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16
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Sperk G, Pirker S, Gasser E, Wieselthaler A, Bukovac A, Kuchukhidze G, Maier H, Drexel M, Baumgartner C, Ortler M, Czech T. Increased expression of GABA A receptor subunits associated with tonic inhibition in patients with temporal lobe epilepsy. Brain Commun 2021; 3:fcab239. [PMID: 34708207 PMCID: PMC8545616 DOI: 10.1093/braincomms/fcab239] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 08/07/2021] [Accepted: 08/26/2021] [Indexed: 11/30/2022] Open
Abstract
Epilepsy animal models indicate pronounced changes in the expression and rearrangement of GABAA receptor subunits in the hippocampus and in para-hippocampal areas, including widespread downregulation of the subunits α5 and δ, and upregulation of α4, subunits that mediate tonic inhibition of GABA. In this case–control study, we investigated changes in the expression of subunits α4, α5 and δ in hippocampal specimens of drug resistant temporal lobe epilepsy patients who underwent epilepsy surgery. Using in situ hybridization, immunohistochemistry and α5-specific receptor autoradiography, we characterized expression of the receptor subunits in specimens from patients with and without Ammon’s horn sclerosis compared to post-mortem controls. Expression of the α5-subunit was abundant throughout all subfields of the hippocampus, including the dentate gyrus, sectors CA1 and CA3, the subiculum and pre- and parasubiculum. Significant but weaker expression was detected for subunits α4 and δ notably in the granule cell/molecular layer of control specimens, but was faint in the other parts of the hippocampus. Expression of all three subunits was similarly altered in sclerotic and non-sclerotic specimens. Respective mRNA levels were increased by about 50–80% in the granule cell layer compared with post-mortem controls. Subunit α5 mRNA levels and immunoreactivities were also increased in the sector CA3 and in the subiculum. Autoradiography for α5-containing receptors using [3H]L-655,708 as ligand showed significantly increased binding in the molecular layer of the dentate gyrus in non-sclerotic specimens. Increased expression of the α5 and δ subunits is in contrast to the previously observed downregulation of these subunits in different epilepsy models, whereas increased expression of α4 in temporal lobe epilepsy patients is consistent with that in the rodent models. Our findings indicate increased tonic inhibition likely representing an endogenous anticonvulsive mechanism in temporal lobe epilepsy.
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Affiliation(s)
- Günther Sperk
- Department of Pharmacology, Medical University of Innsbruck, 6020 Innsbruck, Austria
| | - Susanne Pirker
- Neurological Department, Klinik Hietzing, 1130 Vienna, Austria
| | - Elisabeth Gasser
- Department of Pharmacology, Medical University of Innsbruck, 6020 Innsbruck, Austria
| | - Anna Wieselthaler
- Department of Pharmacology, Medical University of Innsbruck, 6020 Innsbruck, Austria
| | - Anneliese Bukovac
- Department of Pharmacology, Medical University of Innsbruck, 6020 Innsbruck, Austria
| | - Giorgi Kuchukhidze
- Department of Neurology, Christian Doppler Klinik, Affiliated Member of the European Reference Network EpiCARE and Centre for Cognitive Neuroscience, Paracelsus Medical University of Salzburg, 5020 Salzburg, Austria.,Neuroscience Institute, Christian Doppler Klinik, 5020 Salzburg, Austria
| | - Hans Maier
- INNPATH GmbH-Institute of Pathology, 6020 Innsbruck, Austria
| | - Meinrad Drexel
- Department of Pharmacology, Medical University of Innsbruck, 6020 Innsbruck, Austria.,Institute of Molecular and Cellular Pharmacology, Medical University of Innsbruck, 6020 Innsbruck, Austria
| | | | - Marin Ortler
- Department of Neurosurgery, Klinik Landstrasse, Vienna Healthcare Network, 1030Vienna, Austria.,Department of Neurosurgery, Medical University of Innsbruck, 6020 Innsbruck, Austria
| | - Thomas Czech
- Department of Neurosurgery, Medical University Vienna, 1090 Vienna, Austria
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17
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Zhang X, Liu Y, Hong X, Li X, Meshul CK, Moore C, Yang Y, Han Y, Li WG, Qi X, Lou H, Duan S, Xu TL, Tong X. NG2 glia-derived GABA release tunes inhibitory synapses and contributes to stress-induced anxiety. Nat Commun 2021; 12:5740. [PMID: 34593806 PMCID: PMC8484468 DOI: 10.1038/s41467-021-25956-y] [Citation(s) in RCA: 38] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Accepted: 09/09/2021] [Indexed: 11/08/2022] Open
Abstract
NG2 glia, also known as oligodendrocyte precursor cells (OPCs), play an important role in proliferation and give rise to myelinating oligodendrocytes during early brain development. In contrast to other glial cell types, the most intriguing aspect of NG2 glia is their ability to directly sense synaptic inputs from neurons. However, whether this synaptic interaction is bidirectional or unidirectional, or its physiological relevance has not yet been clarified. Here, we report that NG2 glia form synaptic complexes with hippocampal interneurons and that selective photostimulation of NG2 glia (expressing channelrhodopsin-2) functionally drives GABA release and enhances inhibitory synaptic transmission onto proximal interneurons in a microcircuit. The mechanism involves GAD67 biosynthesis and VAMP-2 containing vesicular exocytosis. Further, behavioral assays demonstrate that NG2 glia photoactivation triggers anxiety-like behavior in vivo and contributes to chronic social defeat stress.
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Affiliation(s)
- Xiao Zhang
- Center for Brain Science, Shanghai Children's Medical Center, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Department of Anatomy and Physiology, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Yao Liu
- Center for Brain Science, Shanghai Children's Medical Center, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Department of Anatomy and Physiology, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Xiaoqi Hong
- Center for Brain Science, Shanghai Children's Medical Center, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Department of Anatomy and Physiology, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Xia Li
- Institute of Special Environmental Medicine, Co-innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu, China
| | - Charles K Meshul
- Research Services, VA Medical Center, Portland, OR, USA
- Department of Behavioral Neuroscience and Pathology, Oregon Health & Science University, Portland, OR, USA
| | - Cynthia Moore
- Research Services, VA Medical Center, Portland, OR, USA
| | - Yabing Yang
- Center for Brain Science, Shanghai Children's Medical Center, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Department of Anatomy and Physiology, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Yanfei Han
- Department of Anatomy and Physiology, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Wei-Guang Li
- Center for Brain Science, Shanghai Children's Medical Center, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Department of Anatomy and Physiology, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Xin Qi
- Center for Brain Science, Shanghai Children's Medical Center, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Department of Anatomy and Physiology, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Huifang Lou
- Department of Neurobiology, Key Laboratory of Medical Neurobiology of Ministry of Health of China, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Shumin Duan
- Department of Neurobiology, Key Laboratory of Medical Neurobiology of Ministry of Health of China, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Tian-Le Xu
- Center for Brain Science, Shanghai Children's Medical Center, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Department of Anatomy and Physiology, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Xiaoping Tong
- Center for Brain Science, Shanghai Children's Medical Center, School of Medicine, Shanghai Jiao Tong University, Shanghai, China.
- Department of Anatomy and Physiology, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
- Shanghai Research Center for Brain Science and Brain-Inspired Intelligence, Shanghai, China.
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18
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Xiong B, Karim F, Eloy DJ, Ye JH. Gabra6100Q allele Sprague-Dawley rats have a higher sensitivity to hypnosis induced by isoflurane and ethanol than the wild type rats. Neurosci Lett 2021; 762:136142. [PMID: 34332026 DOI: 10.1016/j.neulet.2021.136142] [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: 05/05/2021] [Revised: 07/24/2021] [Accepted: 07/26/2021] [Indexed: 10/20/2022]
Abstract
BACKGROUND The neurobiological mechanisms underlying how general anesthetics render a patient's unconsciousness (hypnosis) remains elusive. The role of the cerebellum in hypnosis induced by general anesthetics is unknown. Gabra6100Q allele Sprague-Dawley (SD) rats have a naturally occurring single nucleotide polymorphism in the GABAA receptor α6 subunit gene that is expressed exclusively in cerebellum granule cells. METHODS We examined the loss of righting reflex (LORR) induced by isoflurane, and ethanol in Gabra6100Q rats compared with those in wild type (WT) SD rats. We also examined the change of c-Fos expression induced by isoflurane exposure in cerebellum granule cells of both mutant and WT rats. RESULTS Gabra6100Q rats are more sensitive than WT rats to the LORR induced by isoflurane and ethanol. Moreover, isoflurane exposure induced a greater reduction in c-Fos expression in cerebellum granule cells of Gabra6100Q rats than WT rats. CONCLUSIONS Based on these data, we speculate that cerebellum may be involved in the hypnosis induced by some general anesthetics and thus may represent a novel target of general anesthetics.
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Affiliation(s)
- Bo Xiong
- Department of Anesthesiology, Pharmacology and Physiology, Rutgers-New Jersey Medical School, Newark, NJ, USA; Department of Anesthesiology, Shanghai Cancer Center, Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, China
| | - Farabi Karim
- Department of Anesthesiology, Pharmacology and Physiology, Rutgers-New Jersey Medical School, Newark, NJ, USA
| | - Daniel J Eloy
- Department of Anesthesiology, Pharmacology and Physiology, Rutgers-New Jersey Medical School, Newark, NJ, USA
| | - Jiang-Hong Ye
- Department of Anesthesiology, Pharmacology and Physiology, Rutgers-New Jersey Medical School, Newark, NJ, USA.
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19
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Wyroślak M, Lebida K, Mozrzymas JW. Induction of Inhibitory Synaptic Plasticity Enhances Tonic Current by Increasing the Content of α5-Subunit Containing GABA A Receptors in Hippocampal Pyramidal Neurons. Neuroscience 2021; 467:39-46. [PMID: 34033868 DOI: 10.1016/j.neuroscience.2021.05.020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Revised: 05/14/2021] [Accepted: 05/17/2021] [Indexed: 11/16/2022]
Abstract
It is known that besides synaptic inhibition, there is a persistent component of inhibitory drive mediated by tonic currents which is believed to mediate majority of the total inhibitory charge in hippocampal neurons. Tonic currents, depending on cell types, can be mediated by a variety of GABAA receptor (GABAAR) subtypes but in pyramidal neurons, α5-subunit containing receptors were found to be predominant. Importantly, α5-GABAARs were implicated in both inhibitory and excitatory synaptic plasticity as well as in a variety of cognitive tasks. In the present study, we asked whether the protocol that evokes NMDAR-dependent GABAergic inhibitory long-term potentiation (iLTP) also induces the plasticity of tonic inhibition in hippocampal pyramidal neurons. Our whole-cell patch-clamp recordings revealed that the induction of this type of iLTP is associated with a marked increase in tonic current. By using the specific inverse agonist of α5-containing GABAARs (L-655,709) we provide evidence that this plastic change in tonic current is correlated with an increased proportion of this type of GABAARs. On the contrary, the iLTP induction did not affect the tonic current potentiated by THIP, indicating that the pool of δ subunit-containing GABAARs receptors remains unaffected. We conclude that the α5-GABAARs-dependent plasticity of tonic inhibition is a novel dimension of the neuroplasticity of the inhibitory drive in the hippocampal principal neurons. Overall, α5-containing GABAARs emerge as key players in a variety of plasticity mechanisms operating over a large span of time and spatial scales.
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Affiliation(s)
- Marcin Wyroślak
- Department of Biophysics and Neuroscience, Wroclaw Medical University, 50-367 Wroclaw, Poland.
| | - Katarzyna Lebida
- Department of Biophysics and Neuroscience, Wroclaw Medical University, 50-367 Wroclaw, Poland
| | - Jerzy W Mozrzymas
- Department of Biophysics and Neuroscience, Wroclaw Medical University, 50-367 Wroclaw, Poland
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20
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Wu K, Han W, Tian Q, Li Y, Lu W. Activity- and sleep-dependent regulation of tonic inhibition by Shisa7. Cell Rep 2021; 34:108899. [PMID: 33761345 PMCID: PMC8025742 DOI: 10.1016/j.celrep.2021.108899] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Revised: 12/22/2020] [Accepted: 03/03/2021] [Indexed: 02/08/2023] Open
Abstract
Tonic inhibition mediated by extrasynaptic γ-aminobutyric acid type A receptors (GABAARs) critically regulates neuronal excitability and brain function. However, the mechanisms regulating tonic inhibition remain poorly understood. Here, we report that Shisa7 is critical for tonic inhibition regulation in hippocampal neurons. In juvenile Shisa7 knockout (KO) mice, α5-GABAAR-mediated tonic currents are significantly reduced. Mechanistically, Shisa7 is crucial for α5-GABAAR exocytosis. Additionally, Shisa7 regulation of tonic inhibition requires protein kinase A (PKA) that phosphorylates Shisa7 serine 405 (S405). Importantly, tonic inhibition undergoes activity-dependent regulation, and Shisa7 is required for homeostatic potentiation of tonic inhibition. Interestingly, in young adult Shisa7 KOs, basal tonic inhibition in hippocampal neurons is unaltered, largely due to the diminished α5-GABAAR component of tonic inhibition. However, at this stage, tonic inhibition oscillates during the daily sleep/wake cycle, a process requiring Shisa7. Together, these data demonstrate that intricate signaling mechanisms regulate tonic inhibition at different developmental stages and reveal a molecular link between sleep and tonic inhibition.
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Affiliation(s)
- Kunwei Wu
- Synapse and Neural Circuit Research Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
| | - Wenyan Han
- Synapse and Neural Circuit Research Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
| | - Qingjun Tian
- Synapse and Neural Circuit Research Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
| | - Yan Li
- Proteomics Core Facility, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
| | - Wei Lu
- Synapse and Neural Circuit Research Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA.
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21
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Joy MT, Carmichael ST. Encouraging an excitable brain state: mechanisms of brain repair in stroke. Nat Rev Neurosci 2021; 22:38-53. [PMID: 33184469 PMCID: PMC10625167 DOI: 10.1038/s41583-020-00396-7] [Citation(s) in RCA: 85] [Impact Index Per Article: 28.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/04/2020] [Indexed: 02/02/2023]
Abstract
Stroke induces a plastic state in the brain. This period of enhanced plasticity leads to the sprouting of new axons, the formation of new synapses and the remapping of sensory-motor functions, and is associated with motor recovery. This is a remarkable process in the adult brain, which is normally constrained in its levels of neuronal plasticity and connectional change. Recent evidence indicates that these changes are driven by molecular systems that underlie learning and memory, such as changes in cellular excitability during memory formation. This Review examines circuit changes after stroke, the shared mechanisms between memory formation and brain repair, the changes in neuronal excitability that underlie stroke recovery, and the molecular and pharmacological interventions that follow from these findings to promote motor recovery in animal models. From these findings, a framework emerges for understanding recovery after stroke, central to which is the concept of neuronal allocation to damaged circuits. The translation of the concepts discussed here to recovery in humans is underway in clinical trials for stroke recovery drugs.
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Affiliation(s)
- Mary T Joy
- Department of Neurology, David Geffen School of Medicine, UCLA, Los Angeles, CA, USA
| | - S Thomas Carmichael
- Department of Neurology, David Geffen School of Medicine, UCLA, Los Angeles, CA, USA.
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22
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Lévesque M, Biagini G, Avoli M. Neurosteroids and Focal Epileptic Disorders. Int J Mol Sci 2020; 21:ijms21249391. [PMID: 33321734 PMCID: PMC7763947 DOI: 10.3390/ijms21249391] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Revised: 11/27/2020] [Accepted: 12/08/2020] [Indexed: 11/18/2022] Open
Abstract
Neurosteroids are a family of compounds that are synthesized in principal excitatory neurons and glial cells, and derive from the transformation of cholesterol into pregnenolone. The most studied neurosteroids—allopregnanolone and allotetrahydrodeoxycorticosterone (THDOC)—are known to modulate GABAA receptor-mediated transmission, thus playing a role in controlling neuronal network excitability. Given the role of GABAA signaling in epileptic disorders, neurosteroids have profound effects on seizure generation and play a role in the development of chronic epileptic conditions (i.e., epileptogenesis). We review here studies showing the effects induced by neurosteroids on epileptiform synchronization in in vitro brain slices, on epileptic activity in in vivo models, i.e., in animals that were made epileptic with chemoconvulsant treatment, and in epileptic patients. These studies reveal that neurosteroids can modulate ictogenesis and the occurrence of pathological network activity such as interictal spikes and high-frequency oscillations (80–500 Hz). Moreover, they can delay the onset of spontaneous seizures in animal models of mesial temporal lobe epilepsy. Overall, this evidence suggests that neurosteroids represent a new target for the treatment of focal epileptic disorders.
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Affiliation(s)
- Maxime Lévesque
- Montreal Neurological Institute-Hospital & Department of Neurology and Neurosurgery, 3801 University Street, Montreal, QC H3A 2B4, Canada;
- Correspondence: ; Tel.: +1-514-398-8909
| | - Giuseppe Biagini
- Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, Via Università 4, 41121 Modena, Italy;
| | - Massimo Avoli
- Montreal Neurological Institute-Hospital & Department of Neurology and Neurosurgery, 3801 University Street, Montreal, QC H3A 2B4, Canada;
- Department of Physiology, McGill University, Montreal, QC H3A 2B4, Canada
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23
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Hirano AA, Vuong HE, Kornmann HL, Schietroma C, Stella SL, Barnes S, Brecha NC. Vesicular Release of GABA by Mammalian Horizontal Cells Mediates Inhibitory Output to Photoreceptors. Front Cell Neurosci 2020; 14:600777. [PMID: 33335476 PMCID: PMC7735995 DOI: 10.3389/fncel.2020.600777] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Accepted: 11/04/2020] [Indexed: 12/14/2022] Open
Abstract
Feedback inhibition by horizontal cells regulates rod and cone photoreceptor calcium channels that control their release of the neurotransmitter glutamate. This inhibition contributes to synaptic gain control and the formation of the center-surround antagonistic receptive fields passed on to all downstream neurons, which is important for contrast sensitivity and color opponency in vision. In contrast to the plasmalemmal GABA transporter found in non-mammalian horizontal cells, there is evidence that the mechanism by which mammalian horizontal cells inhibit photoreceptors involves the vesicular release of the inhibitory neurotransmitter GABA. Historically, inconsistent findings of GABA and its biosynthetic enzyme, L-glutamate decarboxylase (GAD) in horizontal cells, and the apparent lack of surround response block by GABAergic agents diminished support for GABA's role in feedback inhibition. However, the immunolocalization of the vesicular GABA transporter (VGAT) in the dendritic and axonal endings of horizontal cells that innervate photoreceptor terminals suggested GABA was released via vesicular exocytosis. To test the idea that GABA is released from vesicles, we localized GABA and GAD, multiple SNARE complex proteins, synaptic vesicle proteins, and Cav channels that mediate exocytosis to horizontal cell dendritic tips and axonal terminals. To address the perceived relative paucity of synaptic vesicles in horizontal cell endings, we used conical electron tomography on mouse and guinea pig retinas that revealed small, clear-core vesicles, along with a few clathrin-coated vesicles and endosomes in horizontal cell processes within photoreceptor terminals. Some small-diameter vesicles were adjacent to the plasma membrane and plasma membrane specializations. To assess vesicular release, a functional assay involving incubation of retinal slices in luminal VGAT-C antibodies demonstrated vesicles fused with the membrane in a depolarization- and calcium-dependent manner, and these labeled vesicles can fuse multiple times. Finally, targeted elimination of VGAT in horizontal cells resulted in a loss of tonic, autaptic GABA currents, and of inhibitory feedback modulation of the cone photoreceptor Cai, consistent with the elimination of GABA release from horizontal cell endings. These results in mammalian retina identify the central role of vesicular release of GABA from horizontal cells in the feedback inhibition of photoreceptors.
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Affiliation(s)
- Arlene A. Hirano
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
- Veterans Administration Greater Los Angeles Healthcare System, Los Angeles, CA, United States
| | - Helen E. Vuong
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
| | - Helen L. Kornmann
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
| | - Cataldo Schietroma
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
| | - Salvatore L. Stella
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
| | - Steven Barnes
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
- Department of Ophthalmology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
- Doheny Eye Institute, University of California, Los Angeles, Los Angeles, CA, United States
| | - Nicholas C. Brecha
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
- Veterans Administration Greater Los Angeles Healthcare System, Los Angeles, CA, United States
- Department of Ophthalmology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
- Stein Eye Institute, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
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Klenowski PM, Fogarty MJ, Drieberg-Thompson JR, Bellingham MC, Bartlett SE. Reduced Inhibitory Inputs On Basolateral Amygdala Principal Neurons Following Long-Term Alcohol Consumption. Neuroscience 2020; 452:219-227. [PMID: 33212222 DOI: 10.1016/j.neuroscience.2020.10.039] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Revised: 10/27/2020] [Accepted: 10/28/2020] [Indexed: 12/16/2022]
Abstract
Recent studies have shown that manipulating basolateral amygdala (BLA) activity can affect alcohol consumption, particularly following chronic and/or long-term intake. Although the mechanisms underlying these effects remain unclear, the BLA is highly sensitive to emotional stimuli including stress and anxiety. Negative emotional states facilitate alcohol craving and relapse in patients with alcohol use disorders. Consequently, the aim of this study was to determine the effect of long-term (10 weeks) alcohol drinking on synaptic activity in BLA principal neurons. We utilized an intermittent drinking paradigm in rats, which facilitated escalating, binge-like alcohol intake over the 10 week drinking period. We then recorded spontaneous excitatory and inhibitory postsynaptic currents of BLA principal neurons from long-term alcohol drinking rats and aged-matched water drinking controls. Excitatory postsynaptic current properties from long-term alcohol drinking rats were unchanged compared to those from age-matched water drinking controls. Conversely, we observed significant reductions of inhibitory postsynaptic current amplitude and frequency in long-term ethanol drinking rats compared to age-matched water drinking controls. These results highlight substantive decreases in basal inhibitory synaptic activity of BLA principal neurons following long-term alcohol consumption. A loss of inhibitory control in the BLA could explain the high incidence of compulsive drinking and stress- or anxiety-induced relapse in patients with alcohol use disorders.
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Affiliation(s)
- Paul M Klenowski
- Brudnick Neuropsychiatric Research Institute, Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA 01605, USA.
| | - Matthew J Fogarty
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, USA; School of Biomedical Biosciences, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Joy R Drieberg-Thompson
- School of Biomedical Biosciences, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Mark C Bellingham
- School of Biomedical Biosciences, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Selena E Bartlett
- Translational Research Institute, Queensland University of Technology, Brisbane 4102, Australia.
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25
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Sperk G, Kirchmair E, Bakker J, Sieghart W, Drexel M, Kondova I. Immunohistochemical distribution of 10 GABA A receptor subunits in the forebrain of the rhesus monkey Macaca mulatta. J Comp Neurol 2020; 528:2551-2568. [PMID: 32220012 PMCID: PMC7496627 DOI: 10.1002/cne.24910] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Revised: 03/11/2020] [Accepted: 03/19/2020] [Indexed: 12/23/2022]
Abstract
GABAA receptors are composed of five subunits arranged around a central chloride channel. Their subunits originate from different genes or gene families. The majority of GABAA receptors in the mammalian brain consist of two α-, two β- and one γ- or δ-subunit. This subunit organization crucially determines the physiological and pharmacological properties of the GABAA receptors. Using immunohistochemistry, we investigated the distribution of 10 GABAA receptor subunits (α1, α2, α3, α4, α5, β1, β2, β3, γ2, and δ) in the fore brain of three female rhesus monkeys (Macaca mulatta). Within the cerebral cortex, subunits α1, α5, β2, β3, and γ2 were found in all layers, α2, α3, and β1 were more concentrated in the inner and outer layers. The caudate/putamen was rich in α1, α2, α5, all three β-subunits, γ2, and δ. Subunits α3 and α5 were more concentrated in the caudate than in the putamen. In contrast, α1, α2, β1, β2, γ2, and δ were highest in the pallidum. Most dorsal thalamic nuclei contained subunits α1, α2, α4, β2, β3, and γ2, whereas α1, α3, β1, and γ2 were most abundant in the reticular nucleus. Within the amygdala, subunits α1, α2, α5, β1, β3, γ2, and δ were concentrated in the cortical nucleus, whereas in the lateral and basolateral amygdala α1, α2, α5, β1, β3, and δ, and in the central amygdala α1, α2, β3, and γ2 were most abundant. Interestingly, subunit α3-IR outlined the intercalated nuclei of the amygdala. In the hippocampus, subunits α1, α2, α5, β2, β3, γ2, and δ were highly expressed in the dentate molecular layer, whereas α1, α2, α3, α5, β1, β2, β3, and γ2 were concentrated in sector CA1 and the subiculum. The distribution of GABAA receptor subunits in the rhesus monkey was highly heterogeneous indicating a high number of differently assembled receptors. In most areas investigated, notably in the striatum/pallidum, amygdaloid nuclei and in the hippocampus it was more diverse than in the rat and mouse indicating a more heterogeneous and less defined receptor assembly in the monkey than in rodent brain.
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Key Words
- GABAA receptor subunits
- RRID:AB_2108828
- ab GAD67, RRID:AB_2278725
- ab NeuN, RRID:AB_2278725
- ab α2, RRID:AB_2827793
- ab α3, RRID:AB_2827797
- ab α4, RRID:AB_2827798
- ab α5, RRID:AB_2827799
- ab β1, RRID:AB_2827800
- ab β2, RRID:AB_2827801
- ab β3, RRID:AB_2827802
- ab γ2, RRID:AB_2827803
- ab δ, RRID:AB_2827804
- amygdala
- antibody α1 (BD24)
- basal ganglia
- benzodiazepine
- goat biotinylated anti-rabbit ab, RRID:AB_2336810
- horse anti-mouse ab, RRID:AB_2336811
- immunohistochemistry
- monkey
- primate
- thalamus
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Affiliation(s)
- Günther Sperk
- Department of PharmacologyMedical University InnsbruckInnsbruckAustria
| | - Elke Kirchmair
- Department of PharmacologyMedical University InnsbruckInnsbruckAustria
| | - Jaco Bakker
- Division of Veterinary Care, Animal Science DepartmentBiomedical Primate Research CentreRijswijkThe Netherlands
| | - Werner Sieghart
- Department of Molecular Neurosciences, Center for Brain ResearchMedical University ViennaViennaAustria
| | - Meinrad Drexel
- Department of PharmacologyMedical University InnsbruckInnsbruckAustria
| | - Ivanela Kondova
- Division of Pathology and Microbiology, Animal Science DepartmentBiomedical Primate Research CentreRijswijkThe Netherlands
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26
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Serratto GM, Pizzi E, Murru L, Mazzoleni S, Pelucchi S, Marcello E, Mazzanti M, Passafaro M, Bassani S. The Epilepsy-Related Protein PCDH19 Regulates Tonic Inhibition, GABA AR Kinetics, and the Intrinsic Excitability of Hippocampal Neurons. Mol Neurobiol 2020; 57:5336-5351. [PMID: 32880860 PMCID: PMC7541378 DOI: 10.1007/s12035-020-02099-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Accepted: 08/25/2020] [Indexed: 12/19/2022]
Abstract
PCDH19 encodes for protocadherin-19 (PCDH19), a cell-adhesion molecule of the cadherin superfamily preferentially expressed in the brain. PCDH19 mutations cause a neurodevelopmental syndrome named epileptic encephalopathy, early infantile, 9 (EIEE9) characterized by seizures associated with cognitive and behavioral deficits. We recently reported that PCDH19 binds the alpha subunits of GABAA receptors (GABAARs), modulating their surface availability and miniature inhibitory postsynaptic currents (mIPSCs). Here, we investigated whether PCDH19 regulatory function on GABAARs extends to the extrasynaptic receptor pool that mediates tonic current. In fact, the latter shapes neuronal excitability and network properties at the base of information processing. By combining patch-clamp recordings in whole-cell and cell-attached configurations, we provided a functional characterization of primary hippocampal neurons from embryonic rats of either sex expressing a specific PCDH19 short hairpin (sh)RNA. We first demonstrated that PCDH19 downregulation reduces GABAAR-mediated tonic current, evaluated by current shift and baseline noise analysis. Next, by single-channel recordings, we showed that PCDH19 regulates GABAARs kinetics without altering their conductance. In particular, GABAARs of shRNA-expressing neurons preferentially exhibit brief openings at the expense of long ones, thus displaying a flickering behavior. Finally, we showed that PCDH19 downregulation reduces the rheobase and increases the frequency of action potential firing, thus indicating neuronal hyperexcitability. These findings establish PCDH19 as a critical determinant of GABAAR-mediated tonic transmission and GABAARs gating, and provide the first mechanistic insights into PCDH19-related hyperexcitability and comorbidities.
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Affiliation(s)
| | - Erika Pizzi
- Department of Bioscience, University of Milan, 20133, Milan, Italy
| | - Luca Murru
- Institute of Neuroscience, CNR, 20129, Milan, Italy.,NeuroMI Milan Center for Neuroscience, University of Milano-Bicocca, 20126, Milan, Italy
| | - Sara Mazzoleni
- Institute of Neuroscience, CNR, 20129, Milan, Italy.,Department of Medical Biotechnology and Translational Medicine, University of Milan, 20129, Milan, Italy
| | - Silvia Pelucchi
- Department of Pharmacological and Biomolecular Sciences, University of Milan, 20133, Milan, Italy
| | - Elena Marcello
- Department of Pharmacological and Biomolecular Sciences, University of Milan, 20133, Milan, Italy
| | - Michele Mazzanti
- Department of Bioscience, University of Milan, 20133, Milan, Italy
| | - Maria Passafaro
- Institute of Neuroscience, CNR, 20129, Milan, Italy.,NeuroMI Milan Center for Neuroscience, University of Milano-Bicocca, 20126, Milan, Italy
| | - Silvia Bassani
- Institute of Neuroscience, CNR, 20129, Milan, Italy. .,NeuroMI Milan Center for Neuroscience, University of Milano-Bicocca, 20126, Milan, Italy.
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27
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Hoshino O, Kameno R, Kubo J, Watanabe K. Spatiotemporal regulation of GABA concentration in extracellular space by gliotransmission crucial for extrasynaptic receptor-mediated improvement of sensory tuning performance in schizophrenia. J Comput Neurosci 2020; 48:317-332. [PMID: 32761409 DOI: 10.1007/s10827-020-00755-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2019] [Revised: 06/14/2020] [Accepted: 07/07/2020] [Indexed: 10/23/2022]
Abstract
In schizophrenic patients, sensory tuning performance tends to be deteriorated (i.e., flattened sensory tuning), for which impaired intracortical tonic inhibition arising from a reduction in GABA concentration in extracellular space might be responsible. The δ subunit-containing GABAA receptor, located on extrasynaptic sites, is known to be involved in mediating tonic inhibitory currents in cortical pyramidal cells and is considered to be one of the beneficial therapeutic targets for the treatment of schizophrenia. The transporter GAT-1 in glial (astrocytic) membrane controls concentration of GABA molecules by removing them from extracellular space. We speculated that the upregulation of extrasynaptic receptors might compensate for the impaired tonic inhibition and thus improve their sensory tuning performance, in which the astrocytic GABA transporter might play an important role. To test our hypothesis, we simulated a schizophrenic neural network model with a GABAergic gliotransmission (i.e., GABA transport by transporters embedded in astrocytic membranes) mechanism that modulates local ambient (extracellular) GABA levels in a neuronal activity-dependent manner. Upregulating extrasynaptic GABA receptors compensated the impaired tonic inhibition and sharpened the sensory tuning, provided that ambient GABA molecules around stimulus-sensitive pyramidal cells were actively removed during sensory stimulation. We suggest that the upregulation of extrasynaptic GABA receptors can improve the performance of sensory tuning in schizophrenic patients, for which spatiotemporal regulation of ambient GABA concentration by gliotransmission may be crucial.
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Affiliation(s)
- Osamu Hoshino
- Department of Intelligent Systems Engineering, Ibaraki University, 4-12-1 Nakanarusawa, Hitachi, Ibaraki, 316-8511, Japan. .,Southern Tohoku Research Institute for Neuroscience, Southern Tohoku General Hospital, 7-115 Yatsuyamada, Koriyama, Fukushima, 963-8563, Japan.
| | - Rikiya Kameno
- Southern Tohoku Research Institute for Neuroscience, Southern Tohoku General Hospital, 7-115 Yatsuyamada, Koriyama, Fukushima, 963-8563, Japan
| | - Jin Kubo
- Department of Rehabilitation Medicine, International University of Health and Welfare, Ichikawa Hospital, 6-1-14 Konodai, Ichikawa, Chiba, 272-0827, Japan
| | - Kazuo Watanabe
- Southern Tohoku Research Institute for Neuroscience, Southern Tohoku General Hospital, 7-115 Yatsuyamada, Koriyama, Fukushima, 963-8563, Japan
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28
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Yabuki Y, Liu J, Kawahata I, Izumi H, Shinoda Y, Koga K, Ueno S, Shioda N, Fukunaga K. Anti-Epileptic Effects of FABP3 Ligand MF1 through the Benzodiazepine Recognition Site of the GABA A Receptor. Int J Mol Sci 2020; 21:ijms21155525. [PMID: 32752296 PMCID: PMC7432285 DOI: 10.3390/ijms21155525] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Revised: 07/29/2020] [Accepted: 07/29/2020] [Indexed: 11/16/2022] Open
Abstract
Recently, we developed the fatty acid-binding protein 3 (FABP3) ligand MF1 (4-(2-(1-(2-chlorophenyl)-5-phenyl-1H-pyrazol-3-yl)phenoxy) butanoic acid) as a therapeutic candidate for α-synucleinopathies. MF1 shows affinity towards γ-aminobutyric acid type-A (GABAA) receptor, but its effect on the receptor remains unclear. Here, we investigate the pharmacological properties of MF1 on the GABAA receptor overexpressed in Neuro2A cells. While MF1 (1–100 μm) alone failed to evoke GABA currents, MF1 (1 μm) promoted GABA currents during GABA exposure (1 and 10 μm). MF1-promoted GABA currents were blocked by flumazenil (10 μm) treatment, suggesting that MF1 enhances receptor function via the benzodiazepine recognition site. Acute and chronic administration of MF1 (0.1, 0.3 and 1.0 mg/kg, p.o.) significantly attenuated status epilepticus (SE) and the mortality rate in pilocarpine (PILO: 300 mg/kg, i.p.)-treated mice, similar to diazepam (DZP: 5.0 mg/kg, i.p.). The anti-epileptic effects of DZP (5.0 mg/kg, i.p.) and MF1 (0.3 mg/kg, p.o.) were completely abolished by flumazenil (25 mg/kg, i.p.) treatment. Pentylenetetrazol (PTZ: 90 mg/kg, i.p.)-induced seizures in mice were suppressed by DZP (5.0 mg/kg, i.p.), but not MF1. Collectively, this suggests that MF1 is a mild enhancer of the GABAA receptor and exercises anti-epileptic effects through the receptor’s benzodiazepine recognition site in PILO-induced SE models.
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Affiliation(s)
- Yasushi Yabuki
- Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai 980-8578, Japan; (Y.Y.); (J.L.); (I.K.); (H.I.); (Y.S.)
- Department of Genomic Neurology, Institute of Molecular Embryology and Genetics, Kumamoto University, Kumamoto 860-0811, Japan;
| | - Jiaqi Liu
- Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai 980-8578, Japan; (Y.Y.); (J.L.); (I.K.); (H.I.); (Y.S.)
| | - Ichiro Kawahata
- Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai 980-8578, Japan; (Y.Y.); (J.L.); (I.K.); (H.I.); (Y.S.)
| | - Hisanao Izumi
- Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai 980-8578, Japan; (Y.Y.); (J.L.); (I.K.); (H.I.); (Y.S.)
| | - Yasuharu Shinoda
- Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai 980-8578, Japan; (Y.Y.); (J.L.); (I.K.); (H.I.); (Y.S.)
| | - Kohei Koga
- Department of Neurophysiology, Hyogo College of Medicine, Nishinomiya 663-8501, Japan;
- Department of Neurophysiology, Graduate School of Medicine, Hirosaki University, Hirosaki 036-8216, Japan;
| | - Shinya Ueno
- Department of Neurophysiology, Graduate School of Medicine, Hirosaki University, Hirosaki 036-8216, Japan;
| | - Norifumi Shioda
- Department of Genomic Neurology, Institute of Molecular Embryology and Genetics, Kumamoto University, Kumamoto 860-0811, Japan;
| | - Kohji Fukunaga
- Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai 980-8578, Japan; (Y.Y.); (J.L.); (I.K.); (H.I.); (Y.S.)
- Correspondence: ; Tel.: +81-22-795-6836; Fax: 81-22-795-6835
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29
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Dalby NO, Falk-Petersen CB, Leurs U, Scholze P, Krall J, Frølund B, Wellendorph P. Silencing of spontaneous activity at α4β1/3δ GABA A receptors in hippocampal granule cells reveals different ligand pharmacology. Br J Pharmacol 2020; 177:3975-3990. [PMID: 32484592 DOI: 10.1111/bph.15146] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2019] [Revised: 05/10/2020] [Accepted: 05/14/2020] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND AND PURPOSE The δ-subunit-containing GABAA receptors, α4 β1 δ and α4 β3 δ, in dentate gyrus granule cells (DGGCs) are known to exhibit both spontaneous channel openings (i.e. constitutive activity) and agonist-induced current. The functional implications of spontaneous gating are unclear. In this study, we tested the hypothesis that constitutively active α4 β1/3 δ receptors limit agonist efficacy. EXPERIMENTAL APPROACH Whole-cell electrophysiological recordings of adult male rat and mouse hippocampal DGGCs were used to characterize known agonists and antagonists at δ-subunit-containing GABAA receptors. To separate constitutive and agonist-induced currents, different recording conditions were employed. KEY RESULTS Recordings at either 24°C or 34°C, including the PKC autoinhibitory peptide (19-36) intracellularly, removed spontaneous gating by GABAA receptors. In the absence of spontaneous gating, DGGCs responded to the α4 β1/3 δ orthosteric agonist Thio-THIP with a four-fold increased efficacy relative to recording conditions favouring constitutive activity. Surprisingly, the neutral antagonist gabazine was unable to antagonize the current by Thio-THIP. Furthermore, a current was elicited by gabazine alone only when the constitutive current was silenced (EC50 2.1 μM). The gabazine-induced current was inhibited by picrotoxin, potentiated by DS2, completely absent in δ-/- mice and reduced in β1 -/- mice, but could not be replicated in human α4 β1/3 δ receptors expressed heterologously in HEK cells. CONCLUSION AND IMPLICATIONS Kinase activity infers spontaneous gating in α4 β1/3 δ receptors in DGGCs. This significantly limits the efficacy of GABAA agonists and has implications in pathologies involving aberrant excitability caused by phosphorylation (e.g. addiction and epilepsy). In such cases, the efficacy of δ-preferring GABAA ligands may be reduced.
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Affiliation(s)
- Nils Ole Dalby
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | | | - Ulrike Leurs
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Petra Scholze
- Department of Pathobiology of the Nervous System, Center for Brain Research, Medical University of Vienna, Vienna, Austria
| | - Jacob Krall
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Bente Frølund
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Petrine Wellendorph
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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30
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Gholaminejad A, Gholamipour-Badie H, Nasehi M, Naghdi N. Prelimbic of Medial Prefrontal Cortex GABA Modulation through Testosterone on Spatial Learning and Memory. IRANIAN JOURNAL OF PHARMACEUTICAL RESEARCH : IJPR 2020; 18:1429-1444. [PMID: 32641952 PMCID: PMC6934985 DOI: 10.22037/ijpr.2019.1100745] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Prefrontal cortex (PFC) is involved in multiple functions including attentional processes, spatial orientation, short-term memory, and long-term memory. Our previous study indicated that microinjection of testosterone in CA1 impaired spatial learning and memory. Some evidence suggests that impairment effect of testosterone is mediated by GABAergic system. In the present study, we investigated the interaction of testosterone (androgenic receptor agonist) and bicuculline (GABAA receptor antagonist) on spatial learning and memory performance in the prelimbic (PL) of male Wistar rats. Cannulae were bilaterally implanted into the PL region of PFC and drugs were daily microinjected for two minutes in each side. There are 4 experiments. In the first experiment, three sham groups were operated (solvent of testosterone, bicuculline, testosterone plus bicuculline). In the second experiment, different doses of testosterone (40, 80 μg /0.5 μL DMSO/each side) were injected into the PL before each session. In the third experiment, intra PL injections of bicuculline (2, 4 μg/0.5 μL DMSO/each side) were given before every session. In the last experiment, testosterone (80μg/0.5 μL DMSO/each side) along with bicuculline (2 μg/0.5 μL DMSO/each side) was injected into the PL. The results showed there is no difference between control group and sham operated group. Testosterone 80 μg and bicuculline 2 μg, each given separately, and also in combination increased escape latency to find the platform compared to the sham operated and cause to impaired spatial learning and memory. It is shown that intra PL microinjection of bicuculline after testosterone treatment could not rescue the spatial learning and memory impaired induced by testosterone.
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Affiliation(s)
- Azadeh Gholaminejad
- Department of Physiology and Pharmacology, Pasteur Institute of Iran (IPI), Tehran, Iran.,Department of Cognitive Neuroscience, Institute for Cognitive Science Studies (ICSS), Tehran, Iran
| | | | - Mohammad Nasehi
- Department of Cognitive Neuroscience, Institute for Cognitive Science Studies (ICSS), Tehran, Iran.,Cognitive and neuroscience research center (CNRC), Tehran Medical Sciences, Islamic Azad University, Tehran, Iran
| | - Nasser Naghdi
- Department of Physiology and Pharmacology, Pasteur Institute of Iran (IPI), Tehran, Iran.,Department of Cognitive Neuroscience, Institute for Cognitive Science Studies (ICSS), Tehran, Iran
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31
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Tonic GABA A Conductance Favors Spike-Timing-Dependent over Theta-Burst-Induced Long-Term Potentiation in the Hippocampus. J Neurosci 2020; 40:4266-4276. [PMID: 32327534 DOI: 10.1523/jneurosci.2118-19.2020] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2019] [Revised: 03/21/2020] [Accepted: 04/15/2020] [Indexed: 11/21/2022] Open
Abstract
Synaptic plasticity is triggered by different patterns of network activity. Here, we investigated how LTP in CA3-CA1 synapses induced by different stimulation patterns is affected by tonic GABAA conductances in rat hippocampal slices. Spike-timing-dependent LTP was induced by pairing Schaffer collateral stimulation with antidromic stimulation of CA1 pyramidal neurons. Theta-burst-induced LTP was induced by theta-burst stimulation of Schaffer collaterals. We mimicked increased tonic GABAA conductance by bath application of 30 μm GABA. Surprisingly, tonic GABAA conductance selectively suppressed theta-burst-induced LTP but not spike-timing-dependent LTP. We combined whole-cell patch-clamp electrophysiology, two-photon Ca2+ imaging, glutamate uncaging, and mathematical modeling to dissect the mechanisms underlying these differential effects of tonic GABAA conductance. We found that Ca2+ transients during pairing of an action potential with an EPSP were less sensitive to tonic GABAA conductance-induced shunting inhibition than Ca2+ transients induced by EPSP burst. Our results may explain how different forms of memory are affected by increasing tonic GABAA conductances under physiological or pathologic conditions, as well as under the influence of substances that target extrasynaptic GABAA receptors (e.g., neurosteroids, sedatives, antiepileptic drugs, and alcohol).SIGNIFICANCE STATEMENT Brain activity is associated with neuronal firing and synaptic signaling among neurons. Synaptic plasticity represents a mechanism for learning and memory. However, some neurotransmitters that escape the synaptic cleft or are released by astrocytes can target extrasynaptic receptors. Extrasynaptic GABAA receptors mediate tonic conductances that reduce the excitability of neurons by shunting. This results in the decreased ability for neurons to fire action potentials, but when action potentials are successfully triggered, tonic conductances are unable to reduce them significantly. As such, tonic GABAA conductances have minimal effects on spike-timing-dependent synaptic plasticity while strongly attenuating the plasticity evoked by EPSP bursts. Our findings shed light on how changes in tonic conductances can selectively affect different forms of learning and memory.
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32
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Agoglia AE, Zhu M, Ying R, Sidhu H, Natividad LA, Wolfe SA, Buczynski MW, Contet C, Parsons LH, Roberto M, Herman MA. Corticotropin-Releasing Factor Receptor-1 Neurons in the Lateral Amygdala Display Selective Sensitivity to Acute and Chronic Ethanol Exposure. eNeuro 2020; 7:ENEURO.0420-19.2020. [PMID: 32041742 PMCID: PMC7059189 DOI: 10.1523/eneuro.0420-19.2020] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2019] [Revised: 01/15/2020] [Accepted: 01/28/2020] [Indexed: 12/19/2022] Open
Abstract
The lateral amygdala (LA) serves as the point of entry for sensory information within the amygdala complex, a structure that plays a critical role in emotional processes and has been implicated in alcohol use disorders. Within the amygdala, the corticotropin-releasing factor (CRF) system has been shown to mediate some of the effects of both stress and ethanol, but the effects of ethanol on specific CRF1 receptor circuits in the amygdala have not been fully established. We used male CRF1:GFP reporter mice to characterize CRF1-expressing (CRF1+) and nonexpressing (CRF1-) LA neurons and investigate the effects of acute and chronic ethanol exposure on these populations. The CRF1+ population was found to be composed predominantly of glutamatergic projection neurons with a minority subpopulation of interneurons. CRF1+ neurons exhibited a tonic conductance that was insensitive to acute ethanol. CRF1- neurons did not display a basal tonic conductance, but the application of acute ethanol induced a δ GABAA receptor subunit-dependent tonic conductance and enhanced phasic GABA release onto these cells. Chronic ethanol increased CRF1+ neuronal excitability but did not significantly alter phasic or tonic GABA signaling in either CRF1+ or CRF1- cells. Chronic ethanol and withdrawal also did not alter basal extracellular GABA or glutamate transmitter levels in the LA/BLA and did not alter the sensitivity of GABA or glutamate to acute ethanol-induced increases in transmitter release. Together, these results provide the first characterization of the CRF1+ population of LA neurons and suggest mechanisms for differential acute ethanol sensitivity within this region.
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Affiliation(s)
- Abigail E Agoglia
- Department of Pharmacology, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
- Bowles Center for Alcohol Studies, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
| | - ManHua Zhu
- Neuroscience Curriculum, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
| | - Rose Ying
- Department of Pharmacology, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
- Bowles Center for Alcohol Studies, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
| | - Harpreet Sidhu
- Department of Neuroscience, The Scripps Research Institute, La Jolla, California 92037
| | - Luis A Natividad
- University of Texas at Austin, College of Pharmacy - Division of Pharmacology and Toxicology, Austin, TX 78712
| | - Sarah A Wolfe
- Department of Neuroscience, The Scripps Research Institute, La Jolla, California 92037
| | - Matthew W Buczynski
- School of Neuroscience, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061
| | - Candice Contet
- Department of Neuroscience, The Scripps Research Institute, La Jolla, California 92037
| | - Loren H Parsons
- Department of Neuroscience, The Scripps Research Institute, La Jolla, California 92037
| | - Marisa Roberto
- Department of Neuroscience, The Scripps Research Institute, La Jolla, California 92037
| | - Melissa A Herman
- Department of Pharmacology, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
- Bowles Center for Alcohol Studies, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
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GABA-mediated tonic inhibition differentially modulates gain in functional subtypes of cortical interneurons. Proc Natl Acad Sci U S A 2020; 117:3192-3202. [PMID: 31974304 DOI: 10.1073/pnas.1906369117] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
The binding of GABA (γ-aminobutyric acid) to extrasynaptic GABAA receptors generates tonic inhibition that acts as a powerful modulator of cortical network activity. Despite GABA being present throughout the extracellular space of the brain, previous work has shown that GABA may differentially modulate the excitability of neuron subtypes according to variation in chloride gradient. Here, using biophysically detailed neuron models, we predict that tonic inhibition can differentially modulate the excitability of neuron subtypes according to variation in electrophysiological properties. Surprisingly, tonic inhibition increased the responsiveness (or gain) in models with features typical for somatostatin interneurons but decreased gain in models with features typical for parvalbumin interneurons. Patch-clamp recordings from cortical interneurons supported these predictions, and further in silico analysis was then performed to seek a putative mechanism underlying gain modulation. We found that gain modulation in models was dependent upon the magnitude of tonic current generated at depolarized membrane potential-a property associated with outward rectifying GABAA receptors. Furthermore, tonic inhibition produced two biophysical changes in models of relevance to neuronal excitability: 1) enhanced action potential repolarization via increased current flow into the dendritic compartment, and 2) reduced activation of voltage-dependent potassium channels. Finally, we show theoretically that reduced potassium channel activation selectively increases gain in models possessing action potential dynamics typical for somatostatin interneurons. Potassium channels in parvalbumin-type models deactivate rapidly and are unavailable for further modulation. These findings show that GABA can differentially modulate interneuron excitability and suggest a mechanism through which this occurs in silico via differences of intrinsic electrophysiological properties.
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Γ-Aminobutyric acid in adult brain: an update. Behav Brain Res 2019; 376:112224. [DOI: 10.1016/j.bbr.2019.112224] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2019] [Revised: 09/09/2019] [Accepted: 09/09/2019] [Indexed: 01/21/2023]
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Prestori F, Mapelli L, D'Angelo E. Diverse Neuron Properties and Complex Network Dynamics in the Cerebellar Cortical Inhibitory Circuit. Front Mol Neurosci 2019; 12:267. [PMID: 31787879 PMCID: PMC6854908 DOI: 10.3389/fnmol.2019.00267] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Accepted: 10/17/2019] [Indexed: 12/12/2022] Open
Abstract
Neuronal inhibition can be defined as a spatiotemporal restriction or suppression of local microcircuit activity. The importance of inhibition relies in its fundamental role in shaping signal processing in single neurons and neuronal circuits. In this context, the activity of inhibitory interneurons proved the key to endow networks with complex computational and dynamic properties. In the last 50 years, the prevailing view on the functional role of cerebellar cortical inhibitory circuits was that excitatory and inhibitory inputs sum spatially and temporally in order to determine the motor output through Purkinje cells (PCs). Consequently, cerebellar inhibition has traditionally been conceived in terms of restricting or blocking excitation. This assumption has been challenged, in particular in the cerebellar cortex where all neurons except granule cells (and unipolar brush cells in specific lobules) are inhibitory and fire spontaneously at high rates. Recently, a combination of electrophysiological recordings in vitro and in vivo, imaging, optogenetics and computational modeling, has revealed that inhibitory interneurons play a much more complex role in regulating cerebellar microcircuit functions: inhibition shapes neuronal response dynamics in the whole circuit and eventually regulate the PC output. This review elaborates current knowledge on cerebellar inhibitory interneurons [Golgi cells, Lugaro cells (LCs), basket cells (BCs) and stellate cells (SCs)], starting from their ontogenesis and moving up to their morphological, physiological and plastic properties, and integrates this knowledge with that on the more renown granule cells and PCs. We will focus on the circuit loops in which these interneurons are involved and on the way they generate feed-forward, feedback and lateral inhibition along with complex spatio-temporal response dynamics. In this perspective, inhibitory interneurons emerge as the real controllers of cerebellar functioning.
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Affiliation(s)
- Francesca Prestori
- Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy
| | - Lisa Mapelli
- Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy
| | - Egidio D'Angelo
- Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy.,IRCCS Mondino Foundation, Pavia, Italy
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Neumann S, Boothman-Burrell L, Gowing EK, Jacobsen TA, Ahring PK, Young SL, Sandager-Nielsen K, Clarkson AN. The Delta-Subunit Selective GABA A Receptor Modulator, DS2, Improves Stroke Recovery via an Anti-inflammatory Mechanism. Front Neurosci 2019; 13:1133. [PMID: 31736685 PMCID: PMC6828610 DOI: 10.3389/fnins.2019.01133] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2019] [Accepted: 10/07/2019] [Indexed: 12/22/2022] Open
Abstract
Inflammatory processes are known to contribute to tissue damage in the central nervous system (CNS) across a broad range of neurological conditions, including stroke. Gamma amino butyric acid (GABA), the main inhibitory neurotransmitter in the CNS, has been implicated in modulating peripheral immune responses by acting on GABA A receptors on antigen-presenting cells and lymphocytes. Here, we investigated the effects and mechanism of action of the delta-selective compound, DS2, to improve stroke recovery and modulate inflammation. We report a decrease in nuclear factor (NF)-κB activation in innate immune cells over a concentration range in vitro. Following a photochemically induced motor cortex stroke, treatment with DS2 at 0.1 mg/kg from 1 h post-stroke significantly decreased circulating tumor necrosis factor (TNF)-α, interleukin (IL)-17, and IL-6 levels, reduced infarct size and improved motor function in mice. Free brain concentrations of DS2 were found to be lower than needed for robust modulation of central GABA A receptors and were not affected by the presence and absence of elacridar, an inhibitor of both P-glycoprotein and breast cancer resistance protein (BCRP). Finally, as DS2 appears to dampen peripheral immune activation and only shows limited brain exposure, we assessed the role of DS2 to promote functional recovery after stroke when administered from 3-days after the stroke. Treatment with DS2 from 3-days post-stroke improved motor function on the grid-walking, but not on the cylinder task. These data highlight the need to further develop subunit-selective compounds to better understand change in GABA receptor signaling pathways both centrally and peripherally. Importantly, we show that GABA compounds such as DS2 that only shows limited brain exposure can still afford significant protection and promote functional recovery most likely via modulation of peripheral immune cells and could be given as an adjunct treatment.
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Affiliation(s)
- Silke Neumann
- Department of Pathology, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand.,Department of Anatomy, Brain Health Research Centre, Brain Research New Zealand, University of Otago, Dunedin, New Zealand
| | - Lily Boothman-Burrell
- Department of Anatomy, Brain Health Research Centre, Brain Research New Zealand, University of Otago, Dunedin, New Zealand
| | - Emma K Gowing
- Department of Anatomy, Brain Health Research Centre, Brain Research New Zealand, University of Otago, Dunedin, New Zealand
| | | | - Philip K Ahring
- School of Pharmacy, University of Sydney, Sydney, NSW, Australia
| | - Sarah L Young
- Department of Pathology, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand
| | | | - Andrew N Clarkson
- Department of Anatomy, Brain Health Research Centre, Brain Research New Zealand, University of Otago, Dunedin, New Zealand
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Clarkson AN, Boothman-Burrell L, Dósa Z, Nagaraja RY, Jin L, Parker K, van Nieuwenhuijzen PS, Neumann S, Gowing EK, Gavande N, Ahring PK, Holm MM, Hanrahan JR, Nicolazzo JA, Jensen K, Chebib M. The flavonoid, 2'-methoxy-6-methylflavone, affords neuroprotection following focal cerebral ischaemia. J Cereb Blood Flow Metab 2019; 39:1266-1282. [PMID: 29376464 PMCID: PMC6668512 DOI: 10.1177/0271678x18755628] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Tonic inhibitory currents, mediated by extrasynaptic GABAA receptors, are elevated at a delay following stroke. Flavonoids minimise the extent of cellular damage following stroke, but little is known about their mode of action. We demonstrate that the flavonoid, 2'-methoxy-6-methylflavone (0.1-10 µM; 2'MeO6MF), increases GABAA receptor tonic currents presumably via δ-containing GABAA receptors. Treatment with 2'MeO6MF 1-6 h post focal ischaemia dose dependently decreases infarct volume and improves functional recovery. The effect of 2'MeO6MF was attenuated in δ-/- mice, indicating that the effects of the flavonoid were mediated via δ-containing GABAA receptors. Further, as flavonoids have been shown to have multiple modes of action, we investigated the anti-inflammatory effects of 2'MeO6MF. Using a macrophage cell line, we show that 2'MeO6MF can dampen an LPS-induced elevation in NFkB activity. Assessment of vehicle-treated stroke animals revealed a significant increase in circulating IL1β, TNFα and IFγ levels. Treatment with 2'MeO6MF dampened the stroke-induced increase in circulating cytokines, which was blocked in the presence of the pan-AKT inhibitor, GSK690693. These studies support the hypothesis that compounds that potentiate tonic inhibition via δ-containing GABAA receptors soon after stroke can afford neuroprotection.
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Affiliation(s)
- Andrew N Clarkson
- 1 Department of Anatomy, Brain Health Research Centre and Brain Research New Zealand, University of Otago, Dunedin, New Zealand.,2 Faculty of Pharmacy, The University of Sydney, Sydney, Australia
| | - Lily Boothman-Burrell
- 1 Department of Anatomy, Brain Health Research Centre and Brain Research New Zealand, University of Otago, Dunedin, New Zealand
| | - Zita Dósa
- 3 Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Raghavendra Y Nagaraja
- 1 Department of Anatomy, Brain Health Research Centre and Brain Research New Zealand, University of Otago, Dunedin, New Zealand
| | - Liang Jin
- 4 Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Australia
| | - Kim Parker
- 1 Department of Anatomy, Brain Health Research Centre and Brain Research New Zealand, University of Otago, Dunedin, New Zealand
| | | | - Silke Neumann
- 1 Department of Anatomy, Brain Health Research Centre and Brain Research New Zealand, University of Otago, Dunedin, New Zealand.,5 Department of Pathology, University of Otago, Dunedin, New Zealand
| | - Emma K Gowing
- 1 Department of Anatomy, Brain Health Research Centre and Brain Research New Zealand, University of Otago, Dunedin, New Zealand
| | - Navnath Gavande
- 2 Faculty of Pharmacy, The University of Sydney, Sydney, Australia
| | - Philip K Ahring
- 2 Faculty of Pharmacy, The University of Sydney, Sydney, Australia
| | - Mai M Holm
- 3 Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Jane R Hanrahan
- 2 Faculty of Pharmacy, The University of Sydney, Sydney, Australia
| | - Joseph A Nicolazzo
- 4 Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Australia
| | - Kimmo Jensen
- 3 Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Mary Chebib
- 2 Faculty of Pharmacy, The University of Sydney, Sydney, Australia
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Duan J, Pandey S, Li T, Castellano D, Gu X, Li J, Tian Q, Lu W. Genetic Deletion of GABA A Receptors Reveals Distinct Requirements of Neurotransmitter Receptors for GABAergic and Glutamatergic Synapse Development. Front Cell Neurosci 2019; 13:217. [PMID: 31231192 PMCID: PMC6558517 DOI: 10.3389/fncel.2019.00217] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Accepted: 04/29/2019] [Indexed: 12/13/2022] Open
Abstract
In the adult brain GABAA receptors (GABAARs) mediate the majority of synaptic inhibition that provides inhibitory balance to excitatory drive and controls neuronal output. In the immature brain GABAAR signaling is critical for neuronal development. However, the cell-autonomous role of GABAARs in synapse development remains largely unknown. We have employed the CRISPR-CAS9 technology to genetically eliminate GABAARs in individual hippocampal neurons and examined GABAergic and glutamatergic synapses. We found that development of GABAergic synapses, but not glutamatergic synapses, critically depends on GABAARs. By combining different genetic approaches, we have also removed GABAARs and two ionotropic glutamate receptors, AMPA receptors (AMPARs) and NMDA receptors (NMDARs), in single neurons and discovered a striking dichotomy. Indeed, while development of glutamatergic synapses and spines does not require signaling mediated by these receptors, inhibitory synapse formation is crucially dependent on them. Our data reveal a critical cell-autonomous role of GABAARs in inhibitory synaptogenesis and demonstrate distinct molecular mechanisms for development of inhibitory and excitatory synapses.
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Affiliation(s)
- Jingjing Duan
- Synapse and Neural Circuit Research Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, United States.,Department of Anatomy and Neurobiology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China
| | - Saurabh Pandey
- Synapse and Neural Circuit Research Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, United States
| | - Tianming Li
- Synapse and Neural Circuit Research Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, United States
| | - David Castellano
- Synapse and Neural Circuit Research Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, United States
| | - Xinglong Gu
- Synapse and Neural Circuit Research Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, United States
| | - Jun Li
- Synapse and Neural Circuit Research Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, United States
| | - Qingjun Tian
- Synapse and Neural Circuit Research Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, United States
| | - Wei Lu
- Synapse and Neural Circuit Research Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, United States
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O'Neill N, Sylantyev S. The Functional Role of Spontaneously Opening GABA A Receptors in Neural Transmission. Front Mol Neurosci 2019; 12:72. [PMID: 30983968 PMCID: PMC6447609 DOI: 10.3389/fnmol.2019.00072] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Accepted: 03/08/2019] [Indexed: 12/22/2022] Open
Abstract
Ionotropic type of γ-aminobutyric acid receptors (GABAARs) produce two forms of inhibitory signaling: phasic inhibition generated by rapid efflux of neurotransmitter GABA into the synaptic cleft with subsequent binding to GABAARs, and tonic inhibition generated by persistent activation of extrasynaptic and/or perisynaptic GABAARs by GABA continuously present in the extracellular space. It is widely accepted that phasic and tonic GABAergic inhibition is mediated by receptor groups of distinct subunit composition and modulated by different cytoplasmic mechanisms. Recently, however, it has been demonstrated that spontaneously opening GABAARs (s-GABAARs), which do not need GABA binding to enter an active state, make a significant input into tonic inhibitory signaling. Due to GABA-independent action mode, s-GABAARs promise new safer options for therapy of neural disorders (such as epilepsy) devoid of side effects connected to abnormal fluctuations of GABA concentration in the brain. However, despite the potentially important role of s-GABAARs in neural signaling, they still remain out of focus of neuroscience studies, to a large extent due to technical difficulties in their experimental research. Here, we summarize present data on s-GABAARs functional properties and experimental approaches that allow isolation of s-GABAARs effects from those of conventional (GABA-dependent) GABAARs.
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Affiliation(s)
- Nathanael O'Neill
- Center for Clinical Brain Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Sergiy Sylantyev
- Center for Clinical Brain Sciences, University of Edinburgh, Edinburgh, United Kingdom
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Fischer AU, Müller NIC, Deller T, Del Turco D, Fisch JO, Griesemer D, Kattler K, Maraslioglu A, Roemer V, Xu‐Friedman MA, Walter J, Friauf E. GABA is a modulator, rather than a classical transmitter, in the medial nucleus of the trapezoid body-lateral superior olive sound localization circuit. J Physiol 2019; 597:2269-2295. [PMID: 30776090 PMCID: PMC6462465 DOI: 10.1113/jp277566] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Accepted: 02/18/2019] [Indexed: 12/13/2022] Open
Abstract
KEY POINTS The lateral superior olive (LSO), a brainstem hub involved in sound localization, integrates excitatory and inhibitory inputs from the ipsilateral and the contralateral ear, respectively. In gerbils and rats, inhibition to the LSO reportedly shifts from GABAergic to glycinergic within the first three postnatal weeks. Surprisingly, we found no evidence for synaptic GABA signalling during this time window in mouse LSO principal neurons. However, we found that presynaptic GABAB Rs modulate Ca2+ influx into medial nucleus of the trapezoid body axon terminals, resulting in reduced synaptic strength. Moreover, GABA elicited strong responses in LSO neurons that were mediated by extrasynaptic GABAA Rs. RNA sequencing revealed highly abundant δ subunits, which are characteristic of extrasynaptic receptors. Whereas GABA increased the excitability of neonatal LSO neurons, it reduced the excitability around hearing onset. Collectively, GABA appears to control the excitability of mouse LSO neurons via extrasynaptic and presynaptic signalling. Thus, GABA acts as a modulator, rather than as a classical transmitter. ABSTRACT GABA and glycine mediate fast inhibitory neurotransmission and are coreleased at several synapse types. Here we assessed the contribution of GABA and glycine in synaptic transmission between the medial nucleus of the trapezoid body (MNTB) and the lateral superior olive (LSO), two nuclei involved in sound localization. Whole-cell patch-clamp experiments in acute mouse brainstem slices at postnatal days (P) 4 and 11 during pharmacological blockade of GABAA receptors (GABAA Rs) and/or glycine receptors demonstrated no GABAergic synaptic component on LSO principal neurons. A GABAergic component was absent in evoked inhibitory postsynaptic currents and miniature events. Coimmunofluorescence experiments revealed no codistribution of the presynaptic GABAergic marker GAD65/67 with gephyrin, a postsynaptic marker for GABAA Rs, corroborating the conclusion that GABA does not act synaptically in the mouse LSO. Imaging experiments revealed reduced Ca2+ influx into MNTB axon terminals following activation of presynaptic GABAB Rs. GABAB R activation reduced the synaptic strength at P4 and P11. GABA appears to act on extrasynaptic GABAA Rs as demonstrated by application of 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol, a δ-subunit-specific GABAA R agonist. RNA sequencing showed high mRNA levels for the δ-subunit in the LSO. Moreover, GABA transporters GAT-1 and GAT-3 appear to control extracellular GABA. Finally, we show an age-dependent effect of GABA on the excitability of LSO neurons. Whereas tonic GABA increased the excitability at P4, leading to spike facilitation, it decreased the excitability at P11 via shunting inhibition through extrasynaptic GABAA Rs. Taken together, we demonstrate a modulatory role of GABA in the murine LSO, rather than a function as a classical synaptic transmitter.
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Affiliation(s)
- Alexander U. Fischer
- Animal Physiology Group, Department of BiologyUniversity of KaiserslauternD‐67663KaiserslauternGermany
| | - Nicolas I. C. Müller
- Animal Physiology Group, Department of BiologyUniversity of KaiserslauternD‐67663KaiserslauternGermany
| | - Thomas Deller
- Institute of Clinical Neuroanatomy, Neuroscience CenterGoethe‐University Frankfurt, Theodor‐Stern‐Kai 7D‐60590Frankfurt am MainGermany
| | - Domenico Del Turco
- Institute of Clinical Neuroanatomy, Neuroscience CenterGoethe‐University Frankfurt, Theodor‐Stern‐Kai 7D‐60590Frankfurt am MainGermany
| | - Jonas O. Fisch
- Animal Physiology Group, Department of BiologyUniversity of KaiserslauternD‐67663KaiserslauternGermany
| | - Désirée Griesemer
- Animal Physiology Group, Department of BiologyUniversity of KaiserslauternD‐67663KaiserslauternGermany
| | - Kathrin Kattler
- Genetics/Epigenetic Group, Department of Biological SciencesSaarland UniversityD‐66123Saarbrücken
| | - Ayse Maraslioglu
- Animal Physiology Group, Department of BiologyUniversity of KaiserslauternD‐67663KaiserslauternGermany
| | - Vera Roemer
- Animal Physiology Group, Department of BiologyUniversity of KaiserslauternD‐67663KaiserslauternGermany
| | - Matthew A. Xu‐Friedman
- Department of Biological SciencesUniversity at BuffaloState University of New YorkBuffaloNY14260USA
| | - Jörn Walter
- Genetics/Epigenetic Group, Department of Biological SciencesSaarland UniversityD‐66123Saarbrücken
| | - Eckhard Friauf
- Animal Physiology Group, Department of BiologyUniversity of KaiserslauternD‐67663KaiserslauternGermany
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Hannan S, Minere M, Harris J, Izquierdo P, Thomas P, Tench B, Smart TG. GABA AR isoform and subunit structural motifs determine synaptic and extrasynaptic receptor localisation. Neuropharmacology 2019; 169:107540. [PMID: 30794836 DOI: 10.1016/j.neuropharm.2019.02.022] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2018] [Revised: 02/06/2019] [Accepted: 02/14/2019] [Indexed: 12/27/2022]
Abstract
GABAA receptors (GABAARs) are the principal inhibitory neurotransmitter receptors in the central nervous system. They control neuronal excitability by synaptic and tonic forms of inhibition mostly mediated by different receptor subtypes located in specific cell membrane subdomains. A consensus suggests that α1-3βγ comprise synaptic GABAARs, whilst extrasynaptic α4βδ, α5βγ and αβ isoforms largely underlie tonic inhibition. Although some structural features that enable the spatial segregation of receptors are known, the mobility of key synaptic and extrasynaptic GABAARs are less understood, and yet this is a key determinant of the efficacy of GABA inhibition. To address this aspect, we have incorporated functionally silent α-bungarotoxin binding sites (BBS) into prominent hippocampal GABAAR subunits which mediate synaptic and tonic inhibition. Using single particle tracking with quantum dots we demonstrate that GABAARs that are traditionally considered to mediate synaptic or tonic inhibition are all able to access inhibitory synapses. These isoforms have variable diffusion rates and are differentially retained upon entering the synaptic membrane subdomain. Interestingly, α2 and α4 subunits reside longer at synapses compared to α5 and δ subunits. Furthermore, a high proportion of extrasynaptic δ-containing receptors exhibited slower diffusion compared to δ subunits at synapses. A chimera formed from δ-subunits, with the intracellular domain of γ2L, reversed this behaviour. In addition, we observed that receptor activation affected the diffusion of extrasynaptic, but not of synaptic GABAARs. Overall, we conclude that the differential mobility profiles of key synaptic and extrasynaptic GABAARs are determined by receptor subunit composition and intracellular structural motifs. This article is part of the special issue entitled 'Mobility and trafficking of neuronal membrane proteins'.
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Affiliation(s)
- Saad Hannan
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK.
| | - Marielle Minere
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Joseph Harris
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Pablo Izquierdo
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Philip Thomas
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Becky Tench
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Trevor G Smart
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK.
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Joshi S, Kapur J. Neurosteroid regulation of GABA A receptors: A role in catamenial epilepsy. Brain Res 2019; 1703:31-40. [PMID: 29481795 PMCID: PMC6107446 DOI: 10.1016/j.brainres.2018.02.031] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Revised: 09/08/2017] [Accepted: 02/20/2018] [Indexed: 12/31/2022]
Abstract
The female reproductive hormones progesterone and estrogen regulate network excitability. Fluctuations in the circulating levels of these hormones during the menstrual cycle cause frequent seizures during certain phases of the cycle in women with epilepsy. This seizure exacerbation, called catamenial epilepsy, is a dominant form of drug-refractory epilepsy in women of reproductive age. Progesterone, through its neurosteroid derivative allopregnanolone, increases γ-aminobutyric acid type-A receptor (GABAR)-mediated inhibition in the brain and keeps seizures under control. Catamenial seizures are believed to be a neurosteroid withdrawal symptom, and it was hypothesized that exogenous administration of progesterone to maintain its levels high during luteal phase will treat catamenial seizures. However, in a multicenter, double-blind, phase III clinical trial, progesterone treatment did not suppress catamenial seizures. The expression of GABARs with reduced neurosteroid sensitivity in epileptic animals may explain the failure of the progesterone clinical trial. The expression of neurosteroid-sensitive δ subunit-containing GABARs is reduced, and the expression of α4γ2 subunit-containing GABARs is upregulated, which alters the inhibition of dentate granule cells in epilepsy. These changes reduce the endogenous neurosteroid control of seizures and contribute to catamenial seizures.
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Affiliation(s)
- Suchitra Joshi
- Department of Neurology, University of Virginia, Charlottesville, VA 22908, United States.
| | - Jaideep Kapur
- Department of Neurology, University of Virginia, Charlottesville, VA 22908, United States; Department of Neuroscience, University of Virginia, Charlottesville, VA 22908, United States
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43
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Mohamad FH, Has ATC. The α5-Containing GABA A Receptors-a Brief Summary. J Mol Neurosci 2019; 67:343-351. [PMID: 30607899 DOI: 10.1007/s12031-018-1246-4] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2018] [Accepted: 12/17/2018] [Indexed: 12/21/2022]
Abstract
GABAA receptors are the major inhibitory neurotransmitter receptor in the human brain. The receptors are assembled from combination of protein subunits in pentameric complex which may consist of α1-6, β1-3, γ1-3, ρ1-3, δ, ε, θ, or π subunits. There are a theoretical > 150,000 possible assemblies and arrangements of GABAA subunits, although only a few combinations have been found in human with the most dominant consists of 2α1, 2β2, and 1γ2 in a counterclockwise arrangement as seen from the synaptic cleft. The receptors also possess binding sites for various unrelated substances including benzodiazepines, barbiturates, and anesthetics. The α5-containing GABAARs only make up ≤ 5% of the entire receptor population, but up to 25% of the receptor subtype is located in the crucial learning and memory-associated area of the brain-the hippocampus, which has ignited myriads of hypotheses and theories in regard to its role. As well as exhibiting synaptic phasic inhibition, the α5-containing receptors are also extrasynaptic and mediate tonic inhibition with continuously occurring smaller amplitude. Studies on negative-allosteric modulators for reducing this tonic inhibition have been shown to enhance learning and memory in neurological disorders such as schizophrenia, Down syndrome, and autism with a possible alternative benzodiazepine binding site. Therefore, a few α5 subunit-specific compounds have been developed to address these pharmacological needs. With its small population, the α5-containing receptors could be the key and also the answer for many untreated cognitive dysfunctions and disorders.
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Affiliation(s)
- Fatin H Mohamad
- Department of Neurosciences, School of Medical Sciences, Universiti Sains Malaysia, Kampus Kesihatan, 16150, Kubang Kerian, Kelantan, Malaysia
| | - Ahmad Tarmizi Che Has
- Department of Neurosciences, School of Medical Sciences, Universiti Sains Malaysia, Kampus Kesihatan, 16150, Kubang Kerian, Kelantan, Malaysia.
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Itoi K, Motoike I, Liu Y, Clokie S, Iwasaki Y, Uchida K, Sato T, Aguilera G. Genome-Wide Analysis of Glucocorticoid-Responsive Transcripts in the Hypothalamic Paraventricular Region of Male Rats. Endocrinology 2019; 160:38-54. [PMID: 30364965 PMCID: PMC6302960 DOI: 10.1210/en.2018-00535] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/02/2018] [Accepted: 10/19/2018] [Indexed: 11/19/2022]
Abstract
Glucocorticoids (GCs) are essential for stress adaptation, acting centrally and in the periphery. Corticotropin-releasing factor (CRF), a major regulator of adrenal GC synthesis, is produced in the paraventricular nucleus of the hypothalamus (PVH), which contains multiple neuroendocrine and preautonomic neurons. GCs may be involved in diverse regulatory mechanisms in the PVH, but the target genes of GCs are largely unexplored except for the CRF gene (Crh), a well-known target for GC negative feedback. Using a genome-wide RNA-sequencing analysis, we identified transcripts that changed in response to either high-dose corticosterone (Cort) exposure for 12 days (12-day high Cort), corticoid deprivation for 7 days (7-day ADX), or acute Cort administration. Among others, canonical GC target genes were upregulated prominently by 12-day high Cort. Crh was upregulated or downregulated most prominently by either 7-day ADX or 12-day high Cort, emphasizing the recognized feedback effects of GC on the hypothalamic-pituitary-adrenal (HPA) axis. Concomitant changes in vasopressin and apelin receptor gene expression are likely to contribute to HPA repression. In keeping with the pleotropic cellular actions of GCs, 7-day ADX downregulated numerous genes of a broad functional spectrum. The transcriptome response signature differed markedly between acute Cort injection and 12-day high Cort. Remarkably, six immediate early genes were upregulated 1 hour after Cort injection, which was confirmed by quantitative reverse transcription PCR and semiquantitative in situ hybridization. This study may provide a useful database for studying the regulatory mechanisms of GC-dependent gene expression and repression in the PVH.
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Affiliation(s)
- Keiichi Itoi
- Laboratory of Information Biology, Graduate School of Information Sciences, Tohoku University, Sendai, Japan
- Department of Neuroendocrinology, Graduate School of Medicine, Tohoku University, Sendai, Japan
- Correspondence: Keiichi Itoi, MD, PhD, Graduate School of Information Biology, Tohoku University, 6-3-09, Aramaki-aza Aoba, Sendai 980-8579, Japan. E-mail:
| | - Ikuko Motoike
- Department of Integrative Genomics, Tohoku Medical Megabank Organization, Tohoku University, Sendai, Japan
| | - Ying Liu
- Section on Endocrine Physiology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland
| | - Sam Clokie
- Section of Neuroendocrinology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland
| | | | - Katsuya Uchida
- Laboratory of Information Biology, Graduate School of Information Sciences, Tohoku University, Sendai, Japan
| | - Tatsuya Sato
- Laboratory of Information Biology, Graduate School of Information Sciences, Tohoku University, Sendai, Japan
| | - Greti Aguilera
- Section on Endocrine Physiology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland
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Input-Specific Synaptic Location and Function of the α5 GABA A Receptor Subunit in the Mouse CA1 Hippocampal Neurons. J Neurosci 2018; 39:788-801. [PMID: 30523065 DOI: 10.1523/jneurosci.0567-18.2018] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Revised: 10/01/2018] [Accepted: 10/30/2018] [Indexed: 12/21/2022] Open
Abstract
Hippocampus-dependent learning processes are coordinated via a large diversity of GABAergic inhibitory mechanisms. The α5 subunit-containing GABAA receptor (α5-GABAAR) is abundantly expressed in the hippocampus populating primarily the extrasynaptic domain of CA1 pyramidal cells, where it mediates tonic inhibitory conductance and may cause functional deficits in synaptic plasticity and hippocampus-dependent memory. However, little is known about synaptic expression of the α5-GABAAR and, accordingly, its location site-specific function. We examined the cell- and synapse-specific distribution of the α5-GABAAR in the CA1 stratum oriens/alveus (O/A) using a combination of immunohistochemistry, whole-cell patch-clamp recordings and optogenetic stimulation in hippocampal slices obtained from mice of either sex. In addition, the input-specific role of the α5-GABAAR in spatial learning and anxiety-related behavior was studied using behavioral testing and chemogenetic manipulations. We demonstrate that α5-GABAAR is preferentially targeted to the inhibitory synapses made by the vasoactive intestinal peptide (VIP)- and calretinin-positive terminals onto dendrites of somatostatin-expressing interneurons. In contrast, synapses made by the parvalbumin-positive inhibitory inputs to O/A interneurons showed no or little α5-GABAAR. Inhibiting the α5-GABAAR in control mice in vivo improved spatial learning but also induced anxiety-like behavior. Inhibiting the α5-GABAAR in mice with inactivated CA1 VIP input could still improve spatial learning and was not associated with anxiety. Together, these data indicate that the α5-GABAAR-mediated phasic inhibition via VIP input to interneurons plays a predominant role in the regulation of anxiety while the α5-GABAAR tonic inhibition via this subunit may control spatial learning.SIGNIFICANCE STATEMENT The α5-GABAAR subunit exhibits high expression in the hippocampus, and regulates the induction of synaptic plasticity and the hippocampus-dependent mnemonic processes. In CA1 principal cells, this subunit occupies mostly extrasynaptic sites and mediates tonic inhibition. Here, we provide evidence that, in CA1 somatostatin-expressing interneurons, the α5-GABAAR subunit is targeted to synapses formed by the VIP- and calretinin-expressing inputs, and plays a specific role in the regulation of anxiety-like behavior.
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Kolasinski J, Hinson EL, Divanbeighi Zand AP, Rizov A, Emir UE, Stagg CJ. The dynamics of cortical GABA in human motor learning. J Physiol 2018; 597:271-282. [PMID: 30300446 PMCID: PMC6312422 DOI: 10.1113/jp276626] [Citation(s) in RCA: 95] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2018] [Accepted: 10/04/2018] [Indexed: 12/20/2022] Open
Abstract
Key points The ability to learn new motor skills is supported by plasticity in the structural and functional organisation of the primary motor cortex in the human brain. Changes inhibitory to signalling by GABA are thought to be crucial in inducing motor cortex plasticity. This study used magnetic resonance spectroscopy (MRS) to quantify the concentration of GABA in human motor cortex during a period of motor learning, as well as during a period of movement and a period at rest. We report evidence for a reduction in the MRS‐measured concentration of GABA specific to learning. Further, the GABA concentration early in the learning task was strongly correlated with the magnitude of subsequent learning: higher GABA concentrations were associated with poorer learning. The results provide initial insight into the neurochemical correlates of cortical plasticity associated with motor learning, specifically relevant in therapeutic efforts to induce cortical plasticity during recovery from stroke.
Abstract The ability to learn novel motor skills is a central part of our daily lives and can provide a model for rehabilitation after a stroke. However, there are still fundamental gaps in our understanding of the physiological mechanisms that underpin human motor plasticity. The acquisition of new motor skills is dependent on changes in local circuitry within the primary motor cortex (M1). This reorganisation has been hypothesised to be facilitated by a decrease in local inhibition via modulation of the neurotransmitter GABA, but this link has not been conclusively demonstrated in humans. Here, we used 7 T magnetic resonance spectroscopy to investigate the dynamics of GABA concentrations in human M1 during the learning of an explicit, serial reaction time task. We observed a significant reduction in GABA concentration during motor learning that was not seen in an equivalent motor task lacking a learnable sequence, nor during a passive resting task of the same duration. No change in glutamate was observed in any group. Furthermore, M1 GABA measured early in task performance was strongly correlated with the degree of subsequent learning, such that greater inhibition was associated with poorer subsequent learning. This result suggests that higher levels of cortical inhibition may present a barrier that must be surmounted in order to achieve an increase in M1 excitability, and hence encoding of a new motor skill. These results provide strong support for the mechanistic role of GABAergic inhibition in motor plasticity, raising questions regarding the link between population variability in motor learning and GABA metabolism in the brain. The ability to learn new motor skills is supported by plasticity in the structural and functional organisation of the primary motor cortex in the human brain. Changes inhibitory to signalling by GABA are thought to be crucial in inducing motor cortex plasticity. This study used magnetic resonance spectroscopy (MRS) to quantify the concentration of GABA in human motor cortex during a period of motor learning, as well as during a period of movement and a period at rest. We report evidence for a reduction in the MRS‐measured concentration of GABA specific to learning. Further, the GABA concentration early in the learning task was strongly correlated with the magnitude of subsequent learning: higher GABA concentrations were associated with poorer learning. The results provide initial insight into the neurochemical correlates of cortical plasticity associated with motor learning, specifically relevant in therapeutic efforts to induce cortical plasticity during recovery from stroke.
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Affiliation(s)
- James Kolasinski
- Wellcome Centre for Integrative Neuroimaging, Oxford Centre for fMRI of the Brain, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, OX3 7DU, UK.,Cardiff University Brain Research Imaging Centre, School of Psychology, Cardiff University, Maindy Road, Cardiff, CF24 4HQ, UK
| | - Emily L Hinson
- Wellcome Centre for Integrative Neuroimaging, Oxford Centre for fMRI of the Brain, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, OX3 7DU, UK.,Oxford Centre for Human Brain Activity, Wellcome Centre for Integrative Neuroimaging, Department of Psychiatry, University of Oxford, Oxford, OX3 7JX, UK
| | - Amir P Divanbeighi Zand
- Wellcome Centre for Integrative Neuroimaging, Oxford Centre for fMRI of the Brain, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, OX3 7DU, UK
| | - Assen Rizov
- Wellcome Centre for Integrative Neuroimaging, Oxford Centre for fMRI of the Brain, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, OX3 7DU, UK
| | - Uzay E Emir
- Wellcome Centre for Integrative Neuroimaging, Oxford Centre for fMRI of the Brain, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, OX3 7DU, UK.,Purdue University School of Health Sciences, 550 Stadium Mall Drive, West Lafayette, IN, 47907, USA
| | - Charlotte J Stagg
- Wellcome Centre for Integrative Neuroimaging, Oxford Centre for fMRI of the Brain, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, OX3 7DU, UK.,Oxford Centre for Human Brain Activity, Wellcome Centre for Integrative Neuroimaging, Department of Psychiatry, University of Oxford, Oxford, OX3 7JX, UK
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Agoglia AE, Herman MA. The center of the emotional universe: Alcohol, stress, and CRF1 amygdala circuitry. Alcohol 2018; 72:61-73. [PMID: 30220589 PMCID: PMC6165695 DOI: 10.1016/j.alcohol.2018.03.009] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Revised: 03/15/2018] [Accepted: 03/27/2018] [Indexed: 12/15/2022]
Abstract
The commonalities between different phases of stress and alcohol use as well as the high comorbidity between alcohol use disorders (AUDs) and anxiety disorders suggest common underlying cellular mechanisms governing the rewarding and aversive aspects of these related conditions. As an integrative center that assigns emotional salience to a wide variety of internal and external stimuli, the amygdala complex plays a major role in how alcohol and stress influence cellular physiology to produce disordered behavior. Previous work has illustrated the broad role of the amygdala in alcohol, stress, and anxiety. However, the challenge of current and future studies is to identify the specific dysregulations that occur within distinct amygdala circuits and subpopulations and the commonalities between these alterations in each disorder, with the long-term goal of identifying potential targets for therapeutic intervention. Specific intra-amygdala circuits and cell type-specific subpopulations are emerging as critical targets for stress- and alcohol-induced plasticity, chief among them the corticotropin releasing factor (CRF) and CRF receptor 1 (CRF1) system. CRF and CRF1 have been implicated in the effects of alcohol in several amygdala nuclei, including the basolateral (BLA) and central amygdala (CeA); however, the precise circuitry involved in these effects and the role of these circuits in stress and anxiety are only beginning to be understood.
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Affiliation(s)
- Abigail E Agoglia
- Bowles Center for Alcohol Studies, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, United States
| | - Melissa A Herman
- Bowles Center for Alcohol Studies, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, United States.
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Reddy DS, Chuang SH, Hunn D, Crepeau AZ, Maganti R. Neuroendocrine aspects of improving sleep in epilepsy. Epilepsy Res 2018; 147:32-41. [PMID: 30212766 PMCID: PMC6192845 DOI: 10.1016/j.eplepsyres.2018.08.013] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Revised: 08/27/2018] [Accepted: 08/30/2018] [Indexed: 12/15/2022]
Abstract
Sleep plays an intricate role in epilepsy and can affect the frequency and occurrence of seizures. With nearly 35% of U.S. adults failing to obtain the recommended 7 h of sleep every night, understanding the complex relationship between sleep and epilepsy is of utmost relevance. Sleep deprivation is a common trigger of seizures in many persons with epilepsy and sleep patterns play a role in the occurrence of seizures. Some patients have their first seizure or repeated seizures after an "all-nighter" at college or after a long period of chronic sleep deprivation. The strength of the relationship between sleep and seizures varies between patients, but improving sleep and optimizing seizure control can have significant positive effects on the quality of life for all these patients. Research has shown that the changes in the brain's electrical and hormonal activity occurring during normal sleep-wake cycles can be linked to both sleep and seizure patterns. Many questions remain to be answered about sleep and epilepsy. How can sleep deprivation trigger an epileptic seizure? How do circadian and hormonal changes influence sleep pattern and seizure occurrence? Can hormones or sleeping pills help with sleep in epilepsy? In this article we discuss these and many other questions on sleep in epilepsy, with an emphasis on sleep architecture, hormone changes, mechanistic factors, and possible prevention strategies.
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Affiliation(s)
- Doodipala Samba Reddy
- Department of Neuroscience and Experimental Therapeutics, Texas A&M University Health Science Center College of Medicine, Bryan, TX 77807, USA.
| | - Shu-Hui Chuang
- Department of Neuroscience and Experimental Therapeutics, Texas A&M University Health Science Center College of Medicine, Bryan, TX 77807, USA
| | - Dayton Hunn
- Department of Neuroscience and Experimental Therapeutics, Texas A&M University Health Science Center College of Medicine, Bryan, TX 77807, USA
| | - Amy Z Crepeau
- Department of Neurology, Mayo Clinic Hospital, Phoenix, AZ 85054, USA
| | - Rama Maganti
- Department of Neurology, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705, USA
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Transgenic overexpression of furin increases epileptic susceptibility. Cell Death Dis 2018; 9:1058. [PMID: 30333479 PMCID: PMC6193048 DOI: 10.1038/s41419-018-1076-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2018] [Revised: 09/01/2018] [Accepted: 09/07/2018] [Indexed: 11/28/2022]
Abstract
The proprotein convertase Furin plays crucial roles in the pathology of many diseases. However, the specific role of furin in epilepsy remains unclear. In our study, furin protein was increased in the temporal neocortex of epileptic patients and in the hippocampus and cortex of epileptic mice. The furin transgenic (TG) mice showed increased susceptibility to epilepsy and heightened epileptic activity compared with wild-type (WT) mice. Conversely, lentivirus-mediated knockdown of furin restrained epileptic activity. Using whole-cell patch clamp, furin knockdown and overexpression influenced neuronal inhibitory by regulating postsynaptic gamma-aminobutyric acid A receptor (GABAAR)-mediated synaptic transmission. Importantly, furin influenced the expression of GABAAR β2/3 membrane and total protein in epileptic mice by changing transcription level of GABAAR β2/3, not the protein degradation. These results reveal that furin may regulate GABAAR-mediated inhibitory synaptic transmission by altering the transcription of GABAAR β2/3 subunits in epilepsy; this finding could provide new insight into epilepsy prevention and treatment.
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Sieghart W, Savić MM. International Union of Basic and Clinical Pharmacology. CVI: GABAA Receptor Subtype- and Function-selective Ligands: Key Issues in Translation to Humans. Pharmacol Rev 2018; 70:836-878. [DOI: 10.1124/pr.117.014449] [Citation(s) in RCA: 105] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
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