1
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Muza PM, Bush D, Pérez-González M, Zouhair I, Cleverley K, Sopena ML, Aoidi R, West SJ, Good M, Tybulewicz VL, Walker MC, Fisher EM, Chang P. Cognitive impairments in a Down syndrome model with abnormal hippocampal and prefrontal dynamics and cytoarchitecture. iScience 2023; 26:106073. [PMID: 36818290 PMCID: PMC9929862 DOI: 10.1016/j.isci.2023.106073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Revised: 12/22/2022] [Accepted: 01/24/2023] [Indexed: 01/29/2023] Open
Abstract
The Dp(10)2Yey mouse carries a ∼2.3-Mb intra-chromosomal duplication of mouse chromosome 10 (Mmu10) that has homology to human chromosome 21, making it an essential model for aspects of Down syndrome (DS, trisomy 21). In this study, we investigated neuronal dysfunction in the Dp(10)2Yey mouse and report spatial memory impairment and anxiety-like behavior alongside altered neural activity in the medial prefrontal cortex (mPFC) and hippocampus (HPC). Specifically, Dp(10)2Yey mice showed impaired spatial alternation associated with increased sharp-wave ripple activity in mPFC during a period of memory consolidation, and reduced mobility in a novel environment accompanied by reduced theta-gamma phase-amplitude coupling in HPC. Finally, we found alterations in the number of interneuron subtypes in mPFC and HPC that may contribute to the observed phenotypes and highlight potential approaches to ameliorate the effects of human trisomy 21.
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Affiliation(s)
- Phillip M. Muza
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London WC1N 3BG, UK
| | - Daniel Bush
- Department of Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, London WC1N 3BG, UK
- UCL Institute of Cognitive Neuroscience and UCL Queen Square Institute of Neurology, University College London, London WC1N 3AZ, UK
| | - Marta Pérez-González
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London WC1N 3BG, UK
| | - Ines Zouhair
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London WC1N 3BG, UK
| | - Karen Cleverley
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London WC1N 3BG, UK
| | - Miriam L. Sopena
- Bioinformatics and Biostatistics, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Rifdat Aoidi
- Immune Cell Biology and Down Syndrome Laboratory, The Francis Crick Institute, London NW1 1AT, UK
| | - Steven J. West
- Sainsbury Wellcome Centre, University College London, London W1T 4JG, UK
| | - Mark Good
- School of Psychology, Cardiff University, Cardiff CF10 3AT, UK
| | - Victor L.J. Tybulewicz
- Immune Cell Biology and Down Syndrome Laboratory, The Francis Crick Institute, London NW1 1AT, UK
- Corresponding author
| | - Matthew C. Walker
- Department of Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, London WC1N 3BG, UK
- Corresponding author
| | - Elizabeth M.C. Fisher
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London WC1N 3BG, UK
- Corresponding author
| | - Pishan Chang
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London WC1N 3BG, UK
- Department of Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, London WC1N 3BG, UK
- School of Physiology, Pharmacology, and Neuroscience, University of Bristol, Bristol BS8 1TD, UK
- Corresponding author
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2
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Wen Y, Zhang G, Liu L, Zhang P, lin L, Mei R, Zhang F, Chen Y, Li R. HAP1 interacts with 14-3-3 to regulate epileptic seizure via GABAAR-mediated inhibitory synaptic transmission in pentylenetetrazole rat model. Neurosci Res 2022; 182:7-14. [DOI: 10.1016/j.neures.2022.05.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Revised: 04/23/2022] [Accepted: 05/18/2022] [Indexed: 10/18/2022]
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3
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Agrud A, Subburaju S, Goel P, Ren J, Kumar AS, Caldarone BJ, Dai W, Chavez J, Fukumura D, Jain RK, Kloner RA, Vasudevan A. Gabrb3 endothelial cell-specific knockout mice display abnormal blood flow, hypertension, and behavioral dysfunction. Sci Rep 2022; 12:4922. [PMID: 35318369 PMCID: PMC8941104 DOI: 10.1038/s41598-022-08806-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Accepted: 03/04/2022] [Indexed: 11/17/2022] Open
Abstract
Our recent studies uncovered a novel GABA signaling pathway in embryonic forebrain endothelial cells that works independently from neuronal GABA signaling and revealed that disruptions in endothelial GABAA receptor-GABA signaling from early embryonic stages can directly contribute to the origin of psychiatric disorders. In the GABAA receptor β3 subunit endothelial cell conditional knockout (Gabrb3ECKO) mice, the β3 subunit is deleted selectively from endothelial cells, therefore endothelial GABAA receptors become inactivated and dysfunctional. There is a reduction in vessel densities and increased vessel morphology in the Gabrb3ECKO telencephalon that persists in the adult neocortex. Gabrb3ECKO mice show behavioral deficits such as impaired reciprocal social interactions, communication deficits, heightened anxiety, and depression. Here, we characterize the functional changes in Gabrb3ECKO mice by evaluating cortical blood flow, examine the consequences of loss of endothelial Gabrb3 on cardiac tissue, and define more in-depth altered behaviors. Red blood cell velocity and blood flow were increased in the cortical microcirculation of the Gabrb3ECKO mice. The Gabrb3ECKO mice had a reduction in vessel densities in the heart, similar to the brain; exhibited wavy, myocardial fibers, with elongated 'worm-like' nuclei in their cardiac histology, and developed hypertension. Additional alterations in behavioral function were observed in the Gabrb3ECKO mice such as increased spontaneous exploratory activity and rearing in an open field, reduced short term memory, decreased ambulatory activity in CLAMS testing, and altered prepulse inhibition to startle, an important biomarker of psychiatric diseases such as schizophrenia. Our results imply that vascular Gabrb3 is a key player in the brain as well as the heart, and its loss in both organs can lead to concurrent development of psychiatric and cardiac dysfunction.
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Affiliation(s)
- Anass Agrud
- grid.280933.30000 0004 0452 8371Angiogenesis and Brain Development Laboratory, Huntington Medical Research Institutes (HMRI), 686 S Fair Oaks Avenue, Pasadena, CA 91105 USA
| | - Sivan Subburaju
- grid.280933.30000 0004 0452 8371Angiogenesis and Brain Development Laboratory, Huntington Medical Research Institutes (HMRI), 686 S Fair Oaks Avenue, Pasadena, CA 91105 USA ,grid.38142.3c000000041936754XDepartment of Psychiatry, Harvard Medical School, Boston, MA 02215 USA ,grid.240206.20000 0000 8795 072XDivision of Basic Neuroscience, McLean Hospital, 115 Mill Street, Belmont, MA 02478 USA
| | - Pranay Goel
- grid.280933.30000 0004 0452 8371Angiogenesis and Brain Development Laboratory, Huntington Medical Research Institutes (HMRI), 686 S Fair Oaks Avenue, Pasadena, CA 91105 USA
| | - Jun Ren
- grid.32224.350000 0004 0386 9924Edwin L. Steele Laboratories, Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114 USA
| | - Ashwin Srinivasan Kumar
- grid.32224.350000 0004 0386 9924Edwin L. Steele Laboratories, Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114 USA ,grid.116068.80000 0001 2341 2786Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, MA 02139 USA
| | - Barbara J. Caldarone
- grid.38142.3c000000041936754XMouse Behavior Core, Department of Genetics, Harvard Medical School, Boston, MA USA
| | - Wangde Dai
- grid.280933.30000 0004 0452 8371Huntington Medical Research Institutes, Pasadena, CA USA ,grid.42505.360000 0001 2156 6853Division of Cardiovascular Medicine, Department of Medicine, Keck School of Medicine at University of Southern California, Los Angeles, CA USA
| | - Jesus Chavez
- grid.280933.30000 0004 0452 8371Huntington Medical Research Institutes, Pasadena, CA USA ,grid.42505.360000 0001 2156 6853Division of Cardiovascular Medicine, Department of Medicine, Keck School of Medicine at University of Southern California, Los Angeles, CA USA
| | - Dai Fukumura
- grid.32224.350000 0004 0386 9924Edwin L. Steele Laboratories, Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114 USA
| | - Rakesh K. Jain
- grid.32224.350000 0004 0386 9924Edwin L. Steele Laboratories, Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114 USA
| | - Robert A. Kloner
- grid.280933.30000 0004 0452 8371Huntington Medical Research Institutes, Pasadena, CA USA ,grid.42505.360000 0001 2156 6853Division of Cardiovascular Medicine, Department of Medicine, Keck School of Medicine at University of Southern California, Los Angeles, CA USA
| | - Anju Vasudevan
- Angiogenesis and Brain Development Laboratory, Huntington Medical Research Institutes (HMRI), 686 S Fair Oaks Avenue, Pasadena, CA, 91105, USA.
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4
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Figueroa AG, Benkwitz C, Surges G, Kunz N, Homanics GE, Pearce RA. Hippocampal β2-GABA A receptors mediate LTP suppression by etomidate and contribute to long-lasting feedback but not feedforward inhibition of pyramidal neurons. J Neurophysiol 2021; 126:1090-1100. [PMID: 34406874 PMCID: PMC8560413 DOI: 10.1152/jn.00303.2021] [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] [Indexed: 11/22/2022] Open
Abstract
The general anesthetic etomidate, which acts through γ-aminobutyric acid type A (GABAA) receptors, impairs the formation of new memories under anesthesia. This study addresses the molecular and cellular mechanisms by which this occurs. Here, using a new line of genetically engineered mice carrying the GABAA receptor (GABAAR) β2-N265M mutation, we tested the roles of receptors that incorporate GABAA receptor β2 versus β3 subunits to suppression of long-term potentiation (LTP), a cellular model of learning and memory. We found that brain slices from β2-N265M mice resisted etomidate suppression of LTP, indicating that the β2-GABAARs are an essential target in this model. As these receptors are most heavily expressed by interneurons in the hippocampus, this finding supports a role for interneuron modulation in etomidate control of synaptic plasticity. Nevertheless, β2 subunits are also expressed by pyramidal neurons, so they might also contribute. Therefore, using a previously established line of β3-N265M mice, we also examined the contributions of β2- versus β3-GABAARs to GABAA,slow dendritic inhibition, because dendritic inhibition is particularly well suited to controlling synaptic plasticity. We also examined their roles in long-lasting suppression of population activity through feedforward and feedback inhibition. We found that both β2- and β3-GABAARs contribute to GABAA,slow inhibition and that both β2- and β3-GABAARs contribute to feedback inhibition, whereas only β3-GABAARs contribute to feedforward inhibition. We conclude that modulation of β2-GABAARs is essential to etomidate suppression of LTP. Furthermore, to the extent that this occurs through GABAARs on pyramidal neurons, it is through modulation of feedback inhibition.NEW & NOTEWORTHY Etomidate exerts its anesthetic actions through GABAA receptors. However, the mechanism remains unknown. Here, using a hippocampal brain slice model, we show that β2-GABAARs are essential to this effect. We also show that these receptors contribute to long-lasting dendritic inhibition in feedback but not feedforward inhibition of pyramidal neurons. These findings hold implications for understanding how anesthetics block memory formation and, more generally, how inhibitory circuits control learning and memory.
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Affiliation(s)
- Alexander G Figueroa
- Department of Anesthesiology, University of Wisconsin-Madison, Madison, Wisconsin
| | - Claudia Benkwitz
- Department of Anesthesiology, University of Wisconsin-Madison, Madison, Wisconsin.,Department of Anesthesiology and Perioperative Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Gabe Surges
- Department of Anesthesiology, University of Wisconsin-Madison, Madison, Wisconsin
| | - Nicholas Kunz
- Department of Anesthesiology and Perioperative Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Gregg E Homanics
- Department of Anesthesiology and Perioperative Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Robert A Pearce
- Department of Anesthesiology, University of Wisconsin-Madison, Madison, Wisconsin
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5
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Li R, Wu B, He M, Zhang P, Zhang Q, Deng J, Yuan J, Chen Y. HAP1 Modulates Epileptic Seizures by Regulating GABA AR Function in Patients with Temporal Lobe Epilepsy and in the PTZ-Induced Epileptic Model. Neurochem Res 2020; 45:1997-2008. [PMID: 32419121 DOI: 10.1007/s11064-020-03052-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2019] [Revised: 04/13/2020] [Accepted: 05/06/2020] [Indexed: 01/03/2023]
Abstract
The number of γ-aminobutyric acid type A receptors (GABAARs) expressed on the surface membrane and at synaptic sites is implicated in the enhanced excitation of neuronal circuits and abnormal network oscillations in epilepsy. Huntingtin-associated protein 1 (HAP1), a key mediator of pathological alterations in protein trafficking, directly interacts with GABAARs and facilitates their recycling back to synapses after internalization from the surface; thus, HAP1 regulates the strength of inhibitory synaptic transmission. Here, we show that HAP1 modulates epileptic seizures by regulating GABAAR function in patients with temporal lobe epilepsy (TLE) and in the pentylenetetrazol (PTZ)-induced epileptic model. We demonstrate that GABAARβ2/3 and HAP1 expression are decreased and that the HAP1-GABAARβ2/3 complex is disrupted in the epileptic rat brain. We found that HAP1 upregulation exerts antiepileptic activity in the PTZ-induced seizure and that these changes are associated with increased surface GABAARβ2/3 expression and the amplitude of miniature inhibitory postsynaptic currents (mIPSCs). This study provides evidence that hippocampal HAP1 is linked to GABAARs in evoking seizures and suggests that this mechanism is involved in epileptic seizures in the brain, representing a potential therapeutic target for epilepsy.
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Affiliation(s)
- Rong Li
- Department of Neurology, Second Affiliated Hospital of Chongqing Medical University, Chongqing, 400016, China
| | - Bing Wu
- Department of Neurology, Chongqing Key Laboratory of Neurology, First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Miaoqing He
- Center for Brain Disorders Research, Capital Medical University, Beijing, China.,Beijing Institute for Brain Disorders, Beijing, China
| | - Peng Zhang
- Department of Neurology, Second Affiliated Hospital of Chongqing Medical University, Chongqing, 400016, China
| | - Qinbin Zhang
- Department of Neurology, Second Affiliated Hospital of Chongqing Medical University, Chongqing, 400016, China
| | - Jing Deng
- Department of Neurology, Second Affiliated Hospital of Chongqing Medical University, Chongqing, 400016, China
| | - Jinxian Yuan
- Department of Neurology, Second Affiliated Hospital of Chongqing Medical University, Chongqing, 400016, China
| | - Yangmei Chen
- Department of Neurology, Second Affiliated Hospital of Chongqing Medical University, Chongqing, 400016, China.
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6
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Gwilt M, Bauer M, Bast T. Frequency- and state-dependent effects of hippocampal neural disinhibition on hippocampal local field potential oscillations in anesthetized rats. Hippocampus 2020; 30:1021-1043. [PMID: 32396678 DOI: 10.1002/hipo.23212] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Revised: 03/09/2020] [Accepted: 04/09/2020] [Indexed: 11/11/2022]
Abstract
Reduced inhibitory GABA function, so-called neural disinhibition, has been implicated in cognitive disorders, including schizophrenia and age-related cognitive decline. We previously showed in rats that hippocampal disinhibition by local microinfusion of the GABA-A receptor antagonist picrotoxin disrupted memory and attention and enhanced hippocampal multi-unit burst firing recorded around the infusion site under isoflurane anesthesia. Here, we analyzed the hippocampal local field potential (LFP) recorded alongside the multi-unit data. We predicted frequency-specific LFP changes, based on previous studies implicating GABA in hippocampal oscillations, with the weight of evidence suggesting that disinhibition would facilitate theta and disrupt gamma oscillations. Using a new semi-automated method based on the kurtosis of the LFP peak-amplitude distribution as well as on amplitude envelope thresholding, we separated three distinct hippocampal LFP states under isoflurane anesthesia: "burst" and "suppression" states-high-amplitude LFP spike bursts and the interspersed low-amplitudeperiods-and a medium-amplitude "continuous" state. The burst state showed greater overall power than suppression and continuous states and higher relative delta/theta power, but lower relative beta/gamma power. The burst state also showed reduced functional connectivity across the hippocampal recording area, especially around theta and beta frequencies. Overall neuronal firing was higher in the burst than the other two states, whereas the proportion of burst firing was higher in burst and continuous states than the suppression state. Disinhibition caused state- and frequency-dependent LFP changes, tending to increase power at lower frequencies (<20 Hz), but to decrease power and connectivity at higher frequencies (>20 Hz) in burst and suppression states. The disinhibition-induced enhancement of multi-unit bursting was also state-dependent, tending to be more pronounced in burst and suppression states than the continuous state. Overall, we characterized three distinct hippocampal LFP states in isoflurane-anesthetized rats. Disinhibition changed hippocampal LFP oscillations in a state- and frequency-dependent way. Moreover, the disinhibition-induced enhancement of multi-unit bursting was also LFP state-dependent.
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Affiliation(s)
- Miriam Gwilt
- School of Psychology and Neuroscience@Nottingham, University of Nottingham, Nottingham, UK
| | - Markus Bauer
- School of Psychology and Neuroscience@Nottingham, University of Nottingham, Nottingham, UK
| | - Tobias Bast
- School of Psychology and Neuroscience@Nottingham, University of Nottingham, Nottingham, UK
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7
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Shangguan Y, Xu X, Ganbat B, Li Y, Wang W, Yang Y, Lu X, Du C, Tian X, Wang X. CNTNAP4 Impacts Epilepsy Through GABAA Receptors Regulation: Evidence From Temporal Lobe Epilepsy Patients and Mouse Models. Cereb Cortex 2019; 28:3491-3504. [PMID: 28968899 DOI: 10.1093/cercor/bhx215] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2017] [Indexed: 12/11/2022] Open
Abstract
Epilepsy is a serious neurological condition characterized by recurrent unprovoked seizures. The exact etiology of epilepsy is not fully understood. Here, we demonstrated that the expression of contactin-associated protein-like 4 (CNTNAP4) was decreased in the temporal neocortex of epileptic patients and in the hippocampus and cortex of epileptic mice. Lentivirus-mediated knock-down of CNTNAP4 in the hippocampus increased mice susceptibility to epilepsy. Conversely, lentivirus-mediated overexpression of CNTNAP4 decreased epileptic behavior in mice. CNTNAP4 affected neuronal excitability and inhibitory synaptic transmission via postsynaptic receptors in Mg2+-free epilepsy cell model. Down-regulation or overexpression of CNTNAP4 in the hippocampus influenced the expression of gamma-aminobutyric acid A receptor β2/3 (GABAARβ2/3) membrane protein, without affecting total GABAARβ2/3 protein concentration in epileptic mice. Protein interactions between CNTNAP4, GABAARβ2/3 and gamma-aminobutyric acid receptor-associated protein (GABARAP) were observed in the hippocampus of epileptic mice. These findings suggest CNTNAP4 may be involved in the occurrence and development of epilepsy through the regulation of GABAAR function, and may be a promising target for the development of epilepsy treatment.
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Affiliation(s)
- Yafei Shangguan
- Department of Neurology, Chongqing Key Laboratory of Neurology, The First Affiliated Hospital of Chongqing Medical University, 1 Youyi Road, Chongqing, China
| | - Xin Xu
- Department of Neurology, Chongqing Key Laboratory of Neurology, The First Affiliated Hospital of Chongqing Medical University, 1 Youyi Road, Chongqing, China
| | - Baigalimaa Ganbat
- Department of Neurology, Chongqing Key Laboratory of Neurology, The First Affiliated Hospital of Chongqing Medical University, 1 Youyi Road, Chongqing, China
| | - Yun Li
- Department of Neurology, Chongqing Key Laboratory of Neurology, The First Affiliated Hospital of Chongqing Medical University, 1 Youyi Road, Chongqing, China
| | - Wei Wang
- Department of Neurology, Chongqing Key Laboratory of Neurology, The First Affiliated Hospital of Chongqing Medical University, 1 Youyi Road, Chongqing, China
| | - Yong Yang
- Department of Neurology, Chongqing Key Laboratory of Neurology, The First Affiliated Hospital of Chongqing Medical University, 1 Youyi Road, Chongqing, China
| | - Xi Lu
- Department of Neurology, Chongqing Key Laboratory of Neurology, The First Affiliated Hospital of Chongqing Medical University, 1 Youyi Road, Chongqing, China
| | - Chao Du
- Department of Neurology, Chongqing Key Laboratory of Neurology, The First Affiliated Hospital of Chongqing Medical University, 1 Youyi Road, Chongqing, China
| | - Xin Tian
- Department of Neurology, Chongqing Key Laboratory of Neurology, The First Affiliated Hospital of Chongqing Medical University, 1 Youyi Road, Chongqing, China
| | - Xuefeng Wang
- Department of Neurology, Chongqing Key Laboratory of Neurology, The First Affiliated Hospital of Chongqing Medical University, 1 Youyi Road, Chongqing, China
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8
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Pelkey KA, Chittajallu R, Craig MT, Tricoire L, Wester JC, McBain CJ. Hippocampal GABAergic Inhibitory Interneurons. Physiol Rev 2017; 97:1619-1747. [PMID: 28954853 DOI: 10.1152/physrev.00007.2017] [Citation(s) in RCA: 490] [Impact Index Per Article: 70.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Revised: 05/16/2017] [Accepted: 05/26/2017] [Indexed: 12/11/2022] Open
Abstract
In the hippocampus GABAergic local circuit inhibitory interneurons represent only ~10-15% of the total neuronal population; however, their remarkable anatomical and physiological diversity allows them to regulate virtually all aspects of cellular and circuit function. Here we provide an overview of the current state of the field of interneuron research, focusing largely on the hippocampus. We discuss recent advances related to the various cell types, including their development and maturation, expression of subtype-specific voltage- and ligand-gated channels, and their roles in network oscillations. We also discuss recent technological advances and approaches that have permitted high-resolution, subtype-specific examination of their roles in numerous neural circuit disorders and the emerging therapeutic strategies to ameliorate such pathophysiological conditions. The ultimate goal of this review is not only to provide a touchstone for the current state of the field, but to help pave the way for future research by highlighting where gaps in our knowledge exist and how a complete appreciation of their roles will aid in future therapeutic strategies.
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Affiliation(s)
- Kenneth A Pelkey
- Porter Neuroscience Center, Eunice Kennedy-Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland; Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, Hatherly Laboratories, University of Exeter, Exeter, United Kingdom; and Sorbonne Universités, UPMC University of Paris, INSERM, CNRS, Neurosciences Paris Seine-Institut de Biologie Paris Seine, Paris, France
| | - Ramesh Chittajallu
- Porter Neuroscience Center, Eunice Kennedy-Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland; Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, Hatherly Laboratories, University of Exeter, Exeter, United Kingdom; and Sorbonne Universités, UPMC University of Paris, INSERM, CNRS, Neurosciences Paris Seine-Institut de Biologie Paris Seine, Paris, France
| | - Michael T Craig
- Porter Neuroscience Center, Eunice Kennedy-Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland; Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, Hatherly Laboratories, University of Exeter, Exeter, United Kingdom; and Sorbonne Universités, UPMC University of Paris, INSERM, CNRS, Neurosciences Paris Seine-Institut de Biologie Paris Seine, Paris, France
| | - Ludovic Tricoire
- Porter Neuroscience Center, Eunice Kennedy-Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland; Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, Hatherly Laboratories, University of Exeter, Exeter, United Kingdom; and Sorbonne Universités, UPMC University of Paris, INSERM, CNRS, Neurosciences Paris Seine-Institut de Biologie Paris Seine, Paris, France
| | - Jason C Wester
- Porter Neuroscience Center, Eunice Kennedy-Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland; Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, Hatherly Laboratories, University of Exeter, Exeter, United Kingdom; and Sorbonne Universités, UPMC University of Paris, INSERM, CNRS, Neurosciences Paris Seine-Institut de Biologie Paris Seine, Paris, France
| | - Chris J McBain
- Porter Neuroscience Center, Eunice Kennedy-Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland; Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, Hatherly Laboratories, University of Exeter, Exeter, United Kingdom; and Sorbonne Universités, UPMC University of Paris, INSERM, CNRS, Neurosciences Paris Seine-Institut de Biologie Paris Seine, Paris, France
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9
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Speigel I, Bichler EK, García PS. The Influence of Regional Distribution and Pharmacologic Specificity of GABA AR Subtype Expression on Anesthesia and Emergence. Front Syst Neurosci 2017; 11:58. [PMID: 28878632 PMCID: PMC5572268 DOI: 10.3389/fnsys.2017.00058] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Accepted: 07/19/2017] [Indexed: 01/31/2023] Open
Abstract
Anesthetics produce unconsciousness by modulating ion channels that control neuronal excitability. Research has shown that specific GABAA receptor (GABAAR) subtypes in particular regions of the central nervous system contribute to different hyperpolarizing conductances, and behaviorally to distinct components of the anesthetized state. The expression of these receptors on the neuron cell surface, and thus the strength of inhibitory neurotransmission, is dynamically regulated by intracellular trafficking mechanisms. Pharmacologic or activity-based perturbations to these regulatory systems have been implicated in pathology of several neurological conditions, and can alter the individual response to anesthesia. Furthermore, studies are beginning to uncover how anesthetic exposure itself elicits enduring changes in subcellular physiology, including the processes that regulate ion channel trafficking. Here, we review the mechanisms that determine GABAAR surface expression, and elaborate on influences germane to anesthesia and emergence. We address known trafficking differences between the intrasynaptic receptors that mediate phasic current and the extra-synaptic receptors mediating tonic current. We also describe neurophysiologic consequences and network-level abnormalities in brain function that result from receptor trafficking aberrations. We hypothesize that the relationship between commonly used anesthetic agents and GABAAR surface expression has direct consequences on mature functioning neural networks and by extension ultimately influence the outcome of patients that undergo general anesthesia. Rational design of new anesthetics, anesthetic techniques, EEG-based monitoring strategies, or emergence treatments will need to take these effects into consideration.
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Affiliation(s)
- Iris Speigel
- Department of Anesthesiology, Emory University School of Medicine, AtlantaGA, United States.,Research Division, Atlanta Veteran's Affairs Medical Center, AtlantaGA, United States
| | - Edyta K Bichler
- Department of Anesthesiology, Emory University School of Medicine, AtlantaGA, United States.,Research Division, Atlanta Veteran's Affairs Medical Center, AtlantaGA, United States
| | - Paul S García
- Department of Anesthesiology, Emory University School of Medicine, AtlantaGA, United States.,Research Division, Atlanta Veteran's Affairs Medical Center, AtlantaGA, United States
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10
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Xu X, Shangguan Y, Lu S, Wang W, Du C, Xiao F, Hu Y, Luo J, Wang L, He C, Yang Y, Zhang Y, Lu X, Yang Q, Wang X. Tubulin β-III modulates seizure activity in epilepsy. J Pathol 2017; 242:297-308. [PMID: 28378416 DOI: 10.1002/path.4903] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Revised: 03/14/2017] [Accepted: 03/27/2017] [Indexed: 11/09/2022]
Abstract
Tubulin β-III (TUBB3) is the most dynamic β-tubulin isoform expressed in neurons, and is highly expressed in the central nervous system. However, the relationship between TUBB3 and epileptic seizures has not been thoroughly investigated. The aims of this study were to investigate the expression of TUBB3 in patients with temporal lobe epilepsy and two different rat models of chronic epilepsy, and to determine the specific roles of TUBB3 in epilepsy. TUBB3 expression was upregulated in human and rat epileptic tissue. Moreover, TUBB3 expression was associated with inhibitory GABAergic neurons and the inhibitory postsynaptic scaffold protein gephyrin. TUBB3 downregulation attenuated the behavioural phenotypes of epileptic seizures during the pilocarpine-induced chronic phase of epileptic seizures and the pentylenetetrazole kindling process, whereas TUBB3 overexpression had the opposite effect. Whole-cell clamp recordings and western blotting revealed that the amplitude of GABA-A receptor-mediated miniature inhibitory postsynaptic currents and the surface expression of the GABA-A receptor were increased in rats in which TUBB3 expression was downregulated. Importantly, TUBB3 interacted with GABA-A receptor-associated protein, which is known to be involved in GABA-A receptor trafficking. These results indicate that TUBB3 plays a critical role in the regulation of epileptic seizures via GABA-A receptor trafficking, suggesting a molecular mechanism for new therapeutic strategies. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
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Affiliation(s)
- Xin Xu
- Department of Neurology, the First Affiliated Hospital of Chongqing Medical University, Chongqing Key Laboratory of Neurology, Chongqing, PR China
| | - Yafei Shangguan
- Department of Neurology, the First Affiliated Hospital of Chongqing Medical University, Chongqing Key Laboratory of Neurology, Chongqing, PR China
| | - Shanshan Lu
- Department of Neurology, the First Affiliated Hospital of Chongqing Medical University, Chongqing Key Laboratory of Neurology, Chongqing, PR China
| | - Wei Wang
- Department of Neurology, the First Affiliated Hospital of Chongqing Medical University, Chongqing Key Laboratory of Neurology, Chongqing, PR China
| | - Chao Du
- Department of Neurology, the First Affiliated Hospital of Chongqing Medical University, Chongqing Key Laboratory of Neurology, Chongqing, PR China
| | - Fei Xiao
- Department of Neurology, the First Affiliated Hospital of Chongqing Medical University, Chongqing Key Laboratory of Neurology, Chongqing, PR China
| | - Yida Hu
- Department of Neurology, the First Affiliated Hospital of Chongqing Medical University, Chongqing Key Laboratory of Neurology, Chongqing, PR China
| | - Jing Luo
- Department of Neurology, the First Affiliated Hospital of Chongqing Medical University, Chongqing Key Laboratory of Neurology, Chongqing, PR China
| | - Liang Wang
- Department of Neurology, the First Affiliated Hospital of Chongqing Medical University, Chongqing Key Laboratory of Neurology, Chongqing, PR China
| | - Changlong He
- Institute of Infectious Diseases, Southwest Hospital, Third Military Medical University, Chongqing, PR China
| | - Yong Yang
- Department of Neurology, the First Affiliated Hospital of Chongqing Medical University, Chongqing Key Laboratory of Neurology, Chongqing, PR China
| | - Yanke Zhang
- Department of Neurology, the First Affiliated Hospital of Chongqing Medical University, Chongqing Key Laboratory of Neurology, Chongqing, PR China
| | - Xi Lu
- Department of Neurology, the First Affiliated Hospital of Chongqing Medical University, Chongqing Key Laboratory of Neurology, Chongqing, PR China
| | - Qin Yang
- Department of Neurology, the First Affiliated Hospital of Chongqing Medical University, Chongqing Key Laboratory of Neurology, Chongqing, PR China
| | - Xuefeng Wang
- Department of Neurology, the First Affiliated Hospital of Chongqing Medical University, Chongqing Key Laboratory of Neurology, Chongqing, PR China.,Centre of Epilepsy, Beijing Institute for Brain Disorders, Beijing, PR China
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11
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Yin J, Schaaf CP. Autism genetics - an overview. Prenat Diagn 2016; 37:14-30. [DOI: 10.1002/pd.4942] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Revised: 10/04/2016] [Accepted: 10/11/2016] [Indexed: 12/13/2022]
Affiliation(s)
- Jiani Yin
- Department of Molecular and Human Genetics; Baylor College of Medicine; Houston TX USA
- Jan and Dan Duncan Neurological Research Institute at Texas Children's Hospital; Houston TX USA
| | - Christian P. Schaaf
- Department of Molecular and Human Genetics; Baylor College of Medicine; Houston TX USA
- Jan and Dan Duncan Neurological Research Institute at Texas Children's Hospital; Houston TX USA
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12
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Woll KA, Murlidaran S, Pinch BJ, Hénin J, Wang X, Salari R, Covarrubias M, Dailey WP, Brannigan G, Garcia BA, Eckenhoff RG. A Novel Bifunctional Alkylphenol Anesthetic Allows Characterization of γ-Aminobutyric Acid, Type A (GABAA), Receptor Subunit Binding Selectivity in Synaptosomes. J Biol Chem 2016; 291:20473-86. [PMID: 27462076 PMCID: PMC5034043 DOI: 10.1074/jbc.m116.736975] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Revised: 07/25/2016] [Indexed: 12/19/2022] Open
Abstract
Propofol, an intravenous anesthetic, is a positive modulator of the GABAA receptor, but the mechanistic details, including the relevant binding sites and alternative targets, remain disputed. Here we undertook an in-depth study of alkylphenol-based anesthetic binding to synaptic membranes. We designed, synthesized, and characterized a chemically active alkylphenol anesthetic (2-((prop-2-yn-1-yloxy)methyl)-5-(3-(trifluoromethyl)-3H-diazirin-3-yl)phenol, AziPm-click (1)), for affinity-based protein profiling (ABPP) of propofol-binding proteins in their native state within mouse synaptosomes. The ABPP strategy captured ∼4% of the synaptosomal proteome, including the unbiased capture of five α or β GABAA receptor subunits. Lack of γ2 subunit capture was not due to low abundance. Consistent with this, independent molecular dynamics simulations with alchemical free energy perturbation calculations predicted selective propofol binding to interfacial sites, with higher affinities for α/β than γ-containing interfaces. The simulations indicated hydrogen bonding is a key component leading to propofol-selective binding within GABAA receptor subunit interfaces, with stable hydrogen bonds observed between propofol and α/β cavity residues but not γ cavity residues. We confirmed this by introducing a hydrogen bond-null propofol analogue as a protecting ligand for targeted-ABPP and observed a lack of GABAA receptor subunit protection. This investigation demonstrates striking interfacial GABAA receptor subunit selectivity in the native milieu, suggesting that asymmetric occupancy of heteropentameric ion channels by alkylphenol-based anesthetics is sufficient to induce modulation of activity.
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Affiliation(s)
- Kellie A Woll
- From the Departments of Anesthesiology and Critical Care and Pharmacology and
| | | | - Benika J Pinch
- the Department of Chemistry, University of Pennsylvania School of Arts and Sciences, Philadelphia, Pennsylvania 19104
| | - Jérôme Hénin
- the Laboratoire de Biochimie Théorique, Institut de Biologie Physico-Chimique, CNRS UMR 8251 and Université Paris Diderot, 5013 Paris, France, and
| | - Xiaoshi Wang
- the Epigenetics Program, Department of Biochemistry and Biophysics, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania 19104
| | - Reza Salari
- the Center for Computational and Integrative Biology and Department of Physics, Rutgers University, Camden, New Jersey 08102
| | - Manuel Covarrubias
- the Department of Neuroscience and Farber Institute for Neuroscience, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania 19107
| | - William P Dailey
- the Department of Chemistry, University of Pennsylvania School of Arts and Sciences, Philadelphia, Pennsylvania 19104
| | - Grace Brannigan
- the Center for Computational and Integrative Biology and Department of Physics, Rutgers University, Camden, New Jersey 08102
| | - Benjamin A Garcia
- the Epigenetics Program, Department of Biochemistry and Biophysics, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania 19104
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13
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Kuo TBJ, Lai CT, Chen CY, Yang YC, Yang CCH. The high-frequency component of heart rate variability during extended wakefulness is closely associated with the depth of the ensuing sleep in C57BL6 mice. Neuroscience 2016; 330:257-66. [PMID: 27267244 DOI: 10.1016/j.neuroscience.2016.05.060] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Revised: 05/28/2016] [Accepted: 05/31/2016] [Indexed: 11/29/2022]
Abstract
This study aimed to test the hypothesis that, during extended wakefulness, parasympathetic activity is associated with the depth of the subsequent recovery sleep in mice. Fourteen male C57BL/6 mice were implanted with electrodes for sleep recording. Continuous spectral analysis was performed on the electroencephalogram (EEG) to obtain theta power (6-9Hz) and delta power (0-4Hz), as well as the R-R interval signals in order to quantify the high-frequency power (HF) and normalized low-frequency power (LF%) that are used to assess parasympathetic and sympathetic activity, respectively. All animals underwent a sleep deprivation experiment and a control experiment (6-h intervention and 1-h recovery period) on two separate days. During sleep deprivation, HF and theta power during wakefulness were significantly higher than during the control wakefulness after the second hour and first hour, respectively. During recovery non-rapid eye movement sleep, there was a rebound in sleep time and delta power as well as an elevation in HF relative to control post-intervention sleep. Both the rise in HF and theta power during extended wakefulness were found to be positively correlated with the delta power rebound. Furthermore, the HF change during extended wakefulness was also correlated with the amount of sleep loss and the enhancement of waking theta power. Our finding suggests that waking parasympathetic activity intimately reflects the cumulative sleep pressure, suggesting a potential role to be an autonomic marker for sleep propensity.
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Affiliation(s)
- T B J Kuo
- Institute of Brain Science, National Yang-Ming University, Taipei, Taiwan; Sleep Research Center, National Yang-Ming University, Taipei, Taiwan; Department of Education and Research, Taipei City Hospital, Taipei, Taiwan; Research Center for Adaptive Data Analysis, National Central University, Taoyuan, Taiwan
| | - C T Lai
- Institute of Brain Science, National Yang-Ming University, Taipei, Taiwan; Sleep Research Center, National Yang-Ming University, Taipei, Taiwan
| | - C Y Chen
- Institute of Brain Science, National Yang-Ming University, Taipei, Taiwan; Sleep Research Center, National Yang-Ming University, Taipei, Taiwan; Neurological institute, Taipei Veterans General Hospital, Taipei, Taiwan
| | - Y C Yang
- Institute of Brain Science, National Yang-Ming University, Taipei, Taiwan; Sleep Research Center, National Yang-Ming University, Taipei, Taiwan
| | - C C H Yang
- Institute of Brain Science, National Yang-Ming University, Taipei, Taiwan; Sleep Research Center, National Yang-Ming University, Taipei, Taiwan; Department of Education and Research, Taipei City Hospital, Taipei, Taiwan.
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14
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Nunes D, Kuner T. Disinhibition of olfactory bulb granule cells accelerates odour discrimination in mice. Nat Commun 2015; 6:8950. [PMID: 26592770 PMCID: PMC4673882 DOI: 10.1038/ncomms9950] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2014] [Accepted: 10/20/2015] [Indexed: 11/13/2022] Open
Abstract
Granule cells are the dominant cell type of the olfactory bulb inhibiting mitral and tufted cells via dendrodendritic synapses; yet the factors regulating the strength of their inhibitory output, and, therefore, their impact on odour discrimination, remain unknown. Here we show that GABAAR β3-subunits are distributed in a somatodendritic pattern, mostly sparing the large granule cell spines also known as gemmules. Granule cell-selective deletion of β3-subunits nearly abolishes spontaneous and muscimol-induced currents mediated by GABAA receptors in granule cells, yet recurrent inhibition of mitral cells is strongly enhanced. Mice with disinhibited granule cells require less time to discriminate both dissimilar as well as highly similar odourants, while discrimination learning remains unaffected. Hence, granule cells are controlled by an inhibitory drive that in turn tunes mitral cell inhibition. As a consequence, the olfactory bulb inhibitory network adjusts the speed of early sensory processing. How odour discrimination is influenced by granule cells in the olfactory bulb is poorly understood. Here, the authors show that disinhibition of granule cells in mice increases mitral cell inhibition and accelerates odour discrimination time, independent of odour similarity.
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Affiliation(s)
- Daniel Nunes
- Department of Functional Neuroanatomy, Institute for Anatomy and Cell Biology, Heidelberg University, Im Neuenheimer Feld 307, 69120 Heidelberg, Germany
| | - Thomas Kuner
- Department of Functional Neuroanatomy, Institute for Anatomy and Cell Biology, Heidelberg University, Im Neuenheimer Feld 307, 69120 Heidelberg, Germany
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15
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Plic-1, a new target in repressing epileptic seizure by regulation of GABAAR function in patients and a rat model of epilepsy. Clin Sci (Lond) 2015; 129:1207-23. [PMID: 26415648 DOI: 10.1042/cs20150202] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2015] [Accepted: 09/25/2015] [Indexed: 12/27/2022]
Abstract
Plic-1 regulates GABAAR expression at synaptic sites during epileptic seizure. Plic-1 prolongs the seizure latency and reduces the seizure severity in epileptic rats. Plic-1 affects the inhibitory function by changing the mIPSCs and evoked IPSCs of the phasic GABA-ergic synaptic current.
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16
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Abstract
BACKGROUND Anesthetics enhance γ-aminobutyric acid (GABA)-mediated inhibition in the central nervous system. Different agents have been shown to act on tonic versus synaptic GABA receptors to different degrees, but it remains unknown whether different forms of synaptic inhibition are also differentially engaged. With this in mind, we tested the hypothesis that different types of GABA-mediated synapses exhibit different anesthetic sensitivities. The present study compared effects produced by isoflurane, halothane, pentobarbital, thiopental, and propofol on paired-pulse GABAA receptor-mediated synaptic inhibition. Effects on glutamate-mediated facilitation were also studied. METHODS Synaptic responses were measured in rat hippocampal brain slices. Orthodromic paired-pulse stimulation was used to assess anesthetic effects on either glutamate-mediated excitatory inputs or GABA-mediated inhibitory inputs to CA1 neurons. Antidromic stimulation was used to assess anesthetic effects on CA1 background excitability. Agents were studied at equieffective concentrations for population spike depression to compare their relative degree of effect on synaptic inhibition. RESULTS Differing degrees of anesthetic effect on paired-pulse facilitation at excitatory glutamate synapses were evident, and blocking GABA inhibition revealed a previously unseen presynaptic action for pentobarbital. Although all 5 anesthetics depressed synaptically evoked excitation of CA1 neurons, the involvement of enhanced GABA-mediated inhibition differed considerably among agents. Single-pulse inhibition was enhanced by propofol, thiopental, and pentobarbital, but only marginally by halothane and isoflurane. In contrast, isoflurane enhanced paired-pulse inhibition strongly, as did thiopental, but propofol, pentobarbital, and halothane were less effective. CONCLUSIONS These observations support the idea that different GABA synapses use receptors with differing subunit compositions and that anesthetics exhibit differing degrees of selectivity for these receptors. The differing anesthetic sensitivities seen in the present study, at glutamate and GABA synapses, help explain the unique behavioral/clinical profiles produced by different classes of anesthetics and indicate that there are selective targets for new agent development.
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Affiliation(s)
- M Bruce MacIver
- From the Department of Anesthesia, Stanford School of Medicine, Palo Alto, California
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17
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Dynamic circuit motifs underlying rhythmic gain control, gating and integration. Nat Neurosci 2014; 17:1031-9. [DOI: 10.1038/nn.3764] [Citation(s) in RCA: 251] [Impact Index Per Article: 25.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2014] [Accepted: 06/16/2014] [Indexed: 12/12/2022]
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18
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Luo R, Partridge JG, Vicini S. Distinct roles of synaptic and extrasynaptic GABAAreceptors in striatal inhibition dynamics. Front Neural Circuits 2013; 7:186. [PMID: 24324406 PMCID: PMC3840641 DOI: 10.3389/fncir.2013.00186] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2013] [Accepted: 11/02/2013] [Indexed: 01/15/2023] Open
Abstract
Striatonigral and striatopallidal projecting medium spiny neurons (MSNs) express dopamine D1 (D1+) and D2 receptors (D2+), respectively. Both classes receive extensive GABAergic input via expression of synaptic, perisynaptic, and extrasynaptic GABAA receptors. The activation patterns of different presynaptic GABAergic neurons produce transient and sustained GABAA receptor-mediated conductance that fulfill distinct physiological roles. We performed single and dual whole cell recordings from striatal neurons in mice expressing fluorescent proteins in interneurons and MSNs. We report specific inhibitory dynamics produced by distinct activation patterns of presynaptic GABAergic neurons as source of synaptic, perisynaptic, and extrasynaptic inhibition. Synaptic GABAA receptors in MSNs contain the α2, γ2, and a β subunit. In addition, there is evidence for the developmental increase of the α1 subunit that contributes to faster inhibitory post-synaptic current (IPSC). Tonic GABAergic currents in MSNs from adult mice are carried by extrasynaptic receptors containing the α4 and δ subunit, while in younger mice this current is mediated by receptors that contain the α5 subunit. Both forms of tonic currents are differentially expressed in D1+ and D2+ MSNs. This study extends these findings by relating presynaptic activation with pharmacological analysis of inhibitory conductance in mice where the β3 subunit is conditionally removed in fluorescently labeled D2+ MSNs and in mice with global deletion of the δ subunit. Our results show that responses to low doses of gaboxadol (2 μM), a GABAA receptor agonist with preference to δ subunit, are abolished in the δ but not the β3 subunit knock out mice. This suggests that the β3 subunit is not a component of the adult extrasynaptic receptor pool, in contrast to what has been shown for tonic current in young mice. Deletion of the β3 subunit from D2+ MSNs however, removed slow spontaneous IPSCs, implicating its role in mediating synaptic input from striatal neurogliaform interneurons.
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Affiliation(s)
- Ruixi Luo
- Department of Pharmacology and Physiology, Georgetown University School of Medicine Washington, DC, USA
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19
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Yeung M, Lu L, Hughes AM, Treit D, Dickson CT. FG7142, yohimbine, and βCCE produce anxiogenic-like effects in the elevated plus-maze but do not affect brainstem activated hippocampal theta. Neuropharmacology 2013; 75:47-52. [PMID: 23851259 DOI: 10.1016/j.neuropharm.2013.06.027] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2013] [Revised: 06/20/2013] [Accepted: 06/27/2013] [Indexed: 01/08/2023]
Abstract
The neurobiological underpinnings of anxiety are of paramount importance to selective and efficacious pharmaceutical intervention. Hippocampal theta frequency in urethane anaesthetized rats is suppressed by all known (and some previously unknown) anti-anxiety (anxiolytic) drugs. Although these findings support the predictive validity of this assay, its construct validity (i.e., whether theta frequency actually indexes anxiety per se) has not been a subject of systematic investigation. We reasoned that if anxiolytic drugs suppress hippocampal theta frequency, then drugs that increase anxiety (i.e., anxiogenic agents) should increase theta frequency, thus providing evidence of construct validity. We used three proven anxiogenic drugs--two benzodiazepine receptor inverse agonists, N-methyl-β-carboline-3-carboxamide (FG7142) and β-carboline-3-carboxylate ethyl ester (βCCE), and one α2 noradrenergic receptor antagonist, 17α-hydroxy-yohimban-16α-carboxylic acid methyl ester (yohimbine) as pharmacological probes to assess the construct validity of the theta model. Although all three anxiogenic drugs significantly increased behavioural measures of anxiety in the elevated plus-maze, none of the three increased the frequency of hippocampal theta oscillations in the neurophysiological model. As a positive control, we demonstrated that diazepam, a proven anxiolytic drug, decreased the frequency of hippocampal theta, as in all other studies using this model. Given this discrepancy between the significant effects of anxiogenic drugs in the behavioural model and the null effects of these drugs in the neurophysiological model, we conclude that the construct validity of the hippocampal theta model of anxiety is questionable.
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Affiliation(s)
- Michelle Yeung
- Department of Psychology, University of Alberta, P-449 Biological Sciences Building, Edmonton, AB, Canada T6G 2E9
| | - Lily Lu
- Department of Psychology, University of Alberta, P-449 Biological Sciences Building, Edmonton, AB, Canada T6G 2E9
| | - Adam M Hughes
- Department of Psychology, University of Alberta, P-449 Biological Sciences Building, Edmonton, AB, Canada T6G 2E9
| | - Dallas Treit
- Department of Psychology, University of Alberta, P-449 Biological Sciences Building, Edmonton, AB, Canada T6G 2E9; Centre for Neuroscience, 513 Heritage Medical Research Center, University of Alberta, Edmonton, AB, Canada T6G 2R3.
| | - Clayton T Dickson
- Department of Psychology, University of Alberta, P-449 Biological Sciences Building, Edmonton, AB, Canada T6G 2E9; Centre for Neuroscience, 513 Heritage Medical Research Center, University of Alberta, Edmonton, AB, Canada T6G 2R3; Department of Physiology, 7-55 Medical Sciences Building, University of Alberta, Edmonton, AB, Canada T6G 2H7
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Christian CA, Herbert AG, Holt RL, Peng K, Sherwood KD, Pangratz-Fuehrer S, Rudolph U, Huguenard JR. Endogenous positive allosteric modulation of GABA(A) receptors by diazepam binding inhibitor. Neuron 2013; 78:1063-74. [PMID: 23727119 DOI: 10.1016/j.neuron.2013.04.026] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/12/2013] [Indexed: 11/30/2022]
Abstract
Benzodiazepines (BZs) allosterically modulate γ-aminobutyric acid type-A receptors (GABAARs) to increase inhibitory synaptic strength. Diazepam binding inhibitor (DBI) protein is a BZ site ligand expressed endogenously in the brain, but functional evidence for BZ-mimicking positive modulatory actions has been elusive. We demonstrate an endogenous potentiation of GABAergic synaptic transmission and responses to GABA uncaging in the thalamic reticular nucleus (nRT) that is absent in both nm1054 mice, in which the Dbi gene is deleted, and mice in which BZ binding to α3 subunit-containing GABAARs is disrupted. Viral transduction of DBI into nRT is sufficient to rescue the endogenous potentiation of GABAergic transmission in nm1054 mice. Both mutations enhance thalamocortical spike-and-wave discharges characteristic of absence epilepsy. Together, these results indicate that DBI mediates endogenous nucleus-specific BZ-mimicking ("endozepine") roles to modulate nRT function and suppress thalamocortical oscillations. Enhanced DBI signaling might serve as a therapy for epilepsy and other neurological disorders.
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Affiliation(s)
- Catherine A Christian
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94305, USA.
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Mańko M, Bienvenu TCM, Dalezios Y, Capogna M. Neurogliaform cells of amygdala: a source of slow phasic inhibition in the basolateral complex. J Physiol 2012; 590:5611-27. [PMID: 22930272 DOI: 10.1113/jphysiol.2012.236745] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Synaptic inhibition in the amygdala actively participates in processing emotional information. To improve the understanding of interneurons in amygdala networks it is necessary to characterize the GABAergic cell types, their connectivity and physiological roles. We used a mouse line expressing a green fluorescent protein (GFP) under the neuropeptide Y (NPY) promoter. Paired recordings between presynaptic NPY-GFP-expressing (+) cells and postsynaptic principal neurons (PNs) of the basolateral amygdala (BLA) were performed. The NPY-GFP+ neurons displayed small somata and short dendrites embedded in a cloud of highly arborized axon, suggesting a neurogliaform cell (NGFC) type. We discovered that a NPY-GFP+ cell evoked a GABA(A) receptor-mediated slow inhibitory postsynaptic current (IPSC) in a PN and an autaptic IPSC. The slow kinetics of these IPSCs was likely caused by the low concentration and spillover of extracellular GABA. We also report that NGFCs of the BLA fired action potentials phase-locked to hippocampal theta oscillations in anaesthetized rats. When this firing was re-played in NPY+-NGFCs in vitro, it evoked a transient depression of the IPSCs. Presynaptic GABA(B) receptors and functional depletion of synaptic vesicles determined this short-term plasticity. Synaptic contacts made by recorded NGFCs showed close appositions, and rarely identifiable classical synaptic structures. Thus, we report here a novel interneuron type of the amygdala that generates volume transmission of GABA. The peculiar functional mode of NGFCs makes them unique amongst all GABAergic cell types of the amygdala identified so far.
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Affiliation(s)
- Mirosława Mańko
- MRC Anatomical Neuropharmacology Unit, Mansfield Road, Oxford OX1 3TH, UK
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Múnera A, Cuestas DM, Troncoso J. Peripheral facial nerve lesions induce changes in the firing properties of primary motor cortex layer 5 pyramidal cells. Neuroscience 2012; 223:140-51. [PMID: 22877641 DOI: 10.1016/j.neuroscience.2012.07.063] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2011] [Revised: 07/27/2012] [Accepted: 07/30/2012] [Indexed: 12/30/2022]
Abstract
Facial nerve lesions elicit long-lasting changes in vibrissal primary motor cortex (M1) muscular representation in rodents. Reorganization of cortical representation has been attributed to potentiation of preexisting horizontal connections coming from neighboring muscle representation. However, changes in layer 5 pyramidal neuron activity induced by facial nerve lesion have not yet been explored. To do so, the effect of irreversible facial nerve injury on electrophysiological properties of layer 5 pyramidal neurons was characterized. Twenty-four adult male Wistar rats were randomly subjected to two experimental treatments: either surgical transection of mandibular and buccal branches of the facial nerve (n=18) or sham surgery (n=6). Unitary and population activity of vibrissal M1 layer 5 pyramidal neurons recorded in vivo under general anesthesia was compared between sham-operated and facial nerve-injured animals. Injured animals were allowed either one (n=6), three (n=6), or five (n=6) weeks recovery before recording in order to characterize the evolution of changes in electrophysiological activity. As compared to control, facial nerve-injured animals displayed the following sustained and significant changes in spontaneous activity: increased basal firing frequency, decreased spike-associated local field oscillation amplitude, and decreased spontaneous theta burst firing frequency. Significant changes in evoked-activity with whisker pad stimulation included: increased short latency population spike amplitude, decreased long latency population oscillations amplitude and frequency, and decreased peak frequency during evoked single-unit burst firing. Taken together, such changes demonstrate that peripheral facial nerve lesions induce robust and sustained changes of layer 5 pyramidal neurons in vibrissal motor cortex.
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Affiliation(s)
- A Múnera
- Behavioral Neurophysiology Laboratory, Universidad Nacional de Colombia, Bogotá, Colombia.
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Kaphzan H, Hernandez P, Jung JI, Cowansage KK, Deinhardt K, Chao MV, Abel T, Klann E. Reversal of impaired hippocampal long-term potentiation and contextual fear memory deficits in Angelman syndrome model mice by ErbB inhibitors. Biol Psychiatry 2012; 72:182-90. [PMID: 22381732 PMCID: PMC3368039 DOI: 10.1016/j.biopsych.2012.01.021] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/13/2011] [Revised: 01/20/2012] [Accepted: 01/20/2012] [Indexed: 12/17/2022]
Abstract
BACKGROUND Angelman syndrome (AS) is a human neuropsychiatric disorder associated with autism, mental retardation, motor abnormalities, and epilepsy. In most cases, AS is caused by the deletion of the maternal copy of UBE3A gene, which encodes the enzyme ubiquitin ligase E3A, also termed E6-AP. A mouse model of AS has been generated and these mice exhibit many of the observed neurological alterations in humans. Because of clinical and neuroanatomical similarities between AS and schizophrenia, we examined AS model mice for alterations in the neuregulin-ErbB4 pathway, which has been implicated in the pathophysiology of schizophrenia. We focused our studies on the hippocampus, one of the major brain loci impaired in AS mice. METHODS We determined the expression of neuregulin 1 and ErbB4 receptors in AS mice and wild-type littermates (ages 10-16 weeks) and studied the effects of ErbB inhibition on long-term potentiation in hippocampal area cornu ammonis 1 and on hippocampus-dependent contextual fear memory. RESULTS We observed enhanced neuregulin-ErbB4 signaling in the hippocampus of AS model mice and found that ErbB inhibitors could reverse deficits in long-term potentiation, a cellular substrate for learning and memory. In addition, we found that an ErbB inhibitor enhanced long-term contextual fear memory in AS model mice. CONCLUSIONS Our findings suggest that neuregulin-ErbB4 signaling is involved in synaptic plasticity and memory impairments in AS model mice, suggesting that ErbB inhibitors have therapeutic potential for the treatment of AS.
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Affiliation(s)
- Hanoch Kaphzan
- Center for Neural Science, New York University, New York, NY 10003
| | - Pepe Hernandez
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104
| | - Joo In Jung
- Center for Neural Science, New York University, New York, NY 10003
| | | | - Katrin Deinhardt
- Departments of Cell Biology, Physiology and Neuroscience, New York University School of Medicine, New York, NY 10016,Kimmel Center for Biology and Medicine, Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, NY 10016
| | - Moses V. Chao
- Departments of Cell Biology, Physiology and Neuroscience, New York University School of Medicine, New York, NY 10016,Kimmel Center for Biology and Medicine, Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, NY 10016
| | - Ted Abel
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104
| | - Eric Klann
- Center for Neural Science, New York University, New York, NY 10003,To whom correspondence should be addressed: Eric Klann, Ph.D., Center for Neural Science, New York University, 4 Washington Place, Room 809, New York, NY 10003, phone: (212) 992-9769, , fax: (212) 995-4011
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Paul A, Cai Y, Atwal GS, Huang ZJ. Developmental Coordination of Gene Expression between Synaptic Partners During GABAergic Circuit Assembly in Cerebellar Cortex. Front Neural Circuits 2012; 6:37. [PMID: 22754500 PMCID: PMC3385560 DOI: 10.3389/fncir.2012.00037] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2012] [Accepted: 06/01/2012] [Indexed: 01/14/2023] Open
Abstract
The assembly of neural circuits involves multiple sequential steps such as the specification of cell-types, their migration to proper brain locations, morphological and physiological differentiation, and the formation and maturation of synaptic connections. This intricate and often prolonged process is guided by elaborate genetic mechanisms that regulate each step. Evidence from numerous systems suggests that each cell-type, once specified, is endowed with a genetic program that unfolds in response to, and is regulated by, extrinsic signals, including cell–cell and synaptic interactions. To a large extent, the execution of this intrinsic program is achieved by the expression of specific sets of genes that support distinct developmental processes. Therefore, a comprehensive analysis of the developmental progression of gene expression in synaptic partners of neurons may provide a basis for exploring the genetic mechanisms regulating circuit assembly. Here we examined the developmental gene expression profiles of well-defined cell-types in a stereotyped microcircuit of the cerebellar cortex. We found that the transcriptomes of Purkinje cell and stellate/basket cells are highly dynamic throughout postnatal development. We revealed “phasic expression” of transcription factors, ion channels, receptors, cell adhesion molecules, gap junction proteins, and identified distinct molecular pathways that might contribute to sequential steps of cerebellar inhibitory circuit formation. We further revealed a correlation between genomic clustering and developmental co-expression of hundreds of transcripts, suggesting the involvement of chromatin level gene regulation during circuit formation.
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Affiliation(s)
- Anirban Paul
- Cold Spring Harbor Laboratory, Neuroscience Cold Spring Harbor, New York, NY, USA
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Isoflurane enhances both fast and slow synaptic inhibition in the hippocampus at amnestic concentrations. Anesthesiology 2012; 116:816-23. [PMID: 22343472 DOI: 10.1097/aln.0b013e31824be0e3] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
BACKGROUND Inhibition mediated by γ-aminobutyric acid type A (GABA A) receptors has long been considered an important target for a variety of general anesthetics. In the hippocampus, two types of phasic GABA A receptor-mediated inhibition coexist: GABA A,fast, which is expressed primarily at peri-somatic sites, and GABAA,slow, which is expressed primarily in the dendrites. Their spatial segregation suggests distinct functions: GABA A,slow may control plasticity of dendritic synapses, whereas GABA A,fast controls action potential initiation at the soma. We examined modulation of GABA A,fast and GABA A,slow inhibition by isoflurane at amnesic concentrations, and compared it with modulation by behaviorally equivalent doses of the GABA A receptor-selective drug etomidate. METHODS Whole cell recordings were obtained from pyramidal cells in organotypic hippocampal cultures prepared from C57BL/6 × 129/SvJ F1 hybrid mice. GABA A receptor-mediated currents were isolated using glutamate receptor antagonists. GABAA,slow currents were evoked by electrical stimulation in the stratum lacunosum-moleculare. Miniature GABA A,fast currents were recorded in the presence of tetrodotoxin. RESULTS 100 μM isoflurane (approximately EC50,amnesia) slowed fast- and slow-inhibitory postsynaptic current decay by approximately 25%. Higher concentrations, up to 400 μM, produced proportionally greater effects without altering current amplitudes. The effects on GABA A,slow were approximately one-half those produced by equi-amnesic concentrations of etomidate. CONCLUSIONS Isoflurane enhances both types of phasic GABA A receptor-mediated inhibition to similar degrees at amnesic concentrations. This pattern differs from etomidate, which at low concentrations selectively enhances slow inhibition. These effects of isoflurane are sufficiently large that they may contribute substantially to its suppression of hippocampal learning and memory.
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Hentschke H, Stüttgen MC. Computation of measures of effect size for neuroscience data sets. Eur J Neurosci 2011; 34:1887-94. [DOI: 10.1111/j.1460-9568.2011.07902.x] [Citation(s) in RCA: 286] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Janssen MJ, Yasuda RP, Vicini S. GABA(A) Receptor β3 Subunit Expression Regulates Tonic Current in Developing Striatopallidal Medium Spiny Neurons. Front Cell Neurosci 2011; 5:15. [PMID: 21847370 PMCID: PMC3147169 DOI: 10.3389/fncel.2011.00015] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2011] [Accepted: 07/09/2011] [Indexed: 11/13/2022] Open
Abstract
The striatum is a key structure for movement control, but the mechanisms that dictate the output of distinct subpopulations of medium spiny projection neurons (MSNs), striatonigral projecting and dopamine D1 receptor- (D1+) or striatopallidal projecting and dopamine D2 receptor- (D2+) expressing neurons, remains poorly understood. GABA-mediated tonic inhibition largely controls neuronal excitability and action potential firing rates, and we previously suggested with pharmacological analysis that the GABA(A) receptor β3 subunit plays a large role in the basal tonic current seen in D2+ MSNs from young mice (Ade et al., 2008; Janssen et al., 2009). In this study, we demonstrated the essential role of the β3 GABA(A) receptor subunit in mediating MSN tonic currents using conditional β3 subunit knock-out (β3f/f(Drd2)) mice. Cre-lox genetics were used to generate mice where Cre recombinase was expressed under the D2 receptor (Drd2) promoter. We show that while the wild-type MSN tonic current pattern demonstrates a high degree of variability, tonic current patterns from β3f/f(Drd2) mice are narrow, suggesting that the β3 subunit is essential to striatal MSN GABA-mediated tonic current. Our data also suggest that a distinct population of synaptic receptors upregulate due to β3 subunit removal. Further, deletion of this subunit significantly decreases the D2+ MSN excitability. These results offer insight for target mechanisms in Parkinson's disease, where symptoms arise due to the imbalance in striatal D1+ and D2+ MSN excitability and output.
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Affiliation(s)
- Megan J Janssen
- Department of Pharmacology and Physiology, Georgetown University School of Medicine Washington, DC, USA
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Capogna M. Neurogliaform cells and other interneurons of stratum lacunosum-moleculare gate entorhinal-hippocampal dialogue. J Physiol 2010; 589:1875-83. [PMID: 21135049 DOI: 10.1113/jphysiol.2010.201004] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The stratum lacunosum-moleculare of the hippocampus is an area of integration that receives inputs from extrinsic excitatory fibres including those from the entorhinal cortex, and is under the control of several neuromodulators. A critical aspect is the presence in this hippocampal layer of specific interneurons that are likely to influence the strength and the temporal structure of entorhinal-CA1 hippocampal dynamics. I review here recent data on the physiological role of these interneurons. Special focus is devoted to one interneuron type, the so-called neurogliaform cell, because recent studies have defined its unusual mode of cell-to-cell communication. Neurogliaform cells mediate feedforward inhibition of CA1 pyramidal cells, form a network of cells connected via chemical and electrical synapses, and evoke slow inhibitory synaptic currents mediated by GABA(A) and GABA(B) receptors. The modulation of entorhinal input by neurogliaform cells and their contribution to network theta rhythm are also discussed. I hope that novel information on neurogliaform cells will contribute to the ever-growing appreciation of GABAergic cell type diversity, and will inspire neuroscientists interested not only in synaptic physiology but also in the brain's spatial representation system.
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Affiliation(s)
- Marco Capogna
- MRC Anatomical Neuropharmacology Unit, Mansfield Road, Oxford OX1 3TH, UK.
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Kasugai Y, Swinny JD, Roberts JDB, Dalezios Y, Fukazawa Y, Sieghart W, Shigemoto R, Somogyi P. Quantitative localisation of synaptic and extrasynaptic GABAA receptor subunits on hippocampal pyramidal cells by freeze-fracture replica immunolabelling. Eur J Neurosci 2010; 32:1868-88. [PMID: 21073549 PMCID: PMC4487817 DOI: 10.1111/j.1460-9568.2010.07473.x] [Citation(s) in RCA: 129] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Hippocampal CA1 pyramidal cells, which receive γ-aminobutyric acid (GABA)ergic input from at least 18 types of presynaptic neuron, express 14 subunits of the pentameric GABA(A) receptor. The relative contribution of any subunit to synaptic and extrasynaptic receptors influences the dynamics of GABA and drug actions. Synaptic receptors mediate phasic GABA-evoked conductance and extrasynaptic receptors contribute to a tonic conductance. We used freeze-fracture replica-immunogold labelling, a sensitive quantitative immunocytochemical method, to detect synaptic and extrasynaptic pools of the alpha1, alpha2 and beta3 subunits. Antibodies to the cytoplasmic loop of the subunits showed immunogold particles concentrated on distinct clusters of intramembrane particles (IMPs) on the cytoplasmic face of the plasma membrane on the somata, dendrites and axon initial segments, with an abrupt decrease in labelling at the edge of the IMP cluster. Neuroligin-2, a GABAergic synapse-specific adhesion molecule, co-labels all beta3 subunit-rich IMP clusters, therefore we considered them synapses. Double-labelling for two subunits showed that virtually all somatic synapses contain the alpha1, alpha2 and beta3 subunits. The extrasynaptic plasma membrane of the somata, dendrites and dendritic spines showed low-density immunolabelling. Synaptic labelling densities on somata for the alpha1, alpha2 and beta3 subunits were 78-132, 94 and 79 times higher than on the extrasynaptic membranes, respectively. As GABAergic synapses occupy 0.72% of the soma surface, the fraction of synaptic labelling was 33-48 (alpha1), 40 (alpha2) and 36 (beta3)% of the total somatic surface immunolabelling. Assuming similar antibody access to all receptors, about 60% of these subunits are in extrasynaptic receptors.
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Affiliation(s)
- Yu Kasugai
- Department of Physiological Sciences, School of Life Science, The Graduate University for Advanced Studies (SOKENDAI), Okazaki, Japan.
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Nasrallah FA, Maher AD, Hanrahan JR, Balcar VJ, Rae CD. γ-Hydroxybutyrate and the GABAergic footprint: a metabolomic approach to unpicking the actions of GHB. J Neurochem 2010; 115:58-67. [PMID: 20681954 DOI: 10.1111/j.1471-4159.2010.06901.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Gamma-hydroxybutyrate is found both naturally in the brain and self-administered as a drug of abuse. It has been reported to act at endogenous γ-hydroxybutyrate (GHB) receptors and GABA(B) receptors [GABA(B)R], and may also be metabolized to GABA. Here, the metabolic fingerprints of a range of concentrations of GHB were measured in brain cortical tissue slices and compared with those of ligands active at GHB and GABA-R using principal components analysis (PCA) to identify sites of GHB activity. Low concentrations of GHB (1.0 μM) produced fingerprints similar to those of ligands active at GHB receptors and α4-containing GABA(A)R. A total of 10 μM GHB clustered proximate to mainstream GABAergic synapse ligands, such as 1.0 μM baclofen, a GABA(B)R agonist. Higher concentrations of GHB (30 μM) clustered with GABA(C)R agonists and the metabolic responses induced by blockade of the GABA transporter-1 (GAT1). The metabolic responses induced by 60 and 100 μM GHB were mimicked by simultaneous blockade of GAT1 and GAT3, addition of low concentrations of GABA(C)R antagonists, or increasing cytoplasmic GABA concentrations by incubation with the GABA transaminase inhibitor vigabatrin. These data suggest that at concentrations > 30 μM, GHB may be active via metabolism to GABA, which is then acting upon an unidentified GABAergic master switch receptor (possibly a high-affinity extrasynaptic receptor), or GHB may itself be acting directly on an extrasynaptic GABA-R, capable of turning off large numbers of cells. These results offer an explanation for the steep dose-response curve of GHB seen in vivo, and suggest potential target receptors for further investigation.
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Slow GABA transient and receptor desensitization shape synaptic responses evoked by hippocampal neurogliaform cells. J Neurosci 2010; 30:9898-909. [PMID: 20660272 DOI: 10.1523/jneurosci.5883-09.2010] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The kinetics of GABAergic synaptic currents can vary by an order of magnitude depending on the cell type. The neurogliaform cell (NGFC) has recently been identified as a key generator of slow GABA(A) receptor-mediated volume transmission in the isocortex. However, the mechanisms underlying slow GABA(A) receptor-mediated IPSCs and their use-dependent plasticity remain unknown. Here, we provide experimental and modeling data showing that hippocampal NGFCs generate an unusually prolonged (tens of milliseconds) but low-concentration (micromolar range) GABA transient, which is responsible for the slow response kinetics and which leads to a robust desensitization of postsynaptic GABA(A) receptors. This strongly contributes to the use-dependent synaptic depression elicited by various patterns of NGFC activity including the one detected during theta network oscillations in vivo. Synaptic depression mediated by NGFCs is likely to play an important modulatory role in the feedforward inhibition of CA1 pyramidal cells provided by the entorhinal cortex.
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Heistek TS, Jaap Timmerman A, Spijker S, Brussaard AB, Mansvelder HD. GABAergic synapse properties may explain genetic variation in hippocampal network oscillations in mice. Front Cell Neurosci 2010; 4:18. [PMID: 21082021 PMCID: PMC2901093 DOI: 10.3389/fncel.2010.00018] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2010] [Accepted: 05/06/2010] [Indexed: 11/13/2022] Open
Abstract
Cognitive ability and the properties of brain oscillation are highly heritable in humans. Genetic variation underlying oscillatory activity might give rise to differences in cognition and behavior. How genetic diversity translates into altered properties of oscillations and synchronization of neuronal activity is unknown. To address this issue, we investigated cellular and synaptic mechanisms of hippocampal fast network oscillations in eight genetically distinct inbred mouse strains. The frequency of carbachol-induced oscillations differed substantially between mouse strains. Since GABAergic inhibition sets oscillation frequency, we studied the properties of inhibitory synaptic inputs (IPSCs) received by CA3 and CA1 pyramidal cells of three mouse strains that showed the highest, lowest and intermediate frequencies of oscillations. In CA3 pyramidal cells, the frequency of rhythmic IPSC input showed the same strain differences as the frequency of field oscillations. Furthermore, IPSC decay times in both CA1 and CA3 pyramidal cells were faster in mouse strains with higher oscillation frequencies than in mouse strains with lower oscillation frequency, suggesting that differences in GABA(A)-receptor subunit composition exist between these strains. Indeed, gene expression of GABA(A)-receptor β2 (Gabrb2) and β3 (Gabrb2) subunits was higher in mouse strains with faster decay kinetics compared with mouse strains with slower decay kinetics. Hippocampal pyramidal neurons in mouse strains with higher oscillation frequencies and faster decay kinetics fired action potential at higher frequencies. These data indicate that differences in genetic background may result in different GABA(A)-receptor subunit expression, which affects the rhythm of pyramidal neuron firing and fast network activity through GABA synapse kinetics.
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Affiliation(s)
- Tim S Heistek
- Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, VU University Amsterdam, Netherlands
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