1
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Han J, Ho TW, Stine JM, Overton SN, Herberholz J, Ghodssi R. Simultaneous Dopamine and Serotonin Monitoring in Freely Moving Crayfish Using a Wireless Electrochemical Sensing System. ACS Sens 2024; 9:2346-2355. [PMID: 38713172 DOI: 10.1021/acssensors.3c02304] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/08/2024]
Abstract
Dopamine (DA) and serotonin (5-HT) are neurotransmitters that regulate a wide range of physiological and behavioral processes. Monitoring of both neurotransmitters with real-time analysis offers important insight into the mechanisms that shape animal behavior. However, bioelectronic tools to simultaneously monitor DA and 5-HT interactive dynamics in freely moving animals are underdeveloped. This is mainly due to the limited sensor sensitivity with miniaturized electronics. Here, we present a semi-implantable electrochemical device achieved by integrating a multi-surface-modified carbon fiber microelectrode with a miniaturized potentiostat module to detect DA and 5-HT in vivo with high sensitivity and selectivity. Specifically, carbon fiber microelectrodes were modified through electrochemical treatment and surface coatings to improve sensitivity, selectivity, and antifouling properties. A customized, lightweight potentiostat module was developed for untethered electrochemical measurements. Integrated with the microelectrode, the microsystem is compact (2.8 × 2.3 × 2.1 cm) to minimize its impacts on animal behavior and achieved simultaneous detection of DA and 5-HT with sensitivities of 48.4 and 133.0 nA/μM, respectively, within submicromolar ranges. The system was attached to the crayfish dorsal carapace, allowing electrode implantation into the heart of a crayfish to monitor DA and 5-HT dynamics, followed by drug injections. The semi-implantable biosensor system displayed a significant increase in oxidation peak currents after DA and 5-HT injections. The device successfully demonstrated the application for in vivo simultaneous monitoring of DA and 5-HT in the hemolymph (i.e., blood) of freely behaving crayfish underwater, yielding a valuable experimental tool to expand our understanding of the comodulation of DA and 5-HT.
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Affiliation(s)
- Jinjing Han
- Department of Electrical and Computer Engineering, University of Maryland, College Park, Maryland 20742, United States
- Institute for Systems Research, University of Maryland, College Park, Maryland 20742, United States
- Robert E. Fischell Institute for Biomedical Devices, University of Maryland, College Park, Maryland 20742, United States
| | - Ta-Wen Ho
- Department of Psychology, University of Maryland, College Park, Maryland 20742, United States
- Program in Neuroscience and Cognitive Science, University of Maryland, College Park, Maryland 20742, United States
| | - Justin M Stine
- Department of Electrical and Computer Engineering, University of Maryland, College Park, Maryland 20742, United States
- Institute for Systems Research, University of Maryland, College Park, Maryland 20742, United States
- Robert E. Fischell Institute for Biomedical Devices, University of Maryland, College Park, Maryland 20742, United States
| | - Sydney N Overton
- Department of Electrical and Computer Engineering, University of Maryland, College Park, Maryland 20742, United States
- Institute for Systems Research, University of Maryland, College Park, Maryland 20742, United States
- Robert E. Fischell Institute for Biomedical Devices, University of Maryland, College Park, Maryland 20742, United States
| | - Jens Herberholz
- Department of Psychology, University of Maryland, College Park, Maryland 20742, United States
- Program in Neuroscience and Cognitive Science, University of Maryland, College Park, Maryland 20742, United States
| | - Reza Ghodssi
- Department of Electrical and Computer Engineering, University of Maryland, College Park, Maryland 20742, United States
- Institute for Systems Research, University of Maryland, College Park, Maryland 20742, United States
- Robert E. Fischell Institute for Biomedical Devices, University of Maryland, College Park, Maryland 20742, United States
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2
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Li MQ, Chen C, Ma YQ, Ding HM. Effect of terahertz waves on the aggregation behavior of neurotransmitters. Phys Chem Chem Phys 2024; 26:13751-13761. [PMID: 38683175 DOI: 10.1039/d4cp00556b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/01/2024]
Abstract
Understanding the dynamics of neurotransmitters is crucial for unraveling synaptic transmission mechanisms in neuroscience. In this study, we investigated the impact of terahertz (THz) waves on the aggregation of four common neurotransmitters through all-atom molecular dynamics (MD) simulations. The simulations revealed enhanced nicotine (NCT) aggregation under 11.05 and 21.44 THz, with a minimal effect at 42.55 THz. Structural analysis further indicated strengthened intermolecular interactions and weakened hydration effects under specific THz stimulation. In addition, enhanced aggregation was observed at stronger field strengths, particularly at 21.44 THz. Furthermore, similar investigations on epinephrine (EPI), 5-hydroxytryptamine (5-HT), and γ-aminobutyric acid (GABA) corroborated these findings. Notably, EPI showed increased aggregation at 19.05 THz, emphasizing the influence of vibrational modes on aggregation. However, 5-HT and GABA, with charged or hydrophilic functional groups, exhibited minimal aggregation under THz stimulation. The present study sheds some light on neurotransmitter responses to THz waves, offering implications for neuroscience and interdisciplinary applications.
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Affiliation(s)
- Meng-Qiu Li
- Center for Soft Condensed Matter Physics and Interdisciplinary Research, School of Physical Science and Technology, Soochow University, Suzhou 215006, China.
| | - Chen Chen
- National Laboratory of Solid State Microstructures and Department of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Yu-Qiang Ma
- National Laboratory of Solid State Microstructures and Department of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Hong-Ming Ding
- Center for Soft Condensed Matter Physics and Interdisciplinary Research, School of Physical Science and Technology, Soochow University, Suzhou 215006, China.
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3
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Gupta C, Khullar V, Goyal N, Saini K, Baniwal R, Kumar S, Rastogi R. Cross-Silo, Privacy-Preserving, and Lightweight Federated Multimodal System for the Identification of Major Depressive Disorder Using Audio and Electroencephalogram. Diagnostics (Basel) 2023; 14:43. [PMID: 38201350 PMCID: PMC10795654 DOI: 10.3390/diagnostics14010043] [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: 10/16/2023] [Revised: 12/12/2023] [Accepted: 12/19/2023] [Indexed: 01/12/2024] Open
Abstract
In this day and age, depression is still one of the biggest problems in the world. If left untreated, it can lead to suicidal thoughts and attempts. There is a need for proper diagnoses of Major Depressive Disorder (MDD) and evaluation of the early stages to stop the side effects. Early detection is critical to identify a variety of serious conditions. In order to provide safe and effective protection to MDD patients, it is crucial to automate diagnoses and make decision-making tools widely available. Although there are various classification systems for the diagnosis of MDD, no reliable, secure method that meets these requirements has been established to date. In this paper, a federated deep learning-based multimodal system for MDD classification using electroencephalography (EEG) and audio datasets is presented while meeting data privacy requirements. The performance of the federated learning (FL) model was tested on independent and identically distributed (IID) and non-IID data. The study began by extracting features from several pre-trained models and ultimately decided to use bidirectional short-term memory (Bi-LSTM) as the base model, as it had the highest validation accuracy of 91% compared to a convolutional neural network and LSTM with 85% and 89% validation accuracy on audio data, respectively. The Bi-LSTM model also achieved a validation accuracy of 98.9% for EEG data. The FL method was then used to perform experiments on IID and non-IID datasets. The FL-based multimodal model achieved an exceptional training and validation accuracy of 99.9% when trained and evaluated on both IID and non-IIID datasets. These results show that the FL multimodal system performs almost as well as the Bi-LSTM multimodal system and emphasize its suitability for processing IID and non-IIID data. Several clients were found to perform better than conventional pre-trained models in a multimodal framework for federated learning using EEG and audio datasets. The proposed framework stands out from other classification techniques for MDD due to its special features, such as multimodality and data privacy for edge machines with limited resources. Due to these additional features, the framework concept is the most suitable alternative approach for the early classification of MDD patients.
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Affiliation(s)
- Chetna Gupta
- Chitkara University Institute of Engineering and Technology, Chitkara University, Rajpura 140417, Punjab, India; (C.G.); (V.K.)
| | - Vikas Khullar
- Chitkara University Institute of Engineering and Technology, Chitkara University, Rajpura 140417, Punjab, India; (C.G.); (V.K.)
| | - Nitin Goyal
- Department of Computer Science and Engineering, School of Engineering and Technology, Central University of Haryana, Mahendergarh 123031, Haryana, India;
| | - Kirti Saini
- Department of Electronics and Communication Engineering, University Institute of Engineering and Technology, Kurukshetra University, Kurukshetra 136119, Haryana, India;
| | - Ritu Baniwal
- Department of Computer Science, Jyotiba Phule Government College, Radaur, Yamunanagar 135133, Haryana, India;
| | - Sushil Kumar
- Department of Computer Science and Engineering, School of Engineering and Technology, Central University of Haryana, Mahendergarh 123031, Haryana, India;
| | - Rashi Rastogi
- Department of Computer Applications, Sir Chottu Ram Institute of Engineering & Technology, Ch. Charan Singh University, Meerut 250001, Uttar Pradesh, India;
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4
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Tsai YC, Weng WY, Yeh YT, Chien JC. Dual-Aptamer Drift Canceling Techniques to Improve Long-Term Stability of Real-Time Structure-Switching Aptasensors. ACS Sens 2023; 8:3380-3388. [PMID: 37671977 DOI: 10.1021/acssensors.3c00509] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/07/2023]
Abstract
This paper presents a dual-aptamer scheme to mitigate signal drifts caused by structure-switching aptamers during long-term monitoring. Electrochemical aptamer-based (E-AB) biosensors have recently shown great potential for continuous in vivo monitoring. However, the accuracy of detection is often limited by signaling drifts. Traditional approaches rely on kinetic differential measurements (KDM) coupled with square-wave voltammetry to eliminate these drifts. Yet, we have discovered that KDM does not apply universally to all aptamers, as their responses at different SWV frequencies heavily rely on their structure-switching characteristics and the electron transfer (ET) kinetics of the redox reporters. In light of this, we propose a "dual-aptamer" scheme that utilizes two aptamers, each responding differently to the same target molecule to cancel out drift. These paired aptamers are identified through (1) screening from an existing pool of aptamers and (2) engineering the signaling behavior of the redox reporters. We demonstrate the differential signaling of the aptamer pair in the presence of ampicillin and ATP molecules and show that the pair exhibits similar drifts in undiluted goat serum. By implementing drift cancelation, sensor drift is reduced by a factor of 370. Additionally, the differential signaling enables an increased recording throughput by leveraging differential readout electronics. The authors believe that the proposed technique holds significant benefits for long-term in vivo monitoring.
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Affiliation(s)
- Ya-Chen Tsai
- Department of Electrical Engineering, National Taiwan University, No. 1, Section 4, Roosevelt Rd, Da'an District, Taipei City 10617, Taiwan
| | - Wei-Yang Weng
- Graduate Institute of Electronics Engineering, National Taiwan University, No. 1, Section 4, Roosevelt Rd, Da'an District, Taipei City 10617, Taiwan
| | - Yu-Tung Yeh
- Department of Electrical Engineering, National Taiwan University, No. 1, Section 4, Roosevelt Rd, Da'an District, Taipei City 10617, Taiwan
| | - Jun-Chau Chien
- Department of Electrical Engineering, National Taiwan University, No. 1, Section 4, Roosevelt Rd, Da'an District, Taipei City 10617, Taiwan
- Graduate Institute of Electronics Engineering, National Taiwan University, No. 1, Section 4, Roosevelt Rd, Da'an District, Taipei City 10617, Taiwan
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5
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Rozenfeld E, Tauber M, Ben-Chaim Y, Parnas M. GPCR voltage dependence controls neuronal plasticity and behavior. Nat Commun 2021; 12:7252. [PMID: 34903750 PMCID: PMC8668892 DOI: 10.1038/s41467-021-27593-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2021] [Accepted: 11/29/2021] [Indexed: 12/25/2022] Open
Abstract
G-protein coupled receptors (GPCRs) play a paramount role in diverse brain functions. Almost 20 years ago, GPCR activity was shown to be regulated by membrane potential in vitro, but whether the voltage dependence of GPCRs contributes to neuronal coding and behavioral output under physiological conditions in vivo has never been demonstrated. Here we show that muscarinic GPCR mediated neuronal potentiation in vivo is voltage dependent. This voltage dependent potentiation is abolished in mutant animals expressing a voltage independent receptor. Depolarization alone, without a muscarinic agonist, results in a nicotinic ionotropic receptor potentiation that is mediated by muscarinic receptor voltage dependency. Finally, muscarinic receptor voltage independence causes a strong behavioral effect of increased odor habituation. Together, this study identifies a physiological role for the voltage dependency of GPCRs by demonstrating crucial involvement of GPCR voltage dependence in neuronal plasticity and behavior. Thus, this study suggests that GPCR voltage dependency plays a role in many diverse neuronal functions including learning and memory.
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Affiliation(s)
- Eyal Rozenfeld
- Department of Physiology and Pharmacology, Sackler School of Medicine, Tel Aviv University, Tel Aviv, 69978, Israel
- Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, 69978, Israel
| | - Merav Tauber
- Department of Natural and Life Sciences, The Open University of Israel, Ra'anana, 43107, Israel
| | - Yair Ben-Chaim
- Department of Natural and Life Sciences, The Open University of Israel, Ra'anana, 43107, Israel
| | - Moshe Parnas
- Department of Physiology and Pharmacology, Sackler School of Medicine, Tel Aviv University, Tel Aviv, 69978, Israel.
- Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, 69978, Israel.
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6
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Wei H, Frey AM, Jasanoff A. Molecular fMRI of neurochemical signaling. J Neurosci Methods 2021; 364:109372. [PMID: 34597714 DOI: 10.1016/j.jneumeth.2021.109372] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Revised: 09/23/2021] [Accepted: 09/25/2021] [Indexed: 12/12/2022]
Abstract
Magnetic resonance imaging (MRI) is the most widely applied technique for brain-wide measurement of neural function in humans and animals. In conventional functional MRI (fMRI), brain signaling is detected indirectly, via localized activity-dependent changes in regional blood flow, oxygenation, and volume, to which MRI contrast can be readily sensitized. Although such hemodynamic fMRI methods are powerful tools for analysis of brain activity, they lack specificity for the many molecules and cell types that play functionally distinct roles in neural processing. A suite of techniques collectively known to as "molecular fMRI," addresses this limitation by permitting MRI-based detection of specific molecular processes in deep brain tissue. This review discusses how molecular fMRI is coming to be used in the study of neurochemical dynamics that mediate intercellular communication in the brain. Neurochemical molecular fMRI is a potentially powerful approach for mechanistic analysis of brain-wide function, but the techniques are still in early stages of development. Here we provide an overview of the major advances and results that have been achieved to date, as well as directions for further development.
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Affiliation(s)
- He Wei
- Department of Biological Engineering, Massachusetts Institute of Technology, United States
| | - Abigail M Frey
- Department of Chemical Engineering, Massachusetts Institute of Technology, United States
| | - Alan Jasanoff
- Department of Biological Engineering, Massachusetts Institute of Technology, United States; Department of Brain & Cognitive Sciences, Massachusetts Institute of Technology, United States; Department of Nuclear Science & Engineering, Massachusetts Institute of Technology, United States.
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7
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Maffeis V, Belluati A, Craciun I, Wu D, Novak S, Schoenenberger CA, Palivan CG. Clustering of catalytic nanocompartments for enhancing an extracellular non-native cascade reaction. Chem Sci 2021; 12:12274-12285. [PMID: 34603657 PMCID: PMC8480338 DOI: 10.1039/d1sc04267j] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Accepted: 08/14/2021] [Indexed: 01/10/2023] Open
Abstract
Compartmentalization is fundamental in nature, where the spatial segregation of biochemical reactions within and between cells ensures optimal conditions for the regulation of cascade reactions. While the distance between compartments or their interaction are essential parameters supporting the efficiency of bio-reactions, so far they have not been exploited to regulate cascade reactions between bioinspired catalytic nanocompartments. Here, we generate individual catalytic nanocompartments (CNCs) by encapsulating within polymersomes or attaching to their surface enzymes involved in a cascade reaction and then, tether the polymersomes together into clusters. By conjugating complementary DNA strands to the polymersomes' surface, DNA hybridization drove the clusterization process of enzyme-loaded polymersomes and controlled the distance between the respective catalytic nanocompartments. Owing to the close proximity of CNCs within clusters and the overall stability of the cluster architecture, the cascade reaction between spatially segregated enzymes was significantly more efficient than when the catalytic nanocompartments were not linked together by DNA duplexes. Additionally, residual DNA single strands that were not engaged in clustering, allowed for an interaction of the clusters with the cell surface as evidenced by A549 cells, where clusters decorating the surface endowed the cells with a non-native enzymatic cascade. The self-organization into clusters of catalytic nanocompartments confining different enzymes of a cascade reaction allows for a distance control of the reaction spaces which opens new avenues for highly efficient applications in domains such as catalysis or nanomedicine.
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Affiliation(s)
- Viviana Maffeis
- Department of Chemistry, University of Basel Mattenstrasse 24a, BPR 1096 4058 Basel Switzerland .,NCCR-Molecular Systems Engineering BPR 1095, Mattenstrasse 24a CH-4058 Basel Switzerland
| | - Andrea Belluati
- Department of Chemistry, University of Basel Mattenstrasse 24a, BPR 1096 4058 Basel Switzerland
| | - Ioana Craciun
- Department of Chemistry, University of Basel Mattenstrasse 24a, BPR 1096 4058 Basel Switzerland
| | - Dalin Wu
- Department of Chemistry, University of Basel Mattenstrasse 24a, BPR 1096 4058 Basel Switzerland
| | - Samantha Novak
- Department of Chemistry, University of Basel Mattenstrasse 24a, BPR 1096 4058 Basel Switzerland
| | - Cora-Ann Schoenenberger
- Department of Chemistry, University of Basel Mattenstrasse 24a, BPR 1096 4058 Basel Switzerland .,NCCR-Molecular Systems Engineering BPR 1095, Mattenstrasse 24a CH-4058 Basel Switzerland
| | - Cornelia G Palivan
- Department of Chemistry, University of Basel Mattenstrasse 24a, BPR 1096 4058 Basel Switzerland .,NCCR-Molecular Systems Engineering BPR 1095, Mattenstrasse 24a CH-4058 Basel Switzerland
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8
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Kaczor PT, Wolska AD, Mozrzymas JW. α 1 Subunit Histidine 55 at the Interface between Extracellular and Transmembrane Domains Affects Preactivation and Desensitization of the GABA A Receptor. ACS Chem Neurosci 2021; 12:562-572. [PMID: 33471498 PMCID: PMC7875458 DOI: 10.1021/acschemneuro.0c00781] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
![]()
The
GABAA receptor is a member of the Cys-loop family
and plays a crucial role in the adult mammalian brain inhibition.
Although the static structure of this receptor is emerging, the molecular
mechanisms underlying its conformational transitions remain elusive.
It is known that in the Cys-loop receptors, the interface between
extracellular and transmembrane domains plays a key role in transmitting
the “activation wave” down to the channel gate in the
pore. It has been previously reported that histidine 55 (H55), located
centrally at the interfacial β1−β2 loop of the
α1 subunit, is important in the receptor activation,
but it is unknown which specific gating steps it is affecting. In
the present study, we addressed this issue by taking advantage of
the state-of-the-art macroscopic and single-channel recordings together
with extensive modeling. Considering that H55 is known to affect the
local electrostatic landscape and because it is neighbored by two
negatively charged aspartates, a well conserved feature in the α
subunits, we considered substitution with negative (E) and positive
(K) residues. We found that these mutations markedly affected the
receptor gating, altering primarily preactivation and desensitization
transitions. Importantly, opposite effects were observed for these
two mutations strongly suggesting involvement of electrostatic interactions.
Single-channel recordings suggested also a minor effect on opening/closing
transitions which did not depend on the electric charge of the substituting
amino acid. Altogether, we demonstrate that H55 mutations affect primarily
preactivation and desensitization most likely by influencing local
electrostatic interactions at the receptor interface.
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Affiliation(s)
- Przemyslaw T. Kaczor
- Department of Biophysics and Neuroscience, Wroclaw Medical University, Chalubinskiego 3a, Wroclaw, Dolnoślaskie 50-368, Poland
| | - Aleksandra D. Wolska
- Department of Biophysics and Neuroscience, Wroclaw Medical University, Chalubinskiego 3a, Wroclaw, Dolnoślaskie 50-368, Poland
| | - Jerzy W. Mozrzymas
- Department of Biophysics and Neuroscience, Wroclaw Medical University, Chalubinskiego 3a, Wroclaw, Dolnoślaskie 50-368, Poland
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9
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Vaden RJ, Gonzalez JC, Tsai MC, Niver AJ, Fusilier AR, Griffith CM, Kramer RH, Wadiche JI, Overstreet-Wadiche L. Parvalbumin interneurons provide spillover to newborn and mature dentate granule cells. eLife 2020; 9:54125. [PMID: 32602839 PMCID: PMC7326496 DOI: 10.7554/elife.54125] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Accepted: 06/19/2020] [Indexed: 01/09/2023] Open
Abstract
Parvalbumin-expressing interneurons (PVs) in the dentate gyrus provide activity-dependent regulation of adult neurogenesis as well as maintain inhibitory control of mature neurons. In mature neurons, PVs evoke GABAA postsynaptic currents (GPSCs) with fast rise and decay phases that allow precise control of spike timing, yet synaptic currents with fast kinetics do not appear in adult-born neurons until several weeks after cell birth. Here we used mouse hippocampal slices to address how PVs signal to newborn neurons prior to the appearance of fast GPSCs. Whereas PV-evoked currents in mature neurons exhibit hallmark fast rise and decay phases, newborn neurons display slow GPSCs with characteristics of spillover signaling. We also unmasked slow spillover currents in mature neurons in the absence of fast GPSCs. Our results suggest that PVs mediate slow spillover signaling in addition to conventional fast synaptic signaling, and that spillover transmission mediates activity-dependent regulation of early events in adult neurogenesis.
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Affiliation(s)
- Ryan J Vaden
- Department of Neurobiology, University of Alabama at Birmingham, Birmingham, United States
| | - Jose Carlos Gonzalez
- Department of Neurobiology, University of Alabama at Birmingham, Birmingham, United States
| | - Ming-Chi Tsai
- Department of Molecular and Cellular Biology, University of California Berkeley, Berkeley, United States
| | - Anastasia J Niver
- Department of Neurobiology, University of Alabama at Birmingham, Birmingham, United States
| | - Allison R Fusilier
- Department of Neurobiology, University of Alabama at Birmingham, Birmingham, United States
| | - Chelsea M Griffith
- Department of Neurobiology, University of Alabama at Birmingham, Birmingham, United States
| | - Richard H Kramer
- Department of Molecular and Cellular Biology, University of California Berkeley, Berkeley, United States
| | - Jacques I Wadiche
- Department of Neurobiology, University of Alabama at Birmingham, Birmingham, United States
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10
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Lupascu CA, Morabito A, Ruggeri F, Parisi C, Pimpinella D, Pizzarelli R, Meli G, Marinelli S, Cherubini E, Cattaneo A, Migliore M. Computational Modeling of Inhibitory Transsynaptic Signaling in Hippocampal and Cortical Neurons Expressing Intrabodies Against Gephyrin. Front Cell Neurosci 2020; 14:173. [PMID: 32612513 PMCID: PMC7309579 DOI: 10.3389/fncel.2020.00173] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Accepted: 05/20/2020] [Indexed: 12/25/2022] Open
Abstract
GABAergic transmission regulates neuronal excitability, dendritic integration of synaptic signals and oscillatory activity, thought to be involved in high cognitive functions. By anchoring synaptic receptors just opposite to release sites, the scaffold protein gephyrin plays a key role in these tasks. In addition, by regulating GABAA receptor trafficking, gephyrin contributes to maintain, at the network level, an appropriate balance between Excitation (E) and Inhibition (I), crucial for information processing. An E/I imbalance leads to neuropsychiatric disorders such as epilepsy, schizophrenia and autism. In this article, we exploit a previously published computational method to fit spontaneous synaptic events, using a simplified model of the subcellular pathways involving gephyrin at inhibitory synapses. The model was used to analyze experimental data recorded under different conditions, with the main goal to gain insights on the possible consequences of gephyrin block on IPSCs. The same approach can be useful, in general, to analyze experiments designed to block a single protein. The results suggested possible ways to correlate the changes observed in the amplitude and time course of individual events recorded after different experimental protocols with the changes that may occur in the main subcellular pathways involved in gephyrin-dependent transsynaptic signaling.
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Affiliation(s)
- Carmen A Lupascu
- National Research Council, Institute of Biophysics, Palermo, Italy
| | | | | | | | | | | | | | | | | | | | - Michele Migliore
- National Research Council, Institute of Biophysics, Palermo, Italy
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11
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Lorenzo LE, Godin AG, Ferrini F, Bachand K, Plasencia-Fernandez I, Labrecque S, Girard AA, Boudreau D, Kianicka I, Gagnon M, Doyon N, Ribeiro-da-Silva A, De Koninck Y. Enhancing neuronal chloride extrusion rescues α2/α3 GABA A-mediated analgesia in neuropathic pain. Nat Commun 2020; 11:869. [PMID: 32054836 PMCID: PMC7018745 DOI: 10.1038/s41467-019-14154-6] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2018] [Accepted: 12/16/2019] [Indexed: 02/06/2023] Open
Abstract
Spinal disinhibition has been hypothesized to underlie pain hypersensitivity in neuropathic pain. Apparently contradictory mechanisms have been reported, raising questions on the best target to produce analgesia. Here, we show that nerve injury is associated with a reduction in the number of inhibitory synapses in the spinal dorsal horn. Paradoxically, this is accompanied by a BDNF-TrkB-mediated upregulation of synaptic GABAARs and by an α1-to-α2GABAAR subunit switch, providing a mechanistic rationale for the analgesic action of the α2,3GABAAR benzodiazepine-site ligand L838,417 after nerve injury. Yet, we demonstrate that impaired Cl- extrusion underlies the failure of L838,417 to induce analgesia at high doses due to a resulting collapse in Cl- gradient, dramatically limiting the benzodiazepine therapeutic window. In turn, enhancing KCC2 activity not only potentiated L838,417-induced analgesia, it rescued its analgesic potential at high doses, revealing a novel strategy for analgesia in pathological pain, by combined targeting of the appropriate GABAAR-subtypes and restoring Cl- homeostasis.
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Affiliation(s)
- Louis-Etienne Lorenzo
- CERVO Brain Research Centre, Quebec Mental Health Institute, Québec, QC, Canada
- Department of Pharmacology & Therapeutics, McGill University, Montreal, QC, Canada
| | - Antoine G Godin
- CERVO Brain Research Centre, Quebec Mental Health Institute, Québec, QC, Canada
- Department of Psychiatry & Neuroscience, Université Laval, Québec, QC, Canada
- Graduate program in Neuroscience, Université Laval, Québec, QC, Canada
| | - Francesco Ferrini
- CERVO Brain Research Centre, Quebec Mental Health Institute, Québec, QC, Canada
- Department of Psychiatry & Neuroscience, Université Laval, Québec, QC, Canada
- Graduate program in Neuroscience, Université Laval, Québec, QC, Canada
- Department of Veterinary Sciences, University of Turin, Turin, Italy
| | - Karine Bachand
- CERVO Brain Research Centre, Quebec Mental Health Institute, Québec, QC, Canada
| | - Isabel Plasencia-Fernandez
- CERVO Brain Research Centre, Quebec Mental Health Institute, Québec, QC, Canada
- Graduate program in Neuroscience, Université Laval, Québec, QC, Canada
| | - Simon Labrecque
- CERVO Brain Research Centre, Quebec Mental Health Institute, Québec, QC, Canada
| | - Alexandre A Girard
- CERVO Brain Research Centre, Quebec Mental Health Institute, Québec, QC, Canada
- Ecole Polytechnique, IP Paris, Palaiseau, France
| | - Dominic Boudreau
- CERVO Brain Research Centre, Quebec Mental Health Institute, Québec, QC, Canada
- Graduate program in Neuroscience, Université Laval, Québec, QC, Canada
| | - Irenej Kianicka
- Chlorion Pharma, Laval, Québec, QC, Canada
- Laurent Pharmaceuticals Inc., Montreal, QC, Canada
| | - Martin Gagnon
- CERVO Brain Research Centre, Quebec Mental Health Institute, Québec, QC, Canada
- Centre for Innovation, University of Otago, Dunedin, New Zealand
| | - Nicolas Doyon
- CERVO Brain Research Centre, Quebec Mental Health Institute, Québec, QC, Canada
- Finite Element Interdisciplinary Research Group (GIREF), Université Laval, Québec, QC, Canada
| | - Alfredo Ribeiro-da-Silva
- Department of Pharmacology & Therapeutics, McGill University, Montreal, QC, Canada
- Department of Anatomy & Cell Biology, McGill University, Montreal, QC, Canada
- Alan Edwards Centre for Research on Pain, McGill University, Montreal, QC, Canada
| | - Yves De Koninck
- CERVO Brain Research Centre, Quebec Mental Health Institute, Québec, QC, Canada.
- Department of Pharmacology & Therapeutics, McGill University, Montreal, QC, Canada.
- Department of Psychiatry & Neuroscience, Université Laval, Québec, QC, Canada.
- Graduate program in Neuroscience, Université Laval, Québec, QC, Canada.
- Alan Edwards Centre for Research on Pain, McGill University, Montreal, QC, Canada.
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12
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Kasugai Y, Vogel E, Hörtnagl H, Schönherr S, Paradiso E, Hauschild M, Göbel G, Milenkovic I, Peterschmitt Y, Tasan R, Sperk G, Shigemoto R, Sieghart W, Singewald N, Lüthi A, Ferraguti F. Structural and Functional Remodeling of Amygdala GABAergic Synapses in Associative Fear Learning. Neuron 2019; 104:781-794.e4. [PMID: 31543297 DOI: 10.1016/j.neuron.2019.08.013] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Revised: 07/09/2019] [Accepted: 08/07/2019] [Indexed: 01/12/2023]
Abstract
Associative learning is thought to involve different forms of activity-dependent synaptic plasticity. Although previous studies have mostly focused on learning-related changes occurring at excitatory glutamatergic synapses, we found that associative learning, such as fear conditioning, also entails long-lasting functional and structural plasticity of GABAergic synapses onto pyramidal neurons of the murine basal amygdala. Fear conditioning-mediated structural remodeling of GABAergic synapses was associated with a change in mIPSC kinetics and an increase in the fraction of synaptic benzodiazepine-sensitive (BZD) GABAA receptors containing the α2 subunit without altering the intrasynaptic distribution and overall amount of BZD-GABAA receptors. These structural and functional synaptic changes were partly reversed by extinction training. These findings provide evidence that associative learning, such as Pavlovian fear conditioning and extinction, sculpts inhibitory synapses to regulate inhibition of active neuronal networks, a process that may tune amygdala circuit responses to threats.
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Affiliation(s)
- Yu Kasugai
- Department of Pharmacology, Medical University of Innsbruck, Innsbruck 6020, Austria
| | - Elisabeth Vogel
- Friedrich Miescher Institute for Biomedical Research, Basel 4058, Switzerland
| | - Heide Hörtnagl
- Department of Pharmacology, Medical University of Innsbruck, Innsbruck 6020, Austria
| | - Sabine Schönherr
- Department of Pharmacology, Medical University of Innsbruck, Innsbruck 6020, Austria
| | - Enrica Paradiso
- Department of Pharmacology, Medical University of Innsbruck, Innsbruck 6020, Austria
| | - Markus Hauschild
- Department of Pharmacology and Toxicology, Institute of Pharmacy and CMBI, University of Innsbruck, Innsbruck 6020, Austria
| | - Georg Göbel
- Department of Medical Statistics, Informatics and Health Economics, Medical University of Innsbruck, Innsbruck 6020, Austria
| | - Ivan Milenkovic
- Center for Brain Research, Department of Molecular Neurosciences, Medical University of Vienna, Vienna 1090, Austria
| | - Yvan Peterschmitt
- Department of Pharmacology, Medical University of Innsbruck, Innsbruck 6020, Austria; Center for Brain Research, Department of Molecular Neurosciences, Medical University of Vienna, Vienna 1090, Austria
| | - Ramon Tasan
- Department of Pharmacology, Medical University of Innsbruck, Innsbruck 6020, Austria
| | - Günther Sperk
- Department of Pharmacology, Medical University of Innsbruck, Innsbruck 6020, Austria
| | - Ryuichi Shigemoto
- Institute of Science and Technology Austria, Klosterneuburg 3400, Austria
| | - Werner Sieghart
- Center for Brain Research, Department of Molecular Neurosciences, Medical University of Vienna, Vienna 1090, Austria
| | - Nicolas Singewald
- Department of Pharmacology and Toxicology, Institute of Pharmacy and CMBI, University of Innsbruck, Innsbruck 6020, Austria
| | - Andreas Lüthi
- Friedrich Miescher Institute for Biomedical Research, Basel 4058, Switzerland; University of Basel, Basel, Switzerland
| | - Francesco Ferraguti
- Department of Pharmacology, Medical University of Innsbruck, Innsbruck 6020, Austria.
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13
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Mattei C, Taly A, Soualah Z, Saulais O, Henrion D, Guérineau NC, Verleye M, Legros C. Involvement of the GABA A receptor α subunit in the mode of action of etifoxine. Pharmacol Res 2019; 145:104250. [PMID: 31059790 DOI: 10.1016/j.phrs.2019.04.034] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/21/2018] [Revised: 03/21/2019] [Accepted: 04/27/2019] [Indexed: 12/31/2022]
Abstract
Etifoxine (EFX) is a non-benzodiazepine psychoactive drug which exhibits anxiolytic effects through a dual mechanism, by directly binding to GABAA receptors (GABAARs) and to the mitochondrial 18-kDa translocator protein, resulting in the potentiation of the GABAergic function. The β subunit subtype plays a key role in the EFX-GABAAR interaction, however this does not explain the anxiolytic effects of this drug. Here, we combined behavioral and electrophysiological experiments to challenge the role of the GABAAR α subunit in the EFX mode of action. After single administrations of anxiolytic doses (25-50 mg/kg, intraperitoneal), EFX did not induce any neurological nor locomotor impairments, unlike the benzodiazepine bromazepam (0.5-1 mg/kg, intraperitoneal). We established the EFX pharmacological profile on heteropentameric GABAARs constructed with α1 to α6 subunit expressed in Xenopus oocyte. Unlike what is known for benzodiazepines, neither the γ nor δ subunits influenced EFX-mediated potentiation of GABA-evoked currents. EFX acted first as a partial agonist on α2β3γ2S, α3β3γ2S, α6β3γ2S and α6β3δ GABAARs, but not on α1β3γ2S, α4β3γ2S, α4β3δ nor α5β3γ2S GABAARs. Moreover, EFX exhibited much higher positive allosteric modulation towards α2β3γ2S, α3β3γ2S and α6β3γ2S than for α1β3γ2S, α4β3γ2S and α5β3γ2S GABAARs. At 20 μM, corresponding to brain concentration at anxiolytic doses, EFX increased GABA potency to the highest extent for α3β3γ2S GABAARs. We built a docking model of EFX on α3β3γ2S GABAARs, which is consistent with a binding site located between α and β subunits in the extracellular domain. In conclusion, EFX preferentially potentiates α2β3γ2S and α3β3γ2S GABAARs, which might support its advantageous anxiolytic/sedative balance.
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Affiliation(s)
- César Mattei
- Institut MITOVASC, UMR CNRS 6015 - UMR INSERM U1083, Université d'Angers, 3 Rue Roger Amsler 49100 ANGERS, France.
| | - Antoine Taly
- Theoretical Biochemistry Laboratory, Institute of Physico-Chemical Biology, CNRS UPR9080, University of Paris Diderot Sorbonne Paris Cité, 75005 Paris, France
| | - Zineb Soualah
- Institut MITOVASC, UMR CNRS 6015 - UMR INSERM U1083, Université d'Angers, 3 Rue Roger Amsler 49100 ANGERS, France
| | - Ophélie Saulais
- Institut MITOVASC, UMR CNRS 6015 - UMR INSERM U1083, Université d'Angers, 3 Rue Roger Amsler 49100 ANGERS, France
| | - Daniel Henrion
- Institut MITOVASC, UMR CNRS 6015 - UMR INSERM U1083, Université d'Angers, 3 Rue Roger Amsler 49100 ANGERS, France
| | - Nathalie C Guérineau
- Institut MITOVASC, UMR CNRS 6015 - UMR INSERM U1083, Université d'Angers, 3 Rue Roger Amsler 49100 ANGERS, France
| | - Marc Verleye
- Biocodex, Department of Pharmacology, Zac de Mercières, 60200 Compiègne, France
| | - Christian Legros
- Institut MITOVASC, UMR CNRS 6015 - UMR INSERM U1083, Université d'Angers, 3 Rue Roger Amsler 49100 ANGERS, France.
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14
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Belluati A, Craciun I, Liu J, Palivan CG. Nanoscale Enzymatic Compartments in Tandem Support Cascade Reactions in Vitro. Biomacromolecules 2018; 19:4023-4033. [DOI: 10.1021/acs.biomac.8b01019] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
- Andrea Belluati
- Department of Chemistry, University of Basel, Mattenstrasse 24a, CH-4058 Basel, Switzerland
| | - Ioana Craciun
- Department of Chemistry, University of Basel, Mattenstrasse 24a, CH-4058 Basel, Switzerland
| | - Juan Liu
- Department of Chemistry, University of Basel, Mattenstrasse 24a, CH-4058 Basel, Switzerland
| | - Cornelia G. Palivan
- Department of Chemistry, University of Basel, Mattenstrasse 24a, CH-4058 Basel, Switzerland
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15
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Chen X, Keramidas A, Lynch JW. Physiological and pharmacological properties of inhibitory postsynaptic currents mediated by α5β1γ2, α5β2γ2 and α5β3γ2 GABA A receptors. Neuropharmacology 2017; 125:243-253. [PMID: 28757051 DOI: 10.1016/j.neuropharm.2017.07.027] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2017] [Revised: 07/18/2017] [Accepted: 07/26/2017] [Indexed: 02/07/2023]
Abstract
α5-containing GABAARs are potential therapeutic targets for clinical conditions including age-related dementia, stroke, schizophrenia, Down syndrome, anaesthetic-induced amnesia, anxiety and pain. α5-containing GABAARs are expressed in layer 5 cortical neurons and hippocampal pyramidal neurons where they mediate both tonic currents and slow inhibitory postsynaptic currents (IPSCs). A range of drugs has been developed to specifically modulate these receptors. The main α5-containing GABAARs that are likely to exist in vivo are the α5β1γ2, α5β2γ2 and α5β3γ2 isoforms. We currently have few clues as to how these isoforms are distributed between synaptic and extrasynaptic compartments or their relative roles in controlling neuronal excitability. Accordingly, the aim of this study was to define the basic biophysical and pharmacological properties of IPSCs mediated by the three isoforms in a hippocampal neuron-HEK293 cell co-culture assay. The IPSC decay time constants were slow (α5β1γ2L: 45 ms; α5β1γ2L: 80 ms; α5β3γ2L: 184 ms) and were largely dominated by the intrinsic channel deactivation rates. By comparing IPSC rise times, we inferred that α5β1γ2L GABAARs are located postsynaptically whereas the other two are predominantly perisynaptic. α5β3γ2L GABAARs alone mediated tonic currents. We quantified the effects of four α5-specific inverse agonists (TB-21007, MRK-016, α5IA and L-655708) on IPSCs mediated by the three isoforms. All compounds selectively inhibited IPSC amplitudes and accelerated IPSC decay rates, albeit with distinct isoform specificities. MRK-016 also significantly accelerated IPSC rise times. These results provide a reference for future studies seeking to identify and characterize the properties of IPSCs mediated by α5-containing GABAAR isoforms in neurons.
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Affiliation(s)
- Xiumin Chen
- Queensland Brain Institute, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Angelo Keramidas
- Queensland Brain Institute, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Joseph W Lynch
- Queensland Brain Institute, The University of Queensland, Brisbane, QLD 4072, Australia.
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16
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Chen Z, Liu R, Yang SH, Dillon GH, Huang R. Methylene blue inhibits GABA A receptors by interaction with GABA binding site. Neuropharmacology 2017; 119:100-110. [PMID: 28390894 DOI: 10.1016/j.neuropharm.2017.04.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Revised: 03/23/2017] [Accepted: 04/03/2017] [Indexed: 01/11/2023]
Abstract
Methylene blue (MB) is commonly used in diagnostic procedures and is also used to treat various medical conditions. Neurological effects of MB have been reported in clinical observations and experimental studies. Thus the modulation of GABAA receptor function by MB was investigated. Whole-cell GABA-activated currents were recorded from HEK293 cells expressing various GABAA receptor subunit configurations. MB inhibition of GABA currents was apparent at 3 μM, and it had an IC50 of 31 μM in human α1β2γ2 receptors. The MB action was rapid and reversible. MB inhibition was not mediated via the picrotoxin site, as a mutation (T6'F of the β2 subunit) known to confer resistance to picrotoxin had no effect on MB-induced inhibition. Blockade of GABAA receptors by MB was demonstrated across a range of receptors expressing varying subunits, including those expressed at extrasynaptic sites. The sensitivity of α1β2 receptors to MB was similar to that observed in α1β2γ2 receptors, indicating that MB's action via the benzodiazepine or Zn2+ site is unlikely. MB-induced inhibition of GABA response was competitive with respect to GABA. Furthermore, mutation of α1 F64 to A and β2 Y205 to F in the extracellular N-terminus, both residues which are known to comprise GABA binding pocket, remarkably diminished MB inhibition of GABA currents. These data suggest that MB inhibits GABAA receptor function by direct or allosteric interaction with the GABA binding site. Finally, in mouse hippocampal CA1 pyramidal neurons, MB inhibited GABA-activated currents as well as GABAergic IPSCs. We demonstrate that MB directly inhibits GABAA receptor function, which may underlie some of the effects of MB on the CNS.
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Affiliation(s)
- Zhenglan Chen
- Center for Neuroscience Discovery, Institute of Healthy Aging, University of North Texas Health Science Center at Fort Worth, Fort Worth, TX 76107, United States
| | - Ran Liu
- Center for Neuroscience Discovery, Institute of Healthy Aging, University of North Texas Health Science Center at Fort Worth, Fort Worth, TX 76107, United States
| | - Shao-Hua Yang
- Center for Neuroscience Discovery, Institute of Healthy Aging, University of North Texas Health Science Center at Fort Worth, Fort Worth, TX 76107, United States
| | - Glenn H Dillon
- Center for Neuroscience Discovery, Institute of Healthy Aging, University of North Texas Health Science Center at Fort Worth, Fort Worth, TX 76107, United States
| | - Renqi Huang
- Center for Neuroscience Discovery, Institute of Healthy Aging, University of North Texas Health Science Center at Fort Worth, Fort Worth, TX 76107, United States.
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17
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Nanoscale Molecular Reorganization of the Inhibitory Postsynaptic Density Is a Determinant of GABAergic Synaptic Potentiation. J Neurosci 2017; 37:1747-1756. [PMID: 28073939 DOI: 10.1523/jneurosci.0514-16.2016] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Revised: 12/22/2016] [Accepted: 12/31/2016] [Indexed: 11/21/2022] Open
Abstract
Gephyrin is a key scaffold protein mediating the anchoring of GABAA receptors at inhibitory synapses. Here, we exploited superresolution techniques combined with proximity-based clustering analysis and model simulations to investigate the single-molecule gephyrin reorganization during plasticity of inhibitory synapses in mouse hippocampal cultured neurons. This approach revealed that, during the expression of inhibitory LTP, the increase of gephyrin density at postsynaptic sites is associated with the promoted formation of gephyrin nanodomains. We demonstrate that the gephyrin rearrangement in nanodomains stabilizes the amplitude of postsynaptic currents, indicating that, in addition to the number of synaptic GABAA receptors, the nanoscale distribution of GABAA receptors in the postsynaptic area is a crucial determinant for the expression of inhibitory synaptic plasticity. In addition, the methodology implemented here clears the way to the application of the graph-based theory to single-molecule data for the description and quantification of the spatial organization of the synapse at the single-molecule level.SIGNIFICANCE STATEMENT The mechanisms of inhibitory synaptic plasticity are poorly understood, mainly because the size of the synapse is below the diffraction limit, thus reducing the effectiveness of conventional optical and imaging techniques. Here, we exploited superresolution approaches combined with clustering analysis to study at unprecedented resolution the distribution of the inhibitory scaffold protein gephyrin in response to protocols inducing LTP of inhibitory synaptic responses (iLTP). We found that, during the expression of iLTP, the increase of synaptic gephyrin is associated with the fragmentation of gephyrin in subsynaptic nanodomains. We demonstrate that such synaptic gephyrin nanodomains stabilize the amplitude of inhibitory postsynaptic responses, thus identifying the nanoscale gephyrin rearrangement as a key determinant for inhibitory synaptic plasticity.
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18
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Michałowski MA, Kraszewski S, Mozrzymas JW. Binding site opening by loop C shift and chloride ion-pore interaction in the GABAAreceptor model. Phys Chem Chem Phys 2017; 19:13664-13678. [DOI: 10.1039/c7cp00582b] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Molecular dynamics simulations of the shut α1β2γ2GABAAheteropentamer receptor homology model reveal significant differences between intersubunit interfaces (ligand binding G1, G2 and non-binding) compared to homomeric receptor assemblies and possible ion interaction sites in the top part of the transmembrane domain (TMD).
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Affiliation(s)
- M. A. Michałowski
- Laboratory of Neuroscience
- Department of Biophysics
- Wrocław Medical University
- ul. Chałubińskiego 3a
- 50-358 Wrocław
| | - S. Kraszewski
- Department of Biomedical Engineering
- Faculty of Fundamental Problems of Technology
- Wroclaw University of Science and Technology
- Wyb. Wyspiańskiego 27
- 50-370 Wrocław
| | - J. W. Mozrzymas
- Laboratory of Neuroscience
- Department of Biophysics
- Wrocław Medical University
- ul. Chałubińskiego 3a
- 50-358 Wrocław
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19
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Armstrong E, Abarbanel HDI. Model of the songbird nucleus HVC as a network of central pattern generators. J Neurophysiol 2016; 116:2405-2419. [PMID: 27535375 DOI: 10.1152/jn.00438.2016] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Accepted: 08/10/2016] [Indexed: 01/06/2023] Open
Abstract
We propose a functional architecture of the adult songbird nucleus HVC in which the core element is a "functional syllable unit" (FSU). In this model, HVC is organized into FSUs, each of which provides the basis for the production of one syllable in vocalization. Within each FSU, the inhibitory neuron population takes one of two operational states: 1) simultaneous firing wherein all inhibitory neurons fire simultaneously, and 2) competitive firing of the inhibitory neurons. Switching between these basic modes of activity is accomplished via changes in the synaptic strengths among the inhibitory neurons. The inhibitory neurons connect to excitatory projection neurons such that during state 1 the activity of projection neurons is suppressed, while during state 2 patterns of sequential firing of projection neurons can occur. The latter state is stabilized by feedback from the projection to the inhibitory neurons. Song composition for specific species is distinguished by the manner in which different FSUs are functionally connected to each other. Ours is a computational model built with biophysically based neurons. We illustrate that many observations of HVC activity are explained by the dynamics of the proposed population of FSUs, and we identify aspects of the model that are currently testable experimentally. In addition, and standing apart from the core features of an FSU, we propose that the transition between modes may be governed by the biophysical mechanism of neuromodulation.
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Affiliation(s)
- Eve Armstrong
- BioCircuits Institute, University of California, San Diego, La Jolla, California;
| | - Henry D I Abarbanel
- Department of Physics, University of California, San Diego, La Jolla, California; and.,Marine Physical Laboratory (Scripps Institution of Oceanography), University of California, San Diego, La Jolla, California
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20
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Accardi MV, Daniels BA, Brown PMGE, Fritschy JM, Tyagarajan SK, Bowie D. Mitochondrial reactive oxygen species regulate the strength of inhibitory GABA-mediated synaptic transmission. Nat Commun 2016; 5:3168. [PMID: 24430741 PMCID: PMC4977183 DOI: 10.1038/ncomms4168] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2013] [Accepted: 12/20/2013] [Indexed: 01/08/2023] Open
Abstract
Neuronal communication imposes a heavy metabolic burden in maintaining ionic gradients essential for action potential firing and synaptic signaling. Although cellular metabolism is known to regulate excitatory neurotransmission, it is still unclear whether the brain’s energy supply affects inhibitory signaling. Here we show that mitochondrial-derived reactive oxygen species (mROS) regulate the strength of postsynaptic GABAA receptors at inhibitory synapses of cerebellar stellate cells. Inhibition is strengthened through a mechanism that selectively recruits α3-containing GABAA receptors into synapses with no discernible effect on resident α1-containing receptors. Since mROS promotes the emergence of postsynaptic events with unique kinetic properties, we conclude that newly-recruited α3-containing GABAA receptors are activated by neurotransmitter released onto discrete postsynaptic sites. Although traditionally associated with oxidative stress in neurodegenerative disease, our data identifies mROS as a putative homeostatic signaling molecule coupling cellular metabolism to the strength of inhibitory transmission.
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Affiliation(s)
- Michael V Accardi
- Department of Pharmacology and Therapeutics, McGill University, Montréal, Québec, Canada H3B 0B1
| | - Bryan A Daniels
- Department of Pharmacology and Therapeutics, McGill University, Montréal, Québec, Canada H3B 0B1
| | - Patricia M G E Brown
- Department of Pharmacology and Therapeutics, McGill University, Montréal, Québec, Canada H3B 0B1
| | - Jean-Marc Fritschy
- Institute of Pharmacology and Toxicology, University of Zurich, CH-8057, Zurich, Switzerland
| | - Shiva K Tyagarajan
- Institute of Pharmacology and Toxicology, University of Zurich, CH-8057, Zurich, Switzerland
| | - Derek Bowie
- Department of Pharmacology and Therapeutics, McGill University, Montréal, Québec, Canada H3B 0B1
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21
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Tong XJ, Hu Z, Liu Y, Anderson D, Kaplan JM. A network of autism linked genes stabilizes two pools of synaptic GABA(A) receptors. eLife 2015; 4:e09648. [PMID: 26575289 PMCID: PMC4642926 DOI: 10.7554/elife.09648] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Accepted: 10/15/2015] [Indexed: 01/24/2023] Open
Abstract
Changing receptor abundance at synapses is an important mechanism for regulating synaptic strength. Synapses contain two pools of receptors, immobilized and diffusing receptors, both of which are confined to post-synaptic elements. Here we show that immobile and diffusing GABAA receptors are stabilized by distinct synaptic scaffolds at C. elegans neuromuscular junctions. Immobilized GABAA receptors are stabilized by binding to FRM-3/EPB4.1 and LIN-2A/CASK. Diffusing GABAA receptors are stabilized by the synaptic adhesion molecules Neurexin and Neuroligin. Inhibitory post-synaptic currents are eliminated in double mutants lacking both scaffolds. Neurexin, Neuroligin, and CASK mutations are all linked to Autism Spectrum Disorders (ASD). Our results suggest that these mutations may directly alter inhibitory transmission, which could contribute to the developmental and cognitive deficits observed in ASD. DOI:http://dx.doi.org/10.7554/eLife.09648.001 Behaviors ranging from movement to memory are dependent on the activity of extensive networks of cells called neurons. Within these networks, neurons communicate across junctions called synapses. The arrival of an electrical signal called an action potential at the ‘presynaptic’ neuron on one side of the synapse triggers the neuron to release chemical neurotransmitter molecules into the synapse. These molecules then bind to receptors on the ‘postsynaptic’ cell on the other side of the synapse. At excitatory synapses, the binding of neurotransmitter to postsynaptic receptors increases the likelihood that the postsynaptic cell will fire its own action potential. By contrast, at inhibitory synapses the binding of neurotransmitters reduces the chances of the postsynaptic cell firing. Most inhibitory synapses use a type of neurotransmitter called GABA, which exerts its effects mainly by binding to a class of receptors called GABA-activated chloride channels (also known as GABAA receptors). GABAA receptors at inhibitory synapses can themselves be divided into two groups: ‘mobile’ receptors, which can move within the cell membrane that surrounds the postsynaptic cell; and ‘immobilized’ receptors that form clusters and cannot move. Recent work in mammalian cells identified a protein complex that anchors GABAA receptors to the cell's internal skeleton to immobilize the receptors. However, there is evidence to suggest that these are not the only proteins that control the location of the receptors. By studying the inhibitory synapses formed between neurons and body muscles in the roundworm species Caenorhabditis elegans, Tong, Hu et al. now show that different groups of proteins maintain the positioning of immobilized and mobile receptors. Specifically, proteins called LIN-2A (a component of the cell's internal skeleton) and FRM-3 (which joins receptors to the cell's skeleton) immobilize GABAA receptors, whilst the proteins Neuroligin and Neurexin ensure that mobile GABAA receptors remain within the synapse. Disturbances to the activity of inhibitory synapses are often seen in autism spectrum disorders, and so too are mutations in the genes that encode the mammalian equivalents of Neuroligin, Neurexin and LIN-2A. The work of Tong, Hu et al. thus suggests a mechanism by which these mutations might contribute to information processing impairments in people with autism. Further research could now investigate if (and how) other genes linked to autism spectrum disorders alter inhibitory synapses. DOI:http://dx.doi.org/10.7554/eLife.09648.002
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Affiliation(s)
- Xia-Jing Tong
- Department of Molecular Biology, Massachusetts General Hospital, Harvard Medical School, Boston, United States.,Department of Neurobiology, Harvard Medical School, Boston, United States
| | - Zhitao Hu
- Department of Molecular Biology, Massachusetts General Hospital, Harvard Medical School, Boston, United States.,Department of Neurobiology, Harvard Medical School, Boston, United States
| | - Yu Liu
- Department of Molecular Biology, Massachusetts General Hospital, Harvard Medical School, Boston, United States.,Department of Neurobiology, Harvard Medical School, Boston, United States
| | - Dorian Anderson
- Department of Molecular Biology, Massachusetts General Hospital, Harvard Medical School, Boston, United States.,Department of Neurobiology, Harvard Medical School, Boston, United States
| | - Joshua M Kaplan
- Department of Molecular Biology, Massachusetts General Hospital, Harvard Medical School, Boston, United States.,Department of Neurobiology, Harvard Medical School, Boston, United States
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22
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Wiera G, Mozrzymas JW. Extracellular proteolysis in structural and functional plasticity of mossy fiber synapses in hippocampus. Front Cell Neurosci 2015; 9:427. [PMID: 26582976 PMCID: PMC4631828 DOI: 10.3389/fncel.2015.00427] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2015] [Accepted: 10/09/2015] [Indexed: 02/04/2023] Open
Abstract
Brain is continuously altered in response to experience and environmental changes. One of the underlying mechanisms is synaptic plasticity, which is manifested by modification of synapse structure and function. It is becoming clear that regulated extracellular proteolysis plays a pivotal role in the structural and functional remodeling of synapses during brain development, learning and memory formation. Clearly, plasticity mechanisms may substantially differ between projections. Mossy fiber synapses onto CA3 pyramidal cells display several unique functional features, including pronounced short-term facilitation, a presynaptically expressed long-term potentiation (LTP) that is independent of NMDAR activation, and NMDA-dependent metaplasticity. Moreover, structural plasticity at mossy fiber synapses ranges from the reorganization of projection topology after hippocampus-dependent learning, through intrinsically different dynamic properties of synaptic boutons to pre- and postsynaptic structural changes accompanying LTP induction. Although concomitant functional and structural plasticity in this pathway strongly suggests a role of extracellular proteolysis, its impact only starts to be investigated in this projection. In the present report, we review the role of extracellular proteolysis in various aspects of synaptic plasticity in hippocampal mossy fiber synapses. A growing body of evidence demonstrates that among perisynaptic proteases, tissue plasminogen activator (tPA)/plasmin system, β-site amyloid precursor protein-cleaving enzyme 1 (BACE1) and metalloproteinases play a crucial role in shaping plastic changes in this projection. We discuss recent advances and emerging hypotheses on the roles of proteases in mechanisms underlying mossy fiber target specific synaptic plasticity and memory formation.
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Affiliation(s)
- Grzegorz Wiera
- Department of Animal Molecular Physiology, Institute of Experimental Biology, Wroclaw University Wroclaw, Poland ; Laboratory of Neuroscience, Department of Biophysics, Wroclaw Medical University Wroclaw, Poland
| | - Jerzy W Mozrzymas
- Department of Animal Molecular Physiology, Institute of Experimental Biology, Wroclaw University Wroclaw, Poland ; Laboratory of Neuroscience, Department of Biophysics, Wroclaw Medical University Wroclaw, Poland
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Enhanced GABAA-Mediated Tonic Inhibition in Auditory Thalamus of Rats with Behavioral Evidence of Tinnitus. J Neurosci 2015; 35:9369-80. [PMID: 26109660 DOI: 10.1523/jneurosci.5054-14.2015] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Accumulating evidence suggests a role for inhibitory neurotransmitter dysfunction in the pathology of tinnitus. Opposing hypotheses proposed either a pathologic decrease or increase of GABAergic inhibition in medial geniculate body (MGB). In thalamus, GABA mediates fast synaptic inhibition via synaptic GABAA receptors (GABAARs) and persistent tonic inhibition via high-affinity extrasynaptic GABAARs. Given that extrasynaptic GABAARs control the firing mode of thalamocortical neurons, we examined tonic GABAAR currents in MGB neurons in vitro, using the following three groups of adult rats: unexposed control (Ctrl); sound exposed with behavioral evidence of tinnitus (Tin); and sound exposed with no behavioral evidence of tinnitus (Non-T). Tonic GABAAR currents were evoked using the selective agonist gaboxadol. Months after a tinnitus-inducing sound exposure, gaboxadol-evoked tonic GABAAR currents showed significant tinnitus-related increases contralateral to the sound exposure. In situ hybridization studies found increased mRNA levels for GABAAR δ-subunits contralateral to the sound exposure. Tin rats showed significant increases in the number of spikes per burst evoked using suprathreshold-injected current steps. In summary, we found little evidence of tinnitus-related decreases in GABAergic neurotransmission. Tinnitus and chronic pain may reflect thalamocortical dysrhythmia, which results from abnormal theta-range resonant interactions between thalamus and cortex, due to neuronal hyperpolarization and the initiation of low-threshold calcium spike bursts (Walton and Llinás, 2010). In agreement with this hypothesis, we found tinnitus-related increases in tonic extrasynaptic GABAAR currents, in action potentials/evoked bursts, and in GABAAR δ-subunit gene expression. These tinnitus-related changes in GABAergic function may be markers for tinnitus pathology in the MGB.
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Abstract
Dopamine is a critical neuromodulator that activates GPCRs in mammals or ligand-gated ion channels in invertebrates. The present study demonstrates that dopamine (0.1-10 mm) exerts novel, opposing effects on different populations of mammalian (rat) GABAA receptors. Using whole-cell patch-clamp electrophysiology, we observed direct dopamine-mediated inhibition of tonic-level (1 μm) GABA-evoked currents in untransfected striatal neurons that could be recapitulated in HEK293 cells containing α1β3 or α1β2γ2 subunits. Surprisingly, direct activation by dopamine was seen in the absence of GABA with α1β2γ2, α5β3γ2, or α1β3γ2 transfections. This activity was also present in α1β3γ2 receptors containing a mutant β3 subunit (H267A [(Z)β3]) insensitive to trace levels of inhibitory Zn(2+). Dopamine activation required β and γ subunits but not α subunits ((Z)β3γ2 EC50 value, 660 μm). Dopamine activity was fully blocked by picrotoxin but not GABAA competitive antagonists, and was strongly correlated with spontaneous receptor activity. We also report opposing effects of bicuculline and gabazine, such that bicuculline surprisingly activated non-α-containing (β3γ2) GABAA receptors, whereas gabazine suppressed spontaneous activity in these receptors. Our results suggest that dopamine may directly inhibit GABAA receptors that are both immediately adjacent to dopamine release sites in the striatum and activated by tonic GABA. Furthermore, synaptic/phasic release of dopamine may directly enhance signaling at some spontaneously active noncanonical GABAA receptors that lack α subunits.
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25
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Rivnay J, Leleux P, Hama A, Ramuz M, Huerta M, Malliaras GG, Owens RM. Using white noise to gate organic transistors for dynamic monitoring of cultured cell layers. Sci Rep 2015; 5:11613. [PMID: 26112429 PMCID: PMC4481393 DOI: 10.1038/srep11613] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2015] [Accepted: 06/01/2015] [Indexed: 11/18/2022] Open
Abstract
Impedance sensing of biological systems allows for monitoring of cell and tissue properties, including cell-substrate attachment, layer confluence, and the “tightness” of an epithelial tissue. These properties are critical for electrical detection of tissue health and viability in applications such as toxicological screening. Organic transistors based on conducting polymers offer a promising route to efficiently transduce ionic currents to attain high quality impedance spectra, but collection of complete impedance spectra can be time consuming (minutes). By applying uniform white noise at the gate of an organic electrochemical transistor (OECT), and measuring the resulting current noise, we are able to dynamically monitor the impedance and thus integrity of cultured epithelial monolayers. We show that noise sourcing can be used to track rapid monolayer disruption due to compounds which interfere with dynamic polymerization events crucial for maintaining cytoskeletal integrity, and to resolve sub-second alterations to the monolayer integrity.
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Affiliation(s)
- Jonathan Rivnay
- Department of Bioelectronics, Ecole Nationale Superieure des Mines, CMP-EMSE, MOC, 13541 Gardanne, France
| | - Pierre Leleux
- 1] Department of Bioelectronics, Ecole Nationale Superieure des Mines, CMP-EMSE, MOC, 13541 Gardanne, France [2] Microvitae Technologies, Hôtel Technologique, Europarc Sainte Victoire Bât 6 Route de Valbrillant, 13590 Meyreuil, France
| | - Adel Hama
- Department of Bioelectronics, Ecole Nationale Superieure des Mines, CMP-EMSE, MOC, 13541 Gardanne, France
| | - Marc Ramuz
- Department of Bioelectronics, Ecole Nationale Superieure des Mines, CMP-EMSE, MOC, 13541 Gardanne, France
| | - Miriam Huerta
- Department of Bioelectronics, Ecole Nationale Superieure des Mines, CMP-EMSE, MOC, 13541 Gardanne, France
| | - George G Malliaras
- Department of Bioelectronics, Ecole Nationale Superieure des Mines, CMP-EMSE, MOC, 13541 Gardanne, France
| | - Roisin M Owens
- Department of Bioelectronics, Ecole Nationale Superieure des Mines, CMP-EMSE, MOC, 13541 Gardanne, France
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26
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GABAergic transmission to kisspeptin neurons is differentially regulated by time of day and estradiol in female mice. J Neurosci 2015; 34:16296-308. [PMID: 25471569 DOI: 10.1523/jneurosci.3057-14.2014] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Gonadotropin-releasing hormone (GnRH) secretion is regulated by estradiol feedback. This feedback switches from negative to positive in females; this switch depends on time of day in many species. Estradiol feedback is likely conveyed via afferents. Kisspeptin neurons of the arcuate nucleus and anteroventral-periventricular region (AVPV) may differentially regulate GnRH neurons during negative and positive feedback, respectively. We tested estradiol and time of day regulation of GABAergic transmission and postsynaptic response to GABA in these two populations using transgenic mice with GFP-identified kisspeptin neurons. Ovariectomized (OVX) mice treated or not with estradiol (E) were studied in the AM (negative feedback) or PM (positive feedback). GABAA receptor reversal potential was unaffected by time of day or estradiol. GABA depolarized the membrane potential of arcuate neurons from OVX+E mice; this response was blunted in cells from OVX mice. GABA hyperpolarized AVPV kisspeptin neurons, except in the OVX PM group in which GABA did not alter membrane potential attributable to a PM hyperpolarization of baseline membrane potential. In both kisspeptin neuron populations from OVX mice, the frequency of GABAergic spontaneous postsynaptic currents was increased in the PM; this increase was blunted by estradiol. In arcuate, but not AVPV, kisspeptin neurons, estradiol reduced miniature postsynaptic current amplitude independent of time of day. Using nonstationary fluctuation analysis and diazepam to manipulate GABAA receptor apparent affinity, the decrease in arcuate miniature postsynaptic current amplitude was attributed to decreased number of receptors bound by GABA. Time of day and estradiol feedback thus both target presynaptic and postsynaptic mechanisms to differentially regulate kisspeptin neurons via GABAergic transmission.
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27
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Petrini EM, Barberis A. Diffusion dynamics of synaptic molecules during inhibitory postsynaptic plasticity. Front Cell Neurosci 2014; 8:300. [PMID: 25294987 PMCID: PMC4171989 DOI: 10.3389/fncel.2014.00300] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2014] [Accepted: 09/05/2014] [Indexed: 12/24/2022] Open
Abstract
The plasticity of inhibitory transmission is expected to play a key role in the modulation of neuronal excitability and network function. Over the last two decades, the investigation of the determinants of inhibitory synaptic plasticity has allowed distinguishing presynaptic and postsynaptic mechanisms. While there has been a remarkable progress in the characterization of presynaptically-expressed plasticity of inhibition, the postsynaptic mechanisms of inhibitory long-term synaptic plasticity only begin to be unraveled. At postsynaptic level, the expression of inhibitory synaptic plasticity involves the rearrangement of the postsynaptic molecular components of the GABAergic synapse, including GABAA receptors, scaffold proteins and structural molecules. This implies a dynamic modulation of receptor intracellular trafficking and receptor surface lateral diffusion, along with regulation of the availability and distribution of scaffold proteins. This Review will focus on the mechanisms of the multifaceted molecular reorganization of the inhibitory synapse during postsynaptic plasticity, with special emphasis on the key role of protein dynamics to ensure prompt and reliable activity-dependent adjustments of synaptic strength.
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Affiliation(s)
- Enrica Maria Petrini
- Department of Neuroscience and Brain Technologies, Istituto Italiano di Tecnologia Genoa, Italy
| | - Andrea Barberis
- Department of Neuroscience and Brain Technologies, Istituto Italiano di Tecnologia Genoa, Italy
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28
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Scimemi A. Structure, function, and plasticity of GABA transporters. Front Cell Neurosci 2014; 8:161. [PMID: 24987330 PMCID: PMC4060055 DOI: 10.3389/fncel.2014.00161] [Citation(s) in RCA: 159] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2014] [Accepted: 05/27/2014] [Indexed: 11/13/2022] Open
Abstract
GABA transporters belong to a large family of neurotransmitter:sodium symporters. They are widely expressed throughout the brain, with different levels of expression in different brain regions. GABA transporters are present in neurons and in astrocytes and their activity is crucial to regulate the extracellular concentration of GABA under basal conditions and during ongoing synaptic events. Numerous efforts have been devoted to determine the structural and functional properties of GABA transporters. There is also evidence that the expression of GABA transporters on the cell membrane and their lateral mobility can be modulated by different intracellular signaling cascades. The strength of individual synaptic contacts and the activity of entire neuronal networks may be finely tuned by altering the density, distribution and diffusion rate of GABA transporters within the cell membrane. These findings are intriguing because they suggest the existence of complex regulatory systems that control the plasticity of GABAergic transmission in the brain. Here we review the current knowledge on the structural and functional properties of GABA transporters and highlight the molecular mechanisms that alter the expression and mobility of GABA transporters at central synapses.
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29
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Petrini EM, Ravasenga T, Hausrat TJ, Iurilli G, Olcese U, Racine V, Sibarita JB, Jacob TC, Moss SJ, Benfenati F, Medini P, Kneussel M, Barberis A. Synaptic recruitment of gephyrin regulates surface GABAA receptor dynamics for the expression of inhibitory LTP. Nat Commun 2014; 5:3921. [PMID: 24894704 PMCID: PMC4059940 DOI: 10.1038/ncomms4921] [Citation(s) in RCA: 131] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2014] [Accepted: 04/17/2014] [Indexed: 11/09/2022] Open
Abstract
Postsynaptic long-term potentiation of inhibition (iLTP) can rely on increased GABAA receptors (GABA(A)Rs) at synapses by promoted exocytosis. However, the molecular mechanisms that enhance the clustering of postsynaptic GABA(A)Rs during iLTP remain obscure. Here we demonstrate that during chemically induced iLTP (chem-iLTP), GABA(A)Rs are immobilized and confined at synapses, as revealed by single-particle tracking of individual GABA(A)Rs in cultured hippocampal neurons. Chem-iLTP expression requires synaptic recruitment of the scaffold protein gephyrin from extrasynaptic areas, which in turn is promoted by CaMKII-dependent phosphorylation of GABA(A)R-β3-Ser(383). Impairment of gephyrin assembly prevents chem-iLTP and, in parallel, blocks the accumulation and immobilization of GABA(A)Rs at synapses. Importantly, an increase of gephyrin and GABA(A)R similar to those observed during chem-iLTP in cultures were found in the rat visual cortex following an experience-dependent plasticity protocol that potentiates inhibitory transmission in vivo. Thus, phospho-GABA(A)R-β3-dependent accumulation of gephyrin at synapses and receptor immobilization are crucial for iLTP expression and are likely to modulate network excitability.
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Affiliation(s)
- Enrica Maria Petrini
- Department of Neuroscience and Brain Technologies, The Italian Institute of Technology, Via Morego 30, 16163 Genova, Italy
| | - Tiziana Ravasenga
- Department of Neuroscience and Brain Technologies, The Italian Institute of Technology, Via Morego 30, 16163 Genova, Italy
| | - Torben J Hausrat
- Center for Molecular Neurobiology (ZMNH), University Medical Center Hamburg Eppendorf, D-20251 Hamburg, Germany
| | - Giuliano Iurilli
- Department of Neuroscience and Brain Technologies, The Italian Institute of Technology, Via Morego 30, 16163 Genova, Italy
| | - Umberto Olcese
- Department of Neuroscience and Brain Technologies, The Italian Institute of Technology, Via Morego 30, 16163 Genova, Italy
| | - Victor Racine
- Institute of Molecular and Cell Biology, Proteos, Singapore 138673, Singapore
| | - Jean-Baptiste Sibarita
- 1] Interdisciplinary Institute for Neuroscience, University of Bordeaux, F-33000 Bordeaux, France [2] CNRS UMR 5297, F-33000 Bordeaux, France
| | - Tija C Jacob
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA
| | - Stephen J Moss
- Department of Neuroscience, Tufts University, 136 Harrison Avenue, Arnold 207 Boston, Massachusetts 0211, USA
| | - Fabio Benfenati
- 1] Department of Neuroscience and Brain Technologies, The Italian Institute of Technology, Via Morego 30, 16163 Genova, Italy [2] Department of Experimental Medicine, University of Genova, 16163 Genova, Italy
| | - Paolo Medini
- Department of Neuroscience and Brain Technologies, The Italian Institute of Technology, Via Morego 30, 16163 Genova, Italy
| | - Matthias Kneussel
- Center for Molecular Neurobiology (ZMNH), University Medical Center Hamburg Eppendorf, D-20251 Hamburg, Germany
| | - Andrea Barberis
- Department of Neuroscience and Brain Technologies, The Italian Institute of Technology, Via Morego 30, 16163 Genova, Italy
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30
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Golovko T, Min R, Lozovaya N, Falconer C, Yatsenko N, Tsintsadze T, Tsintsadze V, Ledent C, Harvey RJ, Belelli D, Lambert JJ, Rozov A, Burnashev N. Control of Inhibition by the Direct Action of Cannabinoids on GABAAReceptors. Cereb Cortex 2014; 25:2440-55. [DOI: 10.1093/cercor/bhu045] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
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Romanova EV, Aerts JT, Croushore CA, Sweedler JV. Small-volume analysis of cell-cell signaling molecules in the brain. Neuropsychopharmacology 2014; 39:50-64. [PMID: 23748227 PMCID: PMC3857641 DOI: 10.1038/npp.2013.145] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/26/2013] [Revised: 04/26/2013] [Accepted: 05/06/2013] [Indexed: 12/19/2022]
Abstract
Modern science is characterized by integration and synergy between research fields. Accordingly, as technological advances allow new and more ambitious quests in scientific inquiry, numerous analytical and engineering techniques have become useful tools in biological research. The focus of this review is on cutting edge technologies that aid direct measurement of bioactive compounds in the nervous system to facilitate fundamental research, diagnostics, and drug discovery. We discuss challenges associated with measurement of cell-to-cell signaling molecules in the nervous system, and advocate for a decrease of sample volumes to the nanoliter volume regimen for improved analysis outcomes. We highlight effective approaches for the collection, separation, and detection of such small-volume samples, present strategies for targeted and discovery-oriented research, and describe the required technology advances that will empower future translational science.
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Affiliation(s)
- Elena V Romanova
- Beckman Institute for Advanced Science and Technology and the Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Jordan T Aerts
- Beckman Institute for Advanced Science and Technology and the Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL, USA
- Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Callie A Croushore
- Beckman Institute for Advanced Science and Technology and the Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Jonathan V Sweedler
- Beckman Institute for Advanced Science and Technology and the Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL, USA
- Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, IL, USA
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32
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Abstract
The generation of a synaptic current at the postsynaptic element (PSCs) is the result of a dynamic sequence of events including the release of the neurotransmitter, its diffusion in the synaptic cleft, and the activation of neurotransmitter receptors located at the postsynaptic side. It is widely accepted that the amplitude and the duration of PSCs are largely dictated by the gating properties of postsynaptic receptors. However, the knowledge of the properties of postsynaptic receptors is mostly derived from steady-state analysis, a condition that is substantially different from the non-equilibrium activation of synaptic receptors imposed by submillisecond neurotransmitter exposures. Given the technical limitations to reproduce the brief "synaptic-like" agonist pulse durations, the functioning of postsynaptic receptors during synaptic transmission is not fully elucidated and the "on-demand" postsynaptic activation of synapses cannot be easily achieved. In this chapter, we review the diverse approaches to study receptor gating at times relevant for synaptic transmission and novel optical/optogenetic techniques for controlling synaptic activity at the postsynaptic level. In addition, we emphasize the role of non-equilibrium in unmasking specific features of synaptic receptor gating and the recent advances in photonics for the light-control of neuronal activity at the single-receptor level.
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Affiliation(s)
- Enrica Maria Petrini
- Department of Neuroscience and Brain Technologies, Istituto Italiano di Tecnologia, Via Morego 30, 16163, Genoa, Italy
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33
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Heine M, Karpova A, Gundelfinger ED. Counting gephyrins, one at a time: a nanoscale view on the inhibitory postsynapse. Neuron 2013; 79:213-6. [PMID: 23889929 DOI: 10.1016/j.neuron.2013.07.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Gephyrin is the key scaffolding molecule organizing the postsynaptic density at inhibitory synapses. Utilizing localization microscopy, Specht et al. (2013) report in this issue of Neuron on the quantitative assessment of gephyrin clusters and associated glycine receptors and GABAA receptors.
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Affiliation(s)
- Martin Heine
- Molecular Physiology Research Group, Leibniz Institute for Neurobiology, Brenneckestrasse 6, 39118 Magdeburg, Germany
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34
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Razik DS, Hawellek DJ, Antkowiak B, Hentschke H. Impairment of GABA transporter GAT-1 terminates cortical recurrent network activity via enhanced phasic inhibition. Front Neural Circuits 2013; 7:141. [PMID: 24062646 PMCID: PMC3769619 DOI: 10.3389/fncir.2013.00141] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2013] [Accepted: 08/23/2013] [Indexed: 11/13/2022] Open
Abstract
In the central nervous system, GABA transporters (GATs) very efficiently clear synaptically released GABA from the extracellular space, and thus exert a tight control on GABAergic inhibition. In neocortex, GABAergic inhibition is heavily recruited during recurrent phases of spontaneous action potential activity which alternate with neuronally quiet periods. Therefore, such activity should be quite sensitive to minute alterations of GAT function. Here, we explored the effects of a gradual impairment of GAT-1 and GAT-2/3 on spontaneous recurrent network activity – termed network bursts and silent periods – in organotypic slice cultures of rat neocortex. The GAT-1 specific antagonist NO-711 depressed activity already at nanomolar concentrations (IC50 for depression of spontaneous multiunit firing rate of 42 nM), reaching a level of 80% at 500–1000 nM. By contrast, the GAT-2/3 preferring antagonist SNAP-5114 had weaker and less consistent effects. Several lines of evidence pointed toward an enhancement of phasic GABAergic inhibition as the dominant activity-depressing mechanism: network bursts were drastically shortened, phasic GABAergic currents decayed slower, and neuronal excitability during ongoing activity was diminished. In silent periods, NO-711 had little effect on neuronal excitability or membrane resistance, quite in contrast to the effects of muscimol, a GABA mimetic which activates GABAA receptors tonically. Our results suggest that an enhancement of phasic GABAergic inhibition efficiently curtails cortical recurrent activity and may mediate antiepileptic effects of therapeutically relevant concentrations of GAT-1 antagonists.
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Affiliation(s)
- Daniel S Razik
- Experimental Anesthesiology Section, Department of Anesthesiology, University Hospital of Tübingen Tübingen, Germany
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35
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Pizzarelli R, Cherubini E. Developmental regulation of GABAergic signalling in the hippocampus of neuroligin 3 R451C knock-in mice: an animal model of Autism. Front Cell Neurosci 2013; 7:85. [PMID: 23761734 PMCID: PMC3671185 DOI: 10.3389/fncel.2013.00085] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2013] [Accepted: 05/17/2013] [Indexed: 11/24/2022] Open
Abstract
Autism Spectrum Disorders (ASDs) comprise an heterogeneous group of neuro-developmental abnormalities, mainly of genetic origin, characterized by impaired social interactions, communications deficits, and stereotyped behaviors. In a small percentage of cases, ASDs have been found to be associated with single mutations in genes involved in synaptic function. One of these involves the postsynaptic cell adhesion molecule neuroligin (NL) 3. NLs interact with presynaptic neurexins (Nrxs) to ensure a correct cross talk between post and presynaptic specializations. Here, transgenic mice carrying the human R451C mutation of Nlgn3, were used to study GABAergic signaling in the hippocampus early in postnatal life. Whole cell recordings from CA3 pyramidal neurons in slices from NL3R451C knock-in mice revealed an enhanced frequency of Giant Depolarizing Potentials (GDPs), as compared to controls. This effect was probably dependent on an increased GABAergic drive to principal cells as demonstrated by the enhanced frequency of miniature GABAA-mediated (GPSCs), but not AMPA-mediated postsynaptic currents (EPSCs). Changes in frequency of mGPSCs were associated with an acceleration of their decay kinetics, in the absence of any change in unitary synaptic conductance or in the number of GABAA receptor channels, as assessed by peak scaled non-stationary fluctuation analysis. The enhanced GABAergic but not glutamatergic transmission early in postnatal life may change the excitatory/inhibitory balance known to play a key role in the construction and refinement of neuronal circuits during postnatal development. This may lead to behavioral deficits reminiscent of those observed in ASDs patients.
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Affiliation(s)
- Rocco Pizzarelli
- Department of Neuroscience, Scuola Internazionale Superiore di Studi Avanzati Trieste, Italy
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36
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Cherubini E, Zacchi P. Building up the inhibitory synapse. Front Cell Neurosci 2013; 6:62. [PMID: 23316133 PMCID: PMC3540905 DOI: 10.3389/fncel.2012.00062] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2012] [Accepted: 12/09/2012] [Indexed: 11/13/2022] Open
Affiliation(s)
- Enrico Cherubini
- Department of Neuroscience, Scuola Internazionale Superiore di Studi Avanzati Trieste, Italy
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37
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Shift from phasic to tonic GABAergic transmission following laser-lesions in the rat visual cortex. Pflugers Arch 2012; 465:879-93. [PMID: 23224682 DOI: 10.1007/s00424-012-1191-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2012] [Revised: 11/13/2012] [Accepted: 11/20/2012] [Indexed: 10/27/2022]
Abstract
Reduction in the strength of GABAergic neurotransmission has often been reported following brain lesions. This weakened inhibition is believed to influence neurological deficits, neuronal hyperexcitability and functional recovery after brain injuries. Uncovering the mechanisms underlying the altered inhibition is therefore crucial. In the present study we used an ex vivo-in vitro model of laser lesions in the rat visual cortex to characterize the cellular correlates of changes in GABAergic transmission in the tissue adjacent to the injury. In the first week post-injury the number of VGAT positive GABAergic terminals as well as the expression level of the GABA synthesizing enzymes GAD67 and GAD65 remained unaltered. However, a reduced frequency of miniature inhibitory postsynaptic currents (mIPSCs) together with an increased paired-pulse ratio (PPR) of evoked IPSCs suggested a functional reduction of phasic GABA release. In parallel, we found an enhancement in the GABAA receptor-mediated tonic inhibition. On the basis of these findings, we propose that cortical lesions provoke a shift in GABAergic transmission, decreasing the phasic and reinforcing the tonic component. We therefore suggest that it is not, as traditionally assumed, the overall inhibitory strength to be primarily compromised by a cortical lesion but rather the temporal accuracy of the GABAergic synaptic signaling.
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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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39
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Abstract
High-affinity extrasynaptic GABA(A) receptors are persistently activated by the low ambient GABA levels that are known to be present in extracellular space. The resulting tonic conductance generates a form of shunting inhibition that is capable of altering cellular and network behavior. It has been suggested that this tonic inhibition will be enhanced by neurosteroids, antiepileptics, and sedative/hypnotic drugs. However, we show that the ability of sedative/hypnotic drugs to enhance tonic inhibition in the mouse cerebellum will critically depend on ambient GABA levels. For example, we show that the intravenous anesthetic propofol enhances tonic inhibition only when ambient GABA levels are <100 nm. More surprisingly, the actions of the sleep-promoting drug 4,5,6,7-tetrahydroisothiazolo-[5,4-c]pyridin-3-ol (THIP) are attenuated at ambient GABA levels of just 20 nm. In contrast, our data suggest that neurosteroid enhancement of tonic inhibition will be greater at high ambient GABA concentrations. We present a model that takes into account realistic estimates of ambient GABA levels and predicted extrasynaptic GABA(A) receptor numbers when considering the ability of sedative/hypnotic drugs to enhance tonic inhibition. These issues will be important when considering drug strategies designed to target extrasynaptic GABA(A) receptors in the treatment of sleep disorders and other neurological conditions.
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Szczot M, Czyzewska MM, Appendino G, Mozrzymas JW. Modulation of GABAergic synaptic currents and current responses by α-thujone and dihydroumbellulone. JOURNAL OF NATURAL PRODUCTS 2012; 75:622-629. [PMID: 22364543 DOI: 10.1021/np200863q] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
α-Thujone (1a), a constituent of wormwood, has been suspected to cause adverse psychoactive reactions in addicted drinkers of absinthe. While the content of 1a in absinthe is too low for such effects, at higher doses it can indeed induce seizures and inhibit GABA(A) receptors (GABA(A)Rs). The effect of 1a on GABAergic synaptic currents and the mechanisms by which it modulates GABA(A)Rs remain unknown. To address these issues, cultured hippocampal neurons were used to investigate the action of 1a on GABAergic miniature inhibitory postsynaptic currents (mIPSCs) and on responses to exogenous GABA applications. Since lipophilic compounds often show nonspecific actions related to their hydrophobicity, the action of 1a was compared to that of dihydroumbellulone (2), a configurationally pseudoenantiomeric constitutional isomer. α-Thujone (1a) reduced mIPSC frequency and amplitude and also moderately affected their kinetics, indicating both pre- and postsynaptic mechanisms. Analysis of current responses to exogenous GABA revealed that 1a reduced their amplitude, affecting their onset, desensitization, and deactivation, suggesting an effect on receptor gating. In contrast, 2 caused only a weak or negligible effect on GABAergic currents, supporting the effects of 1a on GABAergic inhibition as being due to specific interactions with GABA(A)Rs.
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Affiliation(s)
- Marcin Szczot
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, ul. Chałubińskiego 3, 50-367 Wrocław, Poland.
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Wyrembek P, Negri R, Kaczor P, Czyżewska M, Appendino G, Mozrzymas JW. Falcarindiol allosterically modulates GABAergic currents in cultured rat hippocampal neurons. JOURNAL OF NATURAL PRODUCTS 2012; 75:610-616. [PMID: 22432736 DOI: 10.1021/np2008522] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Falcarindiol (1), a C-17 polyacetylenic diol, shows a pleiotropic profile of bioactivity, but the mechanism(s) underlying its actions are largely unknown. Large amounts of 1 co-occur in water hemlock (Oenanthe crocata) along with the convulsant polyacetylenic toxin oenanthotoxin (2), a potent GABA(A) receptor (GABA(A)R) inhibitor. Since these compounds are structurally and biogenetically related, it was considered of interest to evaluate whether 1 could affect GABAergic activity, and for this purpose a model of hippocampal cultured neurons was used. Compound 1 significantly increased the amplitude of miniature inhibitory postsynaptic currents, accelerated their onset, and prolonged the decay kinetics. This compound enhanced also the amplitude of currents elicited by 3 μM GABA and accelerated their fading, reducing, however, currents evoked by a saturating (10 mM) GABA concentration. Moreover, kinetic analysis of responses to 10 mM GABA revealed that 1 upregulated the rate and extent of desensitization and slowed the current onset and deactivation. Taken together, these data show that 1 exerts a potent modulatory action on GABA(A)Rs, possibly by modulating agonist binding and desensitization, overall potentially decreasing the toxicity of co-occurring GABA-inhibiting convulsant toxins.
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Affiliation(s)
- Paulina Wyrembek
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, ul. Chałubińskiego 3, 50-358 Wrocław, Poland
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Wyrembek P, Negri R, Appendino G, Mozrzymas JW. Inhibitory effects of oenanthotoxin analogues on GABAergic currents in cultured rat hippocampal neurons depend on the polyacetylenes' polarity. Eur J Pharmacol 2012; 683:35-42. [PMID: 22445880 DOI: 10.1016/j.ejphar.2012.03.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2011] [Revised: 02/21/2012] [Accepted: 03/04/2012] [Indexed: 11/15/2022]
Abstract
Oenanthotoxin (OETX) and dihydro-OETX are polyacetylenic diols occurring in Oenanthe crocata and are known to exert proconvulsant effects. We have recently demonstrated that these compounds downregulated GABAergic currents (Appendino et al., 2009) and that OETX induced open channel block and allosterically modulated GABA(A) receptors (Wyrembek et al., 2010). O. crocata also contains several minor OETX analogues and in the present study we tested whether their effect on GABA(A) receptors depends on the compounds' polarity. We investigated a series of five polyacetylenes characterized by a higher lipophylicity than OETX, (1-acetyl-2,3-dihydrooenanthotoxin - X1, 14-acetyloenanthotoxin-X2, 1-deoxyoenanthotoxin - X3, 14-deoxyoenanthotoxin - X4, 14-dehydro-1-deoxyOETX - X5, polarity sequence: X1>X2>X3>X4>X5). Their effects were tested first on miniature inhibitory postsynaptic currents (mIPSCs). All but X3, significantly decreased the mIPSC amplitudes while X1, X2, X4 decreased, and X3 and X5 increased the mIPSC frequency. The lack of a clear correlation between the compounds' polarity and their effect on mIPSCs might result from their presynaptic effects. We thus considered their impact on current responses to exogenous GABA applications. Amplitude reduction of current responses was most prominent for X1 and virtually absent for X5 indicating a dependence on the compound's polarity. Only X1 and X2 showed open channel block, while the kinetics of currents were affected only by X1 which further supports a dependence of the drug's effects on their polarity. In conclusion, GABA(A) receptors are inhibited and allosterically modulated by naturally occurring OETX analogues (except X5) and these effects are positively correlated with the compounds' polarity.
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Affiliation(s)
- Paulina Wyrembek
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, ul. Chałubińskiego 3, 50-358 Wrocław, Poland
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GABA metabolism and transport: effects on synaptic efficacy. Neural Plast 2012; 2012:805830. [PMID: 22530158 PMCID: PMC3316990 DOI: 10.1155/2012/805830] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2011] [Accepted: 12/19/2011] [Indexed: 11/17/2022] Open
Abstract
GABAergic inhibition is an important regulator of excitability in neuronal networks. In addition, inhibitory synaptic signals contribute crucially to the organization of spatiotemporal patterns of network activity, especially during coherent oscillations. In order to maintain stable network states, the release of GABA by interneurons must be plastic in timing and amount. This homeostatic regulation is achieved by several pre- and postsynaptic mechanisms and is triggered by various activity-dependent local signals such as excitatory input or ambient levels of neurotransmitters. Here, we review findings on the availability of GABA for release at presynaptic terminals of interneurons. Presynaptic GABA content seems to be an important determinant of inhibitory efficacy and can be differentially regulated by changing synthesis, transport, and degradation of GABA or related molecules. We will discuss the functional impact of such regulations on neuronal network patterns and, finally, point towards pharmacological approaches targeting these processes.
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