1
|
Anders S, Breithausen B, Unichenko P, Herde MK, Minge D, Abramian A, Behringer C, Deshpande T, Boehlen A, Domingos C, Henning L, Pitsch J, Kim YB, Bedner P, Steinhäuser C, Henneberger C. Epileptic activity triggers rapid ROCK1-dependent astrocyte morphology changes. Glia 2024; 72:643-659. [PMID: 38031824 PMCID: PMC10842783 DOI: 10.1002/glia.24495] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Revised: 11/16/2023] [Accepted: 11/20/2023] [Indexed: 12/01/2023]
Abstract
Long-term modifications of astrocyte function and morphology are well known to occur in epilepsy. They are implicated in the development and manifestation of the disease, but the relevant mechanisms and their pathophysiological role are not firmly established. For instance, it is unclear how quickly the onset of epileptic activity triggers astrocyte morphology changes and what the relevant molecular signals are. We therefore used two-photon excitation fluorescence microscopy to monitor astrocyte morphology in parallel to the induction of epileptiform activity. We uncovered astrocyte morphology changes within 10-20 min under various experimental conditions in acute hippocampal slices. In vivo, induction of status epilepticus resulted in similarly altered astrocyte morphology within 30 min. Further analysis in vitro revealed a persistent volume reduction of peripheral astrocyte processes triggered by induction of epileptiform activity. In addition, an impaired diffusion within astrocytes and within the astrocyte network was observed, which most likely is a direct consequence of the astrocyte remodeling. These astrocyte morphology changes were prevented by inhibition of the Rho GTPase RhoA and of the Rho-associated kinase (ROCK). Selective deletion of ROCK1 but not ROCK2 from astrocytes also prevented the morphology change after induction of epileptiform activity and reduced epileptiform activity. Together these observations reveal that epileptic activity triggers a rapid ROCK1-dependent astrocyte morphology change, which is mechanistically linked to the strength of epileptiform activity. This suggests that astrocytic ROCK1 signaling is a maladaptive response of astrocytes to the onset of epileptic activity.
Collapse
Affiliation(s)
- Stefanie Anders
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn, Germany
| | - Björn Breithausen
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn, Germany
| | - Petr Unichenko
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn, Germany
| | - Michel K. Herde
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn, Germany
| | - Daniel Minge
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn, Germany
| | - Adlin Abramian
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn, Germany
| | - Charlotte Behringer
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn, Germany
| | - Tushar Deshpande
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn, Germany
| | - Anne Boehlen
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn, Germany
| | - Cátia Domingos
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn, Germany
| | - Lukas Henning
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn, Germany
| | - Julika Pitsch
- Department of Epileptology, University Hospital Bonn, Bonn, Germany
| | - Young-Bum Kim
- Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, Beth Israel Deaconess Medical Center, and Harvard Medical School, Boston, MA, USA
| | - Peter Bedner
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn, Germany
| | - Christian Steinhäuser
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn, Germany
| | - Christian Henneberger
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn, Germany
- German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany
| |
Collapse
|
2
|
Kambali M, Li Y, Unichenko P, Pliego JF, Yadav R, Liu J, McGuinness P, Cobb JG, Wang M, Nagarajan R, Lyu J, Vongsouthi V, Jackson CJ, Engin E, Coyle JT, Shin J, Talkowski ME, Homanics GE, Bolshakov VY, Henneberger C, Rudolph U. A marker chromosome in psychosis identifies glycine decarboxylase (GLDC) as a novel regulator of neuronal and synaptic function in the hippocampus. bioRxiv 2023:2023.05.29.542745. [PMID: 37398055 PMCID: PMC10312439 DOI: 10.1101/2023.05.29.542745] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/04/2023]
Abstract
The biological significance of a small supernumerary marker chromosome that results in dosage alterations to chromosome 9p24.1, including triplication of the GLDC gene encoding glycine decarboxylase, in two patients with psychosis is unclear. In an allelic series of copy number variant mouse models, we identify that triplication of Gldc reduces extracellular glycine levels as determined by optical fluorescence resonance energy transfer (FRET) in dentate gyrus (DG) but not in CA1, suppresses long-term potentiation (LTP) in mPP-DG synapses but not in CA3-CA1 synapses, reduces the activity of biochemical pathways implicated in schizophrenia and mitochondrial bioenergetics, and displays deficits in prepulse inhibition, startle habituation, latent inhibition, working memory, sociability and social preference. Our results thus provide a link between a genomic copy number variation, biochemical, cellular and behavioral phenotypes, and further demonstrate that GLDC negatively regulates long-term synaptic plasticity at specific hippocampal synapses, possibly contributing to the development of neuropsychiatric disorders.
Collapse
|
3
|
Henning L, Unichenko P, Bedner P, Steinhäuser C, Henneberger C. Overview Article Astrocytes as Initiators of Epilepsy. Neurochem Res 2023; 48:1091-1099. [PMID: 36244037 PMCID: PMC10030460 DOI: 10.1007/s11064-022-03773-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Revised: 08/22/2022] [Accepted: 09/27/2022] [Indexed: 10/17/2022]
Abstract
Astrocytes play a dual role in the brain. On the one hand, they are active signaling partners of neurons and can for instance control synaptic transmission and its plasticity. On the other hand, they fulfill various homeostatic functions such as clearance of glutamate and K+ released from neurons. The latter is for instance important for limiting neuronal excitability. Therefore, an impairment or failure of glutamate and K+ clearance will lead to increased neuronal excitability, which could trigger or aggravate brain diseases such as epilepsy, in which neuronal hyperexcitability plays a role. Experimental data indicate that astrocytes could have such a causal role in epilepsy, but the role of astrocytes as initiators of epilepsy and the relevant mechanisms are under debate. In this overview, we will discuss the potential mechanisms with focus on K+ clearance, glutamate uptake and homoeostasis and related mechanisms, and the evidence for their causative role in epilepsy.
Collapse
Affiliation(s)
- Lukas Henning
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, 53127, Bonn, Germany
| | - Petr Unichenko
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, 53127, Bonn, Germany
| | - Peter Bedner
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, 53127, Bonn, Germany
| | - Christian Steinhäuser
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, 53127, Bonn, Germany.
| | - Christian Henneberger
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, 53127, Bonn, Germany.
- German Center for Neurodegenerative Diseases (DZNE), 53127, Bonn, Germany.
| |
Collapse
|
4
|
Vongsouthi V, Whitfield JH, Unichenko P, Mitchell JA, Breithausen B, Khersonsky O, Kremers L, Janovjak H, Monai H, Hirase H, Fleishman SJ, Henneberger C, Jackson CJ. A Rationally and Computationally Designed Fluorescent Biosensor for d-Serine. ACS Sens 2021; 6:4193-4205. [PMID: 34783546 DOI: 10.1021/acssensors.1c01803] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Solute-binding proteins (SBPs) have evolved to balance the demands of ligand affinity, thermostability, and conformational change to accomplish diverse functions in small molecule transport, sensing, and chemotaxis. Although the ligand-induced conformational changes that occur in SBPs make them useful components in biosensors, they are challenging targets for protein engineering and design. Here, we have engineered a d-alanine-specific SBP into a fluorescence biosensor with specificity for the signaling molecule d-serine (D-serFS). This was achieved through binding site and remote mutations that improved affinity (KD = 6.7 ± 0.5 μM), specificity (40-fold increase vs glycine), thermostability (Tm = 79 °C), and dynamic range (∼14%). This sensor allowed measurement of physiologically relevant changes in d-serine concentration using two-photon excitation fluorescence microscopy in rat brain hippocampal slices. This work illustrates the functional trade-offs between protein dynamics, ligand affinity, and thermostability and how these must be balanced to achieve desirable activities in the engineering of complex, dynamic proteins.
Collapse
Affiliation(s)
- Vanessa Vongsouthi
- Research School of Chemistry, Australian National University, Canberra 2601, Australia
| | - Jason H. Whitfield
- Research School of Chemistry, Australian National University, Canberra 2601, Australia
| | - Petr Unichenko
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn 53127, Germany
| | - Joshua A. Mitchell
- Research School of Chemistry, Australian National University, Canberra 2601, Australia
| | - Björn Breithausen
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn 53127, Germany
| | - Olga Khersonsky
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Leon Kremers
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn 53127, Germany
| | - Harald Janovjak
- Australian Regenerative Medicine Institute (ARMI), Faculty of Medicine, Nursing and Health Sciences, Monash University, Clayton/Melbourne 3800, Australia
| | - Hiromu Monai
- Laboratory for Neuron-Glia Circuitry, RIKEN Center for Brain Science, Wako 351-0198, Japan
| | - Hajime Hirase
- Laboratory for Neuron-Glia Circuitry, RIKEN Center for Brain Science, Wako 351-0198, Japan
| | - Sarel J. Fleishman
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Christian Henneberger
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn 53127, Germany
- Institute of Neurology, University College London, London WC1N 3BG, United Kingdom
- German Center for Degenerative Diseases (DZNE), Bonn 53127, Germany
| | - Colin J. Jackson
- Research School of Chemistry, Australian National University, Canberra 2601, Australia
| |
Collapse
|
5
|
Minge D, Domingos C, Unichenko P, Behringer C, Pauletti A, Anders S, Herde MK, Delekate A, Gulakova P, Schoch S, Petzold GC, Henneberger C. Heterogeneity and Development of Fine Astrocyte Morphology Captured by Diffraction-Limited Microscopy. Front Cell Neurosci 2021; 15:669280. [PMID: 34149361 PMCID: PMC8211899 DOI: 10.3389/fncel.2021.669280] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Accepted: 05/06/2021] [Indexed: 12/26/2022] Open
Abstract
The fine processes of single astrocytes can contact many thousands of synapses whose function they can modulate through bi-directional signaling. The spatial arrangement of astrocytic processes and neuronal structures is relevant for such interactions and for the support of neuronal signaling by astrocytes. At the same time, the geometry of perisynaptic astrocyte processes is variable and dynamically regulated. Studying these fine astrocyte processes represents a technical challenge, because many of them cannot be fully resolved by diffraction-limited microscopy. Therefore, we have established two indirect parameters of astrocyte morphology, which, while not fully resolving local geometry by design, provide statistical measures of astrocyte morphology: the fraction of tissue volume that astrocytes occupy and the density of resolvable astrocytic processes. Both are straightforward to obtain using widely available microscopy techniques. We here present the approach and demonstrate its robustness across various experimental conditions using mainly two-photon excitation fluorescence microscopy in acute slices and in vivo as well as modeling. Using these indirect measures allowed us to analyze the morphology of relatively large populations of astrocytes. Doing so we captured the heterogeneity of astrocytes within and between the layers of the hippocampal CA1 region and the developmental profile of astrocyte morphology. This demonstrates that volume fraction (VF) and segment density are useful parameters for describing the structure of astrocytes. They are also suitable for online monitoring of astrocyte morphology with widely available microscopy techniques.
Collapse
Affiliation(s)
- Daniel Minge
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn, Germany
| | - Cátia Domingos
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn, Germany
| | - Petr Unichenko
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn, Germany
| | - Charlotte Behringer
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn, Germany
| | - Alberto Pauletti
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn, Germany
| | - Stefanie Anders
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn, Germany
| | - Michel K Herde
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn, Germany
| | - Andrea Delekate
- German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany
| | - Polina Gulakova
- Department of Neuropathology, University Hospital Bonn, Bonn, Germany
| | - Susanne Schoch
- Department of Neuropathology, University Hospital Bonn, Bonn, Germany
| | - Gabor C Petzold
- German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany.,Division of Vascular Neurology, University Hospital Bonn, Bonn, Germany
| | - Christian Henneberger
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn, Germany.,German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany.,Institute of Neurology, University College London, London, United Kingdom
| |
Collapse
|
6
|
Unichenko P, Yang JW, Kirischuk S, Kolbaev S, Kilb W, Hammer M, Krueger-Burg D, Brose N, Luhmann HJ. Autism Related Neuroligin-4 Knockout Impairs Intracortical Processing but not Sensory Inputs in Mouse Barrel Cortex. Cereb Cortex 2019; 28:2873-2886. [PMID: 29106499 DOI: 10.1093/cercor/bhx165] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Accepted: 06/14/2017] [Indexed: 11/14/2022] Open
Abstract
Neuroligin-4 (Nlgn4) is a cell adhesion protein that regulates synapse organization and function. Mutations in human NLGN4 are among the causes of autism spectrum disorders. In mouse, Nlgn4 knockout (KO) perturbs GABAergic synaptic transmission and oscillatory activity in hippocampus, and causes social interaction deficits. The complex profile of cellular and circuit changes that are caused by Nlgn4-KO is still only partly understood. Using Nlgn4-KO mice, we found that Nlgn4-KO increases the power in the alpha frequency band of spontaneous network activity in the barrel cortex under urethane anesthesia in vivo. Nlgn4-KO did not affect single-whisker-induced local field potentials, but suppressed the late evoked multiunit activity in vivo. Although Nlgn4-KO did not affect evoked EPSCs in layer 4 (L4) spiny stellate cells in acute thalamocortical slices elicited by electrical stimulation of thalamocortical inputs, it caused a lower frequency of both miniature (m) IPSCs and mEPSCs, and a decrease in the number of readily releasable vesicles at GABAergic and glutamatergic connections, weakening both excitatory and inhibitory transmission. However, Nlgn4 deficit strongly suppresses glutamatergic activity, shifting the excitation-inhibition balance to inhibition. We conclude that Nlgn4-KO does not influence the incoming whisker-mediated sensory information to the barrel cortex, but modifies intracortical information processing.
Collapse
Affiliation(s)
- Petr Unichenko
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, Mainz, Germany
| | - Jenq-Wei Yang
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, Mainz, Germany
| | - Sergei Kirischuk
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, Mainz, Germany
| | - Sergei Kolbaev
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, Mainz, Germany
| | - Werner Kilb
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, Mainz, Germany
| | - Matthieu Hammer
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Hermann-Rein-Straße 3, Göttingen, Germany
| | - Dilja Krueger-Burg
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Hermann-Rein-Straße 3, Göttingen, Germany
| | - Nils Brose
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Hermann-Rein-Straße 3, Göttingen, Germany
| | - Heiko J Luhmann
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, Mainz, Germany
| |
Collapse
|
7
|
Yang JW, Kilb W, Kirischuk S, Unichenko P, Stüttgen MC, Luhmann HJ. Development of the whisker-to-barrel cortex system. Curr Opin Neurobiol 2018; 53:29-34. [PMID: 29738998 DOI: 10.1016/j.conb.2018.04.023] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Revised: 04/20/2018] [Accepted: 04/24/2018] [Indexed: 01/30/2023]
Abstract
This review provides an overview on the development of the rodent whisker-to-barrel cortex system from late embryonic stage to the end of the first postnatal month. During this period the system shows a remarkable transition from a mostly genetic-molecular driven generation of crude connectivity, providing the template for activity-dependent structural and functional maturation and plasticity, to the manifestation of a complex behavioral repertoire including social interactions. Spontaneous and sensory-evoked activity is present in neonatal barrel cortex and control the generation of the cortical architecture. Half a century after its first description by Woolsey and van der Loos the whisker-to-barrel cortex system with its unique and clear topographic organization still offers the exceptional opportunity to study sensory processing and complex behavior.
Collapse
Affiliation(s)
- Jenq-Wei Yang
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, D-55128 Mainz, Germany
| | - Werner Kilb
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, D-55128 Mainz, Germany
| | - Sergei Kirischuk
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, D-55128 Mainz, Germany
| | - Petr Unichenko
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, D-55128 Mainz, Germany
| | - Maik C Stüttgen
- Institute of Pathophysiology, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, D-55128 Mainz, Germany
| | - Heiko J Luhmann
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, D-55128 Mainz, Germany.
| |
Collapse
|
8
|
Vogt J, Kirischuk S, Unichenko P, Schlüter L, Pelosi A, Endle H, Yang JW, Schmarowski N, Cheng J, Thalman C, Strauss U, Prokudin A, Bharati BS, Aoki J, Chun J, Lutz B, Luhmann HJ, Nitsch R. Synaptic Phospholipid Signaling Modulates Axon Outgrowth via Glutamate-dependent Ca2+-mediated Molecular Pathways. Cereb Cortex 2018; 27:131-145. [PMID: 27909001 PMCID: PMC5939201 DOI: 10.1093/cercor/bhw370] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2015] [Indexed: 12/28/2022] Open
Abstract
Altered synaptic bioactive lipid signaling has been recently shown to augment neuronal excitation in the hippocampus of adult animals by activation of presynaptic LPA2-receptors leading to increased presynaptic glutamate release. Here, we show that this results in higher postsynaptic Ca2+ levels and in premature onset of spontaneous neuronal activity in the developing entorhinal cortex. Interestingly, increased synchronized neuronal activity led to reduced axon growth velocity of entorhinal neurons which project via the perforant path to the hippocampus. This was due to Ca2+-dependent molecular signaling to the axon affecting stabilization of the actin cytoskeleton. The spontaneous activity affected the entire entorhinal cortical network and thus led to reduced overall axon fiber numbers in the mature perforant path that is known to be important for specific memory functions. Our data show that precise regulation of early cortical activity by bioactive lipids is of critical importance for proper circuit formation.
Collapse
Affiliation(s)
- Johannes Vogt
- Institute for Microscopic Anatomy and Neurobiology, University Medical Center, Johannes Gutenberg-University, 55131 Mainz, Germany
| | - Sergei Kirischuk
- Institute of Physiology, University Medical Center, Johannes Gutenberg-University, 55128 Mainz, Germany
| | - Petr Unichenko
- Institute of Physiology, University Medical Center, Johannes Gutenberg-University, 55128 Mainz, Germany
| | - Leslie Schlüter
- Institute for Microscopic Anatomy and Neurobiology, University Medical Center, Johannes Gutenberg-University, 55131 Mainz, Germany
| | - Assunta Pelosi
- Institute for Microscopic Anatomy and Neurobiology, University Medical Center, Johannes Gutenberg-University, 55131 Mainz, Germany
| | - Heiko Endle
- Institute for Microscopic Anatomy and Neurobiology, University Medical Center, Johannes Gutenberg-University, 55131 Mainz, Germany
| | - Jenq-Wei Yang
- Institute of Physiology, University Medical Center, Johannes Gutenberg-University, 55128 Mainz, Germany
| | - Nikolai Schmarowski
- Institute for Microscopic Anatomy and Neurobiology, University Medical Center, Johannes Gutenberg-University, 55131 Mainz, Germany
| | - Jin Cheng
- Institute for Microscopic Anatomy and Neurobiology, University Medical Center, Johannes Gutenberg-University, 55131 Mainz, Germany
| | - Carine Thalman
- Institute for Microscopic Anatomy and Neurobiology, University Medical Center, Johannes Gutenberg-University, 55131 Mainz, Germany
| | - Ulf Strauss
- Institute of Cell Biology and Neurobiology, Charité - Universitätsmedizin, 10119 Berlin, Germany
| | - Alexey Prokudin
- Institute for Microscopic Anatomy and Neurobiology, University Medical Center, Johannes Gutenberg-University, 55131 Mainz, Germany
| | - B Suman Bharati
- Institute for Microscopic Anatomy and Neurobiology, University Medical Center, Johannes Gutenberg-University, 55131 Mainz, Germany
| | - Junken Aoki
- Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Miyagi, 980-8578, Japan
| | - Jerold Chun
- Dorris Neuroscience Center, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Beat Lutz
- Institute of Physiological Chemistry, University Medical Center, Johannes Gutenberg-University, 55128 Mainz, Germany
| | - Heiko J Luhmann
- Institute of Physiology, University Medical Center, Johannes Gutenberg-University, 55128 Mainz, Germany
| | - Robert Nitsch
- Institute for Microscopic Anatomy and Neurobiology, University Medical Center, Johannes Gutenberg-University, 55131 Mainz, Germany
| |
Collapse
|
9
|
Vogt J, Yang JW, Mobascher A, Cheng J, Li Y, Liu X, Baumgart J, Thalman C, Kirischuk S, Unichenko P, Horta G, Radyushkin K, Stroh A, Richers S, Sahragard N, Distler U, Tenzer S, Qiao L, Lieb K, Tüscher O, Binder H, Ferreiros N, Tegeder I, Morris AJ, Gropa S, Nürnberg P, Toliat MR, Winterer G, Luhmann HJ, Huai J, Nitsch R. Molecular cause and functional impact of altered synaptic lipid signaling due to a prg-1 gene SNP. EMBO Mol Med 2016; 8:25-38. [PMID: 26671989 PMCID: PMC4718157 DOI: 10.15252/emmm.201505677] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Loss of plasticity‐related gene 1 (PRG‐1), which regulates synaptic phospholipid signaling, leads to hyperexcitability via increased glutamate release altering excitation/inhibition (E/I) balance in cortical networks. A recently reported SNP in prg‐1 (R345T/mutPRG‐1) affects ~5 million European and US citizens in a monoallelic variant. Our studies show that this mutation leads to a loss‐of‐PRG‐1 function at the synapse due to its inability to control lysophosphatidic acid (LPA) levels via a cellular uptake mechanism which appears to depend on proper glycosylation altered by this SNP. PRG‐1+/− mice, which are animal correlates of human PRG‐1+/mut carriers, showed an altered cortical network function and stress‐related behavioral changes indicating altered resilience against psychiatric disorders. These could be reversed by modulation of phospholipid signaling via pharmacological inhibition of the LPA‐synthesizing molecule autotaxin. In line, EEG recordings in a human population‐based cohort revealed an E/I balance shift in monoallelic mutPRG‐1 carriers and an impaired sensory gating, which is regarded as an endophenotype of stress‐related mental disorders. Intervention into bioactive lipid signaling is thus a promising strategy to interfere with glutamate‐dependent symptoms in psychiatric diseases.
Collapse
Affiliation(s)
- Johannes Vogt
- Institute for Microscopic Anatomy and Neurobiology, University Medical Center, Johannes Gutenberg-University, Mainz, Germany
| | - Jenq-Wei Yang
- Institute for Physiology and Pathophysiology, University Medical Center, Johannes Gutenberg-University, Mainz, Germany
| | - Arian Mobascher
- Department of Psychiatry and Psychotherapy, University Medical Center, Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Jin Cheng
- Institute for Microscopic Anatomy and Neurobiology, University Medical Center, Johannes Gutenberg-University, Mainz, Germany
| | - Yunbo Li
- Institute for Microscopic Anatomy and Neurobiology, University Medical Center, Johannes Gutenberg-University, Mainz, Germany
| | - Xingfeng Liu
- Institute for Microscopic Anatomy and Neurobiology, University Medical Center, Johannes Gutenberg-University, Mainz, Germany
| | - Jan Baumgart
- Institute for Microscopic Anatomy and Neurobiology, University Medical Center, Johannes Gutenberg-University, Mainz, Germany
| | - Carine Thalman
- Institute for Microscopic Anatomy and Neurobiology, University Medical Center, Johannes Gutenberg-University, Mainz, Germany
| | - Sergei Kirischuk
- Institute for Physiology and Pathophysiology, University Medical Center, Johannes Gutenberg-University, Mainz, Germany
| | - Petr Unichenko
- Institute for Physiology and Pathophysiology, University Medical Center, Johannes Gutenberg-University, Mainz, Germany
| | - Guilherme Horta
- Institute for Microscopic Anatomy and Neurobiology, University Medical Center, Johannes Gutenberg-University, Mainz, Germany
| | - Konstantin Radyushkin
- Focus Program Translational Neuroscience (FTN), University Medical Center, Johannes Gutenberg-University, Mainz, Germany
| | - Albrecht Stroh
- Institute for Microscopic Anatomy and Neurobiology, University Medical Center, Johannes Gutenberg-University, Mainz, Germany
| | - Sebastian Richers
- Institute for Microscopic Anatomy and Neurobiology, University Medical Center, Johannes Gutenberg-University, Mainz, Germany
| | - Nassim Sahragard
- Institute for Microscopic Anatomy and Neurobiology, University Medical Center, Johannes Gutenberg-University, Mainz, Germany
| | - Ute Distler
- Focus Program Translational Neuroscience (FTN), University Medical Center, Johannes Gutenberg-University, Mainz, Germany Institute for Immunology, University Medical Center, Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Stefan Tenzer
- Institute for Immunology, University Medical Center, Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Lianyong Qiao
- Institute for Microscopic Anatomy and Neurobiology, University Medical Center, Johannes Gutenberg-University, Mainz, Germany
| | - Klaus Lieb
- Department of Psychiatry and Psychotherapy, University Medical Center, Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Oliver Tüscher
- Department of Psychiatry and Psychotherapy, University Medical Center, Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Harald Binder
- Institute of Medical Biostatistics, Epidemiology and Informatics, University Medical Center, Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Nerea Ferreiros
- Institute of Clinical Pharmacology Goethe-University Hospital, Frankfurt am Main, Germany
| | - Irmgard Tegeder
- Institute of Clinical Pharmacology Goethe-University Hospital, Frankfurt am Main, Germany
| | - Andrew J Morris
- Division of Cardiovascular Medicine, Gill Heart Institute, University of Kentucky, Lexington, KY, USA
| | - Sergiu Gropa
- Department of Neurology, University Medical Center, Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Peter Nürnberg
- Cologne Center for Genomics (CCG), University of Cologne, Cologne, Germany
| | - Mohammad R Toliat
- Cologne Center for Genomics (CCG), University of Cologne, Cologne, Germany
| | - Georg Winterer
- Cologne Center for Genomics (CCG), University of Cologne, Cologne, Germany
| | - Heiko J Luhmann
- Institute for Physiology and Pathophysiology, University Medical Center, Johannes Gutenberg-University, Mainz, Germany
| | - Jisen Huai
- Institute for Microscopic Anatomy and Neurobiology, University Medical Center, Johannes Gutenberg-University, Mainz, Germany
| | - Robert Nitsch
- Institute for Microscopic Anatomy and Neurobiology, University Medical Center, Johannes Gutenberg-University, Mainz, Germany
| |
Collapse
|
10
|
Unichenko P, Kirischuk S, Yang JW, Baumgart J, Roskoden T, Schneider P, Sommer A, Horta G, Radyushkin K, Nitsch R, Vogt J, Luhmann HJ. Plasticity-Related Gene 1 Affects Mouse Barrel Cortex Function via Strengthening of Glutamatergic Thalamocortical Transmission. Cereb Cortex 2016; 26:3260-72. [PMID: 26980613 PMCID: PMC4898676 DOI: 10.1093/cercor/bhw066] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Plasticity-related gene-1 (PRG-1) is a brain-specific protein that modulates glutamatergic synaptic transmission. Here we investigated the functional role of PRG-1 in adolescent and adult mouse barrel cortex both in vitro and in vivo. Compared with wild-type (WT) animals, PRG-1-deficient (KO) mice showed specific behavioral deficits in tests assessing sensorimotor integration and whisker-based sensory discrimination as shown in the beam balance/walking test and sandpaper tactile discrimination test, respectively. At P25-31, spontaneous network activity in the barrel cortex in vivo was higher in KO mice compared with WT littermates, but not at P16-19. At P16-19, sensory evoked cortical responses in vivo elicited by single whisker stimulation were comparable in KO and WT mice. In contrast, at P25-31 evoked responses were smaller in amplitude and longer in duration in WT animals, whereas KO mice revealed no such developmental changes. In thalamocortical slices from KO mice, spontaneous activity was increased already at P16-19, and glutamatergic thalamocortical inputs to Layer 4 spiny stellate neurons were potentiated. We conclude that genetic ablation of PRG-1 modulates already at P16-19 spontaneous and evoked excitability of the barrel cortex, including enhancement of thalamocortical glutamatergic inputs to Layer 4, which distorts sensory processing in adulthood.
Collapse
Affiliation(s)
- Petr Unichenko
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University Mainz, D-55128 Mainz, Germany
| | - Sergei Kirischuk
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University Mainz, D-55128 Mainz, Germany
| | - Jenq-Wei Yang
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University Mainz, D-55128 Mainz, Germany
| | - Jan Baumgart
- Institute for Microanatomy and Neurobiology, University Medical Center of the Johannes Gutenberg University Mainz, Langenbeckstrasse 1, Building 708, D-55131 Mainz, Germany
| | - Thomas Roskoden
- Institute of Anatomy, Otto-von-Guericke-University of Magdeburg, Leipziger Str. 44, D-39120 Magdeburg, Germany
| | - Patrick Schneider
- Institute of Anatomy, Otto-von-Guericke-University of Magdeburg, Leipziger Str. 44, D-39120 Magdeburg, Germany
| | - Angela Sommer
- Institute of Anatomy, Otto-von-Guericke-University of Magdeburg, Leipziger Str. 44, D-39120 Magdeburg, Germany
| | - Guilherme Horta
- Institute for Microanatomy and Neurobiology, University Medical Center of the Johannes Gutenberg University Mainz, Langenbeckstrasse 1, Building 708, D-55131 Mainz, Germany
| | - Konstantin Radyushkin
- Focus Program Translational Neuroscience, University Medical Center of the Johannes Gutenberg-University, Mainz, Germany
| | - Robert Nitsch
- Institute for Microanatomy and Neurobiology, University Medical Center of the Johannes Gutenberg University Mainz, Langenbeckstrasse 1, Building 708, D-55131 Mainz, Germany
| | - Johannes Vogt
- Institute for Microanatomy and Neurobiology, University Medical Center of the Johannes Gutenberg University Mainz, Langenbeckstrasse 1, Building 708, D-55131 Mainz, Germany
| | - Heiko J. Luhmann
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University Mainz, D-55128 Mainz, Germany
| |
Collapse
|
11
|
Unichenko P, Kirischuk S, Luhmann HJ. GABA transporters control GABAergic neurotransmission in the mouse subplate. Neuroscience 2015; 304:217-27. [PMID: 26232716 DOI: 10.1016/j.neuroscience.2015.07.067] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2015] [Revised: 07/10/2015] [Accepted: 07/24/2015] [Indexed: 10/23/2022]
Abstract
The subplate is a transient layer between the cortical plate and intermediate zone in the developing cortex. Thalamo-cortical axons form temporary synapses on subplate neurons (SPns) before invading the cortical plate. Neuronal activity within the subplate is of critical importance for the development of neocortical circuits and architecture. Although both glutamatergic and GABAergic inputs on SPns were reported, short-term plasticity of GABAergic transmission has not been investigated yet. GABAergic postsynaptic currents (GPSCs) were recorded from SPns in coronal neocortical slices prepared from postnatal day 3-4 mice using whole-cell patch-clamp technique. Evoked GPSCs (eGPSCs) elicited by electrical paired-pulse stimulation demonstrated paired-pulse depression at all interstimulus intervals tested. Baclofen, a specific GABAB receptor (GABABR) agonist, reduced eGPSC amplitudes and increased paired-pulse ratio (PPR), suggesting presynaptic location of functional GABABRs. Baclofen-induced effects were alleviated by (2S)-3-[[(1S)-1-(3,4-dichlorophenyl)ethyl]amino-2-hydroxypropyl](phenylmethyl)phosphinic acid (CGP55845), a selective GABABR blocker. Moreover, CGP55845 increased eGPSC amplitudes and decreased PPR even under control conditions, indicating that GABABRs are tonically activated by ambient GABA. Because extracellular GABA concentration is mainly regulated by GABA transporters (GATs), we asked whether GATs release GABA. 1,2,5,6-tetrahydro-1-[2-[[(diphenylmethylene)amino]oxy]ethyl]-3-pyridinecarboxylic acid (NNC-711) (10μM), a selective GAT-1 blocker, increased eGPSC decay time, decreased eGPSC amplitudes and PPR. The two last effects but not the first one were blocked by CGP55845, indicating that GAT-1 blockade causes an elevation of extracellular GABA concentration and in turn activation of extrasynaptic GABAARs and presynaptic GABABRs. 1-[2-[tris(4-methoxyphenyl)methoxy]ethyl]-(S)-3-piperidinecarboxylic acid (SNAP-5114), a specific GAT-2/3 blocker, failed to affect eGPSC kinetics. However, in contrast to NNC-711 SNAP-5114 increased eGPSC amplitudes and decreased PPR. In the presence of SNAP-5114 CGP55845 did not influence GABAergic transmission, indicating that GABABRs are not activated any longer. We conclude that in the subplate GAT-2/3 operates in reverse mode. GABA released via GAT-2/3 activates presynaptic GABABRs on GABAergic synapses and tonically inhibits GABAergic inputs on SPns.
Collapse
Affiliation(s)
- P Unichenko
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, D-55128 Mainz, Germany
| | - S Kirischuk
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, D-55128 Mainz, Germany.
| | - H J Luhmann
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, D-55128 Mainz, Germany
| |
Collapse
|
12
|
Unichenko P, Yang JW, Luhmann HJ, Kirischuk S. Glutamatergic system controls synchronization of spontaneous neuronal activity in the murine neonatal entorhinal cortex. Pflugers Arch 2014; 467:1565-1575. [PMID: 25163767 DOI: 10.1007/s00424-014-1600-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2014] [Revised: 07/16/2014] [Accepted: 08/20/2014] [Indexed: 12/21/2022]
Abstract
Synchronized spontaneous neuronal activity is a characteristic feature of the developing brain. Rhythmic network discharges in the neonatal medial entorhinal cortex (mEC) in vitro depend on activation of ionotropic glutamate receptors, but spontaneously active neurons are required for their initiation. Field potential recordings revealed synchronized neuronal activity in the mEC in vivo developmentally earlier than in vitro. We suggested that not only ionotropic receptors, but also other components of the glutamatergic system modulate neuronal activity in the mEC. Ca(2+) imaging was used to record neuronal activity in neonatal murine brain slices. Two types of spontaneous events were distinguished: global synchronous discharges (synchronous activity) and asynchronously (not synchronized with global discharges) active cells (asynchronous activity). AMPA receptor blockade strongly reduced the frequency of synchronous discharges, while NMDA receptor inhibition was less effective. AMPA and NMDA receptor blockade or activation of group 2/3 metabotropic glutamate receptors (mGluR2/3) completely suppressed synchronous discharges and increased the number of active cells. Blockade of glutamate transporters with DL-TBOA led to NMDA receptor-mediated hyper-synchronization of neuronal activity. Inhibition of NMDA receptors in the presence of DL-TBOA failed to restore synchronous discharges. The latter were partially reestablished only after blockade of mGluR2/3. We conclude that the glutamatergic system can influence neuronal activity via different receptors/mechanisms. As both NMDA and mGluR2/3 receptors have a high affinity for glutamate, changes in extracellular glutamate levels resulting for instance from glutamate transporter malfunction can balance neuronal activity in the mEC, affecting in turn synapse and network formation.
Collapse
Affiliation(s)
- Petr Unichenko
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, 55128, Mainz, Germany
| | - Jeng-Wei Yang
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, 55128, Mainz, Germany
| | - Heiko J Luhmann
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, 55128, Mainz, Germany.
| | - Sergei Kirischuk
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, 55128, Mainz, Germany
| |
Collapse
|
13
|
Unichenko P, Dvorzhak A, Kirischuk S. Transporter-mediated replacement of extracellular glutamate for GABA in the developing murine neocortex. Eur J Neurosci 2013; 38:3580-8. [DOI: 10.1111/ejn.12380] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2013] [Revised: 08/21/2013] [Accepted: 09/03/2013] [Indexed: 11/29/2022]
Affiliation(s)
- Petr Unichenko
- Institute of Physiology; University Medical Center of the Johannes Gutenberg University Mainz; Duesbergweg 6 55128 Mainz Germany
| | - Anton Dvorzhak
- Department of Experimental Neurology; Cluster of Excellence Neurocure; University Medicine Charitè; Berlin Germany
| | - Sergei Kirischuk
- Institute of Physiology; University Medical Center of the Johannes Gutenberg University Mainz; Duesbergweg 6 55128 Mainz Germany
| |
Collapse
|
14
|
Unichenko P, Myakhar O, Kirischuk S. Intracellular Na+ concentration influences short-term plasticity of glutamate transporter-mediated currents in neocortical astrocytes. Glia 2012; 60:605-14. [PMID: 22279011 DOI: 10.1002/glia.22294] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2011] [Accepted: 12/20/2011] [Indexed: 11/10/2022]
Abstract
Fast synaptic transmission requires a rapid clearance of the released neurotransmitter from the extracellular space. Glial glutamate transporters (excitatory amino acid transporters, EAATs) strongly contribute to glutamate removal. In this work, we investigated the paired-pulse plasticity of synaptically activated, glutamate transporter-mediated currents (STCs) in cortical layer 2/3 astrocytes. STCs were elicited by local electrical stimulation in layer 4 in the presence of ionotropic glutamate (AMPA and NMDA), GABAA, and GABAB receptor antagonists. In experiments with low [Na(+)]i (5 mM) intrapipette solution, STCs elicited by paired-pulse stimulation demonstrated paired-pulse facilitation (PPF) at short (<250 ms) interstimulus intervals (ISIs) and paired-pulse depression at longer ISIs. In experiments with close to physiological, high [Na(+)]i (20 mM) intrapipette solution, PPF of STCs at short ISIs was significantly reduced. In addition, the STC kinetics was slowed in the presence of high [Na(+)]i. Exogenous GABA increased astrocytic [Na(+)]i, reduced the mean STC amplitude, decreased PPF at short ISIs, and slowed STC kinetics. All GABA-induced changes were blocked by NO-711 and SNAP-5114, GABA transporter (GATs) antagonists. In experiments with the low intrapipette solution, GAT blockade under control conditions decreased PPF at short ISIs both at room and at near physiological temperatures. Dialysis of single astrocyte with low [Na(+)]i solution increased the amplitude and reduced PPR of evoked field potentials recorded in the vicinity of the astrocyte. We conclude that (1) endogenous GABA via GATs may influence EAAT functioning and (2) astrocytic [Na(+)]i modulates the short-term plasticity of STCs and in turn the efficacy of glutamate removal.
Collapse
Affiliation(s)
- Petr Unichenko
- Institute of Physiology and Pathophysiology, Universal Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
| | | | | |
Collapse
|
15
|
Dvorzhak A, Myakhar O, Unichenko P, Kirmse K, Kirischuk S. Estimation of ambient GABA levels in layer I of the mouse neonatal cortex in brain slices. J Physiol 2010; 588:2351-60. [PMID: 20421290 DOI: 10.1113/jphysiol.2010.187054] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
GABAergic synapses on Cajal-Retzius neurons in layer I of the murine neocortex experience GABA(B) receptor (GABA(B)R)-mediated tonic inhibition. Extracellular GABA concentration ([GABA](o)) that determines the strength of GABA(B)R-mediated inhibition is controlled by GABA transporters (GATs). In this study, we hypothesized that the strength of presynaptic GABA(B)R activation reflects [GABA](o) in the vicinity of synaptic contacts. Slices obtained from two age groups were used, namely postnatal days (P)2-3 and P5-7. GABAergic postsynaptic currents (IPSCs) were recorded using the whole-cell patch-clamp technique. Minimal electrical stimulation in layer I was applied to elicit evoked IPSCs (eIPSCs) using a paired-pulse protocol. Three parameters were selected for comparison: the mean eIPSC amplitude, paired-pulse ratio, and failure rate. When GAT-1 and GAT-2/3 were blocked by NO-711 (10 microM) and SNAP-5114 (40 microM), respectively, no tonic GABA(B)R-mediated inhibition was observed. In order to restore the control levels of GABA(B)R-mediated inhibition, 250 and 125 nm exogenous GABA was required at P2-3 and P5-7, respectively. Addition of 3-mercaptopropionic acid, a glutamate decarboxylase inhibitor, did not significantly change the obtained values arguing against the suggestion that a mechanism different from GATs contributes to [GABA](o) control. We conclude that juxtasynaptic [GABA](o) is higher (about 250 nM) at P2-3 than at P5-7 (about 125 nM). As both radial cell migration and corticogenesis in general are strongly dependent on [GABA](o) and the formation of the last layer 2/3 is finished by P4 in rodents, the observed [GABA](o) reduction in layer I might reflect this crucial event in the cortical development.
Collapse
Affiliation(s)
- Anton Dvorzhak
- Institute of Physiology and Pathophysiology, University Medical Center of the Johannes Gutenberg University, Duesbergweg 6, Mainz, Germany
| | | | | | | | | |
Collapse
|