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Alhourani A, Fish KN, Wozny TA, Sudhakar V, Hamilton RL, Richardson RM. GABA bouton subpopulations in the human dentate gyrus are differentially altered in mesial temporal lobe epilepsy. J Neurophysiol 2019; 123:392-406. [PMID: 31800363 DOI: 10.1152/jn.00523.2018] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Medically intractable temporal lobe epilepsy is a devastating disease, for which surgical removal of the seizure onset zone is the only known cure. Multiple studies have found evidence of abnormal dentate gyrus network circuitry in human mesial temporal lobe epilepsy (MTLE). Principal neurons within the dentate gyrus gate entorhinal input into the hippocampus, providing a critical step in information processing. Crucial to that role are GABA-expressing neurons, particularly parvalbumin (PV)-expressing basket cells (PVBCs) and chandelier cells (PVChCs), which provide strong, temporally coordinated inhibitory signals. Alterations in PVBC and PVChC boutons have been described in epilepsy, but the value of these studies has been limited due to methodological hurdles associated with studying human tissue. We developed a multilabel immunofluorescence confocal microscopy and a custom segmentation algorithm to quantitatively assess PVBC and PVChC bouton densities and to infer relative synaptic protein content in the human dentate gyrus. Using en bloc specimens from MTLE subjects with and without hippocampal sclerosis, paired with nonepileptic controls, we demonstrate the utility of this approach for detecting cell-type specific synaptic alterations. Specifically, we found increased density of PVBC boutons, while PVChC boutons decreased significantly in the dentate granule cell layer of subjects with hippocampal sclerosis compared with matched controls. In contrast, bouton densities for either PV-positive cell type did not differ between epileptic subjects without sclerosis and matched controls. These results may explain conflicting findings from previous studies that have reported both preserved and decreased PV bouton densities and establish a new standard for quantitative assessment of interneuron boutons in epilepsy.NEW & NOTEWORTHY A state-of-the-art, multilabel immunofluorescence confocal microscopy and custom segmentation algorithm technique, developed previously for studying synapses in the human prefrontal cortex, was modified to study the hippocampal dentate gyrus in specimens surgically removed from patients with temporal lobe epilepsy. The authors discovered that chandelier and basket cell boutons in the human dentate gyrus are differentially altered in mesial temporal lobe epilepsy.
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Affiliation(s)
- Ahmad Alhourani
- Department of Neurological Surgery, University of Louisville School of Medicine, Louisville, Kentucky
| | - Kenneth N Fish
- Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Thomas A Wozny
- Department of Neurological Surgery, University of California, San Francisco, California
| | - Vivek Sudhakar
- Department of Neurological Surgery, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Ronald L Hamilton
- Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - R Mark Richardson
- Department of Neurological Surgery, Massachusetts General Hospital, Boston, Massachusetts.,Harvard Medical School, Boston, Massachusetts
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52
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Aeed F, Shnitzer T, Talmon R, Schiller Y. Layer- and Cell-Specific Recruitment Dynamics during Epileptic Seizures In Vivo. Ann Neurol 2019; 87:97-115. [PMID: 31657482 DOI: 10.1002/ana.25628] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2019] [Revised: 10/22/2019] [Accepted: 10/22/2019] [Indexed: 12/29/2022]
Abstract
OBJECTIVE To investigate the network dynamics mechanisms underlying differential initiation of epileptic interictal spikes and seizures. METHODS We performed combined in vivo 2-photon calcium imaging from different targeted neuronal subpopulations and extracellular electrophysiological recordings during 4-aminopyridine-induced neocortical spikes and seizures. RESULTS Both spikes and seizures were associated with intense synchronized activation of excitatory layer 2/3 pyramidal neurons (PNs) and to a lesser degree layer 4 neurons, as well as inhibitory parvalbumin-expressing interneurons (INs). In sharp contrast, layer 5 PNs and somatostatin-expressing INs were gradually and asynchronously recruited into the ictal activity during the course of seizures. Within layer 2/3, the main difference between onset of spikes and seizures lay in the relative recruitment dynamics of excitatory PNs compared to parvalbumin- and somatostatin-expressing inhibitory INs. Whereas spikes exhibited balanced recruitment of PNs and parvalbumin-expressing INs, during seizures IN responses were reduced and less synchronized than in layer 2/3 PNs. Similar imbalance was not observed in layers 4 or 5 of the neocortex. Machine learning-based algorithms we developed were able to distinguish spikes from seizures based solely on activation dynamics of layer 2/3 PNs at discharge onset. INTERPRETATION During onset of seizures, the recruitment dynamics markedly differed between neuronal subpopulations, with rapid synchronous recruitment of layer 2/3 PNs, layer 4 neurons, and parvalbumin-expressing INs and gradual asynchronous recruitment of layer 5 PNs and somatostatin-expressing INs. Seizures initiated in layer 2/3 due to a dynamic mismatch between local PNs and inhibitory INs, and only later spread to layer 5 by gradually and asynchronously recruiting PNs in this layer. ANN NEUROL 2020;87:97-115.
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Affiliation(s)
- Fadi Aeed
- Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
| | - Tal Shnitzer
- Viterbi Faculty of Electrical Engineering, Technion-Israel Institute of Technology, Haifa, Israel
| | - Ronen Talmon
- Viterbi Faculty of Electrical Engineering, Technion-Israel Institute of Technology, Haifa, Israel
| | - Yitzhak Schiller
- Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel.,Department of Neurology, Rambam Medical Center, Haifa, Israel
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53
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Duy PQ, David WB, Kahle KT. Identification of KCC2 Mutations in Human Epilepsy Suggests Strategies for Therapeutic Transporter Modulation. Front Cell Neurosci 2019; 13:515. [PMID: 31803025 PMCID: PMC6873151 DOI: 10.3389/fncel.2019.00515] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2019] [Accepted: 11/01/2019] [Indexed: 11/28/2022] Open
Abstract
Epilepsy is a common neurological disorder characterized by recurrent and unprovoked seizures thought to arise from impaired balance between neuronal excitation and inhibition. Our understanding of the neurophysiological mechanisms that render the brain epileptogenic remains incomplete, reflected by the lack of satisfactory treatments that can effectively prevent epileptic seizures without significant drug-related adverse effects. Type 2 K+-Cl− cotransporter (KCC2), encoded by SLC12A5, is important for chloride homeostasis and neuronal excitability. KCC2 dysfunction attenuates Cl− extrusion and impairs GABAergic inhibition, and can lead to neuronal hyperexcitability. Converging lines of evidence from human genetics have secured the link between KCC2 dysfunction and the development of epilepsy. Here, we review KCC2 mutations in human epilepsy and discuss potential therapeutic strategies based on the functional impact of these mutations. We suggest that a strategy of augmenting KCC2 activity by antagonizing its critical inhibitory phosphorylation sites may be a particularly efficacious method of facilitating Cl− extrusion and restoring GABA inhibition to treat medication-refractory epilepsy and other seizure disorders.
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Affiliation(s)
- Phan Q Duy
- Department of Neurosurgery, Yale University School of Medicine, New Haven, CT, United States.,Medical Scientist Training Program, Yale University School of Medicine, New Haven, CT, United States
| | - Wyatt B David
- Department of Neurosurgery, Yale University School of Medicine, New Haven, CT, United States
| | - Kristopher T Kahle
- Department of Neurosurgery, Yale University School of Medicine, New Haven, CT, United States.,Department of Genetics, Yale University School of Medicine, New Haven, CT, United States.,Departments of Pediatrics and Cellular & Molecular Physiology, Yale University School of Medicine, New Haven, CT, United States.,Yale-Rockefeller NIH Centers for Mendelian Genomics, Yale University, New Haven, CT, United States.,Yale Stem Cell Center, Yale School of Medicine, New Haven, CT, United States
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54
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Zamay TN, Zamay GS, Shnayder NA, Dmitrenko DV, Zamay SS, Yushchenko V, Kolovskaya OS, Susevski V, Berezovski MV, Kichkailo AS. Nucleic Acid Aptamers for Molecular Therapy of Epilepsy and Blood-Brain Barrier Damages. MOLECULAR THERAPY. NUCLEIC ACIDS 2019; 19:157-167. [PMID: 31837605 PMCID: PMC6920299 DOI: 10.1016/j.omtn.2019.10.042] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Revised: 09/30/2019] [Accepted: 10/28/2019] [Indexed: 01/28/2023]
Abstract
Epilepsy is the fourth most prevalent brain disorder affecting millions of people of all ages. Epilepsy is divided into six categories different in etiology and molecular mechanisms; however, their common denominator is the inability to maintain ionic homeostasis. Antiepileptic drugs have a broad spectrum of action and high toxicity to the whole organism. In many cases, they could not penetrate the blood-brain barrier (BBB) and reach corresponding targets. Nucleic acid aptamers are a new and promising class of antiepileptic drugs as they are non-toxic, specific, and able to regulate the permeability of ion channels or inhibit inflammatory proteins. In this review, we summarize the mechanisms of epileptogenesis and its interconnection with the BBB and show the potential of aptamers for antiepileptic treatment.
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Affiliation(s)
- Tatiana N Zamay
- V.F. Voyno-Yasenetsky Krasnoyarsk State Medical University, Krasnoyarsk, Russia
| | - Galina S Zamay
- V.F. Voyno-Yasenetsky Krasnoyarsk State Medical University, Krasnoyarsk, Russia; Federal Research Center, Krasnoyarsk Research Center Siberian Branch of Russian Academy of Science, Krasnoyarsk, Russia
| | - Natalia A Shnayder
- V.M. Bekhterev National Medical Research Center of Psychiatry and Neurology, Saint Petersburg, Russia
| | - Diana V Dmitrenko
- V.F. Voyno-Yasenetsky Krasnoyarsk State Medical University, Krasnoyarsk, Russia
| | - Sergey S Zamay
- Federal Research Center, Krasnoyarsk Research Center Siberian Branch of Russian Academy of Science, Krasnoyarsk, Russia
| | - Victoria Yushchenko
- V.F. Voyno-Yasenetsky Krasnoyarsk State Medical University, Krasnoyarsk, Russia
| | - Olga S Kolovskaya
- V.F. Voyno-Yasenetsky Krasnoyarsk State Medical University, Krasnoyarsk, Russia; Federal Research Center, Krasnoyarsk Research Center Siberian Branch of Russian Academy of Science, Krasnoyarsk, Russia
| | - Vanessa Susevski
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, ON, Canada
| | - Maxim V Berezovski
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, ON, Canada.
| | - Anna S Kichkailo
- V.F. Voyno-Yasenetsky Krasnoyarsk State Medical University, Krasnoyarsk, Russia; Federal Research Center, Krasnoyarsk Research Center Siberian Branch of Russian Academy of Science, Krasnoyarsk, Russia.
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Klorig DC, Alberto GE, Smith T, Godwin DW. Optogenetically-Induced Population Discharge Threshold as a Sensitive Measure of Network Excitability. eNeuro 2019; 6:ENEURO.0229-18.2019. [PMID: 31619450 PMCID: PMC6838688 DOI: 10.1523/eneuro.0229-18.2019] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Revised: 09/06/2019] [Accepted: 09/27/2019] [Indexed: 12/21/2022] Open
Abstract
Network excitability is governed by synaptic efficacy, intrinsic excitability, and the circuitry in which these factors are expressed. The complex interplay between these factors determines how circuits function and, at the extreme, their susceptibility to seizure. We have developed a sensitive, quantitative estimate of network excitability in freely behaving mice using a novel optogenetic intensity-response procedure. Synchronous activation of deep sublayer CA1 pyramidal cells produces abnormal network-wide epileptiform population discharges (PDs) that are nearly indistinguishable from spontaneously-occurring interictal spikes (IISs). By systematically varying light intensity, and therefore the magnitude of the optogenetically-mediated current, we generated intensity-response curves using the probability of PD as the dependent variable. Manipulations known to increase excitability, such as sub-convulsive doses (20 mg/kg) of the chemoconvulsant pentylenetetrazol (PTZ), produced a leftward shift in the curve compared to baseline. The anti-epileptic drug levetiracetam (LEV; 40 mk/kg), in combination with PTZ, produced a rightward shift. Optogenetically-induced PD threshold (oPDT) baselines were stable over time, suggesting the metric is appropriate for within-subject experimental designs with multiple pharmacological manipulations.
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Affiliation(s)
- D C Klorig
- Department of Neurobiology and Anatomy
- Neuroscience Program
| | - G E Alberto
- Department of Neurobiology and Anatomy
- Neuroscience Program
| | - T Smith
- Department of Neurobiology and Anatomy
| | - D W Godwin
- Department of Neurobiology and Anatomy
- Neuroscience Program
- Department of Physiology and Pharmacology, Wake Forest University, Winston-Salem, NC
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56
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Wang S, Lévesque M, Avoli M. Effects of Diazepam and Ketamine on Pilocarpine-Induced Status Epilepticus in Mice. Neuroscience 2019; 421:112-122. [PMID: 31704492 DOI: 10.1016/j.neuroscience.2019.10.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Revised: 10/02/2019] [Accepted: 10/03/2019] [Indexed: 02/07/2023]
Abstract
Status epilepticus (SE) is a life-threatening condition needing immediate care to prevent brain damage. SE with electrographic and behavioral features similar to those seen in humans is reproduced in rodents by i.p. pilocarpine injection, and can be terminated by diazepam and ketamine treatment but only behaviourally, not electrographically. Little is known on the behavioral and EEG effects induced by a delayed administration of ketamine (25 mg/kg) after diazepam (10 mg/kg) or vice versa. Therefore, we analysed behavior and EEG activity recorded from the mouse hippocampal CA3 region before, during SE and after anticonvulsant treatments. In the first group (n = 4), diazepam was administered one hour before ketamine whereas in the second group (n = 4) ketamine was administered one hour before diazepam. The EEG SE did not disappear after each of the two treatments but progressed within 4 h to a pattern of interictal discharges. However, diazepam administration before ketamine significantly shortened the time of behavioral recovery compared to when ketamine was administered before diazepam (p < 0.05). The two protocols were also associated to distinct EEG changes in gamma and high frequency oscillations. In conclusion, although diazepam and ketamine are not effective in stopping EEG SE, diazepam administration one hour before ketamine shortens behavioral recovery in pilocarpine-treated mice.
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Affiliation(s)
- Siyan Wang
- Montreal Neurological Institute and Departments of Neurology & Neurosurgery, and of Physiology, McGill University, 3801 University Street, Montréal, Qc H3A 2B4, Canada
| | - Maxime Lévesque
- Montreal Neurological Institute and Departments of Neurology & Neurosurgery, and of Physiology, McGill University, 3801 University Street, Montréal, Qc H3A 2B4, Canada
| | - Massimo Avoli
- Montreal Neurological Institute and Departments of Neurology & Neurosurgery, and of Physiology, McGill University, 3801 University Street, Montréal, Qc H3A 2B4, Canada.
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57
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Watanabe M, Zhang J, Mansuri MS, Duan J, Karimy JK, Delpire E, Alper SL, Lifton RP, Fukuda A, Kahle KT. Developmentally regulated KCC2 phosphorylation is essential for dynamic GABA-mediated inhibition and survival. Sci Signal 2019; 12:eaaw9315. [PMID: 31615901 PMCID: PMC7219477 DOI: 10.1126/scisignal.aaw9315] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Despite its importance for γ-aminobutyric acid (GABA) inhibition and involvement in neurodevelopmental disease, the regulatory mechanisms of the K+/Cl- cotransporter KCC2 (encoded by SLC12A5) during maturation of the central nervous system (CNS) are not entirely understood. Here, we applied quantitative phosphoproteomics to systematically map sites of KCC2 phosphorylation during CNS development in the mouse. KCC2 phosphorylation at Thr906 and Thr1007, which inhibits KCC2 activity, underwent dephosphorylation in parallel with the GABA excitatory-inhibitory sequence in vivo. Knockin mice expressing the homozygous phosphomimetic KCC2 mutations T906E/T1007E (Kcc2E/E ), which prevented the normal developmentally regulated dephosphorylation of these sites, exhibited early postnatal death from respiratory arrest and a marked absence of cervical spinal neuron respiratory discharges. Kcc2E/E mice also displayed disrupted lumbar spinal neuron locomotor rhythmogenesis and touch-evoked status epilepticus associated with markedly impaired KCC2-dependent Cl- extrusion. These data identify a previously unknown phosphorylation-dependent KCC2 regulatory mechanism during CNS development that is essential for dynamic GABA-mediated inhibition and survival.
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Affiliation(s)
- Miho Watanabe
- Department of Neurophysiology, Hamamatsu University School of Medicine, Hamamatsu, Shizuoka 431-3192, Japan
| | - Jinwei Zhang
- Institute of Biomedical and Clinical Sciences, Medical School, College of Medicine and Health, University of Exeter, Hatherly Laboratories, Exeter EX4 4PS, UK
| | - M Shahid Mansuri
- Department of Neurosurgery, Yale School of Medicine, New Haven, CT 06510, USA
| | - Jingjing Duan
- Human Aging Research Institute, School of Life Sciences, Nanchang University, Nanchang, Jiangxi 330031, China
| | - Jason K Karimy
- Department of Neurosurgery, Yale School of Medicine, New Haven, CT 06510, USA
| | - Eric Delpire
- Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Seth L Alper
- Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA 02215, USA
- The Broad Institute of Harvard and the Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Richard P Lifton
- Laboratory of Human Genetics and Genomics, The Rockefeller University, New York, NY, USA
- Department of Genetics, Yale University School of Medicine, New Haven, CT 06511, USA
| | - Atsuo Fukuda
- Department of Neurophysiology, Hamamatsu University School of Medicine, Hamamatsu, Shizuoka 431-3192, Japan.
- Advanced Research Facilities and Services, Preeminent Medical Photonics Education and Research Center, Hamamatsu University School of Medicine, Hamamatsu, Shizuoka 431-3192, Japan
| | - Kristopher T Kahle
- Departments of Neurosurgery, Pediatrics, and Cellular and Molecular Physiology, Centers for Mendelian Genomics, Yale School of Medicine, New Haven, CT 06510, USA.
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58
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Codadu NK, Graham RT, Burman RJ, Jackson‐Taylor RT, Raimondo JV, Trevelyan AJ, Parrish RR. Divergent paths to seizure-like events. Physiol Rep 2019; 7:e14226. [PMID: 31587522 PMCID: PMC6778598 DOI: 10.14814/phy2.14226] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Revised: 07/29/2019] [Accepted: 07/31/2019] [Indexed: 12/19/2022] Open
Abstract
Much debate exists about how the brain transitions into an epileptic seizure. One source of confusion is that there are likely to be critical differences between experimental seizure models. To address this, we have compared the evolving activity patterns in two widely used in vitro models of epileptic discharges. Brain slices from young adult mice were prepared in the same way and bathed either in 0 Mg2+ or 100 µmol/L 4AP artificial cerebrospinal fluid. We have found that while local field potential recordings of epileptiform discharges in the two models appear broadly similar, patch-clamp analysis reveals an important difference in the relative degree of glutamatergic involvement. 4AP affects parvalbumin-expressing interneurons more than other cortical populations, destabilizing their resting state and inducing spontaneous bursting behavior. Consequently, the most prominent pattern of transient discharge ("interictal event") in this model is almost purely GABAergic, although the transition to seizure-like events (SLEs) involves pyramidal recruitment. In contrast, interictal discharges in 0 Mg2+ are only maintained by a very large glutamatergic component that also involves transient discharges of the interneurons. Seizure-like events in 0 Mg2+ have significantly higher power in the high gamma frequency band (60-120Hz) than these events do in 4AP, and are greatly delayed in onset by diazepam, unlike 4AP events. We, therefore, conclude that the 0 Mg2+ and 4AP models display fundamentally different levels of glutamatergic drive, demonstrating how ostensibly similar pathological discharges can arise from different sources. We contend that similar interpretative issues will also be relevant to clinical practice.
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Affiliation(s)
- Neela K. Codadu
- Institute of NeuroscienceMedical SchoolNewcastle UniversityNewcastle upon TyneUnited Kingdom
| | - Robert T. Graham
- Institute of NeuroscienceMedical SchoolNewcastle UniversityNewcastle upon TyneUnited Kingdom
| | - Richard J. Burman
- Division of Cell BiologyDepartment of Human Biology, Neuroscience Institute and Institute of Infectious Disease and Molecular MedicineFaculty of Health SciencesUniversity of Cape TownCape TownSouth Africa
| | | | - Joseph V. Raimondo
- Division of Cell BiologyDepartment of Human Biology, Neuroscience Institute and Institute of Infectious Disease and Molecular MedicineFaculty of Health SciencesUniversity of Cape TownCape TownSouth Africa
| | - Andrew J. Trevelyan
- Institute of NeuroscienceMedical SchoolNewcastle UniversityNewcastle upon TyneUnited Kingdom
| | - R. Ryley Parrish
- Institute of NeuroscienceMedical SchoolNewcastle UniversityNewcastle upon TyneUnited Kingdom
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59
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Cela E, Sjöström PJ. Novel Optogenetic Approaches in Epilepsy Research. Front Neurosci 2019; 13:947. [PMID: 31551699 PMCID: PMC6743373 DOI: 10.3389/fnins.2019.00947] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Accepted: 08/22/2019] [Indexed: 11/13/2022] Open
Abstract
Epilepsy is a major neurological disorder characterized by repeated seizures afflicting 1% of the global population. The emergence of seizures is associated with several comorbidities and severely decreases the quality of life of patients. Unfortunately, around 30% of patients do not respond to first-line treatment using anti-seizure drugs (ASDs). Furthermore, it is still unclear how seizures arise in the healthy brain. Therefore, it is critical to have well developed models where a causal understanding of epilepsy can be investigated. While the development of seizures has been studied in several animal models, using chemical or electrical induction, deciphering the results of such studies has been difficult due to the uncertainty of the cell population being targeted as well as potential confounds such as brain damage from the procedure itself. Here we describe novel approaches using combinations of optical and genetic methods for studying epileptogenesis. These approaches can circumvent some shortcomings associated with the classical animal models and may thus increase the likelihood of developing new treatment options.
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Affiliation(s)
- Elvis Cela
- Brain Repair and Integrative Neuroscience Program, Centre for Research in Neuroscience, Department of Medicine, Department of Neurology and Neurosurgery, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, QC, Canada.,Integrated Program in Neuroscience, McGill University, Montreal, QC, Canada
| | - Per Jesper Sjöström
- Brain Repair and Integrative Neuroscience Program, Centre for Research in Neuroscience, Department of Medicine, Department of Neurology and Neurosurgery, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, QC, Canada
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60
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Schevon CA, Tobochnik S, Eissa T, Merricks E, Gill B, Parrish RR, Bateman LM, McKhann GM, Emerson RG, Trevelyan AJ. Multiscale recordings reveal the dynamic spatial structure of human seizures. Neurobiol Dis 2019; 127:303-311. [PMID: 30898669 PMCID: PMC6588430 DOI: 10.1016/j.nbd.2019.03.015] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Revised: 03/11/2019] [Accepted: 03/15/2019] [Indexed: 02/07/2023] Open
Abstract
The cellular activity underlying human focal seizures, and its relationship to key signatures in the EEG recordings used for therapeutic purposes, has not been well characterized despite many years of investigation both in laboratory and clinical settings. The increasing use of microelectrodes in epilepsy surgery patients has made it possible to apply principles derived from laboratory research to the problem of mapping the spatiotemporal structure of human focal seizures, and characterizing the corresponding EEG signatures. In this review, we describe results from human microelectrode studies, discuss some data interpretation pitfalls, and explain the current understanding of the key mechanisms of ictogenesis and seizure spread.
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Affiliation(s)
- Catherine A Schevon
- Department of Neurology, Columbia University Medical Center, New York, NY, USA.
| | - Steven Tobochnik
- Department of Neurology, Columbia University Medical Center, New York, NY, USA
| | - Tahra Eissa
- Department of Applied Mathematics, University of Colorado at Boulder, Boulder, CO, USA
| | - Edward Merricks
- Department of Neurology, Columbia University Medical Center, New York, NY, USA
| | - Brian Gill
- Department of Neurological Surgery, Columbia University Medical Center, New York, NY, USA
| | - R Ryley Parrish
- Institute for Aging, Newcastle University, Newcastle-Upon-Tyne, UK
| | - Lisa M Bateman
- Department of Neurology, Columbia University Medical Center, New York, NY, USA
| | - Guy M McKhann
- Department of Neurological Surgery, Columbia University Medical Center, New York, NY, USA
| | - Ronald G Emerson
- Department of Neurology, Weill Cornell Medical Center, New York, NY, USA
| | - Andrew J Trevelyan
- Department of Neurology, Columbia University Medical Center, New York, NY, USA; Institute for Aging, Newcastle University, Newcastle-Upon-Tyne, UK
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61
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Raimondo JV, Dulla C. When a Good Cop Turns Bad: The Pro-Ictal Action of Parvalbumin Expressing Interneurons During Seizures. Epilepsy Curr 2019; 19:256-257. [PMID: 31161789 PMCID: PMC6891828 DOI: 10.1177/1535759719853548] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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62
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de Curtis M, Librizzi L, Uva L, Gnatkovsky V. GABAA receptor-mediated networks during focal seizure onset and progression in vitro. Neurobiol Dis 2019; 125:190-197. [DOI: 10.1016/j.nbd.2019.02.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2018] [Revised: 01/08/2019] [Accepted: 02/07/2019] [Indexed: 02/02/2023] Open
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63
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Phase Coherent Currents Underlying Neocortical Seizure-Like State Transitions. eNeuro 2019; 6:eN-NWR-0426-18. [PMID: 30923739 PMCID: PMC6437657 DOI: 10.1523/eneuro.0426-18.2019] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Revised: 02/25/2019] [Accepted: 03/01/2019] [Indexed: 02/07/2023] Open
Abstract
In the epileptic brain, phase amplitude cross-frequency coupling (CFC) features have been used to objectively classify seizure-related states, and the inter-seizure state has been demonstrated as being random, in contrast to the seizure state being predictable; however, the excitatory and inhibitory networks underlying their dynamics remain unclear. Therefore, the objectives of this study are to classify the dynamics of seizure sub-states labeling seizure-like event (SLE) onset and termination intervals using CFC features and to obtain their underlying excitatory/inhibitory cellular correlates. SLEs were induced in mouse neocortical brain slices using a low-magnesium perfusate, and were recorded in Layer II/III using simultaneous local field potential (LFP) and whole-cell voltage clamp electrodes. Classification of onset and termination of SLE transitions was investigated using CFC features in conjunction with an unsupervised two-state hidden Markov model (HMM). γ-Distributions of their durations indicated that both are predictable. Furthermore, omitting 4 Hz from the HMM classifier switched both SLE sub-states from statistically deterministic to random without changing the dynamics of the SLE state. These results were generalized to 4-aminopyridine (4-AP)-induced SLEs and human seizure traces. Only during these sub-states, both excitatory and inhibitory currents coupled with the field. Where excitatory currents phase locked to a broad range of frequencies between 1 and 12 Hz, inhibitory currents dominantly phase locked at 4 Hz. We conclude that inhibition underlies the predictability of neocortical CFC-defined SLE transition sub-states.
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Parrish RR, Codadu NK, Mackenzie-Gray Scott C, Trevelyan AJ. Feedforward inhibition ahead of ictal wavefronts is provided by both parvalbumin- and somatostatin-expressing interneurons. J Physiol 2019; 597:2297-2314. [PMID: 30784081 PMCID: PMC6462485 DOI: 10.1113/jp277749] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Accepted: 02/19/2019] [Indexed: 12/29/2022] Open
Abstract
Key points There is a rapid interneuronal response to focal activity in cortex, which restrains laterally propagating activity, including spreading epileptiform activity. The interneuronal response involves intense activation of both parvalbumin‐ and somatostatin‐expressing interneurons. Interneuronal bursting is time‐locked to glutamatergic barrages in the pre‐ictal period. Ca2+ imaging using conditional expression of GCaMP6f provides an accurate readout of the evolving firing patterns in both types of interneuron. The activation profiles of the two interneuronal classes are temporally offset, with the parvalbumin population being activated first, and typically, at higher rates.
Abstract Previous work has described powerful restraints on laterally spreading activity in cortical networks, arising from a rapid feedforward interneuronal response to focal activity. This response is particularly prominent ahead of an ictal wavefront. Parvalbumin‐positive interneurons are considered to be critically involved in this feedforward inhibition, but it is not known what role, if any, is provided by somatostatin‐expressing interneurons, which target the distal dendrites of pyramidal cells. We used a combination of electrophysiology and cell class‐specific Ca2+ imaging in mouse brain slices bathed in 0 Mg2+ medium to characterize the activity profiles of pyramidal cells and parvalbumin‐ and somatostatin‐expressing interneurons during epileptiform activation. The GCaMP6f signal strongly correlates with the level of activity for both interneuronal classes. Both interneuronal classes participate in the feedfoward inhibition. This contrasts starkly with the pattern of pyramidal recruitment, which is greatly delayed. During these barrages, both sets of interneurons show intense bursting, at rates up to 300Hz, which is time‐locked to the glutamatergic barrages. The activity of parvalbumin‐expressing interneurons appears to peak early in the pre‐ictal period, and can display depolarizing block during the ictal event. In contrast, somatostatin‐expressing interneuronal activity peaks significantly later, and firing persists throughout the ictal events. Interictal events appear to be very similar to the pre‐ictal period, albeit with slightly lower firing rates. Thus, the inhibitory restraint arises from a coordinated pattern of activity in the two main classes of cortical interneurons. There is a rapid interneuronal response to focal activity in cortex, which restrains laterally propagating activity, including spreading epileptiform activity. The interneuronal response involves intense activation of both parvalbumin‐ and somatostatin‐expressing interneurons. Interneuronal bursting is time‐locked to glutamatergic barrages in the pre‐ictal period. Ca2+ imaging using conditional expression of GCaMP6f provides an accurate readout of the evolving firing patterns in both types of interneuron. The activation profiles of the two interneuronal classes are temporally offset, with the parvalbumin population being activated first, and typically, at higher rates.
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Affiliation(s)
- R Ryley Parrish
- Institute of Neuroscience, Medical School, Framlington Place, Newcastle upon Tyne, NE2 4HH, UK
| | - Neela K Codadu
- Institute of Neuroscience, Medical School, Framlington Place, Newcastle upon Tyne, NE2 4HH, UK
| | | | - Andrew J Trevelyan
- Institute of Neuroscience, Medical School, Framlington Place, Newcastle upon Tyne, NE2 4HH, UK
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Magloire V, Cornford J, Lieb A, Kullmann DM, Pavlov I. KCC2 overexpression prevents the paradoxical seizure-promoting action of somatic inhibition. Nat Commun 2019; 10:1225. [PMID: 30874549 PMCID: PMC6420604 DOI: 10.1038/s41467-019-08933-4] [Citation(s) in RCA: 58] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2018] [Accepted: 02/01/2019] [Indexed: 11/09/2022] Open
Abstract
Although cortical interneurons are apparently well-placed to suppress seizures, several recent reports have highlighted a paradoxical role of perisomatic-targeting parvalbumin-positive (PV+) interneurons in ictogenesis. Here, we use an acute in vivo model of focal cortical seizures in awake behaving mice, together with closed-loop optogenetic manipulation of PV+ interneurons, to investigate their function during seizures. We show that photo-depolarization of PV+ interneurons rapidly switches from an anti-ictal to a pro-ictal effect within a few seconds of seizure initiation. The pro-ictal effect of delayed photostimulation of PV+ interneurons was not shared with dendrite-targeting somatostatin-positive (SOM+) interneurons. We also show that this switch can be prevented by overexpression of the neuronal potassium-chloride co-transporter KCC2 in principal cortical neurons. These results suggest that strategies aimed at improving the ability of principal neurons to maintain a trans-membrane chloride gradient in the face of excessive network activity can prevent interneurons from contributing to seizure perpetuation.
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Affiliation(s)
- Vincent Magloire
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, University College London, London, WC1N 3BG, UK.
| | - Jonathan Cornford
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, University College London, London, WC1N 3BG, UK
| | - Andreas Lieb
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, University College London, London, WC1N 3BG, UK
| | - Dimitri M Kullmann
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, University College London, London, WC1N 3BG, UK
| | - Ivan Pavlov
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, University College London, London, WC1N 3BG, UK.
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Codadu NK, Parrish RR, Trevelyan AJ. Region-specific differences and areal interactions underlying transitions in epileptiform activity. J Physiol 2019; 597:2079-2096. [PMID: 30681139 PMCID: PMC6441889 DOI: 10.1113/jp277267] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2018] [Accepted: 01/23/2019] [Indexed: 11/10/2022] Open
Abstract
Key points Local neocortical and hippocampal territories show different and sterotypical patterns of acutely evolving, epileptiform activity. Neocortical and entorhinal networks show tonic–clonic‐like events, but the main hippocampal territories do not, unless it is relayed from the other areas. Transitions in the pattern of locally recorded epileptiform activity can be indicative of a shift in the source of pathological activity, and may spread through both synaptic and non‐synaptic means. Hippocampal epileptiform activity is promoted by 4‐aminopyridine and inhibited by GABAB receptor agonists, and appears far more sensitive to these drugs than neocortical activity. These signature features of local epileptiform activity can provide useful insight into the primary source of ictal activity, aiding both experimental and clinical investigation.
Abstract Understanding the nature of epileptic state transitions remains a major goal for epilepsy research. Simple in vitro models offer unique experimental opportunities that we exploit to show that such transitions can arise from shifts in the ictal source of the activity. These transitions reflect the fact that cortical territories differ both in the type of epileptiform activity they can sustain and in their susceptibility to drug manipulation. In the zero‐Mg2+ model, the earliest epileptiform activity is restricted to neocortical and entorhinal networks. Hippocampal bursting only starts much later, and triggers a marked transition in neo‐/entorhinal cortical activity. Thereafter, the hippocampal activity acts as a pacemaker, entraining the other territories to their discharge pattern. This entrainment persists following transection of the major axonal pathways between hippocampus and cortex, indicating that it can be mediated through a non‐synaptic route. Neuronal discharges are associated with large rises in extracellular [K+], but we show that these are very localized, and therefore are not the means of entraining distant cortical areas. We conclude instead that the entrainment occurs through weak field effects distant from the pacemaker, but which are highly effective at recruiting other brain territories that are already hyperexcitable. The hippocampal epileptiform activity appears unusually susceptible to drugs that impact on K+ conductances. These findings demonstrate that the local circuitry gives rise to stereotypical epileptic activity patterns, but these are also influenced by both synaptic and non‐synaptic long‐range effects. Our results have important implications for our understanding of epileptic propagation and anti‐epileptic drug action. Local neocortical and hippocampal territories show different and sterotypical patterns of acutely evolving, epileptiform activity. Neocortical and entorhinal networks show tonic–clonic‐like events, but the main hippocampal territories do not, unless it is relayed from the other areas. Transitions in the pattern of locally recorded epileptiform activity can be indicative of a shift in the source of pathological activity, and may spread through both synaptic and non‐synaptic means. Hippocampal epileptiform activity is promoted by 4‐aminopyridine and inhibited by GABAB receptor agonists, and appears far more sensitive to these drugs than neocortical activity. These signature features of local epileptiform activity can provide useful insight into the primary source of ictal activity, aiding both experimental and clinical investigation.
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Affiliation(s)
- Neela K Codadu
- Institute of Neuroscience, Medical School, Framlington Place, Newcastle upon Tyne, NE2 4HH, UK
| | - R Ryley Parrish
- Institute of Neuroscience, Medical School, Framlington Place, Newcastle upon Tyne, NE2 4HH, UK
| | - Andrew J Trevelyan
- Institute of Neuroscience, Medical School, Framlington Place, Newcastle upon Tyne, NE2 4HH, UK.,Department of Neurology, Columbia University, New York, NY, 10032, USA
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Long-Term, Targeted Delivery of GDNF from Encapsulated Cells Is Neuroprotective and Reduces Seizures in the Pilocarpine Model of Epilepsy. J Neurosci 2019; 39:2144-2156. [PMID: 30665947 DOI: 10.1523/jneurosci.0435-18.2018] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2018] [Revised: 11/14/2018] [Accepted: 12/14/2018] [Indexed: 12/19/2022] Open
Abstract
Neurotrophic factors are candidates for treating epilepsy, but their development has been hampered by difficulties in achieving stable and targeted delivery of efficacious concentrations within the desired brain region. We have developed an encapsulated cell technology that overcomes these obstacles by providing a targeted, continuous, de novo synthesized source of high levels of neurotrophic molecules from human clonal ARPE-19 cells encapsulated into hollow fiber membranes. Here we illustrate the potential of this approach for delivering glial cell line-derived neurotrophic factor (GDNF) directly to the hippocampus of epileptic rats. In vivo studies demonstrated that bilateral intrahippocampal implants continued to secrete GDNF that produced high hippocampal GDNF tissue levels in a long-term manner. Identical implants robustly reduced seizure frequency in the pilocarpine model. Seizures were reduced rapidly, and this effect increased in magnitude over 3 months, ultimately leading to a reduction of seizures by 93%. This effect persisted even after device removal, suggesting potential disease-modifying benefits. Importantly, seizure reduction was associated with normalized changes in anxiety and improved cognitive performance. Immunohistochemical analyses revealed that the neurological benefits of GDNF were associated with the normalization of anatomical alterations accompanying chronic epilepsy, including hippocampal atrophy, cell degeneration, loss of parvalbumin-positive interneurons, and abnormal neurogenesis. These effects were associated with the activation of GDNF receptors. All in all, these results support the concept that the implantation of encapsulated GDNF-secreting cells can deliver GDNF in a sustained, targeted, and efficacious manner, paving the way for continuing preclinical evaluation and eventual clinical translation of this approach for epilepsy.SIGNIFICANCE STATEMENT Epilepsy is one of the most common neurological conditions, affecting millions of individuals of all ages. These patients experience debilitating seizures that frequently increase over time and can associate with significant cognitive decline and psychiatric disorders that are generally poorly controlled by pharmacotherapy. We have developed a clinically validated, implantable cell encapsulation system that delivers high and consistent levels of GDNF directly to the brain. In epileptic animals, this system produced a progressive and permanent reduction (>90%) in seizure frequency. These benefits were accompanied by improvements in cognitive and anxiolytic behavior and the normalization of changes in CNS anatomy that underlie chronic epilepsy. Together, these data suggest a novel means of tackling the frequently intractable neurological consequences of this devastating disorder.
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68
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Spatial propagation of interictal discharges along the cortex. Biochem Biophys Res Commun 2018; 508:1245-1251. [PMID: 30563766 DOI: 10.1016/j.bbrc.2018.12.070] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Accepted: 12/11/2018] [Indexed: 11/22/2022]
Abstract
Interictal discharges (IIDs) accompany epileptic seizures and highlight the mechanisms of pathological activity. The propagation of IIDs along the neural tissue is not well understood. To simulate IID propagation, this study proposes a new mathematical model that uses the conductance-based refractory density approach for glutamatergic and GABAergic neuronal populations. The mathematical model is found to be consistent with experimental double-patch registrations in the 4-aminopyridine in vitro model of epilepsy. In slices, the spontaneous activity of interneurons leads to their synchronization by means of the depolarizing GABAmediated response, thus initiating IIDs. Modeling reveals a clustering of interneuronal synchronization followed by IIDs with activity fronts that propagate along the cortex. The GABA-mediated depolarization either remains to be subthreshold for the principal neurons and thus results in pure GABAergic IIDs (IID1s) or leads to glutamatergic excitation, thus resulting in another type of IIDs (IID2s). In both the model and experiment, IIDs propagate as waves, with constant activity profiles and velocity. The speed of IIDs is of the order of tens of mm/s and is larger for IID2s than for IID1s (40 and 20 mm/s, respectively). The simulations, consistent with experimental observations, show that the wavelike propagation of IIDs initiated by interneurons is determined by local synaptic connectivity under the conditions of depolarizing GABA.
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69
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Wang Y, Wang Y, Chen Z. Double-edged GABAergic synaptic transmission in seizures: The importance of chloride plasticity. Brain Res 2018; 1701:126-136. [PMID: 30201259 DOI: 10.1016/j.brainres.2018.09.008] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Revised: 09/04/2018] [Accepted: 09/06/2018] [Indexed: 12/18/2022]
Abstract
GABAergic synaptic inhibition, which is a critical regulator of neuronal excitability, is closely involved in epilepsy. Interestingly, fast GABAergic transmission mediated by Cl- permeable GABAA receptors can bi-directionally exert both seizure-suppressing and seizure-promoting actions. Accumulating evidence suggests that chloride plasticity, the driving force of GABAA receptor-mediated synaptic transmission, contributes to the double-edged role of GABAergic synapses in seizures. Large amounts of Cl- influx can overwhelm Cl- extrusion during seizures not only in healthy tissue in a short-term "activity-dependent" manner, but also in chronic epilepsy in a long-term, irreversible "pathology-dependent" manner related to the dysfunction of two chloride transporters: the chloride importer NKCC1 and the chloride exporter KCC2. In this review, we address the importance of chloride plasticity for the "activity-dependent" and "pathology-dependent" mechanisms underlying epileptic events and provide possible directions for further research, which may be clinically important for the design of GABAergic synapse-targeted precise therapeutic interventions for epilepsy.
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Affiliation(s)
- Ying Wang
- Institute of Pharmacology & Toxicology, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China
| | - Yi Wang
- Institute of Pharmacology & Toxicology, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China
| | - Zhong Chen
- Institute of Pharmacology & Toxicology, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China; Epilepsy Center, Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China.
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70
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Magloire V, Mercier MS, Kullmann DM, Pavlov I. GABAergic Interneurons in Seizures: Investigating Causality With Optogenetics. Neuroscientist 2018; 25:344-358. [PMID: 30317911 PMCID: PMC6745605 DOI: 10.1177/1073858418805002] [Citation(s) in RCA: 58] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Seizures are complex pathological network events characterized by excessive and
hypersynchronized activity of neurons, including a highly diverse population of
GABAergic interneurons. Although the primary function of inhibitory interneurons
under normal conditions is to restrain excitation in the brain, this system
appears to fail intermittently, allowing runaway excitation. Recent developments
in optogenetics, combined with genetic tools and advanced electrophysiological
and imaging techniques, allow us for the first time to assess the causal roles
of identified cell-types in network dynamics. While these methods have greatly
increased our understanding of cortical microcircuits in epilepsy, the roles
played by individual GABAergic cell-types in controlling ictogenesis remain
incompletely resolved. Indeed, the ability of interneurons to suppress epileptic
discharges varies across different subtypes, and an accumulating body of
evidence paradoxically implicates some interneuron subtypes in the initiation
and maintenance of epileptiform activity. Here, we bring together findings from
this growing field and discuss what can be inferred regarding the causal role of
different GABAergic cell-types in seizures.
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Affiliation(s)
- Vincent Magloire
- Department of Clinical and Experimental Epilepsy, Institute of Neurology, UCL, London, UK
| | - Marion S Mercier
- Department of Clinical and Experimental Epilepsy, Institute of Neurology, UCL, London, UK
| | - Dimitri M Kullmann
- Department of Clinical and Experimental Epilepsy, Institute of Neurology, UCL, London, UK
| | - Ivan Pavlov
- Department of Clinical and Experimental Epilepsy, Institute of Neurology, UCL, London, UK
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71
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Moore YE, Deeb TZ, Chadchankar H, Brandon NJ, Moss SJ. Potentiating KCC2 activity is sufficient to limit the onset and severity of seizures. Proc Natl Acad Sci U S A 2018; 115:10166-10171. [PMID: 30224498 PMCID: PMC6176565 DOI: 10.1073/pnas.1810134115] [Citation(s) in RCA: 70] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The type 2 K+/Cl- cotransporter (KCC2) allows neurons to maintain low intracellular levels of Cl-, a prerequisite for efficient synaptic inhibition. Reductions in KCC2 activity are evident in epilepsy; however, whether these deficits directly contribute to the underlying pathophysiology remains controversial. To address this issue, we created knock-in mice in which threonines 906 and 1007 within KCC2 have been mutated to alanines (KCC2-T906A/T1007A), which prevents its phospho-dependent inactivation. The respective mice appeared normal and did not show any overt phenotypes, and basal neuronal excitability was unaffected. KCC2-T906A/T1007A mice exhibited increased basal neuronal Cl- extrusion, without altering total or plasma membrane accumulation of KCC2. Critically, activity-induced deficits in synaptic inhibition were reduced in the mutant mice. Consistent with this, enhanced KCC2 was sufficient to limit chemoconvulsant-induced epileptiform activity. Furthermore, this increase in KCC2 function mitigated induction of aberrant high-frequency activity during seizures, highlighting depolarizing GABA as a key contributor to the pathological neuronal synchronization seen in epilepsy. Thus, our results demonstrate that potentiating KCC2 represents a therapeutic strategy to alleviate seizures.
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Affiliation(s)
- Yvonne E Moore
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, WC1E 6BT, United Kingdom
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA 02111
| | - Tarek Z Deeb
- AstraZeneca-Tufts University Laboratory for Basic and Translational Neuroscience Research, Tufts University School of Medicine, Boston, MA 02111
| | - Heramb Chadchankar
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA 02111
| | - Nicholas J Brandon
- AstraZeneca-Tufts University Laboratory for Basic and Translational Neuroscience Research, Tufts University School of Medicine, Boston, MA 02111
- Neuroscience, IMED Biotech Unit, AstraZeneca, Boston, MA 02451
| | - Stephen J Moss
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, WC1E 6BT, United Kingdom;
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA 02111
- AstraZeneca-Tufts University Laboratory for Basic and Translational Neuroscience Research, Tufts University School of Medicine, Boston, MA 02111
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Camporeze B, Manica BA, Bonafé GA, Ferreira JJC, Diniz AL, de Oliveira CTP, Mathias Junior LR, de Aguiar PHP, Ortega MM. Optogenetics: the new molecular approach to control functions of neural cells in epilepsy, depression and tumors of the central nervous system. Am J Cancer Res 2018; 8:1900-1918. [PMID: 30416844 PMCID: PMC6220144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Accepted: 09/14/2018] [Indexed: 06/09/2023] Open
Abstract
The optogenetic tools have been described as valuable techniques to study neural activity through light stimulation, as well as potential neuromodulator approaches in the management of several central nervous system (CNS) diseases. Since the first bacteriorhodopsin protein described as a single-component light-activated regulator of transmembrane ion flow description, in 1980's, the focus has been on channel proteins for neurobiology; however, the advances in engineering techniques showed involvement changes in cellular biological behavior in several types of proteins involved in cell cytoskeleton regulation, motility and gene expression. Although the use of this technology has been published in many papers, a question still remains regarding real results and potential clinical applicability in CNS diseases, as well as the publications scarcity that systematically analyses the published results. Lastly, the aim of this review is to discuss the experimental results, molecular mechanisms and potential clinical applications of optogenetic tools in epilepsy and depression treatment, as well as its applicability in the treatment of CNS tumors.
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Affiliation(s)
- Bruno Camporeze
- Postgraduate Program in Health Science, Laboratory of Cellular and Molecular Biology and Bioactive Compounds, São Francisco University (USF)Bragança Paulista-SP, Brazil
- Postgraduate Program in Health Science, Department of Neurosurgery, Institute of Medical Assistance of The State Public Servant (IAMSPE)São Paulo-SP, Brazil
| | - Bruno Alcântara Manica
- Departament of Neurology, Medical School University Pontifical University Catholic of São Paulo (PUCSP)Sorocaba-SP, Brazil
| | - Gabriel Alves Bonafé
- Postgraduate Program in Health Science, Laboratory of Cellular and Molecular Biology and Bioactive Compounds, São Francisco University (USF)Bragança Paulista-SP, Brazil
| | | | - Aurélio Lourenço Diniz
- Departament of Neurology, Medical School University Pontifical University Catholic of São Paulo (PUCSP)Sorocaba-SP, Brazil
| | | | | | - Paulo Henrique Pires de Aguiar
- Postgraduate Program in Health Science, Department of Neurosurgery, Institute of Medical Assistance of The State Public Servant (IAMSPE)São Paulo-SP, Brazil
- Departament of Neurology, Medical School University Pontifical University Catholic of São Paulo (PUCSP)Sorocaba-SP, Brazil
- Departament of Neurosurgery, Hospital Santa PaulaSão Paulo-SP, Brazil
- Department of Research and Innovation, Laboratory of Cellular and Molecular Biology, Medical School of ABC (FMABC)Santo André-SP, Brazil
| | - Manoela Marques Ortega
- Postgraduate Program in Health Science, Laboratory of Cellular and Molecular Biology and Bioactive Compounds, São Francisco University (USF)Bragança Paulista-SP, Brazil
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Cǎlin A, Stancu M, Zagrean AM, Jefferys JGR, Ilie AS, Akerman CJ. Chemogenetic Recruitment of Specific Interneurons Suppresses Seizure Activity. Front Cell Neurosci 2018; 12:293. [PMID: 30233328 PMCID: PMC6134067 DOI: 10.3389/fncel.2018.00293] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Accepted: 08/16/2018] [Indexed: 12/22/2022] Open
Abstract
Current anti-epileptic medications that boost synaptic inhibition are effective in reducing several types of epileptic seizure activity. Nevertheless, these drugs can generate significant side-effects and even paradoxical responses due to the broad nature of their action. Recently developed chemogenetic techniques provide the opportunity to pharmacologically recruit endogenous inhibitory mechanisms in a selective and circuit-specific manner. Here, we use chemogenetics to assess the potential of suppressing epileptiform activity by enhancing the synaptic output from three major interneuron populations in the rodent hippocampus: parvalbumin (PV), somatostatin (SST), and vasoactive intestinal peptide (VIP) expressing interneurons. To target different neuronal populations, promoter-specific cre-recombinase mice were combined with viral-mediated delivery of chemogenetic constructs. Targeted electrophysiological recordings were then conducted in an in vitro model of chronic, drug-resistant epilepsy. In addition, behavioral video-scoring was performed in an in vivo model of acutely triggered seizure activity. Pre-synaptic and post-synaptic whole cell recordings in brain slices revealed that each of the three interneuron types increase their firing rate and synaptic output following chemogenetic activation. However, the interneuron populations exhibited different effects on epileptiform discharges. Recruiting VIP interneurons did not change the total duration of epileptiform discharges. In contrast, recruiting SST or PV interneurons produced robust suppression of epileptiform synchronization. PV interneurons exhibited the strongest effect per cell, eliciting at least a fivefold greater reduction in epileptiform activity than the other cell types. Consistent with this, we found that in vivo chemogenetic recruitment of PV interneurons suppressed convulsive behaviors by more than 80%. Our findings support the idea that selective chemogenetic enhancement of inhibitory synaptic pathways offers potential as an anti-seizure strategy.
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Affiliation(s)
- Alexandru Cǎlin
- Department of Pharmacology, University of Oxford, Oxford, United Kingdom
| | - Mihai Stancu
- Division of Physiology and Neuroscience, Department of Functional Sciences, Carol Davila University of Medicine and Pharmacy, Bucharest, Romania
| | - Ana-Maria Zagrean
- Division of Physiology and Neuroscience, Department of Functional Sciences, Carol Davila University of Medicine and Pharmacy, Bucharest, Romania
| | | | - Andrei S. Ilie
- Department of Pharmacology, University of Oxford, Oxford, United Kingdom
| | - Colin J. Akerman
- Department of Pharmacology, University of Oxford, Oxford, United Kingdom
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Christenson Wick Z, Krook-Magnuson E. Specificity, Versatility, and Continual Development: The Power of Optogenetics for Epilepsy Research. Front Cell Neurosci 2018; 12:151. [PMID: 29962936 PMCID: PMC6010559 DOI: 10.3389/fncel.2018.00151] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2018] [Accepted: 05/15/2018] [Indexed: 12/19/2022] Open
Abstract
Optogenetics is a powerful and rapidly expanding set of techniques that use genetically encoded light sensitive proteins such as opsins. Through the selective expression of these exogenous light-sensitive proteins, researchers gain the ability to modulate neuronal activity, intracellular signaling pathways, or gene expression with spatial, directional, temporal, and cell-type specificity. Optogenetics provides a versatile toolbox and has significantly advanced a variety of neuroscience fields. In this review, using recent epilepsy research as a focal point, we highlight how the specificity, versatility, and continual development of new optogenetic related tools advances our understanding of neuronal circuits and neurological disorders. We additionally provide a brief overview of some currently available optogenetic tools including for the selective expression of opsins.
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Affiliation(s)
- Zoé Christenson Wick
- Graduate Program in Neuroscience and Department of Neuroscience, University of Minnesota, Minneapolis, MN, United States
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75
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Interneurons and the Ictal Orchestra. Epilepsy Curr 2018; 18:184-186. [DOI: 10.5698/1535-7597.18.3.184] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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76
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On the origin of epileptic High Frequency Oscillations observed on clinical electrodes. Clin Neurophysiol 2018; 129:829-841. [DOI: 10.1016/j.clinph.2018.01.062] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Revised: 01/04/2018] [Accepted: 01/15/2018] [Indexed: 11/18/2022]
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77
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Parrish RR, Trevelyan AJ. Stress-testing the brain to understand its breaking points. J Physiol 2018; 596:2033-2034. [PMID: 29604061 PMCID: PMC5983151 DOI: 10.1113/jp276184] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Affiliation(s)
- R Ryley Parrish
- Institute of Neuroscience, Medical School, Framlington Place, Newcastle upon Tyne, NE2 4HH, UK
| | - Andrew J Trevelyan
- Institute of Neuroscience, Medical School, Framlington Place, Newcastle upon Tyne, NE2 4HH, UK
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Parrish RR, Grady J, Codadu NK, Trevelyan AJ, Racca C. Simultaneous profiling of activity patterns in multiple neuronal subclasses. J Neurosci Methods 2018; 303:16-29. [PMID: 29588195 DOI: 10.1016/j.jneumeth.2018.03.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Revised: 02/20/2018] [Accepted: 03/23/2018] [Indexed: 10/17/2022]
Abstract
BACKGROUND Neuronal networks typically comprise heterogeneous populations of neurons. A core objective when seeking to understand such networks, therefore, is to identify what roles these different neuronal classes play. Acquiring single cell electrophysiology data for multiple cell classes can prove to be a large and daunting task. Alternatively, Ca2+ network imaging provides activity profiles of large numbers of neurons simultaneously, but without distinguishing between cell classes. NEW METHOD We therefore developed a strategy for combining cellular electrophysiology, Ca2+ network imaging, and immunohistochemistry to provide activity profiles for multiple cell classes at once. This involves cross-referencing easily identifiable landmarks between imaging of the live and fixed tissue, and then using custom MATLAB functions to realign the two imaging data sets, to correct for distortions of the tissue introduced by the fixation or immunohistochemical processing. RESULTS We illustrate the methodology for analyses of activity profiles during epileptiform events recorded in mouse brain slices. We further demonstrate the activity profile of a population of parvalbumin-positive interneurons prior, during, and following a seizure-like event. COMPARISON WITH EXISTING METHODS Current approaches to Ca2+ network imaging analyses are severely limited in their ability to subclassify neurons, and often rely on transgenic approaches to identify cell classes. In contrast, our methodology is a generic, affordable, and flexible technique to characterize neuronal behaviour with respect to classification based on morphological and neurochemical identity. CONCLUSIONS We present a new approach for analysing Ca2+ network imaging datasets, and use this to explore the parvalbumin-positive interneuron activity during epileptiform events.
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Affiliation(s)
- R Ryley Parrish
- Institute of Neuroscience, Medical School, Framlington Place, Newcastle upon Tyne, NE2 4HH, UK
| | - John Grady
- Institute of Neuroscience, Medical School, Framlington Place, Newcastle upon Tyne, NE2 4HH, UK; Kinghorn Centre for Clinical Genomics, Garvan Institute, 384 Victoria Street, Darlinghurst, Sydney, NSW, 2010, Australia
| | - Neela K Codadu
- Institute of Neuroscience, Medical School, Framlington Place, Newcastle upon Tyne, NE2 4HH, UK
| | - Andrew J Trevelyan
- Institute of Neuroscience, Medical School, Framlington Place, Newcastle upon Tyne, NE2 4HH, UK.
| | - Claudia Racca
- Institute of Neuroscience, Medical School, Framlington Place, Newcastle upon Tyne, NE2 4HH, UK.
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79
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Di Cristo G, Awad PN, Hamidi S, Avoli M. KCC2, epileptiform synchronization, and epileptic disorders. Prog Neurobiol 2018; 162:1-16. [DOI: 10.1016/j.pneurobio.2017.11.002] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Revised: 11/09/2017] [Accepted: 11/28/2017] [Indexed: 12/31/2022]
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Bohannon AS, Hablitz JJ. Optogenetic dissection of roles of specific cortical interneuron subtypes in GABAergic network synchronization. J Physiol 2018; 596:901-919. [PMID: 29274075 PMCID: PMC5830415 DOI: 10.1113/jp275317] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Accepted: 12/13/2017] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS An increase in the excitability of GABAergic cells has typically been assumed to decrease network activity, potentially producing overall anti-epileptic effects. Recent data suggest that inhibitory networks may actually play a role in initiating epileptiform activity. We show that activation of GABAergic interneurons can elicit synchronous long-lasting network activity. Specific interneuron subpopulations differentially contributed to GABA network synchrony, indicating cell type-specific contributions of interneurons to cortical network activity. Interneurons may critically contribute to the generation of aberrant network activity characteristic of epilepsy, warranting further investigation into the contribution of distinct cortical interneuron subpopulations to the propagation and rhythmicity of epileptiform activity. ABSTRACT In the presence of the A-type K+ channel blocker 4-aminopyrdine, spontaneous synchronous network activity develops in the neocortex of mice of either sex. This aberrant synchrony persists in the presence of excitatory amino acid receptor antagonists (EAA blockers) and is considered to arise from synchronous firing of cortical interneurons (INs). Although much attention has been given to the mechanisms underlying this GABAergic synchrony, the contribution of specific IN subtypes to the generation of these long-lasting discharges (LLDs) is incompletely understood. We employed genetically-encoded channelrhodopsin and archaerhodopsin opsins to investigate the sufficiency and necessity, respectively, of activation of parvalbumin (PV), somatostatin (SST) and vasointestinal peptide (VIP)-expressing INs for the generation of synchronous neocortical GABAergic discharges. We found light-induced activation of PV or SST INs to be equally sufficient for the generation of LLDs, whereas activation of VIP INs was not. By contrast, light-induced inhibition of PV INs strongly reduced LLD initiation, whereas suppression of SST or VIP IN activity only partially attenuated LLD magnitude. These results suggest neocortical INs perform cell type-specific roles in the generation of aberrant GABAergic cortical network activity.
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Affiliation(s)
- Andrew S. Bohannon
- Department of NeurobiologyUniversity of Alabama at BirminghamBirminghamALUSA
| | - John J. Hablitz
- Department of NeurobiologyUniversity of Alabama at BirminghamBirminghamALUSA
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81
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Klein P, Dingledine R, Aronica E, Bernard C, Blümcke I, Boison D, Brodie MJ, Brooks-Kayal AR, Engel J, Forcelli PA, Hirsch LJ, Kaminski RM, Klitgaard H, Kobow K, Lowenstein DH, Pearl PL, Pitkänen A, Puhakka N, Rogawski MA, Schmidt D, Sillanpää M, Sloviter RS, Steinhäuser C, Vezzani A, Walker MC, Löscher W. Commonalities in epileptogenic processes from different acute brain insults: Do they translate? Epilepsia 2018; 59:37-66. [PMID: 29247482 PMCID: PMC5993212 DOI: 10.1111/epi.13965] [Citation(s) in RCA: 189] [Impact Index Per Article: 31.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/01/2017] [Indexed: 12/12/2022]
Abstract
The most common forms of acquired epilepsies arise following acute brain insults such as traumatic brain injury, stroke, or central nervous system infections. Treatment is effective for only 60%-70% of patients and remains symptomatic despite decades of effort to develop epilepsy prevention therapies. Recent preclinical efforts are focused on likely primary drivers of epileptogenesis, namely inflammation, neuron loss, plasticity, and circuit reorganization. This review suggests a path to identify neuronal and molecular targets for clinical testing of specific hypotheses about epileptogenesis and its prevention or modification. Acquired human epilepsies with different etiologies share some features with animal models. We identify these commonalities and discuss their relevance to the development of successful epilepsy prevention or disease modification strategies. Risk factors for developing epilepsy that appear common to multiple acute injury etiologies include intracranial bleeding, disruption of the blood-brain barrier, more severe injury, and early seizures within 1 week of injury. In diverse human epilepsies and animal models, seizures appear to propagate within a limbic or thalamocortical/corticocortical network. Common histopathologic features of epilepsy of diverse and mostly focal origin are microglial activation and astrogliosis, heterotopic neurons in the white matter, loss of neurons, and the presence of inflammatory cellular infiltrates. Astrocytes exhibit smaller K+ conductances and lose gap junction coupling in many animal models as well as in sclerotic hippocampi from temporal lobe epilepsy patients. There is increasing evidence that epilepsy can be prevented or aborted in preclinical animal models of acquired epilepsy by interfering with processes that appear common to multiple acute injury etiologies, for example, in post-status epilepticus models of focal epilepsy by transient treatment with a trkB/PLCγ1 inhibitor, isoflurane, or HMGB1 antibodies and by topical administration of adenosine, in the cortical fluid percussion injury model by focal cooling, and in the albumin posttraumatic epilepsy model by losartan. Preclinical studies further highlight the roles of mTOR1 pathways, JAK-STAT3, IL-1R/TLR4 signaling, and other inflammatory pathways in the genesis or modulation of epilepsy after brain injury. The wealth of commonalities, diversity of molecular targets identified preclinically, and likely multidimensional nature of epileptogenesis argue for a combinatorial strategy in prevention therapy. Going forward, the identification of impending epilepsy biomarkers to allow better patient selection, together with better alignment with multisite preclinical trials in animal models, should guide the clinical testing of new hypotheses for epileptogenesis and its prevention.
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Affiliation(s)
- Pavel Klein
- Mid-Atlantic Epilepsy and Sleep Center, Bethesda, MD, USA
| | | | - Eleonora Aronica
- Department of (Neuro) Pathology, Academic Medical Center and Swammerdam Institute for Life Sciences, Center for Neuroscience, University of Amsterdam, Amsterdam, The Netherlands
- Stichting Epilepsie Instellingen Nederland (SEIN), Heemstede, The Netherlands
| | - Christophe Bernard
- Aix Marseille Univ, Inserm, INS, Instit Neurosci Syst, Marseille, 13005, France
| | - Ingmar Blümcke
- Department of Neuropathology, University Hospital Erlangen, Erlangen, Germany
| | - Detlev Boison
- Robert Stone Dow Neurobiology Laboratories, Legacy Research Institute, Portland, OR, USA
| | - Martin J Brodie
- Epilepsy Unit, West Glasgow Ambulatory Care Hospital-Yorkhill, Glasgow, UK
| | - Amy R Brooks-Kayal
- Division of Neurology, Departments of Pediatrics and Neurology, University of Colorado School of Medicine, Aurora, CO, USA
- Children's Hospital Colorado, Aurora, CO, USA
- Neuroscience Program, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Jerome Engel
- Departments of Neurology, Neurobiology, and Psychiatry and Biobehavioral Sciences, David Geffen School of Medicine, Brain Research Institute, University of California, Los Angeles, CA, USA
| | | | | | | | | | - Katja Kobow
- Department of Neuropathology, University Hospital Erlangen, Erlangen, Germany
| | | | - Phillip L Pearl
- Department of Neurology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
| | - Asla Pitkänen
- Department of Neurobiology, A. I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
| | - Noora Puhakka
- Department of Neurobiology, A. I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
| | - Michael A Rogawski
- Department of Neurology, University of California, Davis, Sacramento, CA, USA
| | | | - Matti Sillanpää
- Departments of Child Neurology and General Practice, University of Turku and Turku University Hospital, Turku, Finland
| | - Robert S Sloviter
- Department of Neurobiology, Morehouse School of Medicine, Atlanta, GA, USA
| | - Christian Steinhäuser
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn, Germany
| | - Annamaria Vezzani
- Department of Neuroscience, IRCCS-Istituto di Ricerche Farmacologiche Mario Negri, Institute for Pharmacological Research, Milan,, Italy
| | - Matthew C Walker
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, London, UK
| | - Wolfgang Löscher
- Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine, Hannover, Germany
- Center for Systems Neuroscience, Hannover, Germany
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82
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Raimondo JV, Heinemann U, de Curtis M, Goodkin HP, Dulla CG, Janigro D, Ikeda A, Lin CCK, Jiruska P, Galanopoulou AS, Bernard C. Methodological standards for in vitro models of epilepsy and epileptic seizures. A TASK1-WG4 report of the AES/ILAE Translational Task Force of the ILAE. Epilepsia 2017; 58 Suppl 4:40-52. [PMID: 29105075 DOI: 10.1111/epi.13901] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/13/2017] [Indexed: 01/02/2023]
Abstract
In vitro preparations are a powerful tool to explore the mechanisms and processes underlying epileptogenesis and ictogenesis. In this review, we critically review the numerous in vitro methodologies utilized in epilepsy research. We provide support for the inclusion of detailed descriptions of techniques, including often ignored parameters with unpredictable yet significant effects on study reproducibility and outcomes. In addition, we explore how recent developments in brain slice preparation relate to their use as models of epileptic activity.
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Affiliation(s)
- Joseph V Raimondo
- Division of Cell Biology, Department of Human Biology, Neuroscience Institute, University of Cape Town, Cape Town, South Africa
| | - Uwe Heinemann
- Neuroscience Research Center, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Marco de Curtis
- Epilepsy and Experimental Neurophysiology Unit, The Foundation of the Carlo Besta Neurological Institute, Milan, Italy
| | - Howard P Goodkin
- Departments of Neurology and Pediatrics, University of Virginia, Charlottesville, Virginia, U.S.A
| | - Chris G Dulla
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts, U.S.A
| | - Damir Janigro
- Flocel Inc., Cleveland, Ohio, U.S.A.,Case Western Reserve University, Cleveland, Ohio, U.S.A
| | - Akio Ikeda
- Department of Epilepsy, Movement Disorders, and Physiology, Kyoto University Graduate School of Medicine, Sakyo-ku, Kyoto, Japan
| | - Chou-Ching K Lin
- Department of Neurology, College of Medicine and Hospital, National Cheng Kung University, Tainan, Taiwan
| | - Premysl Jiruska
- Department of Developmental Epileptology, Institute of Physiology, Czech Academy of Sciences, Prague, Czech Republic
| | - Aristea S Galanopoulou
- Laboratory of Developmental Epilepsy, Saul R. Korey Department of Neurology, Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Einstein/Montefiore Epilepsy Center, Montefiore Medical Center, Bronx, New York, U.S.A
| | - Christophe Bernard
- Inserm, Institut de Neurosciences des Systemes UMRS 1106, Aix Marseille University, Marseille, France
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83
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Chang M, Dian JA, Dufour S, Wang L, Moradi Chameh H, Ramani M, Zhang L, Carlen PL, Womelsdorf T, Valiante TA. Brief activation of GABAergic interneurons initiates the transition to ictal events through post-inhibitory rebound excitation. Neurobiol Dis 2017; 109:102-116. [PMID: 29024712 DOI: 10.1016/j.nbd.2017.10.007] [Citation(s) in RCA: 62] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2016] [Revised: 09/12/2017] [Accepted: 10/08/2017] [Indexed: 12/14/2022] Open
Abstract
Activation of γ-aminobutyric acid (GABAA) receptors have been associated with the onset of epileptiform events. To investigate if a causal relationship exists between GABAA receptor activation and ictal event onset, we activated inhibitory GABAergic networks in the superficial layer (2/3) of the somatosensory cortex during hyperexcitable conditions using optogenetic techniques in mice expressing channelrhodopsin-2 in all GABAergic interneurons. We found that a brief 30ms light pulse reliably triggered either an interictal-like event (IIE) or ictal-like ("ictal") event in the in vitro cortical 4-Aminopyridine (4-AP) slice model. The link between light pulse and epileptiform event onset was lost following blockade of GABAA receptors with bicuculline methiodide. Additionally, recording the chronological sequence of events following a light pulse in a variety of configurations (whole-cell, gramicidin-perforated patch, and multi-electrode array) demonstrated an initial hyperpolarization followed by post-inhibitory rebound spiking and a subsequent slow depolarization at the transition to epileptiform activity. Furthermore, the light-triggered ictal events were independent of the duration or intensity of the initiating light pulse, suggesting an underlying regenerative mechanism. Moreover, we demonstrated that brief GABAA receptor activation can initiate ictal events in the in vivo 4-AP mouse model, in another common in vitro model of epileptiform activity, and in neocortical tissue resected from epilepsy patients. Our findings reveal that the synchronous activation of GABAergic interneurons is a robust trigger for ictal event onset in hyperexcitable cortical networks.
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Affiliation(s)
- Michael Chang
- Division of Fundamental Neurobiology, Krembil Research Institute, Toronto, ON, Canada; Institute of Medical Science, Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - Joshua A Dian
- Division of Fundamental Neurobiology, Krembil Research Institute, Toronto, ON, Canada; Department of Electrical and Computer Engineering, University of Toronto, Toronto, ON, Canada
| | - Suzie Dufour
- Division of Fundamental Neurobiology, Krembil Research Institute, Toronto, ON, Canada; Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, ON, Canada
| | - Lihua Wang
- Division of Fundamental Neurobiology, Krembil Research Institute, Toronto, ON, Canada
| | - Homeira Moradi Chameh
- Division of Fundamental Neurobiology, Krembil Research Institute, Toronto, ON, Canada
| | - Meera Ramani
- Division of Fundamental Neurobiology, Krembil Research Institute, Toronto, ON, Canada
| | - Liang Zhang
- Division of Fundamental Neurobiology, Krembil Research Institute, Toronto, ON, Canada; Division of Neurology, Department of Medicine, University of Toronto, Toronto, ON, Canada
| | - Peter L Carlen
- Division of Fundamental Neurobiology, Krembil Research Institute, Toronto, ON, Canada; Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, ON, Canada; Division of Neurology, Department of Medicine, University of Toronto, Toronto, ON, Canada; Department of Physiology, University of Toronto, Toronto, ON, Canada; Institute of Medical Science, Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - Thilo Womelsdorf
- Department of Psychology, Vanderbilt University, Nashville, TN, USA
| | - Taufik A Valiante
- Division of Fundamental Neurobiology, Krembil Research Institute, Toronto, ON, Canada; Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, ON, Canada; Division of Neurosurgery, Department of Surgery, University of Toronto, Toronto, ON, Canada; Institute of Medical Science, Faculty of Medicine, University of Toronto, Toronto, ON, Canada.
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84
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Moore YE, Kelley MR, Brandon NJ, Deeb TZ, Moss SJ. Seizing Control of KCC2: A New Therapeutic Target for Epilepsy. Trends Neurosci 2017; 40:555-571. [PMID: 28803659 DOI: 10.1016/j.tins.2017.06.008] [Citation(s) in RCA: 92] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Revised: 06/20/2017] [Accepted: 06/22/2017] [Indexed: 11/17/2022]
Abstract
Deficits in GABAergic inhibition result in the abnormal neuronal activation and synchronization that underlies seizures. However, the molecular mechanisms responsible for transforming a normal brain into an epileptic one remain largely unknown. Hyperpolarizing inhibition mediated by type A GABA (GABAA) receptors is dependent on chloride extrusion by the neuron-specific type 2K+-Cl- cotransporter (KCC2). Loss-of-function mutations in KCC2 are a known cause of infantile epilepsy in humans and KCC2 dysfunction is present in patients with both idiopathic and acquired epilepsy. Here we discuss the growing evidence that KCC2 dysfunction has a central role in the development and severity of the epilepsies.
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Affiliation(s)
- Yvonne E Moore
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK; Department of Neuroscience, Tufts University School of Medicine, Boston, MA 02111, USA
| | - Matt R Kelley
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA 02111, USA
| | - Nicholas J Brandon
- AstraZeneca Tufts Laboratory for Basic and Translational Neuroscience, Boston, MA 02111, USA; AstraZeneca Neuroscience, Innovative Medicines and Early Development Biotech Unit, R&D Boston, Waltham, MA 024515, USA
| | - Tarek Z Deeb
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA 02111, USA; AstraZeneca Tufts Laboratory for Basic and Translational Neuroscience, Boston, MA 02111, USA
| | - Stephen J Moss
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK; Department of Neuroscience, Tufts University School of Medicine, Boston, MA 02111, USA; AstraZeneca Tufts Laboratory for Basic and Translational Neuroscience, Boston, MA 02111, USA.
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85
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Neumann AR, Raedt R, Steenland HW, Sprengers M, Bzymek K, Navratilova Z, Mesina L, Xie J, Lapointe V, Kloosterman F, Vonck K, Boon PAJM, Soltesz I, McNaughton BL, Luczak A. Involvement of fast-spiking cells in ictal sequences during spontaneous seizures in rats with chronic temporal lobe epilepsy. Brain 2017; 140:2355-2369. [PMID: 29050390 PMCID: PMC6248724 DOI: 10.1093/brain/awx179] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Revised: 05/25/2017] [Accepted: 06/08/2017] [Indexed: 11/14/2022] Open
Abstract
See Lenck-Santini (doi:10.1093/awx205) for a scientific commentary on this article. Epileptic seizures represent altered neuronal network dynamics, but the temporal evolution and cellular substrates of the neuronal activity patterns associated with spontaneous seizures are not fully understood. We used simultaneous recordings from multiple neurons in the hippocampus and neocortex of rats with chronic temporal lobe epilepsy to demonstrate that subsets of cells discharge in a highly stereotypical sequential pattern during ictal events, and that these stereotypical patterns were reproducible across consecutive seizures. In contrast to the canonical view that principal cell discharges dominate ictal events, the ictal sequences were predominantly composed of fast-spiking, putative inhibitory neurons, which displayed unusually strong coupling to local field potential even before seizures. The temporal evolution of activity was characterized by unique dynamics where the most correlated neuronal pairs before seizure onset displayed the largest increases in correlation strength during the seizures. These results demonstrate the selective involvement of fast spiking interneurons in structured temporal sequences during spontaneous ictal events in hippocampal and neocortical circuits in experimental models of chronic temporal lobe epilepsy.
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Affiliation(s)
- Adam R Neumann
- Department of Neuroscience, Canadian Centre for Behavioural
Neuroscience, University of Lethbridge, 4401 University Dr W, Lethbridge, AB, T1K 3M4,
Canada
| | - Robrecht Raedt
- Department of Neurology, Ghent University, Gent, Belgium
| | - Hendrik W Steenland
- Department of Neuroscience, Canadian Centre for Behavioural
Neuroscience, University of Lethbridge, 4401 University Dr W, Lethbridge, AB, T1K 3M4,
Canada
| | | | - Katarzyna Bzymek
- Department of Neuroscience, Canadian Centre for Behavioural
Neuroscience, University of Lethbridge, 4401 University Dr W, Lethbridge, AB, T1K 3M4,
Canada
| | - Zaneta Navratilova
- Department of Neuroscience, Canadian Centre for Behavioural
Neuroscience, University of Lethbridge, 4401 University Dr W, Lethbridge, AB, T1K 3M4,
Canada
- Neuro-Electronics Research Flanders, Leuven, Belgium
| | - Lilia Mesina
- Department of Neuroscience, Canadian Centre for Behavioural
Neuroscience, University of Lethbridge, 4401 University Dr W, Lethbridge, AB, T1K 3M4,
Canada
| | - Jeanne Xie
- Department of Neuroscience, Canadian Centre for Behavioural
Neuroscience, University of Lethbridge, 4401 University Dr W, Lethbridge, AB, T1K 3M4,
Canada
| | - Valerie Lapointe
- Department of Neuroscience, Canadian Centre for Behavioural
Neuroscience, University of Lethbridge, 4401 University Dr W, Lethbridge, AB, T1K 3M4,
Canada
| | - Fabian Kloosterman
- Neuro-Electronics Research Flanders, Leuven, Belgium
- VIB, Leuven, Belgium
- Brain and Cognition Research unit, KU Leuven, Leuven, Belgium
| | - Kristl Vonck
- Department of Neurology, Ghent University, Gent, Belgium
| | | | - Ivan Soltesz
- Department of Neurosurgery, and Stanford Neurosciences Institute,
Stanford University, Stanford, CA, USA
| | - Bruce L McNaughton
- Department of Neuroscience, Canadian Centre for Behavioural
Neuroscience, University of Lethbridge, 4401 University Dr W, Lethbridge, AB, T1K 3M4,
Canada
- Department of Neurobiology and Behavior, University of California at
Irvine, Center for the Neurobiology of Learning and Memory, Irvine, CA, USA
| | - Artur Luczak
- Department of Neuroscience, Canadian Centre for Behavioural
Neuroscience, University of Lethbridge, 4401 University Dr W, Lethbridge, AB, T1K 3M4,
Canada
- Department of Neurosurgery, and Stanford Neurosciences Institute,
Stanford University, Stanford, CA, USA
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86
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Antila H, Ryazantseva M, Popova D, Sipilä P, Guirado R, Kohtala S, Yalcin I, Lindholm J, Vesa L, Sato V, Cordeira J, Autio H, Kislin M, Rios M, Joca S, Casarotto P, Khiroug L, Lauri S, Taira T, Castrén E, Rantamäki T. Isoflurane produces antidepressant effects and induces TrkB signaling in rodents. Sci Rep 2017; 7:7811. [PMID: 28798343 PMCID: PMC5552878 DOI: 10.1038/s41598-017-08166-9] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2017] [Accepted: 07/06/2017] [Indexed: 12/01/2022] Open
Abstract
A brief burst-suppressing isoflurane anesthesia has been shown to rapidly alleviate symptoms of depression in a subset of patients, but the neurobiological basis of these observations remains obscure. We show that a single isoflurane anesthesia produces antidepressant-like behavioural effects in the learned helplessness paradigm and regulates molecular events implicated in the mechanism of action of rapid-acting antidepressant ketamine: activation of brain-derived neurotrophic factor (BDNF) receptor TrkB, facilitation of mammalian target of rapamycin (mTOR) signaling pathway and inhibition of glycogen synthase kinase 3β (GSK3β). Moreover, isoflurane affected neuronal plasticity by facilitating long-term potentiation in the hippocampus. We also found that isoflurane increased activity of the parvalbumin interneurons, and facilitated GABAergic transmission in wild type mice but not in transgenic mice with reduced TrkB expression in parvalbumin interneurons. Our findings strengthen the role of TrkB signaling in the antidepressant responses and encourage further evaluation of isoflurane as a rapid-acting antidepressant devoid of the psychotomimetic effects and abuse potential of ketamine.
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Affiliation(s)
- Hanna Antila
- Neuroscience Center, University of Helsinki, P.O. Box 56, Helsinki, FI-00014, Finland
| | - Maria Ryazantseva
- Neuroscience Center, University of Helsinki, P.O. Box 56, Helsinki, FI-00014, Finland.,Division of Physiology and Neuroscience, Department of Biosciences, Faculty of Biological and Environmental Sciences, University of Helsinki, P.O. Box 66, Helsinki, FI-00014, Finland
| | - Dina Popova
- Neuroscience Center, University of Helsinki, P.O. Box 56, Helsinki, FI-00014, Finland
| | - Pia Sipilä
- Neuroscience Center, University of Helsinki, P.O. Box 56, Helsinki, FI-00014, Finland
| | - Ramon Guirado
- Neuroscience Center, University of Helsinki, P.O. Box 56, Helsinki, FI-00014, Finland
| | - Samuel Kohtala
- Neuroscience Center, University of Helsinki, P.O. Box 56, Helsinki, FI-00014, Finland.,Division of Physiology and Neuroscience, Department of Biosciences, Faculty of Biological and Environmental Sciences, University of Helsinki, P.O. Box 66, Helsinki, FI-00014, Finland
| | - Ipek Yalcin
- Institut des Neurosciences Cellulaires et Intégratives, Centre National de la Recherche Scientifique, FR-67084, Strasbourg Cedex, France
| | - Jesse Lindholm
- Neuroscience Center, University of Helsinki, P.O. Box 56, Helsinki, FI-00014, Finland
| | - Liisa Vesa
- Neuroscience Center, University of Helsinki, P.O. Box 56, Helsinki, FI-00014, Finland
| | - Vinicius Sato
- School of Pharmaceutical Sciences of Ribeirão Preto, 14040-903, Ribeirão Preto, São Paulo, Brazil
| | | | - Henri Autio
- Neuroscience Center, University of Helsinki, P.O. Box 56, Helsinki, FI-00014, Finland
| | - Mikhail Kislin
- Neuroscience Center, University of Helsinki, P.O. Box 56, Helsinki, FI-00014, Finland
| | | | - Sâmia Joca
- School of Pharmaceutical Sciences of Ribeirão Preto, 14040-903, Ribeirão Preto, São Paulo, Brazil
| | - Plinio Casarotto
- Neuroscience Center, University of Helsinki, P.O. Box 56, Helsinki, FI-00014, Finland
| | - Leonard Khiroug
- Neuroscience Center, University of Helsinki, P.O. Box 56, Helsinki, FI-00014, Finland
| | - Sari Lauri
- Neuroscience Center, University of Helsinki, P.O. Box 56, Helsinki, FI-00014, Finland.,Division of Physiology and Neuroscience, Department of Biosciences, Faculty of Biological and Environmental Sciences, University of Helsinki, P.O. Box 66, Helsinki, FI-00014, Finland
| | - Tomi Taira
- Neuroscience Center, University of Helsinki, P.O. Box 56, Helsinki, FI-00014, Finland.,Department of Veterinary Biosciences, Faculty of Veterinary Medicine, University of Helsinki, P.O. Box 66, FI-00014, Helsinki, Finland
| | - Eero Castrén
- Neuroscience Center, University of Helsinki, P.O. Box 56, Helsinki, FI-00014, Finland.
| | - Tomi Rantamäki
- Neuroscience Center, University of Helsinki, P.O. Box 56, Helsinki, FI-00014, Finland. .,Division of Physiology and Neuroscience, Department of Biosciences, Faculty of Biological and Environmental Sciences, University of Helsinki, P.O. Box 66, Helsinki, FI-00014, Finland.
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87
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Tight Coupling of Astrocyte pH Dynamics to Epileptiform Activity Revealed by Genetically Encoded pH Sensors. J Neurosci 2017; 36:7002-13. [PMID: 27358457 DOI: 10.1523/jneurosci.0664-16.2016] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Accepted: 05/23/2016] [Indexed: 12/21/2022] Open
Abstract
UNLABELLED Astrocytes can both sense and shape the evolution of neuronal network activity and are known to possess unique ion regulatory mechanisms. Here we explore the relationship between astrocytic intracellular pH dynamics and the synchronous network activity that occurs during seizure-like activity. By combining confocal and two-photon imaging of genetically encoded pH reporters with simultaneous electrophysiological recordings, we perform pH measurements in defined cell populations and relate these to ongoing network activity. This approach reveals marked differences in the intracellular pH dynamics between hippocampal astrocytes and neighboring pyramidal neurons in rodent in vitro models of epilepsy. With three different genetically encoded pH reporters, astrocytes are observed to alkalinize during epileptiform activity, whereas neurons are observed to acidify. In addition to the direction of pH change, the kinetics of epileptiform-associated intracellular pH transients are found to differ between the two cell types, with astrocytes displaying significantly more rapid changes in pH. The astrocytic alkalinization is shown to be highly correlated with astrocytic membrane potential changes during seizure-like events and mediated by an electrogenic Na(+)/HCO3 (-) cotransporter. Finally, comparisons across different cell-pair combinations reveal that astrocytic pH dynamics are more closely related to network activity than are neuronal pH dynamics. This work demonstrates that astrocytes exhibit distinct pH dynamics during periods of epileptiform activity, which has relevance to multiple processes including neurometabolic coupling and the control of network excitability. SIGNIFICANCE STATEMENT Dynamic changes in intracellular ion concentrations are central to the initiation and progression of epileptic seizures. However, it is not known how changes in intracellular H(+) concentration (ie, pH) differ between different cell types during seizures. Using recently developed pH-sensitive proteins, we demonstrate that astrocytes undergo rapid alkalinization during periods of seizure-like activity, which is in stark contrast to the acidification that occurs in neighboring neurons. Rapid astrocytic pH changes are highly temporally correlated with seizure activity, are mediated by an electrogenic Na(+)/HCO3- cotransporter, and are more tightly coupled to network activity than are neuronal pH changes. As pH has profound effects on signaling in the nervous system, this work has implications for our understanding of seizure dynamics.
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88
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Epilepsy and optogenetics: can seizures be controlled by light? Clin Sci (Lond) 2017; 131:1605-1616. [DOI: 10.1042/cs20160492] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Revised: 03/30/2017] [Accepted: 04/13/2017] [Indexed: 01/12/2023]
Abstract
Over the past decade, ‘optogenetics’ has been consolidated as a game-changing tool in the neuroscience field, by allowing optical control of neuronal activity with high cell-type specificity. The ability to activate or inhibit targeted neurons at millisecond resolution not only offers an investigative tool, but potentially also provides a therapeutic intervention strategy for acute correction of aberrant neuronal activity. As efficient therapeutic tools are in short supply for neurological disorders, optogenetic technology has therefore spurred considerable enthusiasm and fostered a new wave of translational studies in neuroscience. Epilepsy is among the disorders that have been widely explored. Partial epilepsies are characterized by seizures arising from excessive excitatory neuronal activity that emerges from a focal area. Based on the constricted seizure focus, it appears feasible to intercept partial seizures by acutely shutting down excitatory neurons by means of optogenetics. The availability of both inhibitory and excitatory optogenetic probes, along with the available targeting strategies for respective excitatory or inhibitory neurons, allows multiple conceivable scenarios for controlling abnormal circuit activity. Several such scenarios have been explored in the settings of experimental epilepsy and have provided encouraging translational findings and revealed interesting and unexpected new aspects of epileptogenesis. However, it has also emerged that considerable challenges persist before clinical translation becomes feasible. This review provides a general introduction to optogenetics, and an overview of findings that are relevant for understanding how optogenetics may be utilized therapeutically as a highly innovative treatment for epilepsy.
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89
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Simonsen C, Boddum K, von Schoubye NL, Kloppenburg A, Sønderskov K, Hansen SL, Kristiansen U. Anticonvulsive evaluation of THIP in the murine pentylenetetrazole kindling model: lack of anticonvulsive effect of THIP despite functional δ-subunit-containing GABA A receptors in dentate gyrus granule cells. Pharmacol Res Perspect 2017; 5. [PMID: 28805971 PMCID: PMC5684853 DOI: 10.1002/prp2.322] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2017] [Revised: 04/20/2017] [Accepted: 04/21/2017] [Indexed: 12/29/2022] Open
Abstract
THIP (4,5,6,7‐tetrahydroisoxazolo[5,4‐c]pyridin‐3‐ol) is a GABAA receptor agonist with varying potencies and efficacies at γ‐subunit‐containing receptors. More importantly, THIP acts as a selective superagonist at δ‐subunit‐containing receptors (δ‐GABAARs) at clinically relevant concentrations. Evaluation of THIP as a potential anticonvulsant has given contradictory results in different animal models and for this reason, we reevaluated the anticonvulsive properties of THIP in the murine pentylenetetrazole (PTZ) kindling model. As loss of δ‐GABAAR in the dentate gyrus has been associated with several animal models of epilepsy, we first investigated the presence of functional δ‐GABAA receptors. Both immunohistochemistry and Western blot data demonstrated that δ‐GABAAR expression is not only present in the dentate gyrus, but also the expression level was enhanced in the early phase after PTZ kindling. Whole‐cell patch‐clamp studies in acute hippocampal brain slices revealed that THIP was indeed able to induce a tonic inhibition in dentate gyrus granule cells. However, THIP induced a tonic current of similar magnitude in the PTZ‐kindled mice compared to saline‐treated animals despite the observed upregulation of δ‐GABAARs. Even in the demonstrated presence of functional δ‐GABAARs, THIP (0.5–4 mg/kg) showed no anticonvulsive effect in the PTZ kindling model using a comprehensive in vivo evaluation of the anticonvulsive properties.
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Affiliation(s)
- Charlotte Simonsen
- Faculty of Health and Medical Sciences, Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Kim Boddum
- Faculty of Health and Medical Sciences, Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark.,Faculty of Health and Medical Sciences, Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Nadia L von Schoubye
- Faculty of Health and Medical Sciences, Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark.,Faculty of Health and Medical Sciences, Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Alissa Kloppenburg
- Faculty of Health and Medical Sciences, Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Kasper Sønderskov
- Faculty of Health and Medical Sciences, Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Suzanne L Hansen
- Faculty of Health and Medical Sciences, Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Uffe Kristiansen
- Faculty of Health and Medical Sciences, Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
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90
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Wright R, Newey SE, Ilie A, Wefelmeyer W, Raimondo JV, Ginham R, Mcllhinney RAJ, Akerman CJ. Neuronal Chloride Regulation via KCC2 Is Modulated through a GABA B Receptor Protein Complex. J Neurosci 2017; 37:5447-5462. [PMID: 28450542 PMCID: PMC5452337 DOI: 10.1523/jneurosci.2164-16.2017] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Revised: 03/31/2017] [Accepted: 04/06/2017] [Indexed: 01/06/2023] Open
Abstract
GABAB receptors are G-protein-coupled receptors that mediate inhibitory synaptic actions through a series of downstream target proteins. It is increasingly appreciated that the GABAB receptor forms part of larger signaling complexes, which enable the receptor to mediate multiple different effects within neurons. Here we report that GABAB receptors can physically associate with the potassium-chloride cotransporter protein, KCC2, which sets the driving force for the chloride-permeable ionotropic GABAA receptor in mature neurons. Using biochemical, molecular, and functional studies in rodent hippocampus, we show that activation of GABAB receptors results in a decrease in KCC2 function, which is associated with a reduction in the protein at the cell surface. These findings reveal a novel "crosstalk" between the GABA receptor systems, which can be recruited under conditions of high GABA release and which could be important for the regulation of inhibitory synaptic transmission.SIGNIFICANCE STATEMENT Synaptic inhibition in the brain is mediated by ionotropic GABAA receptors (GABAARs) and metabotropic GABAB receptors (GABABRs). To fully appreciate the function and regulation of these neurotransmitter receptors, we must understand their interactions with other proteins. We describe a novel association between the GABABR and the potassium-chloride cotransporter protein, KCC2. This association is significant because KCC2 sets the intracellular chloride concentration found in mature neurons and thereby establishes the driving force for the chloride-permeable GABAAR. We demonstrate that GABABR activation can regulate KCC2 at the cell surface in a manner that alters intracellular chloride and the reversal potential for the GABAAR. Our data therefore support an additional mechanism by which GABABRs are able to modulate fast synaptic inhibition.
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Affiliation(s)
| | | | | | | | | | - Rachel Ginham
- Medical Research Council Anatomical Neuropharmacology Unit, University of Oxford, Oxford, OX1 3QT, United Kingdom
| | - R A Jeffrey Mcllhinney
- Medical Research Council Anatomical Neuropharmacology Unit, University of Oxford, Oxford, OX1 3QT, United Kingdom
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91
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Kim CM, Nykamp DQ. The influence of depolarization block on seizure-like activity in networks of excitatory and inhibitory neurons. J Comput Neurosci 2017; 43:65-79. [PMID: 28528529 DOI: 10.1007/s10827-017-0647-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2015] [Revised: 03/11/2017] [Accepted: 04/26/2017] [Indexed: 11/29/2022]
Abstract
The inhibitory restraint necessary to suppress aberrant activity can fail when inhibitory neurons cease to generate action potentials as they enter depolarization block. We investigate possible bifurcation structures that arise at the onset of seizure-like activity resulting from depolarization block in inhibitory neurons. Networks of conductance-based excitatory and inhibitory neurons are simulated to characterize different types of transitions to the seizure state, and a mean field model is developed to verify the generality of the observed phenomena of excitatory-inhibitory dynamics. Specifically, the inhibitory population's activation function in the Wilson-Cowan model is modified to be non-monotonic to reflect that inhibitory neurons enter depolarization block given strong input. We find that a physiological state and a seizure state can coexist, where the seizure state is characterized by high excitatory and low inhibitory firing rate. Bifurcation analysis of the mean field model reveals that a transition to the seizure state may occur via a saddle-node bifurcation or a homoclinic bifurcation. We explain the hysteresis observed in network simulations using these two bifurcation types. We also demonstrate that extracellular potassium concentration affects the depolarization block threshold; the consequent changes in bifurcation structure enable the network to produce the tonic to clonic phase transition observed in biological epileptic networks.
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Affiliation(s)
- Christopher M Kim
- School of Mathematics, University of Minnesota, Minneapolis, MN, USA. .,Laboratory of Biological Modeling, NIDDK, National Institute of Health, Bethesda, MD, USA.
| | - Duane Q Nykamp
- School of Mathematics, University of Minnesota, Minneapolis, MN, USA
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92
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Forman CJ, Tomes H, Mbobo B, Burman RJ, Jacobs M, Baden T, Raimondo JV. Openspritzer: an open hardware pressure ejection system for reliably delivering picolitre volumes. Sci Rep 2017; 7:2188. [PMID: 28526883 PMCID: PMC5438373 DOI: 10.1038/s41598-017-02301-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Accepted: 04/10/2017] [Indexed: 11/09/2022] Open
Abstract
The ability to reliably and precisely deliver picolitre volumes is an important component of biological research. Here we describe a high-performance, low-cost, open hardware pressure ejection system (Openspritzer), which can be constructed from off the shelf components. The device is capable of delivering minute doses of reagents to a wide range of biological and chemical systems. In this work, we characterise the performance of the device and compare it to a popular commercial system using two-photon fluorescence microscopy. We found that Openspritzer provides the same level of control over delivered reagent dose as the commercial system. Next, we demonstrate the utility of Openspritzer in a series of standard neurobiological applications. First, we used Openspritzer to deliver precise amounts of reagents to hippocampal neurons to elicit time- and dose-precise responses on neuronal voltage. Second, we used Openspritzer to deliver infectious viral and bacterial agents to living tissue. This included viral transfection of hippocampal interneurons with channelrhodopsin for the optogenetic manipulation of hippocampal circuitry with light. We anticipate that due to its high performance and low cost Openspritzer will be of interest to a broad range of researchers working in the life and physical sciences.
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Affiliation(s)
- C J Forman
- School of Life Sciences, University of Sussex, Sussex, United Kingdom.
| | - H Tomes
- Division of Physiology, Department of Human Biology, Neuroscience Institute and Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - B Mbobo
- Division of Physiology, Department of Human Biology, Neuroscience Institute and Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa.,Division of Immunology, Department of Pathology, Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - R J Burman
- Division of Physiology, Department of Human Biology, Neuroscience Institute and Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - M Jacobs
- Division of Immunology, Department of Pathology, Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa.,Immunology of Infectious Disease Research Unit, South African Medical Research Council, Cape Town, South Africa.,National Health Laboratory Service, Sandringham, Johannesburg, South Africa
| | - T Baden
- School of Life Sciences, University of Sussex, Sussex, United Kingdom. .,Institute for Ophthalmic Research, University of Tuebingen, Tuebingen, Germany.
| | - J V Raimondo
- Division of Physiology, Department of Human Biology, Neuroscience Institute and Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa.
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93
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Wozny TA, Lipski WJ, Alhourani A, Kondylis ED, Antony A, Richardson RM. Effects of hippocampal low-frequency stimulation in idiopathic non-human primate epilepsy assessed via a remote-sensing-enabled neurostimulator. Exp Neurol 2017; 294:68-77. [PMID: 28495218 DOI: 10.1016/j.expneurol.2017.05.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2016] [Revised: 04/28/2017] [Accepted: 05/06/2017] [Indexed: 01/06/2023]
Abstract
Individuals with pharmacoresistant epilepsy remain a large and under-treated patient population. Continued technologic advancements in implantable neurostimulators have spurred considerable research efforts directed towards the development of novel antiepileptic stimulation therapies. However, the lack of adequate preclinical experimental platforms has precluded a detailed understanding of the differential effects of stimulation parameters on neuronal activity within seizure networks. In order to chronically monitor seizures and the effects of stimulation in a freely-behaving non-human primate with idiopathic epilepsy, we employed a novel simultaneous video-intracranial EEG recording platform using a state-of-the-art sensing-enabled, rechargeable clinical neurostimulator with real-time seizure detection and wireless data streaming capabilities. Using this platform, we were able to characterize the electrographic and semiologic features of the focal-onset, secondarily generalizing tonic-clonic seizures stably expressed in this animal. A series of acute experiments exploring low-frequency (2Hz) hippocampal stimulation identified a pulse width (150μs) and current amplitude (4mA) combination which maximally suppressed local hippocampal activity. These optimized stimulation parameters were then delivered to the seizure onset-side hippocampus in a series of chronic experiments. This long-term testing revealed that the suppressive effects of low-frequency hippocampal stimulation 1) diminish when delivered continuously but are maintained when stimulation is cycled on and off, 2) are dependent on circadian rhythms, and 3) do not necessarily confer seizure protective effects.
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Affiliation(s)
- Thomas A Wozny
- Brain Modulation Lab, Department of Neurological Surgery, University of Pittsburgh, Pittsburgh, PA 15213, United States
| | - Witold J Lipski
- Brain Modulation Lab, Department of Neurological Surgery, University of Pittsburgh, Pittsburgh, PA 15213, United States
| | - Ahmad Alhourani
- Brain Modulation Lab, Department of Neurological Surgery, University of Pittsburgh, Pittsburgh, PA 15213, United States
| | - Efstathios D Kondylis
- Brain Modulation Lab, Department of Neurological Surgery, University of Pittsburgh, Pittsburgh, PA 15213, United States
| | - Arun Antony
- Department of Neurology, University of Pittsburgh, Pittsburgh, PA 15213, United States; University of Pittsburgh Comprehensive Epilepsy Center, Pittsburgh, PA 15213, United States
| | - R Mark Richardson
- Brain Modulation Lab, Department of Neurological Surgery, University of Pittsburgh, Pittsburgh, PA 15213, United States; University of Pittsburgh Comprehensive Epilepsy Center, Pittsburgh, PA 15213, United States; University of Pittsburgh Brain Institute, Pittsburgh, PA 15213, United States.
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94
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95
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Yekhlef L, Breschi GL, Taverna S. Optogenetic activation of VGLUT2-expressing excitatory neurons blocks epileptic seizure-like activity in the mouse entorhinal cortex. Sci Rep 2017; 7:43230. [PMID: 28230208 PMCID: PMC5322365 DOI: 10.1038/srep43230] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Accepted: 01/20/2017] [Indexed: 01/18/2023] Open
Abstract
We investigated whether an anti-epileptic effect is obtained by selectively activating excitatory neurons expressing ChR2 under the promoter for the synaptic vesicular glutamate transporter 2 (VGLUT2). VGLUT2-expressing cells were optically stimulated while local field potential and whole-cell patch-clamp recordings were performed in mouse entorhinal cortical slices perfused with the proconvulsive compound 4-aminopyridine (4-AP). In control conditions, blue light flashes directly depolarized the majority of putative glutamatergic cells, which in turn synaptically excited GABAergic interneurons. During bath perfusion with 4-AP, photostimuli triggered a fast EPSP-IPSP sequence which was often followed by tonic-clonic seizure-like activity closely resembling spontaneous ictal discharges. The GABAA-receptor antagonist gabazine blocked the progression of both light-induced and spontaneous seizures. Surprisingly, prolonged photostimuli delivered during ongoing seizures caused a robust interruption of synchronous discharges. Such break was correlated with a membrane potential depolarization block in principal cells, while putative GABAergic interneurons changed their firing activity from a burst-like to an irregular single-spike pattern. These data suggest that photostimulation of glutamatergic neurons triggers seizure-like activity only in the presence of an intact GABAergic transmission and that selectively activating the same glutamatergic cells robustly interrupts ongoing seizures by inducing a strong depolarization block, resulting in the disruption of paroxysmal burst-like firing.
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Affiliation(s)
- Latefa Yekhlef
- Division of Neuroscience, San Raffaele Scientific Institute, via Olgettina 58, 20132 Milan, Italy
- Center for Synaptic Neuroscience, Istituto Italiano di Tecnologia, via Morego 30, 16163 Genoa, Italy
| | - Gian Luca Breschi
- Division of Neuroscience, San Raffaele Scientific Institute, via Olgettina 58, 20132 Milan, Italy
| | - Stefano Taverna
- Division of Neuroscience, San Raffaele Scientific Institute, via Olgettina 58, 20132 Milan, Italy
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96
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Bumetanide reduce the seizure susceptibility induced by pentylenetetrazol via inhibition of aberrant hippocampal neurogenesis in neonatal rats after hypoxia-ischemia. Brain Res Bull 2017; 130:188-199. [PMID: 28161194 DOI: 10.1016/j.brainresbull.2017.01.022] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Revised: 01/26/2017] [Accepted: 01/27/2017] [Indexed: 12/29/2022]
Abstract
Hypoxia-ischemia brain damage (HIBD) is one of prevalent causes of neonatal mortality and morbidity. Our data demonstrated that hypoxia-ischemia (HI) induced Na+-K+-Cl--co-transporter 1 (NKCC1) increasing in hippocampus. Previous studies demonstrated that NKCC1 regulates various stages of neurogenesis. In this study, we studied the role of increased NKCC1 in regulating of HI-induced neurogenesis. HIBD model was established in 7days old Sprague-Dawley rat pup, and the expression of NKCC1 was detected by western blot and qPCR. Brain electrical activity in freely rats was monitored by electroencephalography (EEG) recordings. HI-induced neurogenesis was detected by immunofluorescence staining. Neurobehavioral test was to investigate the neuro-protective role of bumetanide, an inhibitor of NKCC1, on neonatal rats after HI. The results showed that bumetanide treatment significantly reduced brain electrical activity and the seizure stage of epilepsy induced by pentylenetetrazol (PTZ) in vivo after HI. In addition, bumetanide restored aberrant hippocampal neurogenesis and associated cognitive function. Our data demonstrated that bumetanide reduces the susceptibility of epilepsy induced by PTZ in rats suffering from HI injury during neonatal period via restoring the ectopic newborn neurons in dentate gyrus (DG) and cognitive function.
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97
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Lapato AS, Szu JI, Hasselmann JPC, Khalaj AJ, Binder DK, Tiwari-Woodruff SK. Chronic demyelination-induced seizures. Neuroscience 2017; 346:409-422. [PMID: 28153692 DOI: 10.1016/j.neuroscience.2017.01.035] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Revised: 01/13/2017] [Accepted: 01/23/2017] [Indexed: 12/11/2022]
Abstract
Multiple sclerosis (MS) patients are three to six times more likely to develop epilepsy compared to the rest of the population. Seizures are more common in patients with early onset or progressive forms of the disease and prognosticate rapid progression to disability and death. Gray matter atrophy, hippocampal lesions, interneuron loss, and elevated juxtacortical lesion burden have been identified in MS patients with seizures; however, translational studies aimed at elucidating the pathophysiological processes underlying MS epileptogenesis are limited. Here, we report that cuprizone-mediated chronically demyelinated (9-12weeks) mice exhibit marked changes to dorsal hippocampal electroencephalography (EEG) and evidence of overt seizure activity. Immunohistochemical (IHC) analyses within the hippocampal CA1 region revealed extensive demyelination, loss of parvalbumin (PV+) interneurons, widespread gliosis, and changes in aquaporin-4 (AQP4) expression. Our results suggest that chronically demyelinated mice are a valuable model with which we may begin to understand the mechanisms underlying demyelination-induced seizures.
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Affiliation(s)
- Andrew S Lapato
- Division of Biomedical Sciences, School of Medicine, University of California Riverside, Riverside, CA 92521, USA; Center for Glial-Neuronal Interactions, University of California Riverside, Riverside, CA 92521, USA
| | - Jenny I Szu
- Neuroscience Graduate Program, University of California Riverside, Riverside, CA 92521, USA
| | - Jonathan P C Hasselmann
- Division of Biomedical Sciences, School of Medicine, University of California Riverside, Riverside, CA 92521, USA
| | - Anna J Khalaj
- Division of Biomedical Sciences, School of Medicine, University of California Riverside, Riverside, CA 92521, USA
| | - Devin K Binder
- Division of Biomedical Sciences, School of Medicine, University of California Riverside, Riverside, CA 92521, USA; Neuroscience Graduate Program, University of California Riverside, Riverside, CA 92521, USA; Center for Glial-Neuronal Interactions, University of California Riverside, Riverside, CA 92521, USA
| | - Seema K Tiwari-Woodruff
- Division of Biomedical Sciences, School of Medicine, University of California Riverside, Riverside, CA 92521, USA; Neuroscience Graduate Program, University of California Riverside, Riverside, CA 92521, USA; Center for Glial-Neuronal Interactions, University of California Riverside, Riverside, CA 92521, USA.
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98
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Khoshkhoo S, Vogt D, Sohal VS. Dynamic, Cell-Type-Specific Roles for GABAergic Interneurons in a Mouse Model of Optogenetically Inducible Seizures. Neuron 2016; 93:291-298. [PMID: 28041880 DOI: 10.1016/j.neuron.2016.11.043] [Citation(s) in RCA: 109] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2016] [Revised: 08/05/2016] [Accepted: 11/16/2016] [Indexed: 01/19/2023]
Abstract
GABAergic interneurons play critical roles in seizures, but it remains unknown whether these vary across interneuron subtypes or evolve during a seizure. This uncertainty stems from the unpredictable timing of seizures in most models, which limits neuronal imaging or manipulations around the seizure onset. Here, we describe a mouse model for optogenetic seizure induction. Combining this with calcium imaging, we find that seizure onset rapidly recruits parvalbumin (PV), somatostatin (SOM), and vasoactive intestinal peptitde (VIP)-expressing interneurons, whereas excitatory neurons are recruited several seconds later. Optogenetically inhibiting VIP interneurons consistently increased seizure threshold and reduced seizure duration. Inhibiting PV+ and SOM+ interneurons had mixed effects on seizure initiation but consistently reduced seizure duration. Thus, while their roles may evolve during seizures, PV+ and SOM+ interneurons ultimately help maintain ongoing seizures. These results show how an optogenetically induced seizure model can be leveraged to pinpoint a new target for seizure control: VIP interneurons. VIDEO ABSTRACT.
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Affiliation(s)
- Sattar Khoshkhoo
- Department of Psychiatry, University of California, San Francisco, San Francisco, CA 94143-0444, USA; Weil Institute for Neurosciences, University of California, San Francisco, San Francisco, CA 94143-0444, USA; Kavli Institute for Fundamental Neuroscience, University of California, San Francisco, San Francisco, CA 94143-0444, USA; Sloan Swartz Center for Theoretical Neurobiology, University of California, San Francisco, San Francisco, CA 94143-0444, USA
| | - Daniel Vogt
- Department of Psychiatry, University of California, San Francisco, San Francisco, CA 94143-0444, USA; Weil Institute for Neurosciences, University of California, San Francisco, San Francisco, CA 94143-0444, USA; Kavli Institute for Fundamental Neuroscience, University of California, San Francisco, San Francisco, CA 94143-0444, USA
| | - Vikaas S Sohal
- Department of Psychiatry, University of California, San Francisco, San Francisco, CA 94143-0444, USA; Weil Institute for Neurosciences, University of California, San Francisco, San Francisco, CA 94143-0444, USA; Kavli Institute for Fundamental Neuroscience, University of California, San Francisco, San Francisco, CA 94143-0444, USA; Sloan Swartz Center for Theoretical Neurobiology, University of California, San Francisco, San Francisco, CA 94143-0444, USA.
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99
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Raimondo JV, Richards BA, Woodin MA. Neuronal chloride and excitability - the big impact of small changes. Curr Opin Neurobiol 2016; 43:35-42. [PMID: 27992777 DOI: 10.1016/j.conb.2016.11.012] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Revised: 10/19/2016] [Accepted: 11/09/2016] [Indexed: 12/18/2022]
Abstract
Synaptic inhibition is a critical regulator of neuronal excitability, and in the mature brain the majority of synaptic inhibition is mediated by Cl--permeable GABAA receptors. Unlike other physiologically relevant ions, Cl- is dynamically regulated, and alterations in the Cl- gradient can have significant impact on neuronal excitability. Due to changes in the neuronal Cl- concentration, GABAergic transmission can bidirectionally regulate the induction of excitatory synaptic plasticity and gate the closing of the critical period for monocular deprivation in visual cortex. GABAergic circuitry can also provide a powerful restraining mechanism for the spread of excitation, however Cl- extrusion mechanisms can become overwhelmed and GABA can paradoxically contribute to pathological excitation such as the propagation of seizure activity.
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Affiliation(s)
- Joseph V Raimondo
- Division of Physiology, Department of Human Biology and Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Anzio Road Observatory, 7925 Cape Town, South Africa
| | - Blake A Richards
- Department of Biological Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, Ontario M1C 1A4, Canada; Department of Cell and Systems Biology, University of Toronto, 25 Harbord Street, Toronto, Ontario M5S 3G5, Canada
| | - Melanie A Woodin
- Department of Cell and Systems Biology, University of Toronto, 25 Harbord Street, Toronto, Ontario M5S 3G5, Canada.
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Alfonsa H, Lakey JH, Lightowlers RN, Trevelyan AJ. Cl-out is a novel cooperative optogenetic tool for extruding chloride from neurons. Nat Commun 2016; 7:13495. [PMID: 27853135 PMCID: PMC5118542 DOI: 10.1038/ncomms13495] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2016] [Accepted: 10/10/2016] [Indexed: 01/11/2023] Open
Abstract
Chloride regulation affects brain function in many ways, for instance, by dictating the GABAergic reversal potential, and thereby influencing neuronal excitability and spike timing. Consistent with this, there is increasing evidence implicating chloride in a range of neurological conditions. Investigations about these conditions, though, are made difficult by the limited range of tools available to manipulate chloride levels. In particular, there has been no way to actively remove chloride from neurons; we now describe an optogenetic strategy, ‘Cl-out', to do exactly this. Cl-out achieves its effect by the cooperative action of two different component opsins: the proton pump, Archaerhodopsin and a chloride channel opsin. The removal of chloride happens when both are activated together, using Archaerhodopsin as an optical voltage clamp to provide the driving force for chloride removal through the concurrently opened, chloride channels. We further show that this novel optogenetic strategy can reverse an in vitro epileptogenic phenotype. Chloride regulation is important for setting GABAergic reversal potential, though tools to manipulate chloride levels are limited. Here, the authors combine Archaerhodopsin with a chloride channel opsin to generate an optogenetic chloride extrusion strategy, ‘Cl-out', which they demonstrate in hippocampal slices.
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Affiliation(s)
- Hannah Alfonsa
- Institute of Neuroscience, Medical School, Framlington Place, Newcastle upon Tyne NE2 4HH, UK
| | - Jeremy H Lakey
- Institute for Cell and Molecular Biosciences, Medical School, Framlington Place, Newcastle upon Tyne NE2 4HH, UK
| | - Robert N Lightowlers
- Institute for Cell and Molecular Biosciences, Medical School, Framlington Place, Newcastle upon Tyne NE2 4HH, UK
| | - Andrew J Trevelyan
- Institute of Neuroscience, Medical School, Framlington Place, Newcastle upon Tyne NE2 4HH, UK
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