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Skrabak D, Bischof H, Pham T, Ruth P, Ehinger R, Matt L, Lukowski R. Slack K + channels limit kainic acid-induced seizure severity in mice by modulating neuronal excitability and firing. Commun Biol 2023; 6:1029. [PMID: 37821582 PMCID: PMC10567740 DOI: 10.1038/s42003-023-05387-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2023] [Accepted: 09/25/2023] [Indexed: 10/13/2023] Open
Abstract
Mutations of the Na+-activated K+ channel Slack (KCNT1) are associated with terrible epilepsy syndromes that already begin in infancy. Here we report increased severity of acute kainic acid-induced seizures in adult and juvenile Slack knockout mice (Slack-/-) in vivo. Fittingly, we find exacerbation of cell death following kainic acid exposure in organotypic hippocampal slices as well as dissociated hippocampal cultures from Slack-/- in vitro. Furthermore, in cultured Slack-/- neurons, kainic acid-triggered Ca2+ influx and K+ efflux as well as depolarization-induced tetrodotoxin-sensitive inward currents are higher compared to the respective controls. This apparent changes in ion homeostasis could possibly explain altered action potential kinetics of Slack-/- neurons: steeper rise slope, decreased threshold, and duration of afterhyperpolarization, which ultimately lead to higher action potential frequencies during kainic acid application or injection of depolarizing currents. Based on our data, we propose Slack as crucial gatekeeper of neuronal excitability to acutely limit seizure severity.
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Affiliation(s)
- David Skrabak
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tübingen, Tübingen, Germany
| | - Helmut Bischof
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tübingen, Tübingen, Germany
| | - Thomas Pham
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tübingen, Tübingen, Germany
| | - Peter Ruth
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tübingen, Tübingen, Germany
| | - Rebekka Ehinger
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tübingen, Tübingen, Germany
| | - Lucas Matt
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tübingen, Tübingen, Germany
| | - Robert Lukowski
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tübingen, Tübingen, Germany.
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2
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Vasilopoulos N, Kaplanian A, Vinos M, Katsaiti Y, Christodoulou O, Denaxa M, Skaliora I. The role of selective SATB1 deletion in somatostatin expressing interneurons on endogenous network activity and the transition to epilepsy. J Neurosci Res 2023; 101:424-447. [PMID: 36541427 DOI: 10.1002/jnr.25156] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2022] [Revised: 10/24/2022] [Accepted: 12/03/2022] [Indexed: 12/24/2022]
Abstract
Somatostatin (SST) expressing interneurons are the second most abundant group of inhibitory neurons in the neocortex. They mainly target the apical dendrites of excitatory pyramidal cells and are implicated in feedforward and feedback inhibition. In the present study, we employ a conditional knockout mouse, in which the transcription factor Satb1 is selectively deleted in SST-expressing interneurons resulting to the reduction of their number across the somatosensory barrel field. Our goal was to investigate the effect of the reduced number of Satb1 mutant SST-interneurons on (i) the endogenous cortical network activity (spontaneously recurring Up/Down states), and (ii) the transition to epileptiform activity. By conducting LFP recordings in acute brain slices from young male and female mice, we demonstrate that mutant animals exhibit significant changes in network excitability, reflected in increased Up state occurrence, decreased Up state duration and higher levels of extracellular spiking activity. Epileptiform activity was induced through two distinct and widely used in vitro protocols: the low magnesium and the 4-Aminopyridine (4-AP) model. In the former, slices from mutant animals manifested shorter latency for the expression of stable seizure-like events. In contrast, when epilepsy was induced by 4-AP, no significant differences were reported. We conclude that normal SST-interneuron function has a significant role both in the regulation of the endogenous network activity, and in the transition to seizure-like discharges in a context-dependent manner.
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Affiliation(s)
- Nikos Vasilopoulos
- Centre for Basic Research, Biomedical Research Foundation of the Academy of Athens (BRFAA), Athens, Greece
| | - Ani Kaplanian
- Centre for Basic Research, Biomedical Research Foundation of the Academy of Athens (BRFAA), Athens, Greece
| | - Michael Vinos
- Centre for Basic Research, Biomedical Research Foundation of the Academy of Athens (BRFAA), Athens, Greece.,Department of History and Philosophy of Science, National and Kapodistrian University of Athens (NKUA), Athens, Greece
| | - Yolanda Katsaiti
- Biomedical Sciences Research Center "Alexander Fleming", Vari, Greece.,Department of Biology, National and Kapodistrian University of Athens (NKUA), Athens, Greece
| | - Ourania Christodoulou
- Biomedical Sciences Research Center "Alexander Fleming", Vari, Greece.,Department of Biology, University of Crete, Heraklion, Greece
| | - Myrto Denaxa
- Biomedical Sciences Research Center "Alexander Fleming", Vari, Greece
| | - Irini Skaliora
- Centre for Basic Research, Biomedical Research Foundation of the Academy of Athens (BRFAA), Athens, Greece.,Department of History and Philosophy of Science, National and Kapodistrian University of Athens (NKUA), Athens, Greece
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3
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Gentiletti D, de Curtis M, Gnatkovsky V, Suffczynski P. Focal seizures are organized by feedback between neural activity and ion concentration changes. eLife 2022; 11:68541. [PMID: 35916367 PMCID: PMC9377802 DOI: 10.7554/elife.68541] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2021] [Accepted: 07/12/2022] [Indexed: 11/13/2022] Open
Abstract
Human and animal EEG data demonstrate that focal seizures start with low-voltage fast activity, evolve into rhythmic burst discharges and are followed by a period of suppressed background activity. This suggests that processes with dynamics in the range of tens of seconds govern focal seizure evolution. We investigate the processes associated with seizure dynamics by complementing the Hodgkin-Huxley mathematical model with the physical laws that dictate ion movement and maintain ionic gradients. Our biophysically realistic computational model closely replicates the electrographic pattern of a typical human focal seizure characterized by low voltage fast activity onset, tonic phase, clonic phase and postictal suppression. Our study demonstrates, for the first time in silico, the potential mechanism of seizure initiation by inhibitory interneurons via the initial build-up of extracellular K+ due to intense interneuronal spiking. The model also identifies ionic mechanisms that may underlie a key feature in seizure dynamics, i.e., progressive slowing down of ictal discharges towards the end of seizure. Our model prediction of specific scaling of inter-burst intervals is confirmed by seizure data recorded in the whole guinea pig brain in vitro and in humans, suggesting that the observed termination pattern may hold across different species. Our results emphasize ionic dynamics as elementary processes behind seizure generation and indicate targets for new therapeutic strategies.
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Liu R, Sun L, Wang Y, Jia M, Wang Q, Cai X, Wu J. Double-edged Role of K Na Channels in Brain Tuning: Identifying Epileptogenic Network Micro-Macro Disconnection. Curr Neuropharmacol 2022; 20:916-928. [PMID: 34911427 PMCID: PMC9881102 DOI: 10.2174/1570159x19666211215104829] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Revised: 11/09/2021] [Accepted: 12/10/2021] [Indexed: 11/22/2022] Open
Abstract
Epilepsy is commonly recognized as a disease driven by generalized hyperexcited and hypersynchronous neural activity. Sodium-activated potassium channels (KNa channels), which are encoded by the Slo 2.2 and Slo 2.1 genes, are widely expressed in the central nervous system and considered as "brakes" to adjust neuronal adaptation through regulating action potential threshold or after-hyperpolarization under physiological condition. However, the variants in KNa channels, especially gain-of-function variants, have been found in several childhood epileptic conditions. Most previous studies focused on mapping the epileptic network on the macroscopic scale while ignoring the value of microscopic changes. Notably, paradoxical role of KNa channels working on individual neuron/microcircuit and the macroscopic epileptic expression highlights the importance of understanding epileptogenic network through combining microscopic and macroscopic methods. Here, we first illustrated the molecular and physiological function of KNa channels on preclinical seizure models and patients with epilepsy. Next, we summarized current hypothesis on the potential role of KNa channels during seizures to provide essential insight into what emerged as a micro-macro disconnection at different levels. Additionally, we highlighted the potential utility of KNa channels as therapeutic targets for developing innovative anti-seizure medications.
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Affiliation(s)
- Ru Liu
- Beijing Tiantan Hospital, Capital Medical University, Beijing, China;,Advanced Innovation Center for Human Brain Protection, Capital Medical University, Beijing, China;,China National Clinical Research Center for Neurological Diseases, Beijing, China
| | - Lei Sun
- Beijing Tiantan Hospital, Capital Medical University, Beijing, China;,Advanced Innovation Center for Human Brain Protection, Capital Medical University, Beijing, China;,China National Clinical Research Center for Neurological Diseases, Beijing, China
| | | | - Meng Jia
- Beijing Tiantan Hospital, Capital Medical University, Beijing, China;,Advanced Innovation Center for Human Brain Protection, Capital Medical University, Beijing, China;,China National Clinical Research Center for Neurological Diseases, Beijing, China
| | - Qun Wang
- Beijing Tiantan Hospital, Capital Medical University, Beijing, China;,China National Clinical Research Center for Neurological Diseases, Beijing, China
| | - Xiang Cai
- Advanced Innovation Center for Human Brain Protection, Capital Medical University, Beijing, China;,Address correspondence to these authors at the Beijing Tiantan Hospital, Capital Medical University, Beijing, China; Tel: +0086-18062552085; E-mail: Advanced Innovation Center for Human Brain Protection, Capital Medical University, Beijing, China; Tel: +0086-13319285082; E-mail:
| | - Jianping Wu
- Beijing Tiantan Hospital, Capital Medical University, Beijing, China;,Advanced Innovation Center for Human Brain Protection, Capital Medical University, Beijing, China;,China National Clinical Research Center for Neurological Diseases, Beijing, China;,Address correspondence to these authors at the Beijing Tiantan Hospital, Capital Medical University, Beijing, China; Tel: +0086-18062552085; E-mail: Advanced Innovation Center for Human Brain Protection, Capital Medical University, Beijing, China; Tel: +0086-13319285082; E-mail:
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5
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Amakhin DV, Soboleva EB, Chizhov AV, Zaitsev AV. Insertion of Calcium-Permeable AMPA Receptors during Epileptiform Activity In Vitro Modulates Excitability of Principal Neurons in the Rat Entorhinal Cortex. Int J Mol Sci 2021; 22:12174. [PMID: 34830051 PMCID: PMC8621524 DOI: 10.3390/ijms222212174] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Revised: 11/05/2021] [Accepted: 11/07/2021] [Indexed: 12/19/2022] Open
Abstract
Epileptic activity leads to rapid insertion of calcium-permeable α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (CP-AMPARs) into the synapses of cortical and hippocampal glutamatergic neurons, which generally do not express them. The physiological significance of this process is not yet fully understood; however, it is usually assumed to be a pathological process that augments epileptic activity. Using whole-cell patch-clamp recordings in rat entorhinal cortex slices, we demonstrate that the timing of epileptiform discharges, induced by 4-aminopyridine and gabazine, is determined by the shunting effect of Ca2+-dependent slow conductance, mediated predominantly by K+-channels. The blockade of CP-AMPARs by IEM-1460 eliminates this extra conductance and consequently increases the rate of discharge generation. The blockade of NMDARs reduced the additional conductance to a lesser extent than the blockade of CP-AMPARs, indicating that CP-AMPARs are a more significant source of intracellular Ca2+. The study's main findings were implemented in a mathematical model, which reproduces the shunting effect of activity-dependent conductance on the generation of discharges. The obtained results suggest that the expression of CP-AMPARs in principal neurons reduces the discharge generation rate and may be considered as a protective mechanism.
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Affiliation(s)
- Dmitry V. Amakhin
- Sechenov Institute of Evolutionary Physiology and Biochemistry, Toreza Prospekt 44, 194223 Saint Petersburg, Russia; (D.V.A.); (E.B.S.); (A.V.C.)
| | - Elena B. Soboleva
- Sechenov Institute of Evolutionary Physiology and Biochemistry, Toreza Prospekt 44, 194223 Saint Petersburg, Russia; (D.V.A.); (E.B.S.); (A.V.C.)
| | - Anton V. Chizhov
- Sechenov Institute of Evolutionary Physiology and Biochemistry, Toreza Prospekt 44, 194223 Saint Petersburg, Russia; (D.V.A.); (E.B.S.); (A.V.C.)
- Ioffe Institute, Russian Academy of Sciences, Polytekhnicheskaya 26, 194021 Saint Petersburg, Russia
| | - Aleksey V. Zaitsev
- Sechenov Institute of Evolutionary Physiology and Biochemistry, Toreza Prospekt 44, 194223 Saint Petersburg, Russia; (D.V.A.); (E.B.S.); (A.V.C.)
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6
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Abstract
This review attempts to give a concise and up-to-date overview on the role of potassium channels in epilepsies. Their role can be defined from a genetic perspective, focusing on variants and de novo mutations identified in genetic studies or animal models with targeted, specific mutations in genes coding for a member of the large potassium channel family. In these genetic studies, a demonstrated functional link to hyperexcitability often remains elusive. However, their role can also be defined from a functional perspective, based on dynamic, aggravating, or adaptive transcriptional and posttranslational alterations. In these cases, it often remains elusive whether the alteration is causal or merely incidental. With ∼80 potassium channel types, of which ∼10% are known to be associated with epilepsies (in humans) or a seizure phenotype (in animals), if genetically mutated, a comprehensive review is a challenging endeavor. This goal may seem all the more ambitious once the data on posttranslational alterations, found both in human tissue from epilepsy patients and in chronic or acute animal models, are included. We therefore summarize the literature, and expand only on key findings, particularly regarding functional alterations found in patient brain tissue and chronic animal models.
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Affiliation(s)
- Rüdiger Köhling
- Oscar Langendorff Institute of Physiology, University of Rostock, Rostock 18057, Germany
| | - Jakob Wolfart
- Oscar Langendorff Institute of Physiology, University of Rostock, Rostock 18057, Germany
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7
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Neske GT. The Slow Oscillation in Cortical and Thalamic Networks: Mechanisms and Functions. Front Neural Circuits 2016; 9:88. [PMID: 26834569 PMCID: PMC4712264 DOI: 10.3389/fncir.2015.00088] [Citation(s) in RCA: 136] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2015] [Accepted: 12/21/2015] [Indexed: 12/03/2022] Open
Abstract
During even the most quiescent behavioral periods, the cortex and thalamus express rich spontaneous activity in the form of slow (<1 Hz), synchronous network state transitions. Throughout this so-called slow oscillation, cortical and thalamic neurons fluctuate between periods of intense synaptic activity (Up states) and almost complete silence (Down states). The two decades since the original characterization of the slow oscillation in the cortex and thalamus have seen considerable advances in deciphering the cellular and network mechanisms associated with this pervasive phenomenon. There are, nevertheless, many questions regarding the slow oscillation that await more thorough illumination, particularly the mechanisms by which Up states initiate and terminate, the functional role of the rhythmic activity cycles in unconscious or minimally conscious states, and the precise relation between Up states and the activated states associated with waking behavior. Given the substantial advances in multineuronal recording and imaging methods in both in vivo and in vitro preparations, the time is ripe to take stock of our current understanding of the slow oscillation and pave the way for future investigations of its mechanisms and functions. My aim in this Review is to provide a comprehensive account of the mechanisms and functions of the slow oscillation, and to suggest avenues for further exploration.
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Affiliation(s)
- Garrett T Neske
- Department of Neuroscience, Division of Biology and Medicine, Brown UniversityProvidence, RI, USA; Department of Neurobiology, Yale UniversityNew Haven, CT, USA
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8
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Raimondo JV, Burman RJ, Katz AA, Akerman CJ. Ion dynamics during seizures. Front Cell Neurosci 2015; 9:419. [PMID: 26539081 PMCID: PMC4612498 DOI: 10.3389/fncel.2015.00419] [Citation(s) in RCA: 101] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2015] [Accepted: 10/04/2015] [Indexed: 12/14/2022] Open
Abstract
Changes in membrane voltage brought about by ion fluxes through voltage and transmitter-gated channels represent the basis of neural activity. As such, electrochemical gradients across the membrane determine the direction and driving force for the flow of ions and are therefore crucial in setting the properties of synaptic transmission and signal propagation. Ion concentration gradients are established by a variety of mechanisms, including specialized transporter proteins. However, transmembrane gradients can be affected by ionic fluxes through channels during periods of elevated neural activity, which in turn are predicted to influence the properties of on-going synaptic transmission. Such activity-induced changes to ion concentration gradients are a feature of both physiological and pathological neural processes. An epileptic seizure is an example of severely perturbed neural activity, which is accompanied by pronounced changes in intracellular and extracellular ion concentrations. Appreciating the factors that contribute to these ion dynamics is critical if we are to understand how a seizure event evolves and is sustained and terminated by neural tissue. Indeed, this issue is of significant clinical importance as status epilepticus—a type of seizure that does not stop of its own accord—is a life-threatening medical emergency. In this review we explore how the transmembrane concentration gradient of the six major ions (K+, Na+, Cl−, Ca2+, H+and HCO3−) is altered during an epileptic seizure. We will first examine each ion individually, before describing how multiple interacting mechanisms between ions might contribute to concentration changes and whether these act to prolong or terminate epileptic activity. In doing so, we will consider how the availability of experimental techniques has both advanced and restricted our ability to study these phenomena.
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Affiliation(s)
- Joseph V Raimondo
- Department of Human Biology, Faculty of Health Sciences, University of Cape Town Cape Town, South Africa ; UCT/MRC Receptor Biology Unit, Department of Integrative Biomedical Sciences and Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town Cape Town, South Africa
| | - Richard J Burman
- UCT/MRC Receptor Biology Unit, Department of Integrative Biomedical Sciences and Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town Cape Town, South Africa
| | - Arieh A Katz
- UCT/MRC Receptor Biology Unit, Department of Integrative Biomedical Sciences and Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town Cape Town, South Africa
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9
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Identification of potential novel interaction partners of the sodium-activated potassium channels Slick and Slack in mouse brain. Biochem Biophys Rep 2015; 4:291-298. [PMID: 29124216 PMCID: PMC5669359 DOI: 10.1016/j.bbrep.2015.09.024] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Revised: 09/18/2015] [Accepted: 09/29/2015] [Indexed: 02/06/2023] Open
Abstract
The sodium-activated potassium channels Slick (Slo2.1, KCNT2) and Slack (Slo2.2, KCNT1) are paralogous channels of the Slo family of high-conductance potassium channels. Slick and Slack channels are widely distributed in the mammalian CNS and they play a role in slow afterhyperpolarization, generation of depolarizing afterpotentials and in setting and stabilizing the resting potential. In the present study we used a combined approach of (co)-immunoprecipitation studies, Western blot analysis, double immunofluorescence and mass spectrometric sequencing in order to investigate protein-protein interactions of the Slick and Slack channels. The data strongly suggest that Slick and Slack channels co-assemble into identical cellular complexes. Double immunofluorescence experiments revealed that Slick and Slack channels co-localize in distinct mouse brain regions. Moreover, we identified the small cytoplasmic protein beta-synuclein and the transmembrane protein 263 (TMEM 263) as novel interaction partners of both, native Slick and Slack channels. In addition, the inactive dipeptidyl-peptidase (DPP 10) and the synapse associated protein 102 (SAP 102) were identified as constituents of the native Slick and Slack channel complexes in the mouse brain. This study presents new insights into protein-protein interactions of native Slick and Slack channels in the mouse brain.
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10
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Ohba C, Kato M, Takahashi N, Osaka H, Shiihara T, Tohyama J, Nabatame S, Azuma J, Fujii Y, Hara M, Tsurusawa R, Inoue T, Ogata R, Watanabe Y, Togashi N, Kodera H, Nakashima M, Tsurusaki Y, Miyake N, Tanaka F, Saitsu H, Matsumoto N. De novo
KCNT
1
mutations in early‐onset epileptic encephalopathy. Epilepsia 2015; 56:e121-8. [DOI: 10.1111/epi.13072] [Citation(s) in RCA: 76] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/08/2015] [Indexed: 11/25/2022]
Affiliation(s)
- Chihiro Ohba
- Department of Human Genetics Graduate School of Medicine Yokohama City University Yokohama Japan
- Department of Clinical Neurology and Stroke Medicine Yokohama City University Yokohama Japan
| | - Mitsuhiro Kato
- Department of Pediatrics Yamagata University Faculty of Medicine Yamagata Japan
| | - Nobuya Takahashi
- Department of Pediatrics Yamagata University Faculty of Medicine Yamagata Japan
| | - Hitoshi Osaka
- Division of Neurology Clinical Research Institute Kanagawa Children's Medical Center Yokohama Japan
- Department of Pediatrics Jichi Medical School Shimotsuke Tochigi Japan
| | - Takashi Shiihara
- Department of Neurology Gunma Children's Medical Center Shibukawa Japan
| | - Jun Tohyama
- Department of Pediatrics Epilepsy Center Nishi‐Niigata Chuo National Hospital Niigata Japan
| | - Shin Nabatame
- Department of Pediatrics Osaka University Graduate School of Medicine Osaka Japan
| | - Junji Azuma
- Department of Pediatrics Osaka University Graduate School of Medicine Osaka Japan
| | - Yuji Fujii
- Department of Pediatrics Hiroshima University Hospital Hiroshima Japan
| | - Munetsugu Hara
- Department of Neonatology Medical Center for Maternal and Child Health St. Mary's Hospital Kurume Japan
- Department of Pediatrics and Child Health Kurume University School of Medicine Kurume Japan
| | - Reimi Tsurusawa
- Department of Pediatrics Fukuoka University Chikushi Hospital Fukuoka Japan
| | - Takahito Inoue
- Department of Pediatrics Fukuoka University Chikushi Hospital Fukuoka Japan
| | - Reina Ogata
- Department of Pediatric Neurology Fukuoka Children's Hospital Fukuoka Japan
| | - Yoriko Watanabe
- Department of Pediatrics and Child Health Kurume University School of Medicine Kurume Japan
| | - Noriko Togashi
- Department of Neurology Miyagi Children's Hospital Sendai Japan
| | - Hirofumi Kodera
- Department of Human Genetics Graduate School of Medicine Yokohama City University Yokohama Japan
| | - Mitsuko Nakashima
- Department of Human Genetics Graduate School of Medicine Yokohama City University Yokohama Japan
| | - Yoshinori Tsurusaki
- Department of Human Genetics Graduate School of Medicine Yokohama City University Yokohama Japan
| | - Noriko Miyake
- Department of Human Genetics Graduate School of Medicine Yokohama City University Yokohama Japan
| | - Fumiaki Tanaka
- Department of Clinical Neurology and Stroke Medicine Yokohama City University Yokohama Japan
| | - Hirotomo Saitsu
- Department of Human Genetics Graduate School of Medicine Yokohama City University Yokohama Japan
| | - Naomichi Matsumoto
- Department of Human Genetics Graduate School of Medicine Yokohama City University Yokohama Japan
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11
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Bausch AE, Dieter R, Nann Y, Hausmann M, Meyerdierks N, Kaczmarek LK, Ruth P, Lukowski R. The sodium-activated potassium channel Slack is required for optimal cognitive flexibility in mice. ACTA ACUST UNITED AC 2015; 22:323-35. [PMID: 26077685 PMCID: PMC4478330 DOI: 10.1101/lm.037820.114] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2014] [Accepted: 05/05/2015] [Indexed: 01/14/2023]
Abstract
Kcnt1 encoded sodium-activated potassium channels (Slack channels) are highly expressed throughout the brain where they modulate the firing patterns and general excitability of many types of neurons. Increasing evidence suggests that Slack channels may be important for higher brain functions such as cognition and normal intellectual development. In particular, recent findings have shown that human Slack mutations produce very severe intellectual disability and that Slack channels interact directly with the Fragile X mental retardation protein (FMRP), a protein that when missing or mutated results in Fragile X syndrome (FXS), the most common form of inherited intellectual disability and autism in humans. We have now analyzed a recently developed Kcnt1 null mouse model in several behavioral tasks to assess which aspects of memory and learning are dependent on Slack. We demonstrate that Slack deficiency results in mildly altered general locomotor activity, but normal working memory, reference memory, as well as cerebellar control of motor functions. In contrast, we find that Slack channels are required for cognitive flexibility, including reversal learning processes and the ability to adapt quickly to unfamiliar situations and environments. Our data reveal that hippocampal-dependent spatial learning capabilities require the proper function of Slack channels.
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Affiliation(s)
- Anne E Bausch
- Pharmakologie, Toxikologie und Klinische Pharmazie, Institut für Pharmazie, 72076 Tübingen, Germany
| | - Rebekka Dieter
- Pharmakologie, Toxikologie und Klinische Pharmazie, Institut für Pharmazie, 72076 Tübingen, Germany
| | - Yvette Nann
- Pharmakologie, Toxikologie und Klinische Pharmazie, Institut für Pharmazie, 72076 Tübingen, Germany
| | - Mario Hausmann
- Pharmakologie, Toxikologie und Klinische Pharmazie, Institut für Pharmazie, 72076 Tübingen, Germany
| | - Nora Meyerdierks
- Pharmakologie, Toxikologie und Klinische Pharmazie, Institut für Pharmazie, 72076 Tübingen, Germany
| | - Leonard K Kaczmarek
- Department of Pharmacology, Yale University School of Medicine, New Haven, Connecticut 06520, USA Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut 06520, USA
| | - Peter Ruth
- Pharmakologie, Toxikologie und Klinische Pharmazie, Institut für Pharmazie, 72076 Tübingen, Germany
| | - Robert Lukowski
- Pharmakologie, Toxikologie und Klinische Pharmazie, Institut für Pharmazie, 72076 Tübingen, Germany
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12
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Novel coupling between TRPC-like and KNa channels modulates low threshold spike-induced afterpotentials in rat thalamic midline neurons. Neuropharmacology 2014; 86:88-96. [PMID: 25014020 DOI: 10.1016/j.neuropharm.2014.06.023] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2014] [Revised: 06/17/2014] [Accepted: 06/21/2014] [Indexed: 11/22/2022]
Abstract
Neurons in thalamic midline and paraventricular nuclei (PVT) display a unique slow afterhyperpolarizing potential (sAHP) following the low threshold spike (LTS) generated by activation of their low voltage Ca(2+) channels. We evaluated the conductances underlying this sAHP using whole-cell patch-clamp recordings in rat brain slice preparations. Initial observations recorded in the presence of TTX revealed a marked dependency of the LTS-induced sAHP on extracellular Na(+): replacing Na(+) with TRIS(+) in the external medium eliminated the LTS-induced sAHP; substitution of Na(+) with either Li(+) or choline(+) in the external medium resulted in a gradual loss of the sAHP and its replacement with a prolonged slow afterdepolarizing potential (sADP). The LTS-induced sAHP was reduced by quinidine and potentiated by loxapine, suggesting involvement of KNa-like channels. Canonical transient receptor potential (TRPC) channels were considered the source for Na(+) based on observations that the sAHP was suppressed by nonselective TRPC channel blockers (2-APB, flufenamic acid and ML204) but unchanged in the presence of TRPV1 channel blocker (SB-366791). In addition, after replacement of Na(+) with Li(+), the isolated LTS-induced sADP was significantly suppressed in the presence of 2-APB or ML204, after replacement of extracellular Ca(2+) with Sr(2+), and by intracellular Ca(2+) chelation with EGTA, data that collectively suggest involvement of Ca(2+)-activated TRPC-like conductances containing TRPC4/5 subunits. The isolated LTS-induced sADP also exhibited a strong voltage dependency, decreasing at hyperpolarizing potentials, further support for involvement of TRPC4/5 subunits. This sADP exhibited neurotransmitter receptor sensitivity, with suppression by 5-CT, a 5-HT7 receptor agonist, and enhancement by the neuropeptide orexin A. These data suggest that LTS-induced slow afterpotentials reflect a simultaneous interplay between KNa and TRPC-like conductances, novel for midline thalamic neurons.
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