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Li L, Liu Y, Hu W, Yang J, Ma S, Tian Z, Cao Z, Pan K, Jiang M, Liu X, Wu S, Luo C, Xie RG. Peripheral CCL2 induces inflammatory pain via regulation of Ih currents in small diameter DRG neurons. Front Mol Neurosci 2023; 16:1144614. [PMID: 37860084 PMCID: PMC10582564 DOI: 10.3389/fnmol.2023.1144614] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2023] [Accepted: 09/14/2023] [Indexed: 10/21/2023] Open
Abstract
The C-C motif chemokine ligand 2 (CCL2) has been implicated in chronic pain, but its exact mechanism of peripheral sensitization is unknown. In this study, we aimed to clarify the mechanism of CCL2 regulation of ion channels. Our behavioral experiments revealed that ZD7288, a blocker of Ih current, can inhibit CFA and CCL2-mediated mechanical and thermal nociceptive sensitization. Furthermore, patch clamp studies demonstrated that CFA-induced peripheral sensitization primarily affects the excitability of small-diameter DRG neurons. Further studies revealed that inflammatory pain caused by CFA or incubation of DRG with CCL2 mainly affected Ih currents in small-diameter DRG neurons, which were blocked by co-incubation CCR2 antagonist INCB3344 or adenylate cyclase inhibitor SQ22536. Immunohistochemical staining showed that both intraplantar injection of CFA as well as DRG injection of CCL2 resulted in significant upregulation of CCR2+/HCN2+ expression. In conclusion, we suggest in the inflammatory pain state, CCL2 can act on small-diameter DRG neurons, leading to upregulation of HCN2 expression and consequently Ih, which in turn leads to neuronal hyperexcitability.
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Affiliation(s)
- Lamei Li
- Department of Neurobiology, School of Basic Medicine, Fourth Military Medical University, Xi’an, China
- School of Life Sciences & Research Center for Resource Peptide Drugs, Shaanxi Engineering & Technological Research Center for Conversation & Utilization of Regional Biological Resources, Yan’an University, Yan’an, China
| | - Yuanying Liu
- Department of Neurobiology, School of Basic Medicine, Fourth Military Medical University, Xi’an, China
- School of Life Sciences & Research Center for Resource Peptide Drugs, Shaanxi Engineering & Technological Research Center for Conversation & Utilization of Regional Biological Resources, Yan’an University, Yan’an, China
| | - Wenchao Hu
- Department of Neurobiology, School of Basic Medicine, Fourth Military Medical University, Xi’an, China
| | - Jing Yang
- Heart Hospital, Xi’an International Medical Center Hospital, Xi’an, China
| | - Suibin Ma
- Department of Neurobiology, School of Basic Medicine, Fourth Military Medical University, Xi’an, China
| | - Zhicheng Tian
- Department of Neurobiology, School of Basic Medicine, Fourth Military Medical University, Xi’an, China
| | - Zixuan Cao
- No.6 Cadet Regiment, School of Basic Medical Sciences, Fourth Military Medical University, Xi’an, China
| | - Kunqing Pan
- No.19 Cadet Regiment, School of Basic Medical Sciences, Fourth Military Medical University, Xi’an, China
| | - Ming Jiang
- School of Life Sciences & Research Center for Resource Peptide Drugs, Shaanxi Engineering & Technological Research Center for Conversation & Utilization of Regional Biological Resources, Yan’an University, Yan’an, China
| | - Xia Liu
- School of Life Sciences & Research Center for Resource Peptide Drugs, Shaanxi Engineering & Technological Research Center for Conversation & Utilization of Regional Biological Resources, Yan’an University, Yan’an, China
| | - Shengxi Wu
- Department of Neurobiology, School of Basic Medicine, Fourth Military Medical University, Xi’an, China
| | - Ceng Luo
- Department of Neurobiology, School of Basic Medicine, Fourth Military Medical University, Xi’an, China
| | - Rou-Gang Xie
- Department of Neurobiology, School of Basic Medicine, Fourth Military Medical University, Xi’an, China
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Kassab NED, Mehlfeld V, Kass J, Biel M, Schneider G, Rammes G. Xenon's Sedative Effect Is Mediated by Interaction with the Cyclic Nucleotide-Binding Domain (CNBD) of HCN2 Channels Expressed by Thalamocortical Neurons of the Ventrobasal Nucleus in Mice. Int J Mol Sci 2023; 24:ijms24108613. [PMID: 37239964 DOI: 10.3390/ijms24108613] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Revised: 04/29/2023] [Accepted: 05/04/2023] [Indexed: 05/28/2023] Open
Abstract
Previous studies have shown that xenon reduces hyperpolarization-activated cyclic nucleotide-gated channels type-2 (HCN2) channel-mediated current (Ih) amplitude and shifts the half-maximal activation voltage (V1/2) in thalamocortical circuits of acute brain slices to more hyperpolarized potentials. HCN2 channels are dually gated by the membrane voltage and via cyclic nucleotides binding to the cyclic nucleotide-binding domain (CNBD) on the channel. In this study, we hypothesize that xenon interferes with the HCN2 CNBD to mediate its effect. Using the transgenic mice model HCN2EA, in which the binding of cAMP to HCN2 was abolished by two amino acid mutations (R591E, T592A), we performed ex-vivo patch-clamp recordings and in-vivo open-field test to prove this hypothesis. Our data showed that xenon (1.9 mM) application to brain slices shifts the V1/2 of Ih to more hyperpolarized potentials in wild-type thalamocortical neurons (TC) (V1/2: -97.09 [-99.56--95.04] mV compared to control -85.67 [-94.47--82.10] mV; p = 0.0005). These effects were abolished in HCN2EA neurons (TC), whereby the V1/2 reached only -92.56 [-93.16- -89.68] mV with xenon compared to -90.03 [-98.99--84.59] mV in the control (p = 0.84). After application of a xenon mixture (70% xenon, 30% O2), wild-type mice activity in the open-field test decreased to 5 [2-10] while in HCN2EA mice it remained at 30 [15-42]%, (p = 0.0006). In conclusion, we show that xenon impairs HCN2 channel function by interfering with the HCN2 CNBD site and provide in-vivo evidence that this mechanism contributes to xenon-mediated hypnotic properties.
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Affiliation(s)
- Nour El Dine Kassab
- Department of Anesthesiology and Intensive Care Medicine, Klinikum Rechts der Isar, School of Medicine, Technical University of Munich, 81675 Munich, Germany
| | - Verena Mehlfeld
- Department of Pharmacy-Center for Drug Research, Ludwig-Maximilians-Universitñt Mnchen, 81377 Munich, Germany
| | - Jennifer Kass
- Department of Pharmacy-Center for Drug Research, Ludwig-Maximilians-Universitñt Mnchen, 81377 Munich, Germany
| | - Martin Biel
- Department of Pharmacy-Center for Drug Research, Ludwig-Maximilians-Universitñt Mnchen, 81377 Munich, Germany
| | - Gerhard Schneider
- Department of Anesthesiology and Intensive Care Medicine, Klinikum Rechts der Isar, School of Medicine, Technical University of Munich, 81675 Munich, Germany
| | - Gerhard Rammes
- Department of Anesthesiology and Intensive Care Medicine, Klinikum Rechts der Isar, School of Medicine, Technical University of Munich, 81675 Munich, Germany
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3
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Majgaard J, Skov FG, Kim S, Hjortdal VE, Boedtkjer DMB. Positive chronotropic action of HCN channel antagonism in human collecting lymphatic vessels. Physiol Rep 2022; 10:e15401. [PMID: 35980021 PMCID: PMC9387113 DOI: 10.14814/phy2.15401] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2022] [Revised: 06/16/2022] [Accepted: 07/09/2022] [Indexed: 06/15/2023] Open
Abstract
Spontaneous action potentials precede phasic contractile activity in human collecting lymphatic vessels. In this study, we investigated the expression of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels in human collecting lymphatics and by pharmacological inhibition ex vivo tested their potential role in controlling contractile function. Spontaneous and agonist-evoked tension changes of isolated thoracic duct and mesenteric lymphatic vessels-obtained from surgical patients with informed consent-were investigated by isometric myography, and ivabradine, ZD7288 or cesium were used to inhibit HCN. Analysis of HCN isoforms by RT-PCR and immunofluorescence revealed HCN2 to be the predominantly expressed mRNA isoform in human thoracic duct and mesenteric lymphatic vessels and HCN2-immunoreactivity confirmed protein expression in both vessel types. However, in functional experiments ex vivo the HCN inhibitors ivabradine, ZD7288, and cesium failed to lower contraction frequency: conversely, all three antagonists induced a positive chronotropic effect with concurrent negative inotropic action, though these effects first occurred at concentrations regarded as supramaximal for HCN inhibition. Based on these results, we conclude that human collecting vessels express HCN channel proteins but under the ex vivo experimental conditions described here HCN channels have little involvement in regulating contraction frequency in human collecting lymphatic vessels. Furthermore, HCN antagonists can produce concentration-dependent positive chronotropic and negative inotropic effects, which are apparently unrelated to HCN antagonism.
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Affiliation(s)
- Jens Majgaard
- Department of BiomedicineAarhus UniversityAarhusDenmark
| | | | - Sukhan Kim
- Department of BiomedicineAarhus UniversityAarhusDenmark
| | - Vibeke Elisabeth Hjortdal
- Department of Clinical MedicineAarhus UniversityAarhusDenmark
- Department of Cardiothoracic and Vascular SurgeryAarhus University HospitalAarhusDenmark
| | - Donna M. B. Boedtkjer
- Department of BiomedicineAarhus UniversityAarhusDenmark
- Department of Clinical MedicineAarhus UniversityAarhusDenmark
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Peters CH, Singh RK, Bankston JR, Proenza C. Regulation of HCN Channels by Protein Interactions. Front Physiol 2022; 13:928507. [PMID: 35795651 PMCID: PMC9251338 DOI: 10.3389/fphys.2022.928507] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Accepted: 06/01/2022] [Indexed: 11/30/2022] Open
Abstract
Hyperpolarization-activated, cyclic nucleotide-sensitive (HCN) channels are key regulators of subthreshold membrane potentials in excitable cells. The four mammalian HCN channel isoforms, HCN1-HCN4, are expressed throughout the body, where they contribute to diverse physiological processes including cardiac pacemaking, sleep-wakefulness cycles, memory, and somatic sensation. While all HCN channel isoforms produce currents when expressed by themselves, an emerging list of interacting proteins shape HCN channel excitability to influence the physiologically relevant output. The best studied of these regulatory proteins is the auxiliary subunit, TRIP8b, which binds to multiple sites in the C-terminus of the HCN channels to regulate expression and disrupt cAMP binding to fine-tune neuronal HCN channel excitability. Less is known about the mechanisms of action of other HCN channel interaction partners like filamin A, Src tyrosine kinase, and MinK-related peptides, which have a range of effects on HCN channel gating and expression. More recently, the inositol trisphosphate receptor-associated cGMP-kinase substrates IRAG1 and LRMP (also known as IRAG2), were discovered as specific regulators of the HCN4 isoform. This review summarizes the known protein interaction partners of HCN channels and their mechanisms of action and identifies gaps in our knowledge.
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Affiliation(s)
- Colin H. Peters
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
| | - Rohit K. Singh
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
| | - John R. Bankston
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
| | - Catherine Proenza
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
- Department of Cardiology, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
- *Correspondence: Catherine Proenza,
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Hammelmann V, Stieglitz MS, Hülle H, Le Meur K, Kass J, Brümmer M, Gruner C, Rötzer RD, Fenske S, Hartmann J, Zott B, Lüthi A, Spahn S, Moser M, Isbrandt D, Ludwig A, Konnerth A, Wahl-Schott C, Biel M. Abolishing cAMP sensitivity in HCN2 pacemaker channels induces generalized seizures. JCI Insight 2019; 4:126418. [PMID: 31045576 DOI: 10.1172/jci.insight.126418] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Accepted: 04/02/2019] [Indexed: 12/17/2022] Open
Abstract
Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are dually gated channels that are operated by voltage and by neurotransmitters via the cAMP system. cAMP-dependent HCN regulation has been proposed to play a key role in regulating circuit behavior in the thalamus. By analyzing a knockin mouse model (HCN2EA), in which binding of cAMP to HCN2 was abolished by 2 amino acid exchanges (R591E, T592A), we found that cAMP gating of HCN2 is essential for regulating the transition between the burst and tonic modes of firing in thalamic dorsal-lateral geniculate (dLGN) and ventrobasal (VB) nuclei. HCN2EA mice display impaired visual learning, generalized seizures of thalamic origin, and altered NREM sleep properties. VB-specific deletion of HCN2, but not of HCN4, also induced these generalized seizures of the absence type, corroborating a key role of HCN2 in this particular nucleus for controlling consciousness. Together, our data define distinct pathological phenotypes resulting from the loss of cAMP-mediated gating of a neuronal HCN channel.
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Affiliation(s)
- Verena Hammelmann
- Department of Pharmacy, Center for Drug Research, Center for Integrated Protein Science Munich, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Marc Sebastian Stieglitz
- Department of Pharmacy, Center for Drug Research, Center for Integrated Protein Science Munich, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Henrik Hülle
- Department of Pharmacy, Center for Drug Research, Center for Integrated Protein Science Munich, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Karim Le Meur
- Department of Pharmacy, Center for Drug Research, Center for Integrated Protein Science Munich, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Jennifer Kass
- Department of Pharmacy, Center for Drug Research, Center for Integrated Protein Science Munich, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Manuela Brümmer
- Department of Pharmacy, Center for Drug Research, Center for Integrated Protein Science Munich, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Christian Gruner
- Department of Pharmacy, Center for Drug Research, Center for Integrated Protein Science Munich, Ludwig-Maximilians-Universität München, Munich, Germany
| | - René Dominik Rötzer
- Department of Pharmacy, Center for Drug Research, Center for Integrated Protein Science Munich, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Stefanie Fenske
- Department of Pharmacy, Center for Drug Research, Center for Integrated Protein Science Munich, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Jana Hartmann
- Institute of Neuroscience, Technical University of Munich, Munich, Germany; and Munich Cluster for Systems Neurology (SyNergy) and Center for Integrated Protein Sciences (CIPSM), Munich, Germany
| | - Benedikt Zott
- Institute of Neuroscience, Technical University of Munich, Munich, Germany; and Munich Cluster for Systems Neurology (SyNergy) and Center for Integrated Protein Sciences (CIPSM), Munich, Germany
| | - Anita Lüthi
- Department of Fundamental Neurosciences, University of Lausanne, Lausanne, Switzerland
| | - Saskia Spahn
- Department of Pharmacy, Center for Drug Research, Center for Integrated Protein Science Munich, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Markus Moser
- Department for Molecular Medicine, Max-Planck-Institut für Biochemie, Martinsried, Germany
| | - Dirk Isbrandt
- DZNE Research Group, Experimental Neurophysiology, Institute for Molecular and Behavioral Neuroscience, University of Cologne, Germany
| | - Andreas Ludwig
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Arthur Konnerth
- Institute of Neuroscience, Technical University of Munich, Munich, Germany; and Munich Cluster for Systems Neurology (SyNergy) and Center for Integrated Protein Sciences (CIPSM), Munich, Germany
| | - Christian Wahl-Schott
- Department of Pharmacy, Center for Drug Research, Center for Integrated Protein Science Munich, Ludwig-Maximilians-Universität München, Munich, Germany.,Institut für Neurophysiologie, Medizinische Hochschule Hannover, Hannover, Germany
| | - Martin Biel
- Department of Pharmacy, Center for Drug Research, Center for Integrated Protein Science Munich, Ludwig-Maximilians-Universität München, Munich, Germany
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6
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Brennan GP, Baram TZ, Poolos NP. Hyperpolarization-Activated Cyclic Nucleotide-Gated (HCN) Channels in Epilepsy. Cold Spring Harb Perspect Med 2016; 6:a022384. [PMID: 26931806 DOI: 10.1101/cshperspect.a022384] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Epilepsy is a common brain disorder characterized by the occurrence of spontaneous seizures. These bursts of synchronous firing arise from abnormalities of neuronal networks. Excitability of individual neurons and neuronal networks is largely governed by ion channels and, indeed, abnormalities of a number of ion channels resulting from mutations or aberrant expression and trafficking underlie several types of epilepsy. Here, we focus on the hyperpolarization-activated cyclic nucleotide-gated ion (HCN) channels that conduct Ih current. This conductance plays complex and diverse roles in the regulation of neuronal and network excitability. We describe the normal function of HCN channels and discuss how aberrant expression, assembly, trafficking, and posttranslational modifications contribute to experimental and human epilepsy.
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Affiliation(s)
- Gary P Brennan
- Department of Pediatrics, University of California-Irvine, Irvine, California 92697-4475
| | - Tallie Z Baram
- Department of Pediatrics, University of California-Irvine, Irvine, California 92697-4475 Departments of Anatomy/Neurobiology and Neurology, University of California-Irvine, Irvine, California 92697-4475
| | - Nicholas P Poolos
- Department of Neurology and Regional Epilepsy Center, University of Washington, Seattle, Washington 98104
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7
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He C, Chen F, Li B, Hu Z. Neurophysiology of HCN channels: From cellular functions to multiple regulations. Prog Neurobiol 2014; 112:1-23. [DOI: 10.1016/j.pneurobio.2013.10.001] [Citation(s) in RCA: 230] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2012] [Revised: 10/01/2013] [Accepted: 10/07/2013] [Indexed: 12/18/2022]
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8
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Cao-Ehlker X, Zong X, Hammelmann V, Gruner C, Fenske S, Michalakis S, Wahl-Schott C, Biel M. Up-regulation of hyperpolarization-activated cyclic nucleotide-gated channel 3 (HCN3) by specific interaction with K+ channel tetramerization domain-containing protein 3 (KCTD3). J Biol Chem 2013; 288:7580-7589. [PMID: 23382386 DOI: 10.1074/jbc.m112.434803] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Most ion channels consist of the principal ion-permeating core subunit(s) and accessory proteins that are assembled with the channel core. The biological functions of the latter proteins are diverse and include the regulation of the biophysical properties of the ion channel, its connection to signaling pathways and the control of its cell surface expression. There is recent evidence that native hyperpolarization-activated cyclic nucleotide-gated channel complexes (HCN1-4) also contain accessory subunits, among which TRIP8b (tetratricopeptide repeat-containing Rab8b-interacting protein) has been most extensively studied. Here, we identify KCTD3, a so far uncharacterized member of the potassium channel tetramerization-domain containing (KCTD) protein family as an HCN3-interacting protein. KCTD3 is widely expressed in brain and some non-neuronal tissues and colocalizes with HCN3 in specific regions of the brain including hypothalamus. Within the HCN channel family, KCTD3 specifically binds to HCN3 and leads to a profound up-regulation of cell surface expression and current density of this channel. HCN3 can also functionally interact with TRIP8b; however, we found no evidence for channel complexes containing both TRIP8b and KCTD3. The C terminus of HCN3 is crucially required for functional interaction with KCTD3. Replacement of the cytosolic C terminus of HCN2 by the corresponding domain of HCN3 renders HCN2 sensitive to regulation by KCTD3. The C-terminal-half of KCTD3 is sufficient for binding to HCN3. However, the complete protein including the N-terminal tetramerization domain is needed for HCN3 current up-regulation. Together, our experiments indicate that KCTD3 is an accessory subunit of native HCN3 complexes.
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Affiliation(s)
- Xiaochun Cao-Ehlker
- Center for Integrated Protein Science CIPS-M and Zentrum für Pharmaforschung, Department Pharmazie, Ludwig-Maximilians-Universität München, 81377 Munich, Germany
| | - Xiangang Zong
- Center for Integrated Protein Science CIPS-M and Zentrum für Pharmaforschung, Department Pharmazie, Ludwig-Maximilians-Universität München, 81377 Munich, Germany
| | - Verena Hammelmann
- Center for Integrated Protein Science CIPS-M and Zentrum für Pharmaforschung, Department Pharmazie, Ludwig-Maximilians-Universität München, 81377 Munich, Germany
| | - Christian Gruner
- Center for Integrated Protein Science CIPS-M and Zentrum für Pharmaforschung, Department Pharmazie, Ludwig-Maximilians-Universität München, 81377 Munich, Germany
| | - Stefanie Fenske
- Center for Integrated Protein Science CIPS-M and Zentrum für Pharmaforschung, Department Pharmazie, Ludwig-Maximilians-Universität München, 81377 Munich, Germany
| | - Stylianos Michalakis
- Center for Integrated Protein Science CIPS-M and Zentrum für Pharmaforschung, Department Pharmazie, Ludwig-Maximilians-Universität München, 81377 Munich, Germany
| | - Christian Wahl-Schott
- Center for Integrated Protein Science CIPS-M and Zentrum für Pharmaforschung, Department Pharmazie, Ludwig-Maximilians-Universität München, 81377 Munich, Germany
| | - Martin Biel
- Center for Integrated Protein Science CIPS-M and Zentrum für Pharmaforschung, Department Pharmazie, Ludwig-Maximilians-Universität München, 81377 Munich, Germany.
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9
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Abstract
Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels have a key role in the control of heart rate and neuronal excitability. Ivabradine is the first compound acting on HCN channels to be clinically approved for the treatment of angina pectoris. HCN channels may offer excellent opportunities for the development of novel anticonvulsant, anaesthetic and analgesic drugs. In support of this idea, some well-established drugs that act on the central nervous system - including lamotrigine, gabapentin and propofol - have been found to modulate HCN channel function. This Review gives an up-to-date summary of compounds acting on HCN channels, and discusses strategies to further explore the potential of these channels for therapeutic intervention.
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10
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Towards an integrated view of HCN channel role in epilepsy. Curr Opin Neurobiol 2011; 21:873-9. [PMID: 21782415 DOI: 10.1016/j.conb.2011.06.013] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2011] [Revised: 06/11/2011] [Accepted: 06/30/2011] [Indexed: 12/17/2022]
Abstract
Epilepsy is the third most common brain disorder and affects millions of people. Epilepsy is characterized by the occurrence of spontaneous seizures, that is, bursts of synchronous firing of large populations of neurons. These are believed to result from abnormal regulation of neuronal excitability that favors hypersynchrony. Among the intrinsic conductances that govern neuronal excitability, the hyperpolarization-activated current (I(h)) plays complex and important roles in the fine-tuning of both cellular and network activity. Not surprisingly, dysregulation of I(h) and/or of its conducting ion-channels (HCN) has been strongly implicated in various experimental models of epilepsy, as well as in human epilepsy. Here we provide an overview of recent findings on the distinct physiological roles played by I(h) in specific contexts, and the cellular mechanisms that underlie these functions, including the subunit make-up of the channels. We further discuss current knowledge of dysregulation of I(h) and HCN channels in epilepsy in light of the multifaceted functions of I(h) in the brain.
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