1
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Burman RJ, Diviney T, Călin A, Gothard G, Jouhanneau JSM, Poulet JFA, Sen A, Akerman CJ. Optogenetic Determination of Dynamic and Cell-Type-Specific Inhibitory Reversal Potentials. J Neurosci 2024; 44:e1392232024. [PMID: 38604778 PMCID: PMC11097265 DOI: 10.1523/jneurosci.1392-23.2024] [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: 07/24/2023] [Revised: 03/31/2024] [Accepted: 04/03/2024] [Indexed: 04/13/2024] Open
Abstract
The reversal potential refers to the membrane potential at which the net current flow through a channel reverses direction. The reversal potential is determined by transmembrane ion gradients and, in turn, determines how the channel's activity will affect the membrane potential. Traditional investigation into the reversal potential of inhibitory ligand-gated ion channels (EInh) has relied upon the activation of endogenous receptors, such as the GABA-A receptor (GABAAR). There are, however, challenges associated with activating endogenous receptors, including agonist delivery, isolating channel responses, and the effects of receptor saturation and desensitization. Here, we demonstrate the utility of using a light-gated anion channel, stGtACR2, to probe EInh in the rodent brain. Using mice of both sexes, we demonstrate that the properties of this optically activated channel make it a suitable proxy for studying GABAAR receptor-mediated inhibition. We validate this agonist-independent optogenetic strategy in vitro and in vivo and further show how it can accurately capture differences in EInh dynamics following manipulations of endogenous ion fluxes. This allows us to explore distinct resting EInh differences across genetically defined neuronal subpopulations. Using this approach to challenge ion homeostasis mechanisms in neurons, we uncover cell-specific EInh dynamics that are supported by the differential expression of endogenous ion handling mechanisms. Our findings therefore establish an effective optical strategy for revealing novel aspects of inhibitory reversal potentials and thereby expand the repertoire of optogenetics.
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Affiliation(s)
- Richard J Burman
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, United Kingdom
- Oxford Epilepsy Research Group, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford OX3 9DU, United Kingdom
| | - Tara Diviney
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, United Kingdom
| | - Alexandru Călin
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, United Kingdom
| | - Gemma Gothard
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, United Kingdom
| | - Jean-Sébastien M Jouhanneau
- Max-Delbrück Center for Molecular Medicine in the Helmholtz Association (MDC), Berlin 13125, Germany
- Neuroscience Research Center, Charité-Universitätsmedizin, Berlin 10117, Germany
| | - James F A Poulet
- Max-Delbrück Center for Molecular Medicine in the Helmholtz Association (MDC), Berlin 13125, Germany
- Neuroscience Research Center, Charité-Universitätsmedizin, Berlin 10117, Germany
| | - Arjune Sen
- Oxford Epilepsy Research Group, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford OX3 9DU, United Kingdom
| | - Colin J Akerman
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, United Kingdom
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2
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Mao F, Yang W. How Merkel cells transduce mechanical stimuli: A biophysical model of Merkel cells. PLoS Comput Biol 2023; 19:e1011720. [PMID: 38117763 PMCID: PMC10732429 DOI: 10.1371/journal.pcbi.1011720] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2023] [Accepted: 11/27/2023] [Indexed: 12/22/2023] Open
Abstract
Merkel cells combine with Aβ afferents, producing slowly adapting type 1(SA1) responses to mechanical stimuli. However, how Merkel cells transduce mechanical stimuli into neural signals to Aβ afferents is still unclear. Here we develop a biophysical model of Merkel cells for mechanical transduction by incorporating main ingredients such as Ca2+ and K+ voltage-gated channels, Piezo2 channels, internal Ca2+ stores, neurotransmitters release, and cell deformation. We first validate our model with several experiments. Then we reveal that Ca2+ and K+ channels on the plasma membrane shape the depolarization of membrane potentials, further regulating the Ca2+ transients in the cells. We also show that Ca2+ channels on the plasma membrane mainly inspire the Ca2+ transients, while internal Ca2+ stores mainly maintain the Ca2+ transients. Moreover, we show that though Piezo2 channels are rapidly adapting mechanical-sensitive channels, they are sufficient to inspire sustained Ca2+ transients in Merkel cells, which further induce the release of neurotransmitters for tens of seconds. Thus our work provides a model that captures the membrane potentials and Ca2+ transients features of Merkel cells and partly explains how Merkel cells transduce the mechanical stimuli by Piezo2 channels.
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Affiliation(s)
- Fangtao Mao
- Research Center for Humanoid Sensing, Intelligent Perception Research Institute of Zhejiang Lab, Hangzhou, Zhejiang, China
| | - Wenzhen Yang
- Research Center for Humanoid Sensing, Intelligent Perception Research Institute of Zhejiang Lab, Hangzhou, Zhejiang, China
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3
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Tescarollo FC, Valdivia D, Chen S, Sun H. Unilateral optogenetic kindling of hippocampus leads to more severe impairments of the inhibitory signaling in the contralateral hippocampus. Front Mol Neurosci 2023; 16:1268311. [PMID: 37942301 PMCID: PMC10627882 DOI: 10.3389/fnmol.2023.1268311] [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: 07/27/2023] [Accepted: 09/20/2023] [Indexed: 11/10/2023] Open
Abstract
The kindling model has been used extensively by researchers to study the neurobiology of temporal lobe epilepsy (TLE) due to its capacity to induce intensification of seizures by the progressive recruitment of additional neuronal clusters into epileptogenic networks. We applied repetitive focal optogenetic activation of putative excitatory neurons in the dorsal CA1 area of the hippocampus of mice to investigate the role of inhibitory signaling during this process. This experimental protocol resulted in a kindling phenotype that was maintained for 2 weeks after the animals were fully kindled. As a result of the different phases of optogenetic kindling (OpK), key inhibitory signaling elements, such as KCC2 and NKCC1, exhibited distinct temporal and spatial dynamics of regulation. These alterations in protein expression were related to the distinct pattern of ictal activity propagation through the different hippocampal sublayers. Our results suggest the KCC2 disruption in the contralateral hippocampus of fully kindled animals progressively facilitated the creation of pathological pathways for seizure propagation through the hippocampal network. Upon completion of kindling, we observed animals that were restimulated after a rest period of 14-day showed, besides a persistent KCC2 downregulation, an NKCC1 upregulation in the bilateral dentate gyrus and hippocampus-wide loss of parvalbumin-positive interneurons. These alterations observed in the chronic phase of OpK suggest that the hippocampus of rekindled animals continued to undergo self-modifications during the rest period. The changes resulting from this period suggest the possibility of the development of a mirror focus on the hippocampus contralateral to the site of optical stimulations. Our results offer perspectives for preventing the recruitment and conversion of healthy neuronal networks into epileptogenic ones among patients with epilepsy.
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Affiliation(s)
| | | | | | - Hai Sun
- Department of Neurosurgery, Rutgers Robert Wood Johnson Medical School, New Brunswick, NJ, United States
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4
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Hudson KE, Grau JW. Ionic Plasticity: Common Mechanistic Underpinnings of Pathology in Spinal Cord Injury and the Brain. Cells 2022; 11:cells11182910. [PMID: 36139484 PMCID: PMC9496934 DOI: 10.3390/cells11182910] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Revised: 09/12/2022] [Accepted: 09/14/2022] [Indexed: 11/16/2022] Open
Abstract
The neurotransmitter GABA is normally characterized as having an inhibitory effect on neural activity in the adult central nervous system (CNS), which quells over-excitation and limits neural plasticity. Spinal cord injury (SCI) can bring about a modification that weakens the inhibitory effect of GABA in the central gray caudal to injury. This change is linked to the downregulation of the potassium/chloride cotransporter (KCC2) and the consequent rise in intracellular Cl- in the postsynaptic neuron. As the intracellular concentration increases, the inward flow of Cl- through an ionotropic GABA-A receptor is reduced, which decreases its hyperpolarizing (inhibitory) effect, a modulatory effect known as ionic plasticity. The loss of GABA-dependent inhibition enables a state of over-excitation within the spinal cord that fosters aberrant motor activity (spasticity) and chronic pain. A downregulation of KCC2 also contributes to the development of a number of brain-dependent pathologies linked to states of neural over-excitation, including epilepsy, addiction, and developmental disorders, along with other diseases such as hypertension, asthma, and irritable bowel syndrome. Pharmacological treatments that target ionic plasticity have been shown to bring therapeutic benefits.
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Affiliation(s)
- Kelsey E. Hudson
- Neuroscience, Texas A&M University, College Station, TX 77843, USA
- Correspondence:
| | - James W. Grau
- Psychological & Brain Sciences, Texas A&M University, College Station, TX 77843, USA
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5
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Lopez-Sola E, Sanchez-Todo R, Lleal È, Köksal Ersöz E, Yochum M, Makhalova J, Mercadal B, Guasch M, Salvador R, Lozano-Soldevilla D, Modolo J, Bartolomei F, Wendling F, Benquet P, Ruffini G. A personalizable autonomous neural mass model of epileptic seizures. J Neural Eng 2022; 19. [PMID: 35995031 DOI: 10.1088/1741-2552/ac8ba8] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2022] [Accepted: 08/22/2022] [Indexed: 11/11/2022]
Abstract
Work in the last two decades has shown that neural mass models (NMM) can realistically reproduce and explain epileptic seizure transitions as recorded by electrophysiological methods (EEG, SEEG). In previous work, advances were achieved by increasing excitation and heuristically varying network inhibitory coupling parameters in the models. Based on these early studies, we provide a laminar NMM capable of realistically reproducing the electrical activity recorded by SEEG in the epileptogenic zone during interictal to ictal states. With the exception of the external noise input into the pyramidal cell population, the model dynamics are autonomous. By setting the system at a point close to bifurcation, seizure-like transitions are generated, including pre-ictal spikes, low voltage fast activity, and ictal rhythmic activity. A novel element in the model is a physiologically motivated algorithm for chloride dynamics: the gain of GABAergic post-synaptic potentials is modulated by the pathological accumulation of chloride in pyramidal cells due to high inhibitory input and/or dysfunctional chloride transport. In addition, in order to simulate SEEG signals for comparison with real seizure recordings, the NMM is embedded first in a layered model of the neocortex and then in a realistic physical model. We compare modeling results with data from four epilepsy patient cases. By including key pathophysiological mechanisms, the proposed framework captures succinctly the electrophysiological phenomenology observed in ictal states, paving the way for robust personalization methods based on NMMs.
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Affiliation(s)
- Edmundo Lopez-Sola
- Neuroelectrics Barcelona SL, Avda Tibidabo, 47 bis, Barcelona, Barcelona, 08035, SPAIN
| | - Roser Sanchez-Todo
- Neuroelectrics Barcelona SL, Avda Tibidabo, 47 bis, Barcelona, Catalunya, 08035, SPAIN
| | - Èlia Lleal
- Neuroelectrics Barcelona SL, Avda Tibidabo, 47 bis, Barcelona, Catalunya, 08035, SPAIN
| | - Elif Köksal Ersöz
- LTSI, Universite de Rennes 1, Campus de Beaulieu, Rennes, Bretagne, 35065, FRANCE
| | - Maxime Yochum
- LTSI, Universite de Rennes 1, Campus Beaulieu, Rennes, Bretagne, 35065, FRANCE
| | - Julia Makhalova
- Neurophysiologie clinique, Service d'Epileptologie et de Rythmologie Cerebrale, Assistance Publique Hopitaux de Marseille, Hôpital de la Timone, Marseille, Provence-Alpes-Côte d'Azu, 13354, FRANCE
| | - Borja Mercadal
- Neuroelectrics Barcelona SL, Avda Tibidabo, 47 bis, Barcelona, Catalunya, 08035, SPAIN
| | - Maria Guasch
- Neuroelectrics Barcelona SL, Avda Tibidabo, 47 bis, Barcelona, Barcelona, 08035, SPAIN
| | - Ricardo Salvador
- Neuroelectrics Barcelona SL, Av Tibidabo, 47bis, Barcelona, Barcelona, Catalunya, 08035, SPAIN
| | | | - Julien Modolo
- LTSI, Universite de Rennes 1, Campus de Beaulieu, Rennes, Bretagne, 35065, FRANCE
| | - Fabrice Bartolomei
- Neurophysiologie clinique, Service d'Epileptologie et de Rythmologie Cerebrale, Assistance Publique Hopitaux de Marseille, Hôpital de la Timone, Marseille, Provence-Alpes-Côte d'Azu, 13354, FRANCE
| | - Fabrice Wendling
- LTSI, Universite de Rennes 1, Campus Beaulieu, Rennes, Bretagne, 35065, FRANCE
| | - Pascal Benquet
- LTSI, Universite de Rennes 1, Campus Beaulieu, Rennes, Bretagne, 35065, FRANCE
| | - Giulio Ruffini
- Neuroelectrics Barcelona SL, Avda Tibidabo, 47 bis, Barcelona, Catalunya, 08035, SPAIN
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6
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Kilb W. When Are Depolarizing GABAergic Responses Excitatory? Front Mol Neurosci 2021; 14:747835. [PMID: 34899178 PMCID: PMC8651619 DOI: 10.3389/fnmol.2021.747835] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2021] [Accepted: 10/28/2021] [Indexed: 11/13/2022] Open
Abstract
The membrane responses upon activation of GABA(A) receptors critically depend on the intracellular Cl− concentration ([Cl−]i), which is maintained by a set of transmembrane transporters for Cl−. During neuronal development, but also under several pathophysiological conditions, the prevailing expression of the Cl− loader NKCC1 and the low expression of the Cl− extruder KCC2 causes elevated [Cl−]i, which result in depolarizing GABAergic membrane responses. However, depolarizing GABAergic responses are not necessarily excitatory, as GABA(A) receptors also reduces the input resistance of neurons and thereby shunt excitatory inputs. To summarize our knowledge on the effect of depolarizing GABA responses on neuronal excitability, this review discusses theoretical considerations and experimental studies illustrating the relation between GABA conductances, GABA reversal potential and neuronal excitability. In addition, evidences for the complex spatiotemporal interaction between depolarizing GABAergic and glutamatergic inputs are described. Moreover, mechanisms that influence [Cl−]i beyond the expression of Cl− transporters are presented. And finally, several in vitro and in vivo studies that directly investigated whether GABA mediates excitation or inhibition during early developmental stages are summarized. In summary, these theoretical considerations and experimental evidences suggest that GABA can act as inhibitory neurotransmitter even under conditions that maintain substantial depolarizing membrane responses.
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Affiliation(s)
- Werner Kilb
- Institute of Physiology, University Medical Center of the Johannes Gutenberg-University Mainz, Mainz, Germany
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7
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Sullivan BJ, Kipnis PA, Carter BM, Shao LR, Kadam SD. Targeting ischemia-induced KCC2 hypofunction rescues refractory neonatal seizures and mitigates epileptogenesis in a mouse model. Sci Signal 2021; 14:eabg2648. [PMID: 34752143 DOI: 10.1126/scisignal.abg2648] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
[Figure: see text].
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Affiliation(s)
- Brennan J Sullivan
- Neuroscience Laboratory, Hugo Moser Research Institute at Kennedy Krieger, Baltimore, MD, USA
| | - Pavel A Kipnis
- Neuroscience Laboratory, Hugo Moser Research Institute at Kennedy Krieger, Baltimore, MD, USA
| | - Brandon M Carter
- Neuroscience Laboratory, Hugo Moser Research Institute at Kennedy Krieger, Baltimore, MD, USA
| | - Li-Rong Shao
- Division of Pediatric Neurology, Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Shilpa D Kadam
- Neuroscience Laboratory, Hugo Moser Research Institute at Kennedy Krieger, Baltimore, MD, USA.,Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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8
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Sergeeva EG, Rosenberg PA, Benowitz LI. Non-Cell-Autonomous Regulation of Optic Nerve Regeneration by Amacrine Cells. Front Cell Neurosci 2021; 15:666798. [PMID: 33935656 PMCID: PMC8085350 DOI: 10.3389/fncel.2021.666798] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Accepted: 03/19/2021] [Indexed: 11/13/2022] Open
Abstract
Visual information is conveyed from the eye to the brain through the axons of retinal ganglion cells (RGCs) that course through the optic nerve and synapse onto neurons in multiple subcortical visual relay areas. RGCs cannot regenerate their axons once they are damaged, similar to most mature neurons in the central nervous system (CNS), and soon undergo cell death. These phenomena of neurodegeneration and regenerative failure are widely viewed as being determined by cell-intrinsic mechanisms within RGCs or to be influenced by the extracellular environment, including glial or inflammatory cells. However, a new concept is emerging that the death or survival of RGCs and their ability to regenerate axons are also influenced by the complex circuitry of the retina and that the activation of a multicellular signaling cascade involving changes in inhibitory interneurons - the amacrine cells (AC) - contributes to the fate of RGCs. Here, we review our current understanding of the role that interneurons play in cell survival and axon regeneration after optic nerve injury.
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Affiliation(s)
- Elena G. Sergeeva
- Department of Neurology, Boston Children’s Hospital, Boston, MA, United States
- Kirby Center for Neuroscience, Boston Children’s Hospital, Boston, MA, United States
- Department of Neurology, Harvard Medical School, Boston, MA, United States
| | - Paul A. Rosenberg
- Department of Neurology, Boston Children’s Hospital, Boston, MA, United States
- Kirby Center for Neuroscience, Boston Children’s Hospital, Boston, MA, United States
- Department of Neurology, Harvard Medical School, Boston, MA, United States
| | - Larry I. Benowitz
- Kirby Center for Neuroscience, Boston Children’s Hospital, Boston, MA, United States
- Laboratories for Neuroscience Research in Neurosurgery, Boston Children’s Hospital, Boston, MA, United States
- Department of Neurosurgery, Boston Children’s Hospital, Boston, MA, United States
- Department of Neurosurgery, Harvard Medical School, Boston, MA, United States
- Department of Ophthalmology, Harvard Medical School, Boston, MA, United States
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9
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Lombardi A, Jedlicka P, Luhmann HJ, Kilb W. Coincident glutamatergic depolarizations enhance GABAA receptor-dependent Cl- influx in mature and suppress Cl- efflux in immature neurons. PLoS Comput Biol 2021; 17:e1008573. [PMID: 33465082 PMCID: PMC7845986 DOI: 10.1371/journal.pcbi.1008573] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Revised: 01/29/2021] [Accepted: 11/30/2020] [Indexed: 11/19/2022] Open
Abstract
The impact of GABAergic transmission on neuronal excitability depends on the Cl--gradient across membranes. However, the Cl--fluxes through GABAA receptors alter the intracellular Cl- concentration ([Cl-]i) and in turn attenuate GABAergic responses, a process termed ionic plasticity. Recently it has been shown that coincident glutamatergic inputs significantly affect ionic plasticity. Yet how the [Cl-]i changes depend on the properties of glutamatergic inputs and their spatiotemporal relation to GABAergic stimuli is unknown. To investigate this issue, we used compartmental biophysical models of Cl- dynamics simulating either a simple ball-and-stick topology or a reconstructed CA3 neuron. These computational experiments demonstrated that glutamatergic co-stimulation enhances GABA receptor-mediated Cl- influx at low and attenuates or reverses the Cl- efflux at high initial [Cl-]i. The size of glutamatergic influence on GABAergic Cl--fluxes depends on the conductance, decay kinetics, and localization of glutamatergic inputs. Surprisingly, the glutamatergic shift in GABAergic Cl--fluxes is invariant to latencies between GABAergic and glutamatergic inputs over a substantial interval. In agreement with experimental data, simulations in a reconstructed CA3 pyramidal neuron with physiological patterns of correlated activity revealed that coincident glutamatergic synaptic inputs contribute significantly to the activity-dependent [Cl-]i changes. Whereas the influence of spatial correlation between distributed glutamatergic and GABAergic inputs was negligible, their temporal correlation played a significant role. In summary, our results demonstrate that glutamatergic co-stimulation had a substantial impact on ionic plasticity of GABAergic responses, enhancing the attenuation of GABAergic inhibition in the mature nervous systems, but suppressing GABAergic [Cl-]i changes in the immature brain. Therefore, glutamatergic shift in GABAergic Cl--fluxes should be considered as a relevant factor of short-term plasticity. Information processing in the brain requires that excitation and inhibition are balanced. The main inhibitory neurotransmitter in the brain is gamma-amino-butyric acid (GABA). GABA actions depend on the Cl--gradient, but activation of ionotropic GABA receptors causes Cl--fluxes and thus reduces GABAergic inhibition. Here, we investigated how a coincident membrane depolarization by excitatory glutamatergic synapses influences GABA-induced Cl--fluxes using a biophysical compartmental model of Cl- dynamics, simulating either simple or realistic neuron topologies. We demonstrate that glutamatergic co-stimulation directly affects GABA-induced Cl--fluxes, with the size of glutamatergic effects depending on the conductance, the decay kinetics, and localization of glutamatergic inputs. We also show that the glutamatergic shift in GABAergic Cl--fluxes is surprisingly stable over a substantial range of latencies between glutamatergic and GABAergic inputs. We conclude from these results that glutamatergic co-stimulation alters GABAergic Cl--fluxes and in turn affects the strength of GABAergic inhibition. These coincidence-dependent ionic changes should be considered as a relevant factor of short-term plasticity in the CNS.
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Affiliation(s)
- Aniello Lombardi
- Institute of Physiology, University Medical Center Mainz, Johannes Gutenberg University, Mainz, Germany
| | - Peter Jedlicka
- ICAR3R - Interdisciplinary Centre for 3Rs in Animal Research, Faculty of Medicine, Justus-Liebig-University, Giessen, Germany
- Institute of Clinical Neuroanatomy, Neuroscience Center, Goethe University, Frankfurt/Main, Germany
- Frankfurt Institute for Advanced Studies, Frankfurt am Main, Germany
| | - Heiko J. Luhmann
- Institute of Physiology, University Medical Center Mainz, Johannes Gutenberg University, Mainz, Germany
| | - Werner Kilb
- Institute of Physiology, University Medical Center Mainz, Johannes Gutenberg University, Mainz, Germany
- * E-mail:
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10
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Kolbaev SN, Mohapatra N, Chen R, Lombardi A, Staiger JF, Luhmann HJ, Jedlicka P, Kilb W. NKCC-1 mediated Cl - uptake in immature CA3 pyramidal neurons is sufficient to compensate phasic GABAergic inputs. Sci Rep 2020; 10:18399. [PMID: 33110147 PMCID: PMC7591924 DOI: 10.1038/s41598-020-75382-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Accepted: 10/09/2020] [Indexed: 12/12/2022] Open
Abstract
Activation of GABAA receptors causes in immature neurons a functionally relevant decrease in the intracellular Cl- concentration ([Cl-]i), a process termed ionic plasticity. Amount and duration of ionic plasticity depends on kinetic properties of [Cl-]i homeostasis. In order to characterize the capacity of Cl- accumulation and to quantify the effect of persistent GABAergic activity on [Cl-]i, we performed gramicidin-perforated patch-clamp recordings from CA3 pyramidal neurons of immature (postnatal day 4-7) rat hippocampal slices. These experiments revealed that inhibition of NKCC1 decreased [Cl-]i toward passive distribution with a time constant of 381 s. In contrast, active Cl- accumulation occurred with a time constant of 155 s, corresponding to a rate of 15.4 µM/s. Inhibition of phasic GABAergic activity had no significant effect on steady state [Cl-]i. Inhibition of tonic GABAergic currents induced a significant [Cl-]i increase by 1.6 mM, while activation of tonic extrasynaptic GABAA receptors with THIP significantly reduced [Cl-]i.. Simulations of neuronal [Cl-]i homeostasis supported the observation, that basal levels of synaptic GABAergic activation do not affect [Cl-]i. In summary, these results indicate that active Cl--uptake in immature hippocampal neurons is sufficient to maintain stable [Cl-]i at basal levels of phasic and to some extent also to compensate tonic GABAergic activity.
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Affiliation(s)
- Sergey N Kolbaev
- Institute of Physiology, University Medical Center Mainz, Johannes Gutenberg University, Duesbergweg 6, 55128, Mainz, Germany.,Research Center of Neurology, Volokolamskoyeshosse, 80, Moscow, Russia, 125367
| | - Namrata Mohapatra
- Institute of Clinical Neuroanatomy, Neuroscience Center, Goethe-University, Theodor-Stern-Kai 7, 60590, Frankfurt, Germany
| | - Rongqing Chen
- Institute of Physiology, University Medical Center Mainz, Johannes Gutenberg University, Duesbergweg 6, 55128, Mainz, Germany.,Department of Neurobiology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, 510515, China
| | - Aniello Lombardi
- Institute of Physiology, University Medical Center Mainz, Johannes Gutenberg University, Duesbergweg 6, 55128, Mainz, Germany
| | - Jochen F Staiger
- Institute of Neuroanatomy, Universitätsmedizin Göttingen, Georg-August-Universität Göttingen, Kreuzbergring 36, 37075, Göttingen, Germany
| | - Heiko J Luhmann
- Institute of Physiology, University Medical Center Mainz, Johannes Gutenberg University, Duesbergweg 6, 55128, Mainz, Germany
| | - Peter Jedlicka
- Institute of Clinical Neuroanatomy, Neuroscience Center, Goethe-University, Theodor-Stern-Kai 7, 60590, Frankfurt, Germany.,ICAR3R-Interdisciplinary Centre for 3Rs in Animal Research, Faculty of Medicine, Justus-Liebig-University, Rudolf-Buchheim-Str. 6, 35392, Giessen, Germany
| | - Werner Kilb
- Institute of Physiology, University Medical Center Mainz, Johannes Gutenberg University, Duesbergweg 6, 55128, Mainz, Germany.
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11
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Phillips RS, Rosner I, Gittis AH, Rubin JE. The effects of chloride dynamics on substantia nigra pars reticulata responses to pallidal and striatal inputs. eLife 2020; 9:e55592. [PMID: 32894224 PMCID: PMC7476764 DOI: 10.7554/elife.55592] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Accepted: 08/14/2020] [Indexed: 11/20/2022] Open
Abstract
As a rodent basal ganglia (BG) output nucleus, the substantia nigra pars reticulata (SNr) is well positioned to impact behavior. SNr neurons receive GABAergic inputs from the striatum (direct pathway) and globus pallidus (GPe, indirect pathway). Dominant theories of action selection rely on these pathways' inhibitory actions. Yet, experimental results on SNr responses to these inputs are limited and include excitatory effects. Our study combines experimental and computational work to characterize, explain, and make predictions about these pathways. We observe diverse SNr responses to stimulation of SNr-projecting striatal and GPe neurons, including biphasic and excitatory effects, which our modeling shows can be explained by intracellular chloride processing. Our work predicts that ongoing GPe activity could tune the SNr operating mode, including its responses in decision-making scenarios, and GPe output may modulate synchrony and low-frequency oscillations of SNr neurons, which we confirm using optogenetic stimulation of GPe terminals within the SNr.
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Affiliation(s)
- Ryan S Phillips
- Department of Mathematics, University of PittsburghPittsburghUnited States
- Center for the Neural Basis of CognitionPittsburghUnited States
| | - Ian Rosner
- Center for the Neural Basis of CognitionPittsburghUnited States
- Department of Biological Sciences, Carnegie Mellon UniversityPittsburghUnited States
| | - Aryn H Gittis
- Center for the Neural Basis of CognitionPittsburghUnited States
- Department of Biological Sciences, Carnegie Mellon UniversityPittsburghUnited States
| | - Jonathan E Rubin
- Department of Mathematics, University of PittsburghPittsburghUnited States
- Center for the Neural Basis of CognitionPittsburghUnited States
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12
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Ferrini F, Perez-Sanchez J, Ferland S, Lorenzo LE, Godin AG, Plasencia-Fernandez I, Cottet M, Castonguay A, Wang F, Salio C, Doyon N, Merighi A, De Koninck Y. Differential chloride homeostasis in the spinal dorsal horn locally shapes synaptic metaplasticity and modality-specific sensitization. Nat Commun 2020; 11:3935. [PMID: 32769979 PMCID: PMC7414850 DOI: 10.1038/s41467-020-17824-y] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Accepted: 07/22/2020] [Indexed: 02/06/2023] Open
Abstract
GABAA/glycine-mediated neuronal inhibition critically depends on intracellular chloride (Cl-) concentration which is mainly regulated by the K+-Cl- co-transporter 2 (KCC2) in the adult central nervous system (CNS). KCC2 heterogeneity thus affects information processing across CNS areas. Here, we uncover a gradient in Cl- extrusion capacity across the superficial dorsal horn (SDH) of the spinal cord (laminae I-II: LI-LII), which remains concealed under low Cl- load. Under high Cl- load or heightened synaptic drive, lower Cl- extrusion is unveiled in LI, as expected from the gradient in KCC2 expression found across the SDH. Blocking TrkB receptors increases KCC2 in LI, pointing to differential constitutive TrkB activation across laminae. Higher Cl- lability in LI results in rapidly collapsing inhibition, and a form of activity-dependent synaptic plasticity expressed as a continuous facilitation of excitatory responses. The higher metaplasticity in LI as compared to LII differentially affects sensitization to thermal and mechanical input. Thus, inconspicuous heterogeneity of Cl- extrusion across laminae critically shapes plasticity for selective nociceptive modalities.
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Affiliation(s)
- Francesco Ferrini
- Department of Veterinary Sciences, University of Turin, Turin, Italy.
- CERVO Brain Research Centre, Québec, QC, Canada.
- Department of Psychiatry and Neuroscience, Université Laval, Québec, QC, Canada.
- Graduate program in Neuroscience, Université Laval, Québec, QC, Canada.
| | - Jimena Perez-Sanchez
- CERVO Brain Research Centre, Québec, QC, Canada
- Graduate program in Neuroscience, Université Laval, Québec, QC, Canada
| | - Samuel Ferland
- CERVO Brain Research Centre, Québec, QC, Canada
- Graduate program in Neuroscience, Université Laval, Québec, QC, Canada
| | | | - Antoine G Godin
- CERVO Brain Research Centre, Québec, QC, Canada
- Department of Psychiatry and Neuroscience, Université Laval, Québec, QC, Canada
- Graduate program in Neuroscience, Université Laval, Québec, QC, Canada
| | - Isabel Plasencia-Fernandez
- CERVO Brain Research Centre, Québec, QC, Canada
- Graduate program in Neuroscience, Université Laval, Québec, QC, Canada
| | | | | | - Feng Wang
- CERVO Brain Research Centre, Québec, QC, Canada
| | - Chiara Salio
- Department of Veterinary Sciences, University of Turin, Turin, Italy
| | - Nicolas Doyon
- CERVO Brain Research Centre, Québec, QC, Canada
- Department of Mathematics and Statistics, Université Laval, Québec, QC, Canada
| | - Adalberto Merighi
- Department of Veterinary Sciences, University of Turin, Turin, Italy
| | - Yves De Koninck
- CERVO Brain Research Centre, Québec, QC, Canada
- Department of Psychiatry and Neuroscience, Université Laval, Québec, QC, Canada
- Graduate program in Neuroscience, Université Laval, Québec, QC, Canada
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13
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Currin CB, Trevelyan AJ, Akerman CJ, Raimondo JV. Chloride dynamics alter the input-output properties of neurons. PLoS Comput Biol 2020; 16:e1007932. [PMID: 32453795 PMCID: PMC7307785 DOI: 10.1371/journal.pcbi.1007932] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Revised: 06/22/2020] [Accepted: 05/06/2020] [Indexed: 12/30/2022] Open
Abstract
Fast synaptic inhibition is a critical determinant of neuronal output, with subcellular targeting of synaptic inhibition able to exert different transformations of the neuronal input-output function. At the receptor level, synaptic inhibition is primarily mediated by chloride-permeable Type A GABA receptors. Consequently, dynamics in the neuronal chloride concentration can alter the functional properties of inhibitory synapses. How differences in the spatial targeting of inhibitory synapses interact with intracellular chloride dynamics to modulate the input-output function of neurons is not well understood. To address this, we developed computational models of multi-compartment neurons that incorporate experimentally parametrised mechanisms to account for neuronal chloride influx, diffusion, and extrusion. We found that synaptic input (either excitatory, inhibitory, or both) can lead to subcellular variations in chloride concentration, despite a uniform distribution of chloride extrusion mechanisms. Accounting for chloride changes resulted in substantial alterations in the neuronal input-output function. This was particularly the case for peripherally targeted dendritic inhibition where dynamic chloride compromised the ability of inhibition to offset neuronal input-output curves. Our simulations revealed that progressive changes in chloride concentration mean that the neuronal input-output function is not static but varies significantly as a function of the duration of synaptic drive. Finally, we found that the observed effects of dynamic chloride on neuronal output were mediated by changes in the dendritic reversal potential for GABA. Our findings provide a framework for understanding the computational effects of chloride dynamics on dendritically targeted synaptic inhibition.
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Affiliation(s)
- Christopher B. Currin
- Division of Cell Biology, 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
| | - Andrew J. Trevelyan
- Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Colin J. Akerman
- Department of Pharmacology, University of Oxford, Oxford, United Kingdom
| | - Joseph V. Raimondo
- Division of Cell Biology, 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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14
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Halbhuber L, Achtner C, Luhmann HJ, Sinning A, Kilb W. Coincident Activation of Glutamate Receptors Enhances GABA A Receptor-Induced Ionic Plasticity of the Intracellular Cl --Concentration in Dissociated Neuronal Cultures. Front Cell Neurosci 2019; 13:497. [PMID: 31787883 PMCID: PMC6856009 DOI: 10.3389/fncel.2019.00497] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Accepted: 10/21/2019] [Indexed: 01/09/2023] Open
Abstract
Massive activation of γ-amino butyric acid A (GABAA) receptors during pathophysiological activity induces an increase in the intracellular Cl--concentration ([Cl-]i), which is sufficient to render GABAergic responses excitatory. However, to what extent physiological levels of GABAergic activity can influence [Cl-]i is not known. Aim of the present study is to reveal whether moderate activation of GABAA receptors mediates functionally relevant [Cl-]i changes and whether these changes can be augmented by coincident glutamatergic activity. To address these questions, we used whole-cell patch-clamp recordings from cultured cortical neurons [at days in vitro (DIV) 6-22] to determine changes in the GABA reversal potential (EGABA) induced by short bursts of GABAergic and/or synchronized glutamatergic stimulation. These experiments revealed that pressure-application of 10 short muscimol pulses at 10 Hz induced voltage-dependent [Cl-]i changes. Under current-clamp conditions this muscimol burst induced a [Cl-]i increase of 3.1 ± 0.4 mM (n = 27), which was significantly enhanced to 4.6 ± 0.5 mM (n = 27) when glutamate was applied synchronously with the muscimol pulses. The muscimol-induced [Cl-]i increase significantly attenuated the inhibitory effect of GABA, as determined by the GABAergic rheobase shift. The synchronous coapplication of glutamate pulses had no additional effect on the attenuation of GABAergic inhibition, despite the larger [Cl-]i transients under these conditions. In summary, these results indicate that moderate GABAergic activity can induce functionally relevant [Cl-]i transients, which were enhanced by coincident glutamate pulses. This ionic plasticity of [Cl-]i may contribute to short-term plasticity of the GABAergic system.
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Affiliation(s)
- Lisa Halbhuber
- Institute of Physiology, University Medical Center Mainz, Johannes Gutenberg University, Mainz, Germany
| | - Cécilia Achtner
- Institute of Physiology, University Medical Center Mainz, Johannes Gutenberg University, Mainz, Germany
| | - Heiko J Luhmann
- Institute of Physiology, University Medical Center Mainz, Johannes Gutenberg University, Mainz, Germany
| | - Anne Sinning
- Institute of Physiology, University Medical Center Mainz, Johannes Gutenberg University, Mainz, Germany
| | - Werner Kilb
- Institute of Physiology, University Medical Center Mainz, Johannes Gutenberg University, Mainz, Germany
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15
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Reply to The small molecule CLP257 does not modify activity of the K +-Cl - co-transporter KCC2 but does potentiate GABA A receptor activity. Nat Med 2019; 23:1396-1398. [PMID: 29216044 DOI: 10.1038/nm.4449] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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16
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Interactions between Membrane Resistance, GABA-A Receptor Properties, Bicarbonate Dynamics and Cl --Transport Shape Activity-Dependent Changes of Intracellular Cl - Concentration. Int J Mol Sci 2019; 20:ijms20061416. [PMID: 30897846 PMCID: PMC6471822 DOI: 10.3390/ijms20061416] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Revised: 03/15/2019] [Accepted: 03/18/2019] [Indexed: 11/17/2022] Open
Abstract
The effects of ionotropic γ-aminobutyric acid receptor (GABA-A, GABAA) activation depends critically on the Cl−-gradient across neuronal membranes. Previous studies demonstrated that the intracellular Cl−-concentration ([Cl−]i) is not stable but shows a considerable amount of activity-dependent plasticity. To characterize how membrane properties and different molecules that are directly or indirectly involved in GABAergic synaptic transmission affect GABA-induced [Cl−]i changes, we performed compartmental modeling in the NEURON environment. These simulations demonstrate that GABA-induced [Cl−]i changes decrease at higher membrane resistance, revealing a sigmoidal dependency between both parameters. Increase in GABAergic conductivity enhances [Cl−]i with a logarithmic dependency, while increasing the decay time of GABAA receptors leads to a nearly linear enhancement of the [Cl−]i changes. Implementing physiological levels of HCO3−-conductivity to GABAA receptors enhances the [Cl−]i changes over a wide range of [Cl−]i, but this effect depends on the stability of the HCO3− gradient and the intracellular pH. Finally, these simulations show that pure diffusional Cl−-elimination from dendrites is slow and that a high activity of Cl−-transport is required to improve the spatiotemporal restriction of GABA-induced [Cl−]i changes. In summary, these simulations revealed a complex interplay between several key factors that influence GABA-induced [Cl]i changes. The results suggest that some of these factors, including high resting [Cl−]i, high input resistance, slow decay time of GABAA receptors and dynamic HCO3− gradient, are specifically adapted in early postnatal neurons to facilitate limited activity-dependent [Cl−]i decreases.
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17
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Klein PM, Lu AC, Harper ME, McKown HM, Morgan JD, Beenhakker MP. Tenuous Inhibitory GABAergic Signaling in the Reticular Thalamus. J Neurosci 2018; 38:1232-1248. [PMID: 29273603 PMCID: PMC5792478 DOI: 10.1523/jneurosci.1345-17.2017] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Revised: 09/20/2017] [Accepted: 11/03/2017] [Indexed: 11/21/2022] Open
Abstract
Maintenance of a low intracellular Cl- concentration ([Cl-]i) is critical for enabling inhibitory neuronal responses to GABAA receptor-mediated signaling. Cl- transporters, including KCC2, and extracellular impermeant anions ([A]o) of the extracellular matrix are both proposed to be important regulators of [Cl-]i Neurons of the reticular thalamic (RT) nucleus express reduced levels of KCC2, indicating that GABAergic signaling may produce excitation in RT neurons. However, by performing perforated patch recordings and calcium imaging experiments in rats (male and female), we find that [Cl-]i remains relatively low in RT neurons. Although we identify a small contribution of [A]o to a low [Cl-]i in RT neurons, our results also demonstrate that reduced levels of KCC2 remain sufficient to maintain low levels of Cl- Reduced KCC2 levels, however, restrict the capacity of RT neurons to rapidly extrude Cl- following periods of elevated GABAergic signaling. In a computational model of a local RT network featuring slow Cl- extrusion kinetics, similar to those we found experimentally, model RT neurons are predisposed to an activity-dependent switch from GABA-mediated inhibition to excitation. By decreasing the activity threshold required to produce excitatory GABAergic signaling, weaker stimuli are able to propagate activity within the model RT nucleus. Our results indicate the importance of even diminished levels of KCC2 in maintaining inhibitory signaling within the RT nucleus and suggest how this important activity choke point may be easily overcome in disorders such as epilepsy.SIGNIFICANCE STATEMENT Precise regulation of intracellular Cl- levels ([Cl-]i) preserves appropriate, often inhibitory, GABAergic signaling within the brain. However, there is disagreement over the relative contribution of various mechanisms that maintain low [Cl-]i We found that the Cl- transporter KCC2 is an important Cl- extruder in the reticular thalamic (RT) nucleus, despite this nucleus having remarkably low KCC2 immunoreactivity relative to other regions of the adult brain. We also identified a smaller contribution of fixed, impermeant anions ([A]o) to lowering [Cl-]i in RT neurons. Inhibitory signaling among RT neurons is important for preventing excessive activation of RT neurons, which can be responsible for generating seizures. Our work suggests that KCC2 critically restricts the spread of activity within the RT nucleus.
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Affiliation(s)
- Peter M Klein
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, Virginia 22903
| | - Adam C Lu
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, Virginia 22903
| | - Megan E Harper
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, Virginia 22903
| | - Hannah M McKown
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, Virginia 22903
| | - Jessica D Morgan
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, Virginia 22903
| | - Mark P Beenhakker
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, Virginia 22903
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18
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Lee-Kubli C, Marshall AG, Malik RA, Calcutt NA. The H-Reflex as a Biomarker for Spinal Disinhibition in Painful Diabetic Neuropathy. Curr Diab Rep 2018; 18:1. [PMID: 29362940 PMCID: PMC6876556 DOI: 10.1007/s11892-018-0969-5] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
PURPOSE OF REVIEW Neuropathic pain may arise from multiple mechanisms and locations. Efficacy of current treatments for painful diabetic neuropathy is limited to an unpredictable subset of patients, possibly reflecting diversity of pain generator mechanisms, and there is a lack of targeted treatments for individual patients. This review summarizes preclinical evidence supporting a role for spinal disinhibition in painful diabetic neuropathy, the physiology and pharmacology of rate-dependent depression (RDD) of the spinal H-reflex and the translational potential of using RDD as a biomarker of spinally mediated pain. RECENT FINDINGS Impaired RDD occurs in animal models of diabetes and was also detected in diabetic patients with painful vs painless neuropathy. RDD status can be determined using standard neurophysiological equipment. Loss of RDD may provide a clinical biomarker of spinal disinhibition, thereby enabling a personalized medicine approach to selection of current treatment options and enrichment of future clinical trial populations.
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Affiliation(s)
| | - Andrew G Marshall
- Faculty of Medical and Human Sciences, Institute of Cardiovascular Sciences, University of Manchester and National Institute for Healthy Research/Wellcome Trust Clinical Research Facility, Manchester, UK
- Department of Clinical Neurophysiology, Salford Royal Hospital, National Health Service Foundation Trust, Manchester Academic Health Science Centre, Manchester, UK
| | - Rayaz A Malik
- Faculty of Medical and Human Sciences, Institute of Cardiovascular Sciences, University of Manchester and National Institute for Healthy Research/Wellcome Trust Clinical Research Facility, Manchester, UK
- Department of Medicine, Weill Cornell Medicine-Qatar, Doha, Qatar
| | - Nigel A Calcutt
- Department of Pathology, University of California San Diego, La Jolla, CA, USA.
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19
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Follwaczny P, Schieweck R, Riedemann T, Demleitner A, Straub T, Klemm AH, Bilban M, Sutor B, Popper B, Kiebler MA. Pumilio2-deficient mice show a predisposition for epilepsy. Dis Model Mech 2017; 10:1333-1342. [PMID: 29046322 PMCID: PMC5719250 DOI: 10.1242/dmm.029678] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Accepted: 09/06/2017] [Indexed: 01/18/2023] Open
Abstract
Epilepsy is a neurological disease that is caused by abnormal hypersynchronous activities of neuronal ensembles leading to recurrent and spontaneous seizures in human patients. Enhanced neuronal excitability and a high level of synchrony between neurons seem to trigger these spontaneous seizures. The molecular mechanisms, however, regarding the development of neuronal hyperexcitability and maintenance of epilepsy are still poorly understood. Here, we show that pumilio RNA-binding family member 2 (Pumilio2; Pum2) plays a role in the regulation of excitability in hippocampal neurons of weaned and 5-month-old male mice. Almost complete deficiency of Pum2 in adult Pum2 gene-trap mice (Pum2 GT) causes misregulation of genes involved in neuronal excitability control. Interestingly, this finding is accompanied by the development of spontaneous epileptic seizures in Pum2 GT mice. Furthermore, we detect an age-dependent increase in Scn1a (Nav1.1) and Scn8a (Nav1.6) mRNA levels together with a decrease in Scn2a (Nav1.2) transcript levels in weaned Pum2 GT that is absent in older mice. Moreover, field recordings of CA1 pyramidal neurons show a tendency towards a reduced paired-pulse inhibition after stimulation of the Schaffer-collateral-commissural pathway in Pum2 GT mice, indicating a predisposition to the development of spontaneous seizures at later stages. With the onset of spontaneous seizures at the age of 5 months, we detect increased protein levels of Nav1.1 and Nav1.2 as well as decreased protein levels of Nav1.6 in those mice. In addition, GABA receptor subunit alpha-2 (Gabra2) mRNA levels are increased in weaned and adult mice. Furthermore, we observe an enhanced GABRA2 protein level in the dendritic field of the CA1 subregion in the Pum2 GT hippocampus. We conclude that altered expression levels of known epileptic risk factors such as Nav1.1, Nav1.2, Nav1.6 and GABRA2 result in enhanced seizure susceptibility and manifestation of epilepsy in the hippocampus. Thus, our results argue for a role of Pum2 in epileptogenesis and the maintenance of epilepsy. Summary: Epileptogenic risk factors are misregulated in Pumilio2-deficient mice, determining a predisposition to develop seizures. This article has an associated First Person interview with the first author of the paper as part of the supplementary information.
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Affiliation(s)
- Philipp Follwaczny
- Biomedical Center (BMC), Department for Cell Biology, Faculty of Medicine, LMU, Munich, 82152 Planegg-Martinsried, Germany
| | - Rico Schieweck
- Biomedical Center (BMC), Department for Cell Biology, Faculty of Medicine, LMU, Munich, 82152 Planegg-Martinsried, Germany
| | - Therese Riedemann
- Biomedical Center (BMC), Department of Physiological Genomics, Ludwig-Maximilians-University, Munich, 82152 Planegg-Martinsried, Germany
| | - Antonia Demleitner
- Biomedical Center (BMC), Department for Cell Biology, Faculty of Medicine, LMU, Munich, 82152 Planegg-Martinsried, Germany
| | - Tobias Straub
- Biomedical Center (BMC), Core Facility Bioinformatics, Ludwig-Maximilians-University, Munich, 82152 Planegg-Martinsried, Germany
| | - Anna H Klemm
- Biomedical Center (BMC), Core Facility Bioimaging, Ludwig-Maximilians-University, Munich, 82152 Planegg-Martinsried, Germany.,Walter Brendel Centre of Experimental Medicine, Ludwig-Maximilians-University, 81377 Munich, Germany
| | - Martin Bilban
- Department of Laboratory Medicine and Core Facility Genomics, Medical University of Vienna, 1090 Vienna, Austria
| | - Bernd Sutor
- Biomedical Center (BMC), Department of Physiological Genomics, Ludwig-Maximilians-University, Munich, 82152 Planegg-Martinsried, Germany
| | - Bastian Popper
- Biomedical Center (BMC), Department for Cell Biology, Faculty of Medicine, LMU, Munich, 82152 Planegg-Martinsried, Germany .,Biomedical Center (BMC), Core Facility Animal Models, Ludwig-Maximilians-University, Munich, 82152 Planegg-Martinsried, Germany
| | - Michael A Kiebler
- Biomedical Center (BMC), Department for Cell Biology, Faculty of Medicine, LMU, Munich, 82152 Planegg-Martinsried, Germany
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20
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Ferrini F, Lorenzo LE, Godin AG, Quang ML, De Koninck Y. Enhancing KCC2 function counteracts morphine-induced hyperalgesia. Sci Rep 2017. [PMID: 28634406 PMCID: PMC5478677 DOI: 10.1038/s41598-017-04209-3] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Morphine-induced hyperalgesia (MIH) is a severe adverse effect accompanying repeated morphine treatment, causing a paradoxical decrease in nociceptive threshold. Previous reports associated MIH with a decreased expression of the Cl− extruder KCC2 in the superficial dorsal horn (SDH) of the spinal cord, weakening spinal GABAA/glycine-mediated postsynaptic inhibition. Here, we tested whether the administration of small molecules enhancing KCC2, CLP257 and its pro-drug CLP290, may counteract MIH. MIH was typically expressed within 6–8 days of morphine treatment. Morphine-treated rats exhibited decreased withdrawal threshold to mechanical stimulation and increased vocalizing behavior to subcutaneous injections. Chloride extrusion was impaired in SDH neurons measured as a depolarizing shift in EGABA under Cl− load. Delivering CLP257 to spinal cord slices obtained from morphine-treated rats was sufficient to restore Cl− extrusion capacity in SDH neurons. In vivo co-treatment with morphine and oral CLP290 prevented membrane KCC2 downregulation in SDH neurons. Concurrently, co-treatment with CLP290 significantly mitigated MIH and acute administration of CLP257 in established MIH restored normal nociceptive behavior. Our data indicate that enhancing KCC2 activity is a viable therapeutic approach for counteracting MIH. Chloride extrusion enhancers may represent an effective co-adjuvant therapy to improve morphine analgesia by preventing and reversing MIH.
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Affiliation(s)
- Francesco Ferrini
- Department of Veterinary Sciences, University of Turin, Turin, Italy.,CERVO Brain Research Centre, Institut universitaire en santé mentale de Québec, Québec, Canada
| | - Louis-Etienne Lorenzo
- CERVO Brain Research Centre, Institut universitaire en santé mentale de Québec, Québec, Canada
| | - Antoine G Godin
- CERVO Brain Research Centre, Institut universitaire en santé mentale de Québec, Québec, Canada
| | - Miorie Le Quang
- CERVO Brain Research Centre, Institut universitaire en santé mentale de Québec, Québec, Canada
| | - Yves De Koninck
- CERVO Brain Research Centre, Institut universitaire en santé mentale de Québec, Québec, Canada. .,Department of Psychiatry and Neuroscience, Université Laval, Québec, Canada.
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21
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Yelhekar TD, Druzin M, Johansson S. Contribution of Resting Conductance, GABA A-Receptor Mediated Miniature Synaptic Currents and Neurosteroid to Chloride Homeostasis in Central Neurons. eNeuro 2017; 4:ENEURO.0019-17.2017. [PMID: 28374007 PMCID: PMC5362935 DOI: 10.1523/eneuro.0019-17.2017] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2017] [Revised: 02/27/2017] [Accepted: 03/12/2017] [Indexed: 01/20/2023] Open
Abstract
Maintenance of a low intraneuronal Cl- concentration, [Cl-]i, is critical for inhibition in the CNS. Here, the contribution of passive, conductive Cl- flux to recovery of [Cl-]i after a high load was analyzed in mature central neurons from rat. A novel method for quantifying the resting Cl- conductance, important for [Cl-]i recovery, was developed and the possible contribution of GABAA and glycine receptors and of ClC-2 channels to this conductance was analyzed. The hypothesis that spontaneous, action potential-independent release of GABA is important for [Cl-]i recovery was tested. [Cl-]i was examined by gramicidin-perforated patch recordings in medial preoptic neurons. Cells were loaded with Cl- by combining GABA or glycine application with a depolarized voltage, and the time course of [Cl-]i was followed by measurements of the Cl- equilibrium potential, as obtained from the current recorded during voltage ramps combined with GABA or glycine application. The results show that passive Cl- flux contributes significantly, in the same order of magnitude as does K+-Cl- cotransporter 2 (KCC2), to [Cl-]i recovery and that Cl- conductance accounts for ∼ 6% of the total resting conductance. A major fraction of this resting Cl- conductance is picrotoxin (PTX)-sensitive and likely due to open GABAA receptors, but ClC-2 channels do not contribute. The results also show that when the decay of GABAA receptor-mediated miniature postsynaptic currents (minis) is slowed by the neurosteroid allopregnanolone, such minis may significantly quicken [Cl-]i recovery, suggesting a possible steroid-regulated role for minis in the control of Cl- homeostasis.
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Affiliation(s)
- Tushar D Yelhekar
- Department of Integrative Medical Biology, Umeå University , Umeå, SE-901 87, Sweden
| | - Michael Druzin
- Department of Integrative Medical Biology, Umeå University , Umeå, SE-901 87, Sweden
| | - Staffan Johansson
- Department of Integrative Medical Biology, Umeå University , Umeå, SE-901 87, Sweden
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22
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Doyon N, Vinay L, Prescott SA, De Koninck Y. Chloride Regulation: A Dynamic Equilibrium Crucial for Synaptic Inhibition. Neuron 2016; 89:1157-1172. [PMID: 26985723 DOI: 10.1016/j.neuron.2016.02.030] [Citation(s) in RCA: 156] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2015] [Revised: 12/24/2015] [Accepted: 02/18/2016] [Indexed: 01/02/2023]
Abstract
Fast synaptic inhibition relies on tight regulation of intracellular Cl(-). Chloride dysregulation is implicated in several neurological and psychiatric disorders. Beyond mere disinhibition, the consequences of Cl(-) dysregulation are multifaceted and best understood in terms of a dynamical system involving complex interactions between multiple processes operating on many spatiotemporal scales. This dynamical perspective helps explain many unintuitive manifestations of Cl(-) dysregulation. Here we discuss how taking into account dynamical regulation of intracellular Cl(-) is important for understanding how synaptic inhibition fails, how to best detect that failure, why Cl(-) regulation is energetically so expensive, and the overall consequences for therapeutics.
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Affiliation(s)
- Nicolas Doyon
- Institut Universitaire en Santé Mentale de Québec, Québec, QC G1J 2G3, Canada; Department of Mathematics and Statistics, Université Laval, Québec, QC G1V 0A6, Canada
| | - Laurent Vinay
- Team P3M, Institut de Neurosciences de la Timone, UMR 7289, CNRS and Aix Marseille Université, F-13385 Marseille, France
| | - Steven A Prescott
- Program in Neurosciences and Mental Health, Hospital for Sick Children, Toronto, ON M5G 1X8, Canada; Department of Physiology, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Yves De Koninck
- Institut Universitaire en Santé Mentale de Québec, Québec, QC G1J 2G3, Canada; Department of Psychiatry and Neuroscience, Université Laval, Québec, QC, G1V 0A6, Canada.
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