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van Versendaal D, Levelt CN. Inhibitory interneurons in visual cortical plasticity. Cell Mol Life Sci 2016; 73:3677-91. [PMID: 27193323 PMCID: PMC5002041 DOI: 10.1007/s00018-016-2264-4] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2015] [Revised: 04/30/2016] [Accepted: 05/03/2016] [Indexed: 01/01/2023]
Abstract
For proper maturation of the neocortex and acquisition of specific functions and skills, exposure to sensory stimuli is vital during critical periods of development when synaptic connectivity is highly malleable. To preserve reliable cortical processing, it is essential that these critical periods end after which learning becomes more conditional and active interaction with the environment becomes more important. How these age-dependent forms of plasticity are regulated has been studied extensively in the primary visual cortex. This has revealed that inhibitory innervation plays a crucial role and that a temporary decrease in inhibition is essential for plasticity to take place. Here, we discuss how different interneuron subsets regulate plasticity during different stages of cortical maturation. We propose a theory in which different interneuron subsets select the sources of neuronal input that undergo plasticity.
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Affiliation(s)
- Daniëlle van Versendaal
- Department of Molecular Visual Plasticity, Netherlands Institute for Neuroscience, Institute of the Royal Netherlands Academy of Arts and Sciences, Meibergdreef 47, 1105 BA, Amsterdam, The Netherlands
| | - Christiaan N Levelt
- Department of Molecular Visual Plasticity, Netherlands Institute for Neuroscience, Institute of the Royal Netherlands Academy of Arts and Sciences, Meibergdreef 47, 1105 BA, Amsterdam, The Netherlands. .,Department of Molecular and Cellular Neurobiology, Center for Neurogenomics and Cognitive Research, VU University Amsterdam, de Boelelaan 1085, 1081HV, Amsterdam, The Netherlands.
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52
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Dengler CG, Coulter DA. Normal and epilepsy-associated pathologic function of the dentate gyrus. PROGRESS IN BRAIN RESEARCH 2016; 226:155-78. [PMID: 27323942 DOI: 10.1016/bs.pbr.2016.04.005] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The dentate gyrus plays critical roles both in cognitive processing, and in regulation of the induction and propagation of pathological activity. The cellular and circuit mechanisms underlying these diverse functions overlap extensively. At the cellular level, the intrinsic properties of dentate granule cells combine to endow these neurons with a fundamental reluctance to activate, one of their hallmark traits. At the circuit level, the dentate gyrus constitutes one of the more heavily inhibited regions of the brain, with strong, fast feedforward and feedback GABAergic inhibition dominating responses to afferent activation. In pathologic states such as epilepsy, a number of alterations within the dentate gyrus combine to compromise the regulatory properties of this circuit, culminating in a collapse of its normal function. This epilepsy-associated transformation in the fundamental properties of this critical regulatory hippocampal circuit may contribute both to seizure propensity, and cognitive and emotional comorbidities characteristic of this disease state.
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Affiliation(s)
- C G Dengler
- Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - D A Coulter
- Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States; The Research Institute of the Children's Hospital of Philadelphia, Philadelphia, PA, United States.
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53
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Bidirectional Signaling of Neuregulin-2 Mediates Formation of GABAergic Synapses and Maturation of Glutamatergic Synapses in Newborn Granule Cells of Postnatal Hippocampus. J Neurosci 2016; 35:16479-93. [PMID: 26674872 DOI: 10.1523/jneurosci.1585-15.2015] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
UNLABELLED Expression of neuregulin-2 (NRG2) is intense in a few regions of the adult brain where neurogenesis persists; however, little is understood about its role in developments of newborn neurons. To study the role of NRG2 in synaptogenesis at different developmental stages, newborn granule cells in rat hippocampal slice cultures were labeled with retrovirus encoding tetracycline-inducible microRNA targeting NRG2 and treated with doxycycline (Dox) at the fourth or seventh postinfection day (dpi). The developmental increase of GABAergic postsynaptic currents (GPSCs) was suppressed by the early Dox treatment (4 dpi), but not by late treatment (7 dpi). The late Dox treatment was used to study the effect of NRG2 depletion specific to excitatory synaptogenesis. The Dox effect on EPSCs emerged 4 d after the impairment in dendritic outgrowth became evident (10 dpi). Notably, Dox treatment abolished the developmental increases of AMPA-receptor mediated EPSCs and the AMPA/NMDA ratio, indicating impaired maturation of glutamatergic synapses. In contrast to GPSCs, Dox effects on EPSCs and dendritic growth were independent of ErbB4 and rescued by concurrent overexpression of NRG2 intracellular domain. These results suggest that forward signaling of NRG2 mediates GABAergic synaptogenesis and its reverse signaling contributes to dendritic outgrowth and maturation of glutamatergic synapses. SIGNIFICANCE STATEMENT The hippocampal dentate gyrus is one of special brain regions where neurogenesis persists throughout adulthood. Synaptogenesis is a critical step for newborn neurons to be integrated into preexisting neural network. Because neuregulin-2 (NRG2), a growth factor, is intensely expressed in these regions, we investigated whether it plays a role in synaptogenesis and dendritic growth. We found that NRG2 has dual roles in the development of newborn neurons. For GABAergic synaptogenesis, the extracellular domain of NRG2 acts as a ligand for a receptor on GABAergic neurons. In contrast, its intracellular domain was essential for dendritic outgrowth and glutamatergic synapse maturation. These results imply that NRG2 may play a critical role in network integration of newborn neurons.
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Anstötz M, Huang H, Marchionni I, Haumann I, Maccaferri G, Lübke JHR. Developmental Profile, Morphology, and Synaptic Connectivity of Cajal-Retzius Cells in the Postnatal Mouse Hippocampus. Cereb Cortex 2015; 26:855-72. [PMID: 26582498 PMCID: PMC4712808 DOI: 10.1093/cercor/bhv271] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Cajal–Retzius (CR) cells are early generated neurons, involved in the assembly of developing neocortical and hippocampal circuits. However, their roles in networks of the postnatal brain remain poorly understood. In order to get insights into these latter functions, we have studied their morphological and synaptic properties in the postnatal hippocampus of the CXCR4-EGFP mouse, where CR cells are easily identifiable. Our data indicate that CR cells are nonuniformly distributed along different subfields of the hippocampal formation, and that their postnatal decline is regulated in a region-specific manner. In fact, CR cells persist in distinct areas of fully mature animals. Subclasses of CR cells project and target either local (molecular layers) or distant regions [subicular complex and entorhinal cortex (EC)] of the hippocampal formation, but have similar firing patterns. Lastly, CR cells are biased toward targeting dendritic shafts compared with spines, and produce large-amplitude glutamatergic unitary postsynaptic potentials on γ-aminobutyric acid (GABA) containing interneurons. Taken together, our results suggest that CR cells are involved in a novel excitatory loop of the postnatal hippocampal formation, which potentially contributes to shaping the flow of information between the hippocampus, parahippocampal regions and entorhinal cortex, and to the low seizure threshold of these brain areas.
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Affiliation(s)
- Max Anstötz
- Institute of Neuroscience and Medicine INM-2, Research Centre Jülich GmbH, Jülich 52425, Germany Institute for Neuroanatomy, University/University Hospital Hamburg, Hamburg 20246, Germany
| | - Hao Huang
- Department of Physiology, Northwestern University, Feinberg School of Medicine, IL 60611-3008, USA
| | - Ivan Marchionni
- Department of Physiology, Northwestern University, Feinberg School of Medicine, IL 60611-3008, USA Current address: Instituto Italiano di Tecnologia, Neuroscience and Brain Technologies, Genova 16163, Italy
| | - Iris Haumann
- Institute for Neuroanatomy, University/University Hospital Hamburg, Hamburg 20246, Germany
| | - Gianmaria Maccaferri
- Department of Physiology, Northwestern University, Feinberg School of Medicine, IL 60611-3008, USA
| | - Joachim H R Lübke
- Institute of Neuroscience and Medicine INM-2, Research Centre Jülich GmbH, Jülich 52425, Germany Department of Psychiatry, Psychotherapy and Psychosomatics, RWTH/University Hospital Aachen, Aachen 52074, Germany JARA Translational Medicine, Jülich/Aachen, Germany
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55
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Abstract
Recent research into local-circuit GABAergic inhibitory interneurons of the mammalian central nervous system has provided unprecedented insight into the mechanics of neuronal circuitry and its dysfunction. Inhibitory interneurons consist of a broad array of anatomically and neurochemically diverse cell types, and this suggests that each occupies an equally diverse functional role. Although neurogliaform cells were observed by Cajal over a century ago, our understanding of the functional role of this class of interneurons is in its infancy. However, it is rapidly becoming clear that this cell type operates under a distinct repertoire of rules to provide novel forms of inhibitory control of numerous afferent pathways.
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56
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Krook-Magnuson E, Armstrong C, Bui A, Lew S, Oijala M, Soltesz I. In vivo evaluation of the dentate gate theory in epilepsy. J Physiol 2015; 593:2379-88. [PMID: 25752305 PMCID: PMC4457198 DOI: 10.1113/jp270056] [Citation(s) in RCA: 154] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2014] [Accepted: 02/25/2015] [Indexed: 01/21/2023] Open
Abstract
The dentate gyrus is a region subject to intense study in epilepsy because of its posited role as a 'gate', acting to inhibit overexcitation in the hippocampal circuitry through its unique synaptic, cellular and network properties that result in relatively low excitability. Numerous changes predicted to produce dentate hyperexcitability are seen in epileptic patients and animal models. However, recent findings question whether changes are causative or reactive, as well as the pathophysiological relevance of the dentate in epilepsy. Critically, direct in vivo modulation of dentate 'gate' function during spontaneous seizure activity has not been explored. Therefore, using a mouse model of temporal lobe epilepsy with hippocampal sclerosis, a closed-loop system and selective optogenetic manipulation of granule cells during seizures, we directly tested the dentate 'gate' hypothesis in vivo. Consistent with the dentate gate theory, optogenetic gate restoration through granule cell hyperpolarization efficiently stopped spontaneous seizures. By contrast, optogenetic activation of granule cells exacerbated spontaneous seizures. Furthermore, activating granule cells in non-epileptic animals evoked acute seizures of increasing severity. These data indicate that the dentate gyrus is a critical node in the temporal lobe seizure network, and provide the first in vivo support for the dentate 'gate' hypothesis.
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Affiliation(s)
| | - Caren Armstrong
- Department of Anatomy and Neurobiology, University of CaliforniaIrvine, USA
| | - Anh Bui
- Department of Anatomy and Neurobiology, University of CaliforniaIrvine, USA
| | - Sean Lew
- Department of Anatomy and Neurobiology, University of CaliforniaIrvine, USA
| | - Mikko Oijala
- Department of Anatomy and Neurobiology, University of CaliforniaIrvine, USA
| | - Ivan Soltesz
- Department of Anatomy and Neurobiology, University of CaliforniaIrvine, USA
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57
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Opioid receptor-dependent sex differences in synaptic plasticity in the hippocampal mossy fiber pathway of the adult rat. J Neurosci 2015; 35:1723-38. [PMID: 25632146 DOI: 10.1523/jneurosci.0820-14.2015] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The mossy fiber (MF) pathway is critical to hippocampal function and influenced by gonadal hormones. Physiological data are limited, so we asked whether basal transmission and long-term potentiation (LTP) differed in slices of adult male and female rats. The results showed small sex differences in basal transmission but striking sex differences in opioid receptor sensitivity and LTP. When slices were made from females on proestrous morning, when serum levels of 17β-estradiol peak, the nonspecific opioid receptor antagonist naloxone (1 μm) enhanced MF transmission but there was no effect in males, suggesting preferential opioid receptor-dependent inhibition in females when 17β-estradiol levels are elevated. The μ-opioid receptor (MOR) antagonist Cys2,Tyr3,Orn5,Pen7-amide (CTOP; 300 nm) had a similar effect but the δ-opioid receptor (DOR) antagonist naltrindole (NTI; 1 μm) did not, implicating MORs in female MF transmission. The GABAB receptor antagonist saclofen (200 μm) occluded effects of CTOP but the GABAA receptor antagonist bicuculline (10 μm) did not. For LTP, a low-frequency (LF) protocol was used because higher frequencies elicited hyperexcitability in females. Proestrous females exhibited LF-LTP but males did not, suggesting a lower threshold for synaptic plasticity when 17β-estradiol is elevated. NTI blocked LF-LTP in proestrous females, but CTOP did not. Electron microscopy revealed more DOR-labeled spines of pyramidal cells in proestrous females than males. Therefore, we suggest that increased postsynaptic DORs mediate LF-LTP in proestrous females. The results show strong MOR regulation of MF transmission only in females and identify a novel DOR-dependent form of MF LTP specific to proestrus.
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58
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Puighermanal E, Biever A, Espallergues J, Gangarossa G, De Bundel D, Valjent E. drd2-cre:ribotagmouse line unravels the possible diversity of dopamine d2 receptor-expressing cells of the dorsal mouse hippocampus. Hippocampus 2015; 25:858-75. [DOI: 10.1002/hipo.22408] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2014] [Revised: 12/19/2014] [Accepted: 12/19/2014] [Indexed: 02/03/2023]
Affiliation(s)
- Emma Puighermanal
- CNRS, UMR-5203, Institut de Génomique Fonctionnelle; Montpellier F-34094 France
- INSERM, U661; Montpellier F-34094 France
- Universités de Montpellier 1 & 2, UMR-5203; Montpellier F-34094 France
| | - Anne Biever
- CNRS, UMR-5203, Institut de Génomique Fonctionnelle; Montpellier F-34094 France
- INSERM, U661; Montpellier F-34094 France
- Universités de Montpellier 1 & 2, UMR-5203; Montpellier F-34094 France
| | - Julie Espallergues
- CNRS, UMR-5203, Institut de Génomique Fonctionnelle; Montpellier F-34094 France
- INSERM, U661; Montpellier F-34094 France
- Universités de Montpellier 1 & 2, UMR-5203; Montpellier F-34094 France
| | - Giuseppe Gangarossa
- CNRS, UMR-5203, Institut de Génomique Fonctionnelle; Montpellier F-34094 France
- INSERM, U661; Montpellier F-34094 France
- Universités de Montpellier 1 & 2, UMR-5203; Montpellier F-34094 France
| | - Dimitri De Bundel
- CNRS, UMR-5203, Institut de Génomique Fonctionnelle; Montpellier F-34094 France
- INSERM, U661; Montpellier F-34094 France
- Universités de Montpellier 1 & 2, UMR-5203; Montpellier F-34094 France
| | - Emmanuel Valjent
- CNRS, UMR-5203, Institut de Génomique Fonctionnelle; Montpellier F-34094 France
- INSERM, U661; Montpellier F-34094 France
- Universités de Montpellier 1 & 2, UMR-5203; Montpellier F-34094 France
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59
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Physiological properties of supragranular cortical inhibitory interneurons expressing retrograde persistent firing. Neural Plast 2015; 2015:608141. [PMID: 25763283 PMCID: PMC4339824 DOI: 10.1155/2015/608141] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Accepted: 01/15/2015] [Indexed: 11/17/2022] Open
Abstract
Neurons are polarized functional units. The somatodendritic compartment receives and integrates synaptic inputs while the axon relays relevant synaptic information in form of action potentials (APs) across long distance. Despite this well accepted notion, recent research has shown that, under certain circumstances, the axon can also generate APs independent of synaptic inputs at axonal sites distal from the soma. These ectopic APs travel both toward synaptic terminals and antidromically toward the soma. This unusual form of neuronal communication seems to preferentially occur in cortical inhibitory interneurons following a period of intense neuronal activity and might have profound implications for neuronal information processing. Here we show that trains of ectopically generated APs can be induced in a large portion of neocortical layer 2/3 GABAergic interneurons following a somatic depolarization inducing hundreds of APs. Sparsely occurring ectopic spikes were also observed in a large portion of layer 1 interneurons even in absence of prior somatic depolarization. Remarkably, we found that interneurons which produce ectopic APs display specific membrane and morphological properties significantly different from the remaining GABAergic cells and may therefore represent a functionally unique interneuronal subpopulation.
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60
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Optogenetic activation of cajal-retzius cells reveals their glutamatergic output and a novel feedforward circuit in the developing mouse hippocampus. J Neurosci 2014; 34:13018-32. [PMID: 25253849 DOI: 10.1523/jneurosci.1407-14.2014] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Cajal-Retzius cells orchestrate the development of cortical circuits by secreting the glycoprotein reelin. However, their computational functions are still unknown. In fact, the nature of their postsynaptic targets, major neurotransmitter released, as well as the class of postsynaptic receptors activated by their firing remain unclear. Here, we have addressed these questions by activating Cajal-Retzius cells optogenetically in mouse hippocampal slices. Light delivered to stratum lacunosum-moleculare triggered EPSCs both on local interneurons and on pyramidal cells. Responses recorded under voltage-clamp conditions had identical short latencies and similar amplitudes, but were kinetically different (i.e., faster in interneurons vs pyramidal cells). In both cases, responses were blocked by TTX, indicating that they were generated by action potential-dependent release. Responses in interneurons were rescued by the addition of 4-AP to TTX, and decreased when presynaptic firing in Cajal-Retzius cells was reduced by the chemokine CXCL12, indicating the existence of a direct Cajal-Retzius cell-interneuron monosynaptic connection. Although the combined application of 4-AP and TTX did not rescue responses in pyramidal cells, neither were they affected by the GABAA receptor blocker gabazine, which would be expected if they were polysynaptic. Both connections showed physiological and pharmacological properties indicating the involvement of AMPA- and NMDA-type glutamate receptors. The connectivity from presynaptic Cajal-Retzius cells to interneurons was strong enough to generate long-latency feedforward GABAergic input onto pyramidal cells. We propose that this newly defined Cajal-Retzius cell-dependent microcircuit may regulate synaptic plasticity and dendritic development in stratum lacunosum-moleculare, thus impacting the integrative properties of the developing hippocampus.
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61
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Scharfman HE, Brooks-Kayal AR. Is plasticity of GABAergic mechanisms relevant to epileptogenesis? ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014; 813:133-50. [PMID: 25012373 DOI: 10.1007/978-94-017-8914-1_11] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Numerous changes in GABAergic neurons, receptors, and inhibitory mechanisms have been described in temporal lobe epilepsy (TLE), either in humans or in animal models. Nevertheless, there remains a common assumption that epilepsy can be explained by simply an insufficiency of GABAergic inhibition. Alternatively, investigators have suggested that there is hyperinhibition that masks an underlying hyperexcitability. Here we examine the status epilepticus (SE) models of TLE and focus on the dentate gyrus of the hippocampus, where a great deal of data have been collected. The types of GABAergic neurons and GABAA receptors are summarized under normal conditions and after SE. The role of GABA in development and in adult neurogenesis is discussed. We suggest that instead of "too little or too much" GABA there is a complexity of changes after SE that makes the emergence of chronic seizures (epileptogenesis) difficult to understand mechanistically, and difficult to treat. We also suggest that this complexity arises, at least in part, because of the remarkable plasticity of GABAergic neurons and GABAA receptors in response to insult or injury.
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Affiliation(s)
- Helen E Scharfman
- The Nathan S. Kline Institute for Psychiatric Research, Orangeburg, NY, USA,
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62
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Krook-Magnuson E, Ledri M, Soltesz I, Kokaia M. How might novel technologies such as optogenetics lead to better treatments in epilepsy? ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014; 813:319-36. [PMID: 25012388 DOI: 10.1007/978-94-017-8914-1_26] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Recent technological advances open exciting avenues for improving the understanding of mechanisms in a broad range of epilepsies. This chapter focuses on the development of optogenetics and on-demand technologies for the study of epilepsy and the control of seizures. Optogenetics is a technique which, through cell-type selective expression of light-sensitive proteins called opsins, allows temporally precise control via light delivery of specific populations of neurons. Therefore, it is now possible not only to record interictal and ictal neuronal activity, but also to test causality and identify potential new therapeutic approaches. We first discuss the benefits and caveats to using optogenetic approaches and recent advances in optogenetics related tools. We then turn to the use of optogenetics, including on-demand optogenetics in the study of epilepsies, which highlights the powerful potential of optogenetics for epilepsy research.
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Affiliation(s)
- Esther Krook-Magnuson
- Department of Anatomy and Neurobiology, University of California, 192 Irvine Hall, Irvine, CA, 92697, USA,
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63
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Interneuronal GABAA receptors inside and outside of synapses. Curr Opin Neurobiol 2013; 26:57-63. [PMID: 24650505 DOI: 10.1016/j.conb.2013.12.001] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2013] [Revised: 11/17/2013] [Accepted: 12/03/2013] [Indexed: 01/04/2023]
Abstract
About 20% of the total number of neurons in the brain are interneurons (INs) that utilize GABA as their neurotransmitter. The receptors for GABA have been well studied in principal cells, but INs also express GABA receptors, in particular the GABAA type (GABAARs), which may also be activated in an autocrine manner by the transmitter released by the INs themselves. As more and more neurological and psychiatric disorders are being discovered to be linked to malfunction or deficits of INs, this review will cover how INs communicate with each other through the activation of synaptic and extrasynaptic GABAARs. The properties of GABAARs specific to INs may differ significantly from those found on principal cells to open the prospect of developing IN-specific drugs.
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64
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Sultan KT, Brown KN, Shi SH. Production and organization of neocortical interneurons. Front Cell Neurosci 2013; 7:221. [PMID: 24312011 PMCID: PMC3836051 DOI: 10.3389/fncel.2013.00221] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2013] [Accepted: 11/03/2013] [Indexed: 12/30/2022] Open
Abstract
Inhibitory GABA (γ-aminobutyric acid)-ergic interneurons are a vital component of the neocortex responsible for shaping its output through a variety of inhibitions. Consisting of many flavors, interneuron subtypes are predominantly defined by their morphological, physiological, and neurochemical properties that help to determine their functional role within the neocortex. During development, these cells are born in the subpallium where they then tangentially migrate over long distances before being radially positioned to their final location in the cortical laminae. As development progresses into adolescence, these cells mature and form chemical and electrical connections with both glutamatergic excitatory neurons and other interneurons ultimately establishing the cortical network. The production, migration, and organization of these cells are determined by vast array of extrinsic and intrinsic factors that work in concert in order to assemble a proper functioning cortical inhibitory network. Failure of these cells to undergo these processes results in abnormal positioning and cortical function. In humans, this can bring about several neurological disorders including schizophrenia, epilepsy, and autism spectrum disorders. In this article, we will review previous literature that has revealed the framework for interneuron neurogenesis and migratory behavior as well as discuss recent findings that aim to elucidate the spatial and functional organization of interneurons within the neocortex.
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Affiliation(s)
- Khadeejah T Sultan
- Developmental Biology Program, Memorial Sloan-Kettering Cancer Center New York, NY, USA ; Graduate Program in Neuroscience, Weill Cornell Medical College New York, NY, USA
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65
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Bartolini G, Ciceri G, Marín O. Integration of GABAergic Interneurons into Cortical Cell Assemblies: Lessons from Embryos and Adults. Neuron 2013; 79:849-64. [DOI: 10.1016/j.neuron.2013.08.014] [Citation(s) in RCA: 143] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/14/2013] [Indexed: 01/31/2023]
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66
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Bezaire MJ, Soltesz I. Quantitative assessment of CA1 local circuits: knowledge base for interneuron-pyramidal cell connectivity. Hippocampus 2013; 23:751-85. [PMID: 23674373 DOI: 10.1002/hipo.22141] [Citation(s) in RCA: 226] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2013] [Revised: 04/25/2013] [Accepted: 04/26/2013] [Indexed: 12/17/2022]
Abstract
In this work, through a detailed literature review, data-mining, and extensive calculations, we provide a current, quantitative estimate of the cellular and synaptic constituents of the CA1 region of the rat hippocampus. Beyond estimating the cell numbers of GABAergic interneuron types, we calculate their convergence onto CA1 pyramidal cells and compare it with the known input synapses on CA1 pyramidal cells. The convergence calculation and comparison are also made for excitatory inputs to CA1 pyramidal cells. In addition, we provide a summary of the excitatory and inhibitory convergence onto interneurons. The quantitative knowledge base assembled and synthesized here forms the basis for data-driven, large-scale computational modeling efforts. Additionally, this work highlights specific instances where the available data are incomplete, which should inspire targeted experimental projects toward a more complete quantification of the CA1 neurons and their connectivity.
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Affiliation(s)
- Marianne J Bezaire
- Department of Anatomy and Neurobiology, University of California, Irvine, California
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67
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Pohlkamp T, Dávid C, Cauli B, Gallopin T, Bouché E, Karagiannis A, May P, Herz J, Frotscher M, Staiger JF, Bock HH. Characterization and distribution of Reelin-positive interneuron subtypes in the rat barrel cortex. ACTA ACUST UNITED AC 2013; 24:3046-58. [PMID: 23803971 DOI: 10.1093/cercor/bht161] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
GABAergic inhibitory interneurons (IN) represent a heterogeneous population with different electrophysiological, morphological, and molecular properties. The correct balance between interneuronal subtypes is important for brain function and is impaired in several neurological and psychiatric disorders. Here we show the data of 123 molecularly and electrophysiologically characterized neurons of juvenile rat barrel cortex acute slices, 48 of which expressed Reelin (Reln). Reln mRNA was exclusively detected in Gad65/67-positive cells but was found in interneuronal subtypes in different proportions: all cells of the adapting-Somatostatin (SST) cluster expressed Reln, whereas 63% of the adapting-neuropeptide Y (NPY, 50% of the fast-spiking Parvalbumin (PVALB), and 27% of the adapting/bursting-Vasoactive Intestinal Peptide (VIP) cluster were Reln-positive. Silhouette analysis revealed a high impact of the parameter Reln on cluster quality. By analyzing the co-localization of RELN immunoreactivity with those of different IN-markers, we found that RELN is produced layer-independently in SST-, NPY-, and NOS1-expressing INs, whereas co-localization of RELN and VIP was mostly absent. Of note, RELN co-localized with PVALB, predominantly in INs of layers IV/V (>30%). Our findings emphasize RELN's role as an important IN-marker protein and provide a basis for the functional characterization of Reln-expressing INs and its role in the regulation of inhibitory IN networks.
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Affiliation(s)
- Theresa Pohlkamp
- Center for Neuroscience, Department of Neuroanatomy, Albert-Ludwigs-University, D79104 Freiburg, Germany Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75235, USA
| | - Csaba Dávid
- Center for Neuroscience, Department of Neuroanatomy, Albert-Ludwigs-University, D79104 Freiburg, Germany Department of Human Morphology and Developmental Biology, Semmelweis University, H1094 Budapest, Hungary
| | - Bruno Cauli
- Neurobiologie des Processus Adaptatifs, CNRS UMR7102, Université Pierre et Marie Curie, F75005 Paris, France
| | - Thierry Gallopin
- Laboratoire de Neurobiologie, CNRS UMR7637, Ecole Supérieure de Physique et de Chimie Industrielles de Paris, F75005 Paris, France
| | - Elisabeth Bouché
- Center for Neuroscience, Department of Neuroanatomy, Albert-Ludwigs-University, D79104 Freiburg, Germany
| | - Anastassios Karagiannis
- Neurobiologie des Processus Adaptatifs, CNRS UMR7102, Université Pierre et Marie Curie, F75005 Paris, France
| | - Petra May
- Center for Neuroscience, Department of Neuroanatomy, Albert-Ludwigs-University, D79104 Freiburg, Germany Clinic for Gastroenterology, Hepatology and Infectiology, Heinrich-Heine-University, D40225 Düsseldorf, Germany
| | - Joachim Herz
- Center for Neuroscience, Department of Neuroanatomy, Albert-Ludwigs-University, D79104 Freiburg, Germany Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75235, USA
| | - Michael Frotscher
- Center for Neuroscience, Department of Neuroanatomy, Albert-Ludwigs-University, D79104 Freiburg, Germany Institute for Structural Neurobiology, Center for Molecular Neurobiology, D20251 Hamburg, Germany and
| | - Jochen F Staiger
- Center for Neuroscience, Department of Neuroanatomy, Albert-Ludwigs-University, D79104 Freiburg, Germany Institute for Neuroanatomy, UMG, Georg-August-University, D37075 Göttingen, Germany
| | - Hans H Bock
- Center for Neuroscience, Department of Neuroanatomy, Albert-Ludwigs-University, D79104 Freiburg, Germany Clinic for Gastroenterology, Hepatology and Infectiology, Heinrich-Heine-University, D40225 Düsseldorf, Germany
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Novel GABAergic circuits mediating excitation/inhibition of Cajal-Retzius cells in the developing hippocampus. J Neurosci 2013; 33:5486-98. [PMID: 23536064 DOI: 10.1523/jneurosci.5680-12.2013] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Cajal-Retzius cells are a class of neurons believed to play critical roles during cortical development. However, their network computational functions remain poorly understood. Although work in the neocortex and hippocampus has shown that Cajal-Retzius cells receive predominantly, if not exclusively, spontaneous GABA(A) receptor-mediated input, the cellular sources originating these events remain unclear. However, a precise definition of the presynaptic GABAergic interneurons contacting Cajal-Retzius cells is important to understand the microcircuits and network patterns controlling their activation. Here, we have taken advantage of electrophysiological and anatomical techniques applied to mouse hippocampal slices in vitro to directly address this question. Our paired recording experiments indicate that Cajal-Retzius cells receive small-amplitude, kinetically slow synaptic input from stratum lacunosum-moleculare interneurons, anatomically identified as neurogliaform cells. In addition, a convergence of optogenetic, electrophysiological, and pharmacological experiments shows that Cajal-Retzius cells receive GABAergic input from oriens lacunosum-moleculare cells and that this input has different physiological properties (i.e., larger amplitude and faster kinetics) from the one provided by neurogliaform cells. Last, we show that GABAergic evoked synaptic input onto Cajal-Retzius cells may either increase their excitability and trigger action potentials or inhibit spontaneous firing by depolarization block. We propose that the specific type of response depends on both the membrane potential of Cajal-Retzius cells and the kinetics of the received GABAergic input. In conclusion, we have unraveled a novel hippocampal microcircuit with complex GABAergic synaptic signaling, which we suggest may play a role in the refinement of the hippocampal network and connections during development.
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Scharfman HE, Myers CE. Hilar mossy cells of the dentate gyrus: a historical perspective. Front Neural Circuits 2013; 6:106. [PMID: 23420672 PMCID: PMC3572871 DOI: 10.3389/fncir.2012.00106] [Citation(s) in RCA: 113] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2012] [Accepted: 12/02/2012] [Indexed: 11/24/2022] Open
Abstract
The circuitry of the dentate gyrus (DG) of the hippocampus is unique compared to other hippocampal subfields because there are two glutamatergic principal cells instead of one: granule cells, which are the vast majority of the cells in the DG, and the so-called “mossy cells.” The distinctive appearance of mossy cells, the extensive divergence of their axons, and their vulnerability to excitotoxicity relative to granule cells has led to a great deal of interest in mossy cells. Nevertheless, there is no consensus about the normal functions of mossy cells and the implications of their vulnerability. There even seems to be some ambiguity about exactly what mossy cells are. Here we review initial studies of mossy cells, characteristics that define them, and suggest a practical definition to allow investigators to distinguish mossy cells from other hilar neurons even if all morphological and physiological information is unavailable due to technical limitations of their experiments. In addition, hypotheses are discussed about the role of mossy cells in the DG network, reasons for their vulnerability and their implications for disease.
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Affiliation(s)
- Helen E Scharfman
- New York University Langone Medical Center New York, NY, USA ; Center for Dementia Research, The Nathan Kline Institute for Psychiatric Research Orangeburg, NY, USA
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Ferando I, Mody I. GABAAreceptor modulation by neurosteroids in models of temporal lobe epilepsies. Epilepsia 2012; 53 Suppl 9:89-101. [DOI: 10.1111/epi.12038] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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