1
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Gola L, Bierhansl L, Csatári J, Schroeter CB, Korn L, Narayanan V, Cerina M, Abdolahi S, Speicher A, Hermann AM, König S, Dinkova-Kostova AT, Shekh-Ahmad T, Meuth SG, Wiendl H, Gorji A, Pawlowski M, Kovac S. NOX4-derived ROS are neuroprotective by balancing intracellular calcium stores. Cell Mol Life Sci 2023; 80:127. [PMID: 37081190 PMCID: PMC10119225 DOI: 10.1007/s00018-023-04758-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Revised: 03/06/2023] [Accepted: 03/14/2023] [Indexed: 04/22/2023]
Abstract
Hyperexcitability is associated with neuronal dysfunction, cellular death, and consequently neurodegeneration. Redox disbalance can contribute to hyperexcitation and increased reactive oxygen species (ROS) levels are observed in various neurological diseases. NOX4 is an NADPH oxidase known to produce ROS and might have a regulating function during oxidative stress. We, therefore, aimed to determine the role of NOX4 on neuronal firing, hyperexcitability, and hyperexcitability-induced changes in neural network function. Using a multidimensional approach of an in vivo model of hyperexcitability, proteomic analysis, and cellular function analysis of ROS, mitochondrial integrity, and calcium levels, we demonstrate that NOX4 is neuroprotective by regulating ROS and calcium homeostasis and thereby preventing hyperexcitability and consequently neuronal death. These results implicate NOX4 as a potential redox regulator that is beneficial in hyperexcitability and thereby might have an important role in neurodegeneration.
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Affiliation(s)
- Lukas Gola
- Department of Neurology with Institute of Translational Neurology, University Hospital Münster, 48149, Münster, Germany
| | - Laura Bierhansl
- Department of Neurology with Institute of Translational Neurology, University Hospital Münster, 48149, Münster, Germany
| | - Júlia Csatári
- Department of Neurology with Institute of Translational Neurology, University Hospital Münster, 48149, Münster, Germany
| | - Christina B Schroeter
- Department of Neurology, Medical Faculty, Heinrich Heine University Düsseldorf, 40225, Düsseldorf, Germany
| | - Lisanne Korn
- Department of Neurology with Institute of Translational Neurology, University Hospital Münster, 48149, Münster, Germany
| | - Venu Narayanan
- Department of Neurology with Institute of Translational Neurology, University Hospital Münster, 48149, Münster, Germany
| | - Manuela Cerina
- Department of Neurology with Institute of Translational Neurology, University Hospital Münster, 48149, Münster, Germany
| | - Sara Abdolahi
- Shefa Neuroscience Research Center, Khatam Alanbia Hospital, Tehran, Iran
| | - Anna Speicher
- Department of Neurology with Institute of Translational Neurology, University Hospital Münster, 48149, Münster, Germany
| | - Alexander M Hermann
- Department of Neurology, Medical Faculty, Heinrich Heine University Düsseldorf, 40225, Düsseldorf, Germany
| | - Simone König
- Core Unit Proteomics, Interdisciplinary Center for Clinical Research, Medical Faculty, University of Münster, 48149, Münster, Germany
| | | | - Tawfeeq Shekh-Ahmad
- Institute for Drug Research, The School of Pharmacy, Faculty of Medicine, The Hebrew University of Jerusalem, 91120, Jerusalem, Israel
| | - Sven G Meuth
- Department of Neurology, Medical Faculty, Heinrich Heine University Düsseldorf, 40225, Düsseldorf, Germany
| | - Heinz Wiendl
- Department of Neurology with Institute of Translational Neurology, University Hospital Münster, 48149, Münster, Germany
| | - Ali Gorji
- Shefa Neuroscience Research Center, Khatam Alanbia Hospital, Tehran, Iran
- Epilepsy Research Center, Westfälische Wilhelms-Universität Münster, 48149, Münster, Germany
| | - Matthias Pawlowski
- Department of Neurology with Institute of Translational Neurology, University Hospital Münster, 48149, Münster, Germany
| | - Stjepana Kovac
- Department of Neurology with Institute of Translational Neurology, University Hospital Münster, 48149, Münster, Germany.
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Richardson BD, Sottile SY, Caspary DM. Mechanisms of GABAergic and cholinergic neurotransmission in auditory thalamus: Impact of aging. Hear Res 2020; 402:108003. [PMID: 32703637 DOI: 10.1016/j.heares.2020.108003] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/04/2020] [Revised: 05/15/2020] [Accepted: 05/23/2020] [Indexed: 12/18/2022]
Abstract
Age-related hearing loss is a complex disorder affecting a majority of the elderly population. As people age, speech understanding becomes a challenge especially in complex acoustic settings and negatively impacts the ability to accurately analyze the auditory scene. This is in part due to an inability to focus auditory attention on a particular stimulus source while simultaneously filtering out other sound stimuli. The present review examines the impact of aging on two neurotransmitter systems involved in accurate temporal processing and auditory gating in auditory thalamus (medial geniculate body; MGB), a critical brain region involved in the coding and filtering of auditory information. The inhibitory neurotransmitter GABA and its synaptic receptors (GABAARs) are key to maintaining accurate temporal coding of complex sounds, such as speech, throughout the central auditory system. In the MGB, synaptic and extrasynaptic GABAARs mediate fast phasic and slow tonic inhibition respectively, which in turn regulate MGB neuron excitability, firing modes, and engage thalamocortical oscillations that shape coding and gating of acoustic content. Acoustic coding properties of MGB neurons are further modulated through activation of tegmental cholinergic afferents that project to MGB to potentially modulate attention and help to disambiguate difficult to understand or novel sounds. Acetylcholine is released onto MGB neurons and presynaptic terminals in MGB activating neuronal nicotinic and muscarinic acetylcholine receptors (nAChRs, mAChRs) at a subset of MGB afferents to optimize top-down and bottom-up information flow. Both GABAergic and cholinergic neurotransmission is significantly altered with aging and this review will detail how age-related changes in these circuits within the MGB may impact coding of acoustic stimuli.
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Affiliation(s)
- B D Richardson
- WWAMI Medical Education, University of Idaho, Moscow, ID, 83844, USA; Biological Engineering, University of Idaho, Moscow, ID, 83844, USA
| | - S Y Sottile
- Center for Clinical Research Southern Illinois University - School of Medicine, Springfield, IL, 62702, USA
| | - D M Caspary
- Department of Pharmacology Southern Illinois University - School of Medicine, Springfield, IL, 62702, USA.
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3
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Hundehege P, Cerina M, Eichler S, Thomas C, Herrmann AM, Göbel K, Müntefering T, Fernandez-Orth J, Bock S, Narayanan V, Budde T, Speckmann EJ, Wiendl H, Schubart A, Ruck T, Meuth SG. The next-generation sphingosine-1 receptor modulator BAF312 (siponimod) improves cortical network functionality in focal autoimmune encephalomyelitis. Neural Regen Res 2019; 14:1950-1960. [PMID: 31290453 PMCID: PMC6676873 DOI: 10.4103/1673-5374.259622] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Autoimmune diseases of the central nervous system (CNS) like multiple sclerosis (MS) are characterized by inflammation and demyelinated lesions in white and grey matter regions. While inflammation is present at all stages of MS, it is more pronounced in the relapsing forms of the disease, whereas progressive MS (PMS) shows significant neuroaxonal damage and grey and white matter atrophy. Hence, disease-modifying treatments beneficial in patients with relapsing MS have limited success in PMS. BAF312 (siponimod) is a novel sphingosine-1-phosphate receptor modulator shown to delay progression in PMS. Besides reducing inflammation by sequestering lymphocytes in lymphoid tissues, BAF312 crosses the blood-brain barrier and binds its receptors on neurons, astrocytes and oligodendrocytes. To evaluate potential direct neuroprotective effects, BAF312 was systemically or locally administered in the CNS of experimental autoimmune encephalomyelitis mice with distinct grey- and white-matter lesions (focal experimental autoimmune encephalomyelitis using an osmotic mini-pump). Ex-vivo flow cytometry revealed that systemic but not local BAF312 administration lowered immune cell infiltration in animals with both grey and white matter lesions. Ex-vivo voltage-sensitive dye imaging of acute brain slices revealed an altered spatio-temporal pattern of activation in the lesioned cortex compared to controls in response to electrical stimulation of incoming white-matter fiber tracts. Here, BAF312 administration showed partial restore of cortical neuronal circuit function. The data suggest that BAF312 exerts a neuroprotective effect after crossing the blood-brain barrier independently of peripheral effects on immune cells. Experiments were carried out in accordance with German and EU animal protection law and approved by local authorities (Landesamt für Natur, Umwelt und Verbraucherschutz Nordrhein-Westfalen; 87-51.04.2010.A331) on December 28, 2010.
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Affiliation(s)
- Petra Hundehege
- Department of Neurology with Institute of Translational Neurology, Westfälische Wilhelms-Universität, Münster, Germany
| | - Manuela Cerina
- Department of Neurology with Institute of Translational Neurology, Westfälische Wilhelms-Universität, Münster, Germany
| | - Susann Eichler
- Department of Neurology with Institute of Translational Neurology, Westfälische Wilhelms-Universität, Münster, Germany
| | - Christian Thomas
- Department of Neurology with Institute of Translational Neurology, Westfälische Wilhelms-Universität, Münster, Germany
| | - Alexander M Herrmann
- Department of Neurology with Institute of Translational Neurology, Westfälische Wilhelms-Universität, Münster, Germany
| | - Kerstin Göbel
- Department of Neurology with Institute of Translational Neurology, Westfälische Wilhelms-Universität, Münster, Germany
| | - Thomas Müntefering
- Department of Neurology with Institute of Translational Neurology, Westfälische Wilhelms-Universität, Münster, Germany
| | - Juncal Fernandez-Orth
- Department of Neurology with Institute of Translational Neurology, Westfälische Wilhelms-Universität, Münster, Germany
| | - Stefanie Bock
- Department of Neurology with Institute of Translational Neurology, Westfälische Wilhelms-Universität, Münster, Germany
| | - Venu Narayanan
- Department of Neurology with Institute of Translational Neurology, Westfälische Wilhelms-Universität, Münster, Germany
| | - Thomas Budde
- Institute of Physiology I, Westfälische Wilhelms-Universität, Münster, Germany
| | | | - Heinz Wiendl
- Department of Neurology with Institute of Translational Neurology, Westfälische Wilhelms-Universität, Münster, Germany
| | - Anna Schubart
- Novartis Institutes of Biomedical Research, Basel, Switzerland
| | - Tobias Ruck
- Department of Neurology with Institute of Translational Neurology, Westfälische Wilhelms-Universität, Münster, Germany
| | - Sven G Meuth
- Department of Neurology with Institute of Translational Neurology, Westfälische Wilhelms-Universität, Münster, Germany
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Protective potential of dimethyl fumarate in a mouse model of thalamocortical demyelination. Brain Struct Funct 2018; 223:3091-3106. [PMID: 29744572 PMCID: PMC6132667 DOI: 10.1007/s00429-018-1680-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Accepted: 05/04/2018] [Indexed: 12/16/2022]
Abstract
Alterations in cortical cellular organization, network functionality, as well as cognitive and locomotor deficits were recently suggested to be pathological hallmarks in multiple sclerosis and corresponding animal models as they might occur following demyelination. To investigate functional changes following demyelination in a well-defined, topographically organized neuronal network, in vitro and in vivo, we focused on the primary auditory cortex (A1) of mice in the cuprizone model of general de- and remyelination. Following myelin loss in this model system, the spatiotemporal propagation of incoming stimuli in A1 was altered and the hierarchical activation of supra- and infragranular cortical layers was lost suggesting a profound effect exerted on neuronal network level. In addition, the response latency in field potential recordings and voltage-sensitive dye imaging was increased following demyelination. These alterations were accompanied by a loss of auditory discrimination abilities in freely behaving animals, a reduction of the nuclear factor-erythroid 2-related factor-2 (Nrf-2) protein in the nucleus in histological staining and persisted during remyelination. To find new strategies to restore demyelination-induced network alteration in addition to the ongoing remyelination, we tested the cytoprotective potential of dimethyl fumarate (DMF). Therapeutic treatment with DMF during remyelination significantly modified spatiotemporal stimulus propagation in the cortex, reduced the cognitive impairment, and prevented the demyelination-induced decrease in nuclear Nrf-2. These results indicate the involvement of anti-oxidative mechanisms in regulating spatiotemporal cortical response pattern following changes in myelination and point to DMF as therapeutic compound for intervention.
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Mesgari M, Krüger J, Riemer CT, Khaleghi Ghadiri M, Kovac S, Gorji A. Gabapentin prevents cortical spreading depolarization-induced disinhibition. Neuroscience 2017; 361:1-5. [DOI: 10.1016/j.neuroscience.2017.08.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Revised: 07/28/2017] [Accepted: 08/03/2017] [Indexed: 01/29/2023]
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6
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Graebenitz S, Cerina M, Lesting J, Kedo O, Gorji A, Pannek H, Hans V, Zilles K, Pape HC, Speckmann EJ. Directional spread of activity in synaptic networks of the human lateral amygdala. Neuroscience 2017; 349:330-340. [PMID: 28315444 DOI: 10.1016/j.neuroscience.2017.03.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Revised: 02/22/2017] [Accepted: 03/07/2017] [Indexed: 11/18/2022]
Abstract
Spontaneous epileptiform activity has previously been observed in lateral amygdala (LA) slices derived from patients with intractable-temporal lobe epilepsy. The present study aimed to characterize intranuclear LA synaptic connectivity and to test the hypothesis that differences in the spread of flow of neuronal activity may relate to spontaneous epileptiform activity occurrence. Electrical activity was evoked through electrical microstimulation in acute human brain slices containing the LA, signals were recorded as local field potentials combined with fast optical imaging of voltage-sensitive dye fluorescence. Sites of stimulation and recording were systematically varied. Following recordings, slices were anatomically reconstructed using two-dimensional unitary slices as a reference for coronal and parasagittal planes. Local spatial patterns and spread of activity were assessed by incorporating the coordinates of electrical and optical recording sites into the respective unitary slice. A preferential directional spread of evoked electrical signals was observed from ventral to dorsal, rostral to caudal and medial to lateral regions in the LA. No differences in spread of evoked activity were observed between spontaneously and non-spontaneously active LA slices, i.e. basic properties of evoked synaptic responses were similar in the two functional types of LA slices, including input-output relationship, and paired-pulse depression. These results indicate a directed propagation of synaptic signals within the human LA in spontaneously active epileptic slices. We suggest that the lack of differences in local and in systemic information processing has to be found in confined epileptiform circuits within the amygdala likely involving well-known "epileptic neurons".
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Affiliation(s)
| | - Manuela Cerina
- Department of Neurology and Institute of Translational Neurology, University Hospital and Westfaelische Wilhelms-University Muenster, Germany.
| | - Jörg Lesting
- Institute of Physiology I, Westfaelische Wilhelms-University Muenster, Germany
| | - Olga Kedo
- Institute of Neuroscience and Medicine, Research Center Juelich, Germany
| | - Ali Gorji
- Epilepsy Research Center, Westfaelische Wilhelms-University Muenster, Germany; Shefa Neuroscience Research Center, Khatam Alanbia Hospital, Tehran, Iran
| | - Heinz Pannek
- Bethel Epilepsy Center Bethel, Mara, Bielefeld, Germany
| | - Volkmar Hans
- Institute of Neuropathology, Bethel, Bielefeld, Germany
| | - Karl Zilles
- Institute of Neuroscience and Medicine, Research Center Juelich, Germany
| | - Hans-Christian Pape
- Institute of Physiology I, Westfaelische Wilhelms-University Muenster, Germany
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7
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Ghaffarian N, Mesgari M, Cerina M, Göbel K, Budde T, Speckmann EJ, Meuth SG, Gorji A. Thalamocortical-auditory network alterations following cuprizone-induced demyelination. J Neuroinflammation 2016; 13:160. [PMID: 27334140 PMCID: PMC4918138 DOI: 10.1186/s12974-016-0629-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Accepted: 06/15/2016] [Indexed: 12/14/2022] Open
Abstract
Background Demyelination and remyelination are common pathological processes in many neurological disorders, including multiple sclerosis (MS). Clinical evidence suggests extensive involvement of the thalamocortical (TC) system in patients suffering from MS. Methods Using murine brain slices of the primary auditory cortex, we investigated the functional consequences of cuprizone-induced de- and remyelination on neuronal activity and auditory TC synaptic transmission in vitro. Results Our results revealed an impact of myelin loss and restoration on intrinsic cellular firing patterns, synaptic transmission, and neuronal plasticity in layer 3 and 4 neurons of the auditory TC network. While there was a complex hyper- and depolarizing shift of the resting membrane potential, spontaneous and induced action potential firing was reduced during demyelination and early remyelination. In addition, excitatory postsynaptic potential amplitudes were decreased and induction of LTP was reduced during demyelination. Conclusions These data indicate that demyelination-induced impairment of neurons and network activity within the TC system may underlie clinical symptoms observed in demyelinating diseases, corroborating human findings that disease progression is significantly correlated with microstructural tissue damage of the TC system. Further investigation into focal inflammation-induced demyelination models ex vivo and in vivo are needed to understand the functional implication of local and remote lesion formation on TC network activity in MS.
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Affiliation(s)
- Nikoo Ghaffarian
- Epilepsy Research Center, Westfälische Wilhelms-Universität Münster, University of Münster, Robert-Koch-Straße 27a, 48149, Münster, Germany
| | - Masoud Mesgari
- Epilepsy Research Center, Westfälische Wilhelms-Universität Münster, University of Münster, Robert-Koch-Straße 27a, 48149, Münster, Germany
| | - Manuela Cerina
- Department of Neurology, Westfälische Wilhelms-Universität, University of Münster, Albert-Schweitzer-Campus 1, Building A1, 48149, Münster, Germany
| | - Kerstin Göbel
- Department of Neurology, Westfälische Wilhelms-Universität, University of Münster, Albert-Schweitzer-Campus 1, Building A1, 48149, Münster, Germany
| | - Thomas Budde
- Institute of Physiology I, Westfälische Wilhelms-Universität, Münster, Germany
| | - Erwin-Josef Speckmann
- Epilepsy Research Center, Westfälische Wilhelms-Universität Münster, University of Münster, Robert-Koch-Straße 27a, 48149, Münster, Germany
| | - Sven G Meuth
- Department of Neurology, Westfälische Wilhelms-Universität, University of Münster, Albert-Schweitzer-Campus 1, Building A1, 48149, Münster, Germany.
| | - Ali Gorji
- Epilepsy Research Center, Westfälische Wilhelms-Universität Münster, University of Münster, Robert-Koch-Straße 27a, 48149, Münster, Germany. .,Department of Neurology, Westfälische Wilhelms-Universität, University of Münster, Albert-Schweitzer-Campus 1, Building A1, 48149, Münster, Germany. .,Department of Neurosurgery, Westfälische Wilhelms-Universität Münster, Münster, Germany. .,Shefa Neuroscience Research Center, Khatam-Alanbia Hospital, Tehran, Iran.
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8
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Geissler DB, Schmidt HS, Ehret G. Knowledge About Sounds-Context-Specific Meaning Differently Activates Cortical Hemispheres, Auditory Cortical Fields, and Layers in House Mice. Front Neurosci 2016; 10:98. [PMID: 27013959 PMCID: PMC4789409 DOI: 10.3389/fnins.2016.00098] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Accepted: 02/26/2016] [Indexed: 11/13/2022] Open
Abstract
Activation of the auditory cortex (AC) by a given sound pattern is plastic, depending, in largely unknown ways, on the physiological state and the behavioral context of the receiving animal and on the receiver's experience with the sounds. Such plasticity can be inferred when house mouse mothers respond maternally to pup ultrasounds right after parturition and naïve females have to learn to respond. Here we use c-FOS immunocytochemistry to quantify highly activated neurons in the AC fields and layers of seven groups of mothers and naïve females who have different knowledge about and are differently motivated to respond to acoustic models of pup ultrasounds of different behavioral significance. Profiles of FOS-positive cells in the AC primary fields (AI, AAF), the ultrasonic field (UF), the secondary field (AII), and the dorsoposterior field (DP) suggest that activation reflects in AI, AAF, and UF the integration of sound properties with animal state-dependent factors, in the higher-order field AII the news value of a given sound in the behavioral context, and in the higher-order field DP the level of maternal motivation and, by left-hemisphere activation advantage, the recognition of the meaning of sounds in the given context. Anesthesia reduced activation in all fields, especially in cortical layers 2/3. Thus, plasticity in the AC is field-specific preparing different output of AC fields in the process of perception, recognition and responding to communication sounds. Further, the activation profiles of the auditory cortical fields suggest the differentiation between brains hormonally primed to know (mothers) and brains which acquired knowledge via implicit learning (naïve females). In this way, auditory cortical activation discriminates between instinctive (mothers) and learned (naïve females) cognition.
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Affiliation(s)
| | | | - Günter Ehret
- Institute of Neurobiology, University of Ulm Ulm, Germany
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9
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Stebbings KA, Choi HW, Ravindra A, Caspary DM, Turner JG, Llano DA. Ageing-related changes in GABAergic inhibition in mouse auditory cortex, measured using in vitro flavoprotein autofluorescence imaging. J Physiol 2015; 594:207-21. [PMID: 26503482 DOI: 10.1113/jp271221] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2015] [Accepted: 10/18/2015] [Indexed: 12/24/2022] Open
Abstract
KEY POINTS Ageing is associated with hearing loss and changes in GABAergic signalling in the auditory system. We tested whether GABAergic signalling in an isolated forebrain preparation also showed ageing-related changes. A novel approach was used, whereby population imaging was coupled to quantitative pharmacological sensitivity. Sensitivity to GABAA blockade was inversely associated with age and cortical thickness, but hearing loss did not independently contribute to the change in GABAA ergic sensitivity. Redox states in the auditory cortex of young and aged animals were similar, suggesting that the differences in GABAA ergic sensitivity are unlikely to be due to differences in slice health. To examine ageing-related changes in the earliest stages of auditory cortical processing, population auditory cortical responses to thalamic afferent stimulation were studied in brain slices obtained from young and aged CBA/CAj mice (up to 28 months of age). Cortical responses were measured using flavoprotein autofluorescence imaging, and ageing-related changes in inhibition were assessed by measuring the sensitivity of these responses to blockade of GABAA receptors using bath-applied SR95531. The maximum auditory cortical response to afferent stimulation was not different between young and aged animals under control conditions, but responses to afferent stimulation in aged animals showed a significantly lower sensitivity to GABA blockade with SR95531. Cortical thickness, but not hearing loss, improved the prediction of all imaging variables when combined with age, particularly sensitivity to GABA blockade for the maximum response. To determine if the observed differences between slices from young and aged animals were due to differences in slice health, the redox state in the auditory cortex was assessed by measuring the FAD+/NADH ratio using fluorescence imaging. We found that this ratio is highly sensitive to known redox stressors such as H2 O2 and NaCN; however, no difference was found between young and aged animals. By using a new approach to quantitatively assess pharmacological sensitivity of population-level cortical responses to afferent stimulation, these data demonstrate that auditory cortical inhibition diminishes with ageing. Furthermore, these data establish a significant relationship between cortical thickness and GABAergic sensitivity, which had not previously been observed in an animal model of ageing.
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Affiliation(s)
- K A Stebbings
- Neuroscience Program, University of Illinois at Urbana-Champaign, IL, USA
| | - H W Choi
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, IL, USA
| | - A Ravindra
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, IL, USA
| | - D M Caspary
- Department of Pharmacology, Southern Illinois University College of Medicine, IL, USA
| | - J G Turner
- Department of Pharmacology, Southern Illinois University College of Medicine, IL, USA.,Department of Psychology, Illinois College, IL, USA
| | - D A Llano
- Neuroscience Program, University of Illinois at Urbana-Champaign, IL, USA.,Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, IL, USA
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10
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Lee CC, Yanagawa Y, Imaizumi K. Commissural functional topography of the inferior colliculus assessed in vitro. Hear Res 2015; 328:94-101. [PMID: 26319767 DOI: 10.1016/j.heares.2015.08.011] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Revised: 08/12/2015] [Accepted: 08/19/2015] [Indexed: 10/23/2022]
Abstract
The inferior colliculus (IC) receives ascending and descending information from several convergent neural sources. As such, exploring the neural pathways that converge in the IC is crucial to uncovering their multi-varied roles in the integration of auditory and other sensory information. Among these convergent pathways, the IC commissural connections represent an important route for the integration of bilateral information in the auditory system. Here, we describe the preparation and validation of a novel in vitro slice preparation for examining the functional topography and synaptic properties of the commissural and intrinsic projections in the IC of the mouse. This preparation, in combination with modern genetic approaches in the mouse, enables the specific examination of these pathways, which potentially can reveal cell-type specific processing channels in the auditory midbrain.
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Affiliation(s)
- Charles C Lee
- Department of Comparative Biomedical Sciences, Louisiana State University, School of Veterinary Medicine, Baton Rouge, LA 70803, USA.
| | - Yuchio Yanagawa
- Department of Genetic and Behavioral Neuroscience, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan
| | - Kazuo Imaizumi
- Department of Comparative Biomedical Sciences, Louisiana State University, School of Veterinary Medicine, Baton Rouge, LA 70803, USA; Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
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11
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Ehling P, Melzer N, Budde T, Meuth SG. CD8(+) T Cell-Mediated Neuronal Dysfunction and Degeneration in Limbic Encephalitis. Front Neurol 2015; 6:163. [PMID: 26236280 PMCID: PMC4502349 DOI: 10.3389/fneur.2015.00163] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2015] [Accepted: 07/02/2015] [Indexed: 12/31/2022] Open
Abstract
Autoimmune inflammation of the limbic gray matter structures of the human brain has recently been identified as major cause of mesial temporal lobe epilepsy with interictal temporal epileptiform activity and slowing of the electroencephalogram, progressive memory disturbances, as well as a variety of other behavioral, emotional, and cognitive changes. Magnetic resonance imaging exhibits volume and signal changes of the amygdala and hippocampus, and specific anti-neuronal antibodies binding to either intracellular or plasma membrane neuronal antigens can be detected in serum and cerebrospinal fluid. While effects of plasma cell-derived antibodies on neuronal function and integrity are increasingly becoming characterized, potentially contributing effects of T cell-mediated immune mechanisms remain poorly understood. CD8+ T cells are known to directly interact with major histocompatibility complex class I-expressing neurons in an antigen-specific manner. Here, we summarize current knowledge on how such direct CD8+ T cell–neuron interactions may impact neuronal excitability, plasticity, and integrity on a single cell and network level and provide an overview on methods to further corroborate the in vivo relevance of these mechanisms mainly obtained from in vitro studies.
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Affiliation(s)
- Petra Ehling
- Department of Neurology, Westfälische Wilhelms-University of Münster , Münster , Germany ; Institute of Physiology I - Neuropathophysiology, Westfälische Wilhelms-University , Münster , Germany
| | - Nico Melzer
- Department of Neurology, Westfälische Wilhelms-University of Münster , Münster , Germany
| | - Thomas Budde
- Institute of Physiology I, Westfälische Wilhelms-University , Münster , Germany
| | - Sven G Meuth
- Department of Neurology, Westfälische Wilhelms-University of Münster , Münster , Germany ; Institute of Physiology I - Neuropathophysiology, Westfälische Wilhelms-University , Münster , Germany
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Pál I, Kardos J, Dobolyi Á, Héja L. Appearance of fast astrocytic component in voltage-sensitive dye imaging of neural activity. Mol Brain 2015; 8:35. [PMID: 26043770 PMCID: PMC4455916 DOI: 10.1186/s13041-015-0127-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2014] [Accepted: 05/24/2015] [Indexed: 12/21/2022] Open
Abstract
Background Voltage-sensitive dye (VSD) imaging and intrinsic optical signals (IOS) are widely used methods for monitoring spatiotemporal neural activity in extensive networks. In spite of that, identification of their major cellular and molecular components has not been concluded so far. Results We addressed these issues by imaging spatiotemporal spreading of IOS and VSD transients initiated by Schaffer collateral stimulation in rat hippocampal slices with temporal resolution comparable to standard field potential recordings using a 464-element photodiode array. By exploring the potential neuronal and astroglial molecular players in VSD and IOS generation, we identified multiple astrocytic mechanisms that significantly contribute to the VSD signal, in addition to the expected neuronal targets. Glutamate clearance through the astroglial glutamate transporter EAAT2 has been shown to be a significant player in VSD generation within a very short (<5 ms) time-scale, indicating that astrocytes do contribute to the development of spatiotemporal VSD transients previously thought to be essentially neuronal. In addition, non-specific anion channels, astroglial K+ clearance through Kir4.1 channel and astroglial Na+/K+ ATPase also contribute to IOS and VSD transients. Conclusion VSD imaging cannot be considered as a spatially extended field potential measurement with predominantly neuronal origin, instead it also reflects a fast communication between neurons and astrocytes.
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Affiliation(s)
- Ildikó Pál
- Group of Functional Pharmacology, Institute of Cognitive Neuroscience and Psychology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Magyar tudósok körútja 2, H-1117, Budapest, Hungary.
| | - Julianna Kardos
- Group of Functional Pharmacology, Institute of Cognitive Neuroscience and Psychology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Magyar tudósok körútja 2, H-1117, Budapest, Hungary.
| | - Árpád Dobolyi
- MTA-ELTE-NAP B Laboratory of Molecular and Systems Neurobiology, H-1117, Budapest, Hungary. .,Department of Anatomy, Human Brain Tissue Bank, Semmelweis University, H-1450, Budapest, Hungary.
| | - László Héja
- Group of Functional Pharmacology, Institute of Cognitive Neuroscience and Psychology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Magyar tudósok körútja 2, H-1117, Budapest, Hungary.
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Kratz MB, Manis PB. Spatial organization of excitatory synaptic inputs to layer 4 neurons in mouse primary auditory cortex. Front Neural Circuits 2015; 9:17. [PMID: 25972787 PMCID: PMC4413692 DOI: 10.3389/fncir.2015.00017] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2015] [Accepted: 04/07/2015] [Indexed: 12/28/2022] Open
Abstract
Layer 4 (L4) of primary auditory cortex (A1) receives a tonotopically organized projection from the medial geniculate nucleus of the thalamus. However, individual neurons in A1 respond to a wider range of sound frequencies than would be predicted by their thalamic input, which suggests the existence of cross-frequency intracortical networks. We used laser scanning photostimulation and uncaging of glutamate in brain slices of mouse A1 to characterize the spatial organization of intracortical inputs to L4 neurons. Slices were prepared to include the entire tonotopic extent of A1. We find that L4 neurons receive local vertically organized (columnar) excitation from layers 2 through 6 (L6) and horizontally organized excitation primarily from L4 and L6 neurons in regions centered ~300–500 μm caudal and/or rostral to the cell. Excitatory horizontal synaptic connections from layers 2 and 3 were sparse. The origins of horizontal projections from L4 and L6 correspond to regions in the tonotopic map that are approximately an octave away from the target cell location. Such spatially organized lateral connections may contribute to the detection and processing of auditory objects with specific spectral structures.
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Affiliation(s)
- Megan B Kratz
- Department of Otolaryngology/Head and Neck Surgery, University of North Carolina at Chapel Hill Chapel Hill, NC, USA ; The Curriculum in Neurobiology, University of North Carolina Chapel Hill, NC, USA
| | - Paul B Manis
- Department of Otolaryngology/Head and Neck Surgery, University of North Carolina at Chapel Hill Chapel Hill, NC, USA ; The Curriculum in Neurobiology, University of North Carolina Chapel Hill, NC, USA ; Department of Cell Biology and Physiology, University of North Carolina Chapel Hill, NC, USA
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14
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Imaizumi K, Lee CC. Frequency transformation in the auditory lemniscal thalamocortical system. Front Neural Circuits 2014; 8:75. [PMID: 25071456 PMCID: PMC4086294 DOI: 10.3389/fncir.2014.00075] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2014] [Accepted: 06/16/2014] [Indexed: 12/02/2022] Open
Abstract
The auditory lemniscal thalamocortical (TC) pathway conveys information from the ventral division of the medial geniculate body to the primary auditory cortex (A1). Although their general topographic organization has been well characterized, functional transformations at the lemniscal TC synapse still remain incompletely codified, largely due to the need for integration of functional anatomical results with the variability observed with various animal models and experimental techniques. In this review, we discuss these issues with classical approaches, such as in vivo extracellular recordings and tracer injections to physiologically identified areas in A1, and then compare these studies with modern approaches, such as in vivo two-photon calcium imaging, in vivo whole-cell recordings, optogenetic methods, and in vitro methods using slice preparations. A surprising finding from a comparison of classical and modern approaches is the similar degree of convergence from thalamic neurons to single A1 neurons and clusters of A1 neurons, although, thalamic convergence to single A1 neurons is more restricted from areas within putative thalamic frequency lamina. These comparisons suggest that frequency convergence from thalamic input to A1 is functionally limited. Finally, we consider synaptic organization of TC projections and future directions for research.
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Affiliation(s)
- Kazuo Imaizumi
- Department of Comparative Biomedical Sciences, Louisiana State University, School of Veterinary Medicine Baton Rouge, LA, USA
| | - Charles C Lee
- Department of Comparative Biomedical Sciences, Louisiana State University, School of Veterinary Medicine Baton Rouge, LA, USA
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15
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Functional convergence of thalamic and intrinsic projections to cortical layers 4 and 6. NEUROPHYSIOLOGY+ 2013; 45:396-406. [PMID: 24563558 DOI: 10.1007/s11062-013-9385-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Ascending sensory information is conveyed from the thalamus to layers 4 and 6 of sensory cortical areas. Interestingly, receptive field properties of cortical layer 6 neurons are different from those in layer 4. Do such differences reflect distinct inheritance patterns from the thalamus or are they derived instead from local cortical circuits? To distinguish between these possibilities, we utilized in vitro slice preparations containing the thalamocortical pathways in the auditory and somatosensory systems. Responses from neurons in layers 4 and 6 that resided in the same column were recorded using whole-cell patch clamp. Laser-scanning photostimulation via uncaging of glutamate in the thalamus and cortex was used to map the functional topography of thalamocortical and intracortical inputs to each layer. In addition, we assessed the functional divergence of thalamocortical inputs by optical imaging of flavoprotein autofluorescence. We found that the thalamocortical inputs to layers 4 and 6 originated from the same thalamic domain, but the intracortical projections to the same neurons differed dramatically. Our results suggest that the intracortical projections, rather than the thalamic inputs, to each layer contribute more to the differences in their receptive field properties.
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Straka MM, Schendel D, Lim HH. Neural integration and enhancement from the inferior colliculus up to different layers of auditory cortex. J Neurophysiol 2013; 110:1009-20. [PMID: 23719210 DOI: 10.1152/jn.00022.2013] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
While the cochlear implant has successfully restored hearing to many deaf patients, it cannot benefit those without a functional auditory nerve or an implantable cochlea. As an alternative, the auditory midbrain implant (AMI) has been developed and implanted into deaf patients. Consisting of a single-shank array, the AMI is designed for stimulation along the tonotopic gradient of the inferior colliculus (ICC). Although the AMI can provide frequency cues, it appears to insufficiently transmit temporal cues for speech understanding because repeated stimulation of a single site causes strong suppressive and refractory effects. Applying the electrical stimulation to at least two sites within an isofrequency lamina can circumvent these refractory processes. Moreover, coactivation with short intersite delays (<5 ms) can elicit cortical activation which is enhanced beyond the summation of activity induced by the individual sites. The goal of our study was to further investigate the role of the auditory cortex in this enhancement effect. In guinea pigs, we electrically stimulated two locations within an ICC lamina or along different laminae with varying interpulse intervals (0-10 ms) and recorded activity in different locations and layers of primary auditory cortex (A1). Our findings reveal a neural mechanism that integrates activity only from neurons located within the same ICC lamina for short spiking intervals (<6 ms). This mechanism leads to enhanced activity into layers III-V of A1 that is further magnified in supragranular layers. This integration mechanism may contribute to perceptual coding of different sound features that are relevant for improving AMI performance.
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Affiliation(s)
- Malgorzata M Straka
- Department of Biomedical Engineering, University of Minnesota, Twin Cities, Minneapolis, Minnesota, USA.
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17
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Abstract
Flavoprotein autofluorescence imaging was used to examine auditory cortical synaptic responses in aged animals with behavioral evidence of tinnitus and hearing loss. Mice were exposed to noise trauma at 1-3 months of age and were assessed for behavioral evidence of tinnitus and hearing loss immediately after the noise trauma and again at ~24-30 months of age. Within 2 months of the final behavioral assessment, auditory cortical synaptic transmission was examined in brain slices using electrical stimulation of putative thalamocortical afferents, and flavoprotein autofluorescence imaging was used to measure cortical activation. Noise-exposed animals showed a 68% increase in amplitude of cortical activation compared with controls (p = 0.008), and these animals showed a diminished sensitivity to GABA(A)ergic blockade (p = 0.008, using bath-applied 200 nm SR 95531 [6-Imino-3-(4-methoxyphenyl)-1(6H)-p yridazinebutanoic acid hydrobromide]). The strength of cortical activation was significantly correlated to the degree of tinnitus behavior, assessed via a loss of gap detection in a startle paradigm. The decrease in GABA(A) sensitivity was greater in the regions of the cortex farther away from the stimulation site, potentially reflecting a greater sensitivity of corticocortical versus thalamocortical projections to the effects of noise trauma. Finally, there was no relationship between auditory cortical activation and activation of the somatosensory cortex in the same slices, suggesting that the increases in auditory cortical activation were not attributable to a generalized hyperexcitable state in noise-exposed animals. These data suggest that noise trauma can cause long-lasting changes in the auditory cortical physiology and may provide specific targets to ameliorate the effects of chronic tinnitus.
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Calixto R, Lenarz M, Neuheiser A, Scheper V, Lenarz T, Lim HH. Coactivation of different neurons within an isofrequency lamina of the inferior colliculus elicits enhanced auditory cortical activation. J Neurophysiol 2012; 108:1199-210. [PMID: 22623485 DOI: 10.1152/jn.00111.2012] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The phenomenal success of the cochlear implant (CI) is attributed to its ability to provide sufficient temporal and spectral cues for speech understanding. Unfortunately, the CI is ineffective for those without a functional auditory nerve or an implantable cochlea required for CI implementation. As an alternative, our group developed and implanted in deaf patients a new auditory midbrain implant (AMI) to stimulate the central nucleus of the inferior colliculus (ICC). Although the AMI can provide frequency cues, it appears to insufficiently transmit temporal cues for speech understanding. The three-dimensional ICC consists of two-dimensional isofrequency laminae. The single-shank AMI only stimulates one site in any given ICC lamina and does not exhibit enhanced activity (i.e., louder percepts or lower thresholds) for repeated pulses on the same site with intervals <2-5 ms, as occurs for CI pulse or acoustic click stimulation. This enhanced activation, related to short-term temporal integration, is important for tracking the rapid temporal fluctuations of a speech signal. Therefore, we investigated the effects of coactivation of different regions within an ICC lamina on primary auditory cortex activity in ketamine-anesthetized guinea pigs. Interestingly, our findings reveal an enhancement mechanism for integrating converging inputs from an ICC lamina on a fast scale (<6-ms window) that is compromised when stimulating just a single ICC location. Coactivation of two ICC regions also reduces the strong and long-term (>100 ms) suppressive effects induced by repeated stimulation of just a single location. Improving AMI performance may require at least two shanks implanted along the tonotopic gradient of the ICC that enables coactivation of multiple regions along an ICC lamina with the appropriate interstimulus delays.
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Affiliation(s)
- Roger Calixto
- Institute of Audioneurotechnology and Department of Experimental Otology, Hannover Medical University, Hannover, Germany
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Schachtele SJ, Losh J, Dailey ME, Green SH. Spine formation and maturation in the developing rat auditory cortex. J Comp Neurol 2012; 519:3327-45. [PMID: 21800311 DOI: 10.1002/cne.22728] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The rat auditory cortex is organized as a tonotopic map of sound frequency. This map is broadly tuned at birth and is refined during the first 3 weeks postnatal. The structural correlates underlying tonotopic map maturation and reorganization during development are poorly understood. We employed fluorescent dye ballistic labeling ("DiOlistics") alone, or in conjunction with immunohistochemistry, to quantify synaptogenesis in the auditory cortex of normal hearing rats. We show that the developmental appearance of dendritic protrusions, which include both immature filopodia and mature spines, on layers 2/3, 4, and 5 pyramidal and layer 4 spiny nonpyramidal neurons occurs in three phases: slow addition of dendritic protrusions from postnatal day 4 (P4) to P9, rapid addition of dendritic protrusions from P9 to P19, and a final phase where mature protrusion density is achieved (>P21). Next, we combined DiOlistics with immunohistochemical labeling of bassoon, a presynaptic scaffolding protein, as a novel method to categorize dendritic protrusions as either filopodia or mature spines in cortex fixed in vivo. Using this method we observed an increase in the spine-to-filopodium ratio from P9-P16, indicating a period of rapid spine maturation. Previous studies report mature spines as being shorter in length compared to filopodia. We similarly observed a reduction in protrusion length between P9 and P16, corroborating our immunohistochemical spine maturation data. These studies show that dendritic protrusion formation and spine maturation occur rapidly at a time previously shown to correspond to auditory cortical tonotopic map refinement (P11-P14), providing a structural correlate of physiological maturation.
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Affiliation(s)
- Scott J Schachtele
- Department of Biological Sciences, University of Iowa, Iowa City, Iowa 52242-1109, USA
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Living Human Brain Slices: Network Analysis Using Voltage-Sensitive Dyes. ISOLATED CENTRAL NERVOUS SYSTEM CIRCUITS 2012. [DOI: 10.1007/978-1-62703-020-5_9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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21
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Abstract
The mouse sensory neocortex is reported to lack several hallmark features of topographic organization such as ocular dominance and orientation columns in primary visual cortex or fine-scale tonotopy in primary auditory cortex (AI). Here, we re-examined the question of auditory functional topography by aligning ultra-dense receptive field maps from the auditory cortex and thalamus of the mouse in vivo with the neural circuitry contained in the auditory thalamocortical slice in vitro. We observed precisely organized tonotopic maps of best frequency (BF) in the middle layers of AI and the anterior auditory field as well as in the ventral and medial divisions of the medial geniculate body (MGBv and MGBm, respectively). Tracer injections into distinct zones of the BF map in AI retrogradely labeled topographically organized MGBv projections and weaker, mixed projections from MGBm. Stimulating MGBv along the tonotopic axis in the slice produced an orderly shift of voltage-sensitive dye (VSD) signals along the AI tonotopic axis, demonstrating topography in the mouse thalamocortical circuit that is preserved in the slice. However, compared with BF maps of neuronal spiking activity, the topographic order of subthreshold VSD maps was reduced in layer IV and even further degraded in layer II/III. Therefore, the precision of AI topography varies according to the source and layer of the mapping signal. Our findings further bridge the gap between in vivo and in vitro approaches for the detailed cellular study of auditory thalamocortical circuit organization and plasticity in the genetically tractable mouse model.
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Laramée ME, Kurotani T, Rockland KS, Bronchti G, Boire D. Indirect pathway between the primary auditory and visual cortices through layer V pyramidal neurons in V2L in mouse and the effects of bilateral enucleation. Eur J Neurosci 2011; 34:65-78. [PMID: 21676038 DOI: 10.1111/j.1460-9568.2011.07732.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Visual cortical areas are activated by auditory stimuli in blind mice. Direct heteromodal cortical connections have been shown between the primary auditory cortex (A1) and primary visual cortex (V1), and between A1 and secondary visual cortex (V2). Auditory afferents to V2 terminate in close proximity to neurons that project to V1, and potentially constitute an effective indirect pathway between A1 and V1. In this study, we injected a retrograde adenoviral vector that expresses enhanced green fluorescent protein under a synapsin promotor in V1 and biotinylated dextran amine as an anterograde tracer in A1 to determine: (i) whether A1 axon terminals establish synaptic contacts onto the lateral part of V2 (V2L) neurons that project to V1; and (ii) if this indirect cortical pathway is altered by a neonatal enucleation in mice. Complete dendritic arbors of layer V pyramidal neurons were reconstructed in 3D, and putative contacts between pre-synaptic auditory inputs and postsynaptic visual neurons were analysed using a laser-scanning confocal microscope. Putative synaptic contacts were classified as high-confidence and low-confidence contacts, and charted onto dendritic trees. As all reconstructed layer V pyramidal neurons received auditory inputs by these criteria, we conclude that V2L acts as an important relay between A1 and V1. Auditory inputs are preferentially located onto lower branch order dendrites in enucleated mice. Also, V2L neurons are subject to morphological reorganizations in both apical and basal dendrites after the loss of vision. The A1-V2L-V1 pathway could be involved in multisensory processing and contribute to the auditory activation of the occipital cortex in the blind rodent.
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Affiliation(s)
- M E Laramée
- Groupe de Recherche en Neurosciences, Département de Chimie-Biologie, Université du Québec à Trois-Rivières, Trois-Rivières, QC, Canada
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Ojima H. Interplay of excitation and inhibition elicited by tonal stimulation in pyramidal neurons of primary auditory cortex. Neurosci Biobehav Rev 2010; 35:2084-93. [PMID: 21144861 DOI: 10.1016/j.neubiorev.2010.11.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2010] [Revised: 10/19/2010] [Accepted: 11/12/2010] [Indexed: 11/15/2022]
Abstract
Tonal responses of neurons in the primary auditory cortex are a function of frequency, intensity and ear of stimulation. These responses occasionally display suppression. This review discusses how excitatory and inhibitory synaptic inputs interact to form suppressive responses and how changes in stimulus attributes affect the magnitude and timing of those responses. Stimulation at the characteristic frequency evokes a stereotyped sequence of depolarization (excitatory) and then hyperpolarization (inhibitory), as predicted from the canonical circuitry. Some neurons stimulated at higher sound intensities display a prominent increase in the magnitude of hyperpolarization or a decrease in its latency, both enabling counteraction with the preceding excitation. These interactions, in part, underlie the non-monotonic suppression. Furthermore, monaural non-dominant ear stimulation elicits such a powerful hyperpolarization as to cancel out the depolarization elicited at dominant ear stimulation, suggesting a linear mechanism for the binaural suppression. Alternatively, it elicits a depolarization almost equal in magnitude and time course to that elicited at binaural stimulation, suggesting a nonlinear interaction responsible for the suppression. Laminar differences are also noted for these inhibitory interactions.
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Affiliation(s)
- Hisayuki Ojima
- Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo, Japan.
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Tominaga T, Tominaga Y. GABAA receptor-mediated modulation of neuronal activity propagation upon tetanic stimulation in rat hippocampal slices. Pflugers Arch 2010; 460:875-89. [DOI: 10.1007/s00424-010-0870-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2010] [Revised: 07/29/2010] [Accepted: 08/09/2010] [Indexed: 11/24/2022]
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Effects of pulse phase duration and location of stimulation within the inferior colliculus on auditory cortical evoked potentials in a guinea pig model. J Assoc Res Otolaryngol 2010; 11:689-708. [PMID: 20717834 DOI: 10.1007/s10162-010-0229-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2009] [Accepted: 07/23/2010] [Indexed: 12/19/2022] Open
Abstract
The auditory midbrain implant (AMI), which consists of a single shank array designed for stimulation within the central nucleus of the inferior colliculus (ICC), has been developed for deaf patients who cannot benefit from a cochlear implant. Currently, performance levels in clinical trials for the AMI are far from those achieved by the cochlear implant and vary dramatically across patients, in part due to stimulation location effects. As an initial step towards improving the AMI, we investigated how stimulation of different regions along the isofrequency domain of the ICC as well as varying pulse phase durations and levels affected auditory cortical activity in anesthetized guinea pigs. This study was motivated by the need to determine in which region to implant the single shank array within a three-dimensional ICC structure and what stimulus parameters to use in patients. Our findings indicate that complex and unfavorable cortical activation properties are elicited by stimulation of caudal-dorsal ICC regions with the AMI array. Our results also confirm the existence of different functional regions along the isofrequency domain of the ICC (i.e., a caudal-dorsal and a rostral-ventral region), which has been traditionally unclassified. Based on our study as well as previous animal and human AMI findings, we may need to deliver more complex stimuli than currently used in the AMI patients to effectively activate the caudal ICC or ensure that the single shank AMI is only implanted into a rostral-ventral ICC region in future patients.
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