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Roll L, Eysel UT, Faissner A. Laser Lesion in the Mouse Visual Cortex Induces a Stem Cell Niche-Like Extracellular Matrix, Produced by Immature Astrocytes. Front Cell Neurosci 2020; 14:102. [PMID: 32508592 PMCID: PMC7253582 DOI: 10.3389/fncel.2020.00102] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Accepted: 04/03/2020] [Indexed: 12/27/2022] Open
Abstract
The mammalian central nervous system (CNS) is characterized by a severely limited regeneration capacity. Comparison with lower species like amphibians, which are able to restore even complex tissues after damage, indicates the presence of an inhibitory environment that restricts the cellular response in mammals. In this context, signals provided by the extracellular matrix (ECM) are important regulators of events like cell survival, proliferation, migration, differentiation or neurite outgrowth. Therefore, knowledge of the post-lesional ECM and of cells that produce these factors might support development of new treatment strategies for patients suffering from traumatic brain injury and other types of CNS damage. In the present study, we analyzed the surround of focal infrared laser lesions of the adult mouse visual cortex. This lesion paradigm avoids direct contact with the brain, as the laser beam passes the intact bone. Cell type-specific markers revealed a distinct spatial distribution of different astroglial subtypes in the penumbra after injury. Glial fibrillary acidic protein (GFAP) as marker for reactive astrocytes was found broadly up-regulated, whereas the more immature markers vimentin and nestin were only expressed by a subset of cells. Dividing astrocytes could be identified via the proliferation marker Ki-67. Different ECM molecules, among others the neural stem cell-associated glycoprotein tenascin-C and the DSD-1 chondroitin sulfate epitope, were found on astrocytes in the penumbra. Wisteria floribunda agglutinin (WFA) and aggrecan as markers for perineuronal nets, a specialized ECM limiting synaptic plasticity, appeared normal in the vicinity of the necrotic lesion core. In sum, expression of progenitor markers by astrocyte subpopulations and the identification of proliferating astrocytes in combination with an ECM that contains components typically associated with neural stem/progenitor cells suggest that an immature cell fate is facilitated as response to the injury.
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Affiliation(s)
- Lars Roll
- Department of Cell Morphology and Molecular Neurobiology, Faculty of Biology and Biotechnology, Ruhr University Bochum, Bochum, Germany.,International Graduate School of Neuroscience, Ruhr University Bochum, Bochum, Germany
| | - Ulf T Eysel
- International Graduate School of Neuroscience, Ruhr University Bochum, Bochum, Germany.,Department of Neurophysiology, Faculty of Medicine, Ruhr University Bochum, Bochum, Germany
| | - Andreas Faissner
- Department of Cell Morphology and Molecular Neurobiology, Faculty of Biology and Biotechnology, Ruhr University Bochum, Bochum, Germany.,International Graduate School of Neuroscience, Ruhr University Bochum, Bochum, Germany
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Seo HY, Kim GW, Won YH, Park SH, Seo JH, Ko MH. Changes in Intracortical Excitability of Affected and Unaffected Hemispheres After Stroke Evaluated by Paired-Pulse Transcranial Magnetic Stimulation. Ann Rehabil Med 2018; 42:495-501. [PMID: 30180517 PMCID: PMC6129700 DOI: 10.5535/arm.2018.42.4.495] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Accepted: 10/10/2017] [Indexed: 11/05/2022] Open
Abstract
OBJECTIVE To assess the altered pattern of intracortical excitability of the affected and unaffected hemispheres in stroke patients using paired-pulse transcranial magnetic stimulation (TMS). METHODS We evaluated intracortical inhibition (ICI) and intracortical facilitation (ICF) in both hemispheres at acute and subacute stages of 103 stroke patients using paired-pulse TMS. The patients were divided into two groups: mild-to-moderate patients whose motor evoked potential (MEP) was recorded in the affected hemisphere; and severe patients whose MEP was not recorded in the affected hemisphere. RESULTS In mild-to-moderate patients, the value of ICI in the affected hemisphere was increased from 70.3% to 77.9% and the value of ICI in the unaffected hemisphere was decreased from 74.8% to 70.3% with eventual progression in acute to subacute stages of stroke. In severe patients, the value of ICI in the unaffected hemisphere was increased from 65.4% to 75.6%. The changes in ICF were not significantly different in this study. CONCLUSION We conclude that the unaffected hemisphere was more disinhibited than the affected hemisphere in acute phase of mild-to-moderate stroke, and the affected hemisphere was more disinhibited in the subacute stage. The unaffected hemisphere was inhibited in severe cases in acute-to-subacute phases of stroke. This finding facilitates appropriate neuromodulation of acute-to-subacute phases in mild-to-severe stroke patients.
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Affiliation(s)
- Ho Youn Seo
- Department of Physical Medicine and Rehabilitation, Chonbuk National University Hospital, Chonbuk National University Medical School, Jeonju, Korea
| | - Gi-Wook Kim
- Department of Physical Medicine and Rehabilitation, Chonbuk National University Hospital, Chonbuk National University Medical School, Jeonju, Korea.,Research Institute of Clinical Medicine of Chonbuk National University- Biomedical Research Institute of Chonbuk National University Hospital, Jeonju, Korea
| | - Yu Hui Won
- Department of Physical Medicine and Rehabilitation, Chonbuk National University Hospital, Chonbuk National University Medical School, Jeonju, Korea.,Research Institute of Clinical Medicine of Chonbuk National University- Biomedical Research Institute of Chonbuk National University Hospital, Jeonju, Korea
| | - Sung-Hee Park
- Department of Physical Medicine and Rehabilitation, Chonbuk National University Hospital, Chonbuk National University Medical School, Jeonju, Korea.,Research Institute of Clinical Medicine of Chonbuk National University- Biomedical Research Institute of Chonbuk National University Hospital, Jeonju, Korea
| | - Jeong-Hwan Seo
- Department of Physical Medicine and Rehabilitation, Chonbuk National University Hospital, Chonbuk National University Medical School, Jeonju, Korea.,Research Institute of Clinical Medicine of Chonbuk National University- Biomedical Research Institute of Chonbuk National University Hospital, Jeonju, Korea
| | - Myoung-Hwan Ko
- Department of Physical Medicine and Rehabilitation, Chonbuk National University Hospital, Chonbuk National University Medical School, Jeonju, Korea.,Research Institute of Clinical Medicine of Chonbuk National University- Biomedical Research Institute of Chonbuk National University Hospital, Jeonju, Korea
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Hsieh TH, Lee HHC, Hameed MQ, Pascual-Leone A, Hensch TK, Rotenberg A. Trajectory of Parvalbumin Cell Impairment and Loss of Cortical Inhibition in Traumatic Brain Injury. Cereb Cortex 2018; 27:5509-5524. [PMID: 27909008 DOI: 10.1093/cercor/bhw318] [Citation(s) in RCA: 59] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Accepted: 09/21/2016] [Indexed: 11/13/2022] Open
Abstract
Many neuropsychiatric symptoms that follow traumatic brain injury (TBI), including mood disorders, sleep disturbance, chronic pain, and posttraumatic epilepsy (PTE) are attributable to compromised cortical inhibition. However, the temporal trajectory of cortical inhibition loss and its underlying mechanisms are not known. Using paired-pulse transcranial magnetic stimulation (ppTMS) and immunohistochemistry, we tracked functional and cellular changes of cortical inhibitory network elements after fluid-percussion injury (FPI) in rats. ppTMS revealed a progressive loss of cortical inhibition as early as 2 weeks after FPI. This profile paralleled the increasing levels of cortical oxidative stress, which was accompanied by a gradual loss of parvalbumin (PV) immunoreactivity in perilesional cortex. Preceding the PV loss, we identified a degradation of the perineuronal net (PNN)-a specialized extracellular structure enwrapping cortical PV-positive (PV+) inhibitory interneurons which binds the PV+ cell maintenance factor, Otx2. The trajectory of these impairments underlies the reduced inhibitory tone, which can contribute to posttraumatic neurological conditions, such as PTE. Taken together, our results highlight the use of ppTMS as a biomarker to track the course of cortical inhibitory dysfunction post-TBI. Moreover, the neuroprotective role of PNNs on PV+ cell function suggests antioxidant treatment or Otx2 enhancement as a promising prophylaxis for post-TBI symptoms.
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Affiliation(s)
- Tsung-Hsun Hsieh
- Neuromodulation Program, Division of Epilepsy and Clinical Neurophysiology, Department of Neurology, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA.,Department of Physical Therapy and Graduate Institute of Rehabilitation Science, College of Medicine, Chang Gung University, Taoyuan 33302, Taiwan.,Neuroscience Research Center, Chang Gung Memorial Hospital, Linkou Medical Center, Taoyuan 33305, Taiwan
| | - Henry Hing Cheong Lee
- Department of Neurology, F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Mustafa Qadir Hameed
- Neuromodulation Program, Division of Epilepsy and Clinical Neurophysiology, Department of Neurology, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA.,Department of Neurology, F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA.,Department of Neurosurgery, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Alvaro Pascual-Leone
- Berenson-Allen Center for Noninvasive Brain Stimulation, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02115, USA
| | - Takao K Hensch
- Department of Neurology, F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA.,Department of Molecular and Cellular Biology, Center for Brain Science, Harvard University, MA 02138, USA
| | - Alexander Rotenberg
- Neuromodulation Program, Division of Epilepsy and Clinical Neurophysiology, Department of Neurology, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA.,Department of Neurology, F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA.,Berenson-Allen Center for Noninvasive Brain Stimulation, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02115, USA
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le Feber J, Dummer A, Hassink GC, van Putten MJAM, Hofmeijer J. Evolution of Excitation-Inhibition Ratio in Cortical Cultures Exposed to Hypoxia. Front Cell Neurosci 2018; 12:183. [PMID: 30018536 PMCID: PMC6037832 DOI: 10.3389/fncel.2018.00183] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Accepted: 06/11/2018] [Indexed: 11/24/2022] Open
Abstract
In the core of a brain infarct, neuronal death occurs within minutes after loss of perfusion. In the penumbra, a surrounding area with some residual perfusion, neurons initially remain structurally intact, but hypoxia-induced synaptic failure impedes neuronal activity. Penumbral activity may recover or further deteriorate, reflecting cell death. Mechanisms leading to either outcome remain ill-understood, but may involve changes in the excitation to inhibition (E/I) ratio. The E/I ratio is determined by structural (relative densities of excitatory and inhibitory synapses) and functional factors (synaptic strengths). Clinical studies demonstrated excitability alterations in regions surrounding the infarct core. These may be related to structural E/I changes, but the effects of hypoxia /ischemia on structural connectivity have not yet been investigated, and the role of structural connectivity changes in excitability alterations remains unclear. We investigated the evolution of the structural E/I ratio and associated network excitability in cortical cultures exposed to severe hypoxia of varying duration. 6–12 h of hypoxia reduced the total synaptic density. In particular, the inhibitory synaptic density dropped significantly, resulting in an elevated E/I ratio. Initially, this does not lead to increased excitability due to hypoxia-induced synaptic failure. Increased excitability becomes apparent upon reoxygenation after 6 or 12 h, but not after 24 h. After 24 h of hypoxia, structural patterns of vesicular glutamate stainings change. This possibly reflects disassembly of excitatory synapses, and may account for the irreversible reduction of activity and stimulus responses seen after 24 h.
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Affiliation(s)
- Joost le Feber
- Clinical Neurophysiology, TechMed Centre, University of Twente, Enschede, Netherlands
| | - Anneloes Dummer
- Clinical Neurophysiology, TechMed Centre, University of Twente, Enschede, Netherlands
| | - Gerco C Hassink
- Clinical Neurophysiology, TechMed Centre, University of Twente, Enschede, Netherlands.,Biomedical Signals and Systems, TechMed Centre, University of Twente, Enschede, Netherlands
| | - Michel J A M van Putten
- Clinical Neurophysiology, TechMed Centre, University of Twente, Enschede, Netherlands.,Department of Clinical Neurophysiology, Medisch Spectrum Twente, Enschede, Netherlands
| | - Jeannette Hofmeijer
- Clinical Neurophysiology, TechMed Centre, University of Twente, Enschede, Netherlands.,Department of Neurology, Rijnstate Hospital, Arnhem, Netherlands
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Kokinovic B, Medini P. Loss of GABA B -mediated interhemispheric synaptic inhibition in stroke periphery. J Physiol 2018; 596:1949-1964. [PMID: 29508394 DOI: 10.1113/jp275690] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Accepted: 02/22/2018] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Recovery from the potentially devastating consequences of stroke depends largely upon plastic changes occurring in the lesion periphery and its inputs. In a focal model of stroke in mouse somatosensory cortex, we found that the recovery of sensory responsiveness occurs at the level of synaptic inputs, without gross changes of the intrinsic electrical excitability of neurons, and also that recovered responses had longer than normal latencies. Under normal conditions, one somatosensory cortex inhibits the responsiveness of the other located in the opposite hemisphere (interhemispheric inhibition) via activation of GABAB receptors. In stroke-recovered animals, the powerful interhemispheric inhibition normally present in controls is lost in the lesion periphery. By contrast, contralateral hemisphere activation selective contributes to the recovery of sensory responsiveness after stroke. ABSTRACT Recovery after stroke is mediated by plastic changes largely occurring in the lesion periphery. However, little is known about the microcircuit changes underlying recovery, the extent to which perilesional plasticity occurs at synaptic input vs. spike output level, and the connectivity behind such synaptic plasticity. We combined intrinsic imaging with extracellular and intracellular recordings and pharmacological inactivation in a focal stroke in mouse somatosensory cortex (S1). In vivo whole-cell recordings in hindlimb S1 (hS1) showed synaptic responses also to forelimb stimulation in controls, and such responses were abolished by stroke in the neighbouring forelimb area (fS1), suggesting that, under normal conditions, they originate via horizontal connections from the neighbouring fS1. Synaptic and spike responses to forelimb stimulation in hS1 recovered to quasi-normal levels 2 weeks after stroke, without changes in intrinsic excitability and hindlimb-evoked spike responses. Recovered synaptic responses had longer latencies, suggesting a long-range origin of the recovery, prompting us to investigate the role of callosal inputs in the recovery process. Contralesional S1 silencing unmasked significantly larger responses to both limbs in controls, a phenomenon that was not observed when GABAB receptors were antagonized in the recorded area. Conversely, such GABAB -mediated interhemispheric inhibition was not detectable after stroke: callosal input silencing failed to change hindlimb responses, whereas it robustly reduced recovered forelimb responses. Thus, recovery of subthreshold responsiveness in the stroke periphery is accompanied by a loss of interhemispheric inhibition and this is a result of pathway-specific facilitatory action on the affected sensory response from the contralateral cortex.
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Affiliation(s)
- Bojana Kokinovic
- Department of Integrative Medical Biology (IMB), Physiology section, Umeå University, Umeå, Sweden.,Department of Neuroscience and Brain Technologies (NBT), Italian Institute of Technology (IIT), Genova, Italy
| | - Paolo Medini
- Department of Integrative Medical Biology (IMB), Physiology section, Umeå University, Umeå, Sweden
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Julkunen P, Määttä S, Säisänen L, Kallioniemi E, Könönen M, Jäkälä P, Vanninen R, Vaalto S. Functional and structural cortical characteristics after restricted focal motor cortical infarction evaluated at chronic stage - Indications from a preliminary study. Clin Neurophysiol 2016; 127:2775-2784. [PMID: 27417053 DOI: 10.1016/j.clinph.2016.05.013] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Revised: 05/04/2016] [Accepted: 05/10/2016] [Indexed: 02/01/2023]
Abstract
OBJECTIVE To assess the inter-hemispheric differences in neuronal function and structure of the motor cortex in a small group of chronic stroke patients having suffered a restricted ischemic lesion affecting hand motor representation. GABAergic intracortical inhibition, known to be affected by stroke lesion, was also investigated. METHODS Eight patients exhibiting little or no motor impairment were studied using transcranial magnetic stimulation (TMS) and diffusion weighted imaging (DWI) >15months from diagnosis. Resting motor threshold (MT) for 50μV and 2mV motor evoked potentials, and short-interval intracortical inhibition (SICI) were measured from hand muscles. Apparent diffusion coefficients (ADCs) were analyzed from the DWI for the primary motor cortex (M1), the supplementary motor area (SMA) and thalamus for reflecting changes in neuronal organization. RESULTS The MTs did not differ between the affected (AH) and unaffected hemisphere (UH) in 50μV responses, while the MTs for 2mV responses were higher (p=0.018) in AH. SICI was weakened in AH (p=0.008). ADCs were higher in the affected M1 compared to the unaffected M1 (p=0.018) while there were no inter-hemispheric differences in SMA or thalamus. CONCLUSIONS Inter-hemispheric asymmetry and neuronal organization demonstrated abnormalities in the M1. However, no confident inference can be made whether the observed alterations in neurophysiological and imaging measures have causal role for motor rehabilitation in these patients. SIGNIFICANCE Neurophysiological changes persist and are detectable using TMS years after stroke even though clinical symptoms have normalized.
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Affiliation(s)
- Petro Julkunen
- Department of Clinical Neurophysiology, Kuopio University Hospital, Kuopio, Finland; Department of Applied Physics, University of Eastern Finland, Kuopio, Finland.
| | - Sara Määttä
- Department of Clinical Neurophysiology, Kuopio University Hospital, Kuopio, Finland; Department of Clinical Neurophysiology, Institute of Clinical Medicine, Faculty of Health Sciences, University of Eastern Finland, Kuopio, Finland
| | - Laura Säisänen
- Department of Clinical Neurophysiology, Kuopio University Hospital, Kuopio, Finland; Department of Clinical Neurophysiology, Institute of Clinical Medicine, Faculty of Health Sciences, University of Eastern Finland, Kuopio, Finland
| | - Elisa Kallioniemi
- Department of Clinical Neurophysiology, Kuopio University Hospital, Kuopio, Finland; Department of Applied Physics, University of Eastern Finland, Kuopio, Finland
| | - Mervi Könönen
- Department of Clinical Neurophysiology, Kuopio University Hospital, Kuopio, Finland; Department of Clinical Radiology, Kuopio University Hospital, Kuopio, Finland
| | - Pekka Jäkälä
- Department of Neurology, Kuopio University Hospital, Kuopio, Finland; Department of Neurology, Institute of Clinical Medicine, Faculty of Health Sciences, University of Eastern Finland, Kuopio, Finland
| | - Ritva Vanninen
- Department of Clinical Radiology, Kuopio University Hospital, Kuopio, Finland; Department of Clinical Radiology, Institute of Clinical Medicine, Faculty of Health Sciences, University of Eastern Finland, Kuopio, Finland
| | - Selja Vaalto
- Department of Clinical Neurophysiology, Helsinki University Hospital, Helsinki, Finland; Department of Neuroscience and Biomedical Engineering, Aalto University School of Science, Espoo, Finland
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Brain stimulation: Neuromodulation as a potential treatment for motor recovery following traumatic brain injury. Brain Res 2016; 1640:130-138. [PMID: 26855256 DOI: 10.1016/j.brainres.2016.01.056] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2015] [Revised: 01/27/2016] [Accepted: 01/29/2016] [Indexed: 02/05/2023]
Abstract
There is growing evidence that electrical and magnetic brain stimulation can improve motor function and motor learning following brain damage. Rodent and primate studies have strongly demonstrated that combining cortical stimulation (CS) with skilled motor rehabilitative training enhances functional motor recovery following stroke. Brain stimulation following traumatic brain injury (TBI) is less well studied, but early pre-clinical and human pilot studies suggest that it is a promising treatment for TBI-induced motor impairments as well. This review will first discuss the evidence supporting brain stimulation efficacy derived from the stroke research field as proof of principle and then will review the few studies exploring neuromodulation in experimental TBI studies. This article is part of a Special Issue entitled SI:Brain injury and recovery.
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Huynh W, Vucic S, Krishnan AV, Lin CSY, Kiernan MC. Exploring the Evolution of Cortical Excitability Following Acute Stroke. Neurorehabil Neural Repair 2015; 30:244-57. [PMID: 26150146 DOI: 10.1177/1545968315593804] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
BACKGROUND Evolution of changes in intracortical excitability following stroke, particularly in the contralesional hemisphere, is being increasingly recognized in relation to maximizing the potential for functional recovery. OBJECTIVE The present study utilized a prospective longitudinal design over a 12-month period from stroke onset, to investigate the evolution of intracortical excitability involving both motor cortices and their relationship to recovery, and whether such changes were influenced by baseline stroke characteristics. METHODS Thirty-one patients with acute unilateral ischemic stroke were recruited from a tertiary hospital stroke unit. Comprehensive clinical assessments and cortical excitability were undertaken at stroke onset using a novel threshold-tracking paired-pulse transcranial magnetic stimulation technique, and repeated at 3-, 6-, and 12-month follow-up in 17 patients who completed the longitudinal assessment. RESULTS Shortly following stroke, short-interval intracortical inhibition (SICI) was significantly reduced in both lesioned and contralesional hemispheres that correlated with degree of recovery over the subsequent 3 months. Over the follow-up period, ipsilesional SICI remained reduced in all patient groups, while SICI over the contralesional hemisphere remained reduced only in the groups with cortical stroke or more baseline functional impairment. CONCLUSIONS The current study has demonstrated that evolution of intracortical excitability, particularly over the contralesional hemisphere, may vary between patients with differing baseline stroke and clinical characteristics, suggesting that ongoing contralesional network recruitment may be necessary for those patients who have significant disruptions to the integrity of ipsilesional motor pathways. Results from the present series have implications for the development of neuromodulatory brain stimulation protocols to harness and thereby facilitate stroke recovery.
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Affiliation(s)
- William Huynh
- Brain and Mind Research Institute, University of Sydney, New South Wales, Australia Prince of Wales Clinical School, University of New South Wales, New South Wales, Australia
| | - Steve Vucic
- Western Clinical School, University of Sydney, New South Wales, Australia
| | - Arun V Krishnan
- Prince of Wales Clinical School, University of New South Wales, New South Wales, Australia
| | - Cindy S-Y Lin
- University of New South Wales, New South Wales, Australia
| | - Matthew C Kiernan
- Brain and Mind Research Institute, University of Sydney, New South Wales, Australia
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Imbrosci B, Neitz A, Mittmann T. Focal cortical lesions induce bidirectional changes in the excitability of fast spiking and non fast spiking cortical interneurons. PLoS One 2014; 9:e111105. [PMID: 25347396 PMCID: PMC4210267 DOI: 10.1371/journal.pone.0111105] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2014] [Accepted: 09/28/2014] [Indexed: 11/29/2022] Open
Abstract
A physiological brain function requires neuronal networks to operate within a well-defined range of activity. Indeed, alterations in neuronal excitability have been associated with several pathological conditions, ranging from epilepsy to neuropsychiatric disorders. Changes in inhibitory transmission are known to play a key role in the development of hyperexcitability. However it is largely unknown whether specific interneuronal subpopulations contribute differentially to such pathological condition. In the present study we investigated functional alterations of inhibitory interneurons embedded in a hyperexcitable cortical circuit at the border of chronically induced focal lesions in mouse visual cortex. Interestingly, we found opposite alterations in the excitability of non fast-spiking (Non Fs) and fast-spiking (Fs) interneurons in acute cortical slices from injured animals. Non Fs interneurons displayed a depolarized membrane potential and a higher frequency of spontaneous excitatory postsynaptic currents (sEPSCs). In contrast, Fs interneurons showed a reduced sEPSCs amplitude. The observed downscaling of excitatory synapses targeting Fs interneurons may prevent the recruitment of this specific population of interneurons to the hyperexcitable network. This mechanism is likely to seriously affect neuronal network function and to exacerbate hyperexcitability but it may be important to protect this particular vulnerable population of GABAegic neurons from excitotoxicity.
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Affiliation(s)
- Barbara Imbrosci
- Institute of Physiology, University Medical Center of the Johannes-Gutenberg University Mainz, Mainz, Germany
- * E-mail: (BI); (TM)
| | - Angela Neitz
- Institute of Physiology, University Medical Center of the Johannes-Gutenberg University Mainz, Mainz, Germany
| | - Thomas Mittmann
- Institute of Physiology, University Medical Center of the Johannes-Gutenberg University Mainz, Mainz, Germany
- * E-mail: (BI); (TM)
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10
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Medini P. Experience-dependent plasticity of visual cortical microcircuits. Neuroscience 2014; 278:367-84. [PMID: 25171791 DOI: 10.1016/j.neuroscience.2014.08.022] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2014] [Revised: 08/05/2014] [Accepted: 08/07/2014] [Indexed: 11/18/2022]
Abstract
The recent decade testified a tremendous increase in our knowledge on how cell-type-specific microcircuits process sensory information in the neocortex and on how such circuitry reacts to manipulations of the sensory environment. Experience-dependent plasticity has now been investigated with techniques endowed with cell resolution during both postnatal development and in adult animals. This review recapitulates the main recent findings in the field using mainly the primary visual cortex as a model system to highlight the more important questions and physiological principles (such as the role of non-competitive mechanisms, the role of inhibition in excitatory cell plasticity, the functional importance of spine and axonal plasticity on a microscale level). I will also discuss on which scientific problems the debate and controversies are more pronounced. New technologies that allow to perturbate cell-type-specific subcircuits will certainly shine new light in the years to come at least on some of the still open questions.
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Affiliation(s)
- P Medini
- Institutionen för Molekylärbiologi, and Institutionen för Integrativ Medicinsk Biologi (IMB), Fysiologi Avdelning, Umeå Universitet, 90187 Umeå, Sweden.
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11
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Guerra A, Curcio G, Pasqualetti P, Bressi F, Petrichella S, Scrascia F, Ponzo D, Ferilli M, Vernieri F, Rossini PM, Ferreri F. Unilateral cortical hyperexcitability in congenital hydrocephalus: a TMS study. Neurocase 2014; 20:456-65. [PMID: 23682715 DOI: 10.1080/13554794.2013.791866] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
INTRODUCTION Changes in cortical excitability are considered to play an important role in promoting brain plasticity both in healthy people and in neurological diseases. Hydrocephalus is a brain development disorder related to an excessive accumulation of cerebrospinal fluid (CSF) in the ventricular system. The functional relevance of cortical structural changes described in this disease is largely unexplored in human. We investigated cortical excitability using multimodal transcranial magnetic stimulation (TMS) in a case of congenital hydrocephalus with almost no neurological signs. METHODS A caucasian 40 years old, ambidextrous and multilingual woman affected by occult spina bifida and congenital symmetrical hydrocephalous underwent a TMS study. The intracortical and interhemispheric paired pulse paradigms were used, together with the mapping technique. RESULTS No significant differences were found in the resting motor thresholds between the two hemispheres. Instead, the intracortical excitability curves were statistically different between the two hemispheres (with short intracortical inhibition (SICI) being strongly reduced and intracortical facilitation (ICF) enhanced in the right one), and the interhemispheric curves showed a general hyper-excitability on the right hemisphere (when conditioned by the left one) and a general hypo-excitability in the left hemisphere (when conditioned by the right one). It is noteworthy that an asymmetric right hemisphere (RH) change of excitability was observed by means of mapping technique. CONCLUSION We hypothesize that in this ambidextrous subject, the observed RH hyper-excitability could represent a mechanism of plasticity to preserve functionality of specific brain areas possibly devoted to some special skills, such as multilingualism.
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Affiliation(s)
- Andrea Guerra
- a Department of Neurology , University Campus Bio-Medico , Rome , Italy
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12
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Xerri C, Zennou-Azogui Y. Early and moderate sensory stimulation exerts a protective effect on perilesion representations of somatosensory cortex after focal ischemic damage. PLoS One 2014; 9:e99767. [PMID: 24914807 PMCID: PMC4051766 DOI: 10.1371/journal.pone.0099767] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Accepted: 05/19/2014] [Indexed: 02/05/2023] Open
Abstract
Previous studies have shown that intensive training within an early critical time window after focal cortical ischemia increases the area of damaged tissue and is detrimental to behavioral recovery. We postulated that moderate stimulation initiated soon after the lesion could have protective effects on peri-infarct cortical somatotopic representations. Therefore, we have assessed the effects of mild cutaneous stimulation delivered in an attention-demanding behavioral context on the functional organization of the perilesion somatosensory cortex using high-density electrophysiological mapping. We compared the effects of 6-day training initiated on the 3rd day postlesion (early training; ET) to those of same-duration training started on the 8th day (delayed training; DT). Our findings confirm previous work showing that the absence of training aggravates representational loss in the perilesion zone. In addition, ET was found to be sufficient to limit expansion of the ischemic lesion and reduce tissue loss, and substantially maintain the neuronal responsiveness to tactile stimulation, thereby preserving somatotopic map arrangement in the peri-infarct cortical territories. By contrast, DT did not prevent tissue loss and only partially reinstated lost representations in a use-dependent manner within the spared peri-infarct cortical area. This study differentiates the effects of early versus delayed training on perilesion tissue and cortical map reorganization, and underscores the neuroprotective influence of mild rehabilitative stimulation on neuronal response properties in the peri-infarct cortex during an early critical period.
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Affiliation(s)
- Christian Xerri
- Neurosciences Intégratives et Adaptatives, Aix-Marseille Université, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7260, Fédération de Recherches Comportement-Cerveau-Cognition 3512, Marseille, France
- * E-mail:
| | - Yoh'i Zennou-Azogui
- Neurosciences Intégratives et Adaptatives, Aix-Marseille Université, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7260, Fédération de Recherches Comportement-Cerveau-Cognition 3512, Marseille, France
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Adult cortical plasticity following injury: Recapitulation of critical period mechanisms? Neuroscience 2014; 283:4-16. [PMID: 24791715 DOI: 10.1016/j.neuroscience.2014.04.029] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2014] [Revised: 04/16/2014] [Accepted: 04/17/2014] [Indexed: 12/12/2022]
Abstract
A primary goal of research on developmental critical periods (CPs) is the recapitulation of a juvenile-like state of malleability in the adult brain that might enable recovery from injury. These ambitions are often framed in terms of the simple reinstatement of enhanced plasticity in the growth-restricted milieu of an injured adult brain. Here, we provide an analysis of the similarities and differences between deprivation-induced and injury-induced cortical plasticity, to provide for a nuanced comparison of these remarkably similar processes. As a first step, we review the factors that drive ocular dominance plasticity in the primary visual cortex of the uninjured brain during the CP and in adults, to highlight processes that might confer adaptive advantage. In addition, we directly compare deprivation-induced cortical plasticity during the CP and plasticity following acute injury or ischemia in mature brain. We find that these two processes display a biphasic response profile following deprivation or injury: an initial decrease in GABAergic inhibition and synapse loss transitions into a period of neurite expansion and synaptic gain. This biphasic response profile emphasizes the transition from a period of cortical healing to one of reconnection and recovery of function. Yet while injury-induced plasticity in adult shares several salient characteristics with deprivation-induced plasticity during the CP, the degree to which the adult injured brain is able to functionally rewire, and the time required to do so, present major limitations for recovery. Attempts to recapitulate a measure of CP plasticity in an adult injury context will need to carefully dissect the circuit alterations and plasticity mechanisms involved while measuring functional behavioral output to assess their ultimate success.
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Neuronal mechanisms underlying transhemispheric diaschisis following focal cortical injuries. Brain Struct Funct 2014; 220:1649-64. [DOI: 10.1007/s00429-014-0750-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2013] [Accepted: 03/03/2014] [Indexed: 12/18/2022]
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15
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Imbrosci B, Mittmann T. Alterations in membrane and firing properties of layer 2/3 pyramidal neurons following focal laser lesions in rat visual cortex. Neuroscience 2013; 250:208-21. [PMID: 23845747 DOI: 10.1016/j.neuroscience.2013.06.063] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2013] [Revised: 06/27/2013] [Accepted: 06/27/2013] [Indexed: 11/19/2022]
Abstract
Focal cortical injuries are well known to cause changes in function and excitability of the surviving cortical areas but the cellular correlates of these physiological alterations are not fully understood. In the present study we employed a well established ex vivo-in vitro model of focal laser lesions in the rat visual cortex and we studied membrane and firing properties of the surviving layer 2/3 pyramidal neurons. Patch-clamp recordings, performed in the first week post-injury, revealed an increased input resistance, a depolarized spike threshold as well as alterations in the firing pattern of neurons in the cortex ipsilateral to the lesion. Notably, the reported lesion-induced alterations emerged or became more evident when an exciting perfusing solution, known as modified artificial cerebrospinal fluid, was used to increase the ongoing synaptic activity in cortical slices. Conversely, application of glutamatergic or GABAA receptor blockers reduced the observed alterations and GABAB receptor blockers abolished the differences completely. All together the present findings suggest that changes in synaptic receptors function, following focal cortical injuries, can modulate membrane and firing properties of layer 2/3 pyramidal neurons. This previously unknown functional interplay between synaptic and membrane properties may constitute a novel cellular mechanism to explain alterations in neuronal network function and excitability following focal cortical injuries.
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Affiliation(s)
- B Imbrosci
- Institute of Physiology and Pathophysiology, University Medical Center of the Johannes-Gutenberg University Mainz, D-55128 Mainz, Germany.
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16
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Corticospinal excitability in patients with anoxic, traumatic, and non-traumatic diffuse brain injury. Brain Stimul 2013; 6:130-7. [DOI: 10.1016/j.brs.2012.03.010] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2011] [Revised: 02/13/2012] [Accepted: 03/12/2012] [Indexed: 11/21/2022] Open
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17
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Lapitskaya N, Gosseries O, De Pasqua V, Pedersen AR, Nielsen JF, de Noordhout AM, Laureys S. Abnormal corticospinal excitability in patients with disorders of consciousness. Brain Stimul 2013; 6:590-7. [PMID: 23403267 DOI: 10.1016/j.brs.2013.01.002] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2012] [Revised: 01/04/2013] [Accepted: 01/05/2013] [Indexed: 11/16/2022] Open
Abstract
BACKGROUND Transcranial magnetic stimulation (TMS) has been frequently used to explore changes in the human motor cortex in different conditions, while the extent of motor cortex reorganization in patients in vegetative state (VS) (now known as unresponsive wakefulness syndrome, UWS) and minimally conscious (MCS) states due to severe brain damage remains largely unknown. OBJECTIVE/HYPOTHESIS It was hypothesized that cortical motor excitability would be decreased and would correlate to the level of consciousness in patients with disorders of consciousness. METHODS Corticospinal excitability was assessed in 47 patients (24 VS/UWS and 23 MCS) and 14 healthy controls. The test parameters included maximal peak-to-peak M-wave (Mmax), F-wave persistence, peripheral and central motor conduction times, sensory (SEP) and motor evoked (MEP) potential latencies and amplitudes, resting motor threshold (RMT), stimulus/response curves, and short latency afferent inhibition (SAI). TMS measurements were correlated to the level of consciousness (assessed using the Coma Recovery Scale-Revised). RESULTS On average, the patient group had lower Mmax, lower MEP and SEP amplitudes, higher RMTs, narrower stimulus/response curves, and reduced SAI compared to the healthy controls (P < 0.05). The SAI alterations were correlated to the level of consciousness (P < 0.05). CONCLUSIONS The findings demonstrated the impairment of the cortical inhibitory circuits in patients with disorders of consciousness. Moreover, the significant relationship was found between cortical inhibition and clinical consciousness dysfunction.
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Affiliation(s)
- Natallia Lapitskaya
- Research Department, Hammel Neurorehabilitation and Research Centre, Voldbyvej 15, 8450 Hammel, Denmark.
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18
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Shift from phasic to tonic GABAergic transmission following laser-lesions in the rat visual cortex. Pflugers Arch 2012; 465:879-93. [PMID: 23224682 DOI: 10.1007/s00424-012-1191-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2012] [Revised: 11/13/2012] [Accepted: 11/20/2012] [Indexed: 10/27/2022]
Abstract
Reduction in the strength of GABAergic neurotransmission has often been reported following brain lesions. This weakened inhibition is believed to influence neurological deficits, neuronal hyperexcitability and functional recovery after brain injuries. Uncovering the mechanisms underlying the altered inhibition is therefore crucial. In the present study we used an ex vivo-in vitro model of laser lesions in the rat visual cortex to characterize the cellular correlates of changes in GABAergic transmission in the tissue adjacent to the injury. In the first week post-injury the number of VGAT positive GABAergic terminals as well as the expression level of the GABA synthesizing enzymes GAD67 and GAD65 remained unaltered. However, a reduced frequency of miniature inhibitory postsynaptic currents (mIPSCs) together with an increased paired-pulse ratio (PPR) of evoked IPSCs suggested a functional reduction of phasic GABA release. In parallel, we found an enhancement in the GABAA receptor-mediated tonic inhibition. On the basis of these findings, we propose that cortical lesions provoke a shift in GABAergic transmission, decreasing the phasic and reinforcing the tonic component. We therefore suggest that it is not, as traditionally assumed, the overall inhibitory strength to be primarily compromised by a cortical lesion but rather the temporal accuracy of the GABAergic synaptic signaling.
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19
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Affiliation(s)
- Christiaan N. Levelt
- Department of Molecular Visual Plasticity, Netherlands Institute for Neuroscience, an Institute of the Royal Netherlands Academy of Arts and Sciences, 1105BA Amsterdam, The Netherlands;
| | - Mark Hübener
- Max Planck Institute of Neurobiology, D-82152 Martinsried, Germany;
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20
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Imbrosci B, Mittmann T. Functional consequences of the disturbances in the GABA-mediated inhibition induced by injuries in the cerebral cortex. Neural Plast 2011; 2011:614329. [PMID: 21766043 PMCID: PMC3135051 DOI: 10.1155/2011/614329] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2011] [Accepted: 04/05/2011] [Indexed: 11/18/2022] Open
Abstract
Cortical injuries are often reported to induce a suppression of the intracortical GABAergic inhibition in the surviving, neighbouring neuronal networks. Since GABAergic transmission provides the main source of inhibition in the mammalian brain, this condition may lead to hyperexcitability and epileptiform activity of cortical networks. However, inhibition plays also a crucial role in limiting the plastic properties of neuronal circuits, and as a consequence, interventions aiming to reestablish a normal level of inhibition might constrain the plastic capacity of the cortical tissue. A promising strategy to minimize the deleterious consequences of a modified inhibitory transmission without preventing the potential beneficial effects on cortical plasticity may be to unravel distinct GABAergic signaling pathways separately mediating these positive and negative events. Here, gathering data from several recent studies, we provide new insights to better face with this "double coin" condition in the attempt to optimize the functional recovery of patients.
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Affiliation(s)
- Barbara Imbrosci
- Institute of Physiology and Pathophysiology, Medical Center of the Johannes Gutenberg University, Duesbergweg 6, 55128 Mainz, Germany.
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21
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Imbrosci B, Eysel UT, Mittmann T. Metaplasticity of horizontal connections in the vicinity of focal laser lesions in rat visual cortex. J Physiol 2010; 588:4695-703. [PMID: 20961999 DOI: 10.1113/jphysiol.2010.198192] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Focal cortical injuries are accompanied by a reorganization of the adjacent neuronal networks. An increased synaptic plasticity has been suggested to mediate, at least in part, this functional reorganization. Previous studies showed an increased long-term potentiation (LTP) at synapses formed by ascending fibres projecting onto layers 2/3 pyramidal cells following lesions in rat visual cortex. This could be important to establish new functional connections within a vertical cortical column. Importantly, horizontal intracortical connections constitute an optimal substrate to mediate the functional reorganization across different cortical columns. However, so far little is known about their potential implication in the functional rewiring post-lesion. Here, we investigated possible alterations of synaptic plasticity of horizontal connections in layers 2/3 in an 'ex vivo-in vitro' model of focal laser lesion in rat visual cortex. LTP at these synapses was found to be enhanced post-lesion, whereas long-term depression (LTD) was impaired, revealing a metaplastic shift toward strengthening of these synapses. Furthermore, we disclosed a prolonged decay-time constant of NMDAR-dependent currents, which can contribute to the enhanced LTP. Taken together these data revealed that a laser lesion-induced focal damage of the visual cortex is accompanied by a facilitated potentiation of horizontal synaptic connections in the vicinity of the focal injury. This specific strengthening of synaptic plasticity at horizontal connections in layers 2/3 might be one important cellular mechanism to compensate focal injury-mediated dysfunction in the cerebral cortex.
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Affiliation(s)
- B Imbrosci
- Institute of Physiology and Pathophysiology, Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany.
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22
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Spatial distribution of long-term potentiation in the surround of visual cortex lesions in vitro. Exp Brain Res 2009; 199:423-33. [DOI: 10.1007/s00221-009-1964-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2009] [Accepted: 07/23/2009] [Indexed: 11/26/2022]
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23
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A double blind placebo RCT to investigate the effects of serotonergic modulation on brain excitability and motor recovery in stroke patients. J Neurol 2009; 256:1152-8. [DOI: 10.1007/s00415-009-5093-7] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2007] [Revised: 11/12/2008] [Accepted: 11/21/2008] [Indexed: 10/21/2022]
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24
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Juhász C, Asano E, Shah A, Chugani DC, Batista CEA, Muzik O, Sood S, Chugani HT. Focal decreases of cortical GABAA receptor binding remote from the primary seizure focus: what do they indicate? Epilepsia 2008; 50:240-50. [PMID: 18637829 DOI: 10.1111/j.1528-1167.2008.01721.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
PURPOSE To determine the electroclinical significance and histopathological correlates of cortical gamma-aminobutyric acid(A)(GABA(A)) receptor abnormalities detected in and remote from human neocortical epileptic foci. METHODS Cortical areas with decreased(11)C-flumazenil (FMZ) binding were objectively identified on positron emission tomography (PET) images and correlated to intracranial electroencephalography (EEG) findings, clinical seizure variables, histology findings, and surgical outcome in 20 patients (mean age, 9.9 years) with intractable partial epilepsy of neocortical origin and nonlocalizing magnetic resonance imaging (MRI). RESULTS Focal decrease of cortical FMZ binding was detected in the lobe of seizure onset in 17 (85%) patients. Eleven patients (55%) had 17 remote cortical areas with decreased FMZ binding outside the lobe of seizure onset. Thirteen of those 16 (81%) of the 17 remote cortical regions that were covered by subdural EEG were around cortex showing rapid seizure spread on intracranial EEG. Remote FMZ PET abnormalities were associated with high seizure frequency and, when resected, showed gliosis in all six cases where material was available. Higher number of unresected cortical regions with decreased FMZ binding was associated with poorer surgical outcome. CONCLUSIONS Focal decreases of cortical GABA(A) receptor binding on PET may include cortical regions remote from the primary focus, particularly in patients with high seizure frequency, and these regions are commonly involved in rapid seizure propagation. Although these regions may not always need to be resected to achieve seizure freedom, a careful evaluation of cortex with decreased GABA(A) receptor binding prior to resection using intracranial EEG may facilitate optimal surgical outcome in patients with intractable neocortical epilepsy.
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Affiliation(s)
- Csaba Juhász
- Carman and Ann Adams Department of Pediatrics, Children's Hospital of Michigan and Harper University Hospital, Detroit Medical Center, Wayne State University School of Medcine, Detroit, Michigan, USA.
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25
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Eyre JA, Smith M, Dabydeen L, Clowry GJ, Petacchi E, Battini R, Guzzetta A, Cioni G. Is hemiplegic cerebral palsy equivalent to amblyopia of the corticospinal system? Ann Neurol 2007; 62:493-503. [PMID: 17444535 DOI: 10.1002/ana.21108] [Citation(s) in RCA: 186] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
OBJECTIVE Subjects with severe hemiplegic cerebral palsy have increased ipsilateral corticospinal projections from their noninfarcted cortex. We investigated whether their severe impairment might, in part, be caused by activity-dependent, competitive displacement of surviving contralateral corticospinal projections from the affected cortex by more active ipsilateral corticospinal projections from the nonaffected cortex, thereby compounding the impairment. METHODS Transcranial magnetic stimulation (TMS) characterized corticospinal tract development from each hemisphere over the first 2 years in 32 healthy children, 14 children with unilateral stroke, and 25 with bilateral lesions. Magnetic resonance imaging and anatomic studies compared corticospinal tract growth in 13 patients with perinatal stroke with 46 healthy subjects. RESULTS Infants with unilateral lesions initially had responses after TMS of the affected cortex, which became progressively more abnormal, and seven were eventually lost. There was associated hypertrophy of the ipsilateral corticospinal axons projecting from the noninfarcted cortex. Magnetic resonance imaging and anatomic studies demonstrated hypertrophy of the corticospinal tract from the noninfarcted hemisphere. TMS findings soon after the stroke did not predict impairment; subsequent loss of responses and hypertrophy of ipsilateral corticospinal axons from the noninfarcted cortex predicted severe impairment at 2 years. Infants with bilateral lesions maintained responses to TMS from both hemispheres with a normal pattern of development. INTERPRETATION Rather than representing "reparative plasticity," increased ipsilateral projections from the noninfarcted cortex compound disability by competitively displacing surviving contralateral corticospinal projections from the infarcted cortex. This may provide a pathophysiological explanation for why signs of hemiplegic cerebral palsy appear late and progress over the first 2 years of life.
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Affiliation(s)
- Janet A Eyre
- Department of Developmental Neuroscience, School of Clinical Medical Sciences, University of Newcastle, Newcastle upon Tyne, United Kingdom.
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26
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Manganotti P, Acler M, Zanette GP, Smania N, Fiaschi A. Motor Cortical Disinhibition During Early and Late Recovery After Stroke. Neurorehabil Neural Repair 2007; 22:396-403. [DOI: 10.1177/1545968307313505] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Background. Functional neuroimaging studies show adaptive changes in areas adjacent and distant from the stroke. This longitudinal study assessed whether changes in cortical excitability in affected and unaffected motor areas after acute stroke correlates with functional and motor recovery. Methods. We studied 13 patients with moderate to severe hemiparesis 5 to 7 days (T1), 30 days (T2), and 90 days (T3) after acute unilateral stroke, as well as 10 healthy controls. We used paired-pulse transcranial magnetic stimulation to study intracortical inhibition and facilitation, recording from the bilateral thenar eminences. F waves were also recorded. Results. At T1, all patients showed significantly reduced intracortical inhibition in the unaffected hemisphere. At T2, in patients whose motor function recovered, intracortical inhibition in the unaffected hemisphere returned to normal. In patients with poor clinical motor recovery, abnormal disinhibition persisted in both hemispheres. At T3, in patients whose motor function progressively recovered, the abnormal disinhibition in the unaffected hemisphere decreased further, whereas in patients whose motor function remained poor, abnormal inhibition in the unaffected hemisphere persisted. No modification of F-wave latency and amplitude were found in patients and controls. Conclusions. During early days after stroke, motor cortical disinhibition involves both cerebral hemispheres. Longitudinal changes in motor disinhibition of the unaffected hemisphere may reflect the degree of clinical motor recovery.
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Affiliation(s)
- P. Manganotti
- Department of Neurological and Visual Science, University of Verona, Policlinico “Gianbattista Rossi," Verona, Italy,
| | - M. Acler
- Department of Neurological and Visual Science, University of Verona, Policlinico “Gianbattista Rossi," Verona, Italy
| | - G. P. Zanette
- Department of Neurological and Visual Science, University of Verona, Policlinico “Gianbattista Rossi," Verona, Italy
| | - N. Smania
- Department of Neurological and Visual Science, University of Verona, Policlinico “Gianbattista Rossi," Verona, Italy
| | - A. Fiaschi
- Department of Neurological and Visual Science, University of Verona, Policlinico “Gianbattista Rossi," Verona, Italy
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Epsztein J, Ben-Ari Y, Represa A, Crépel V. Late-onset epileptogenesis and seizure genesis: lessons from models of cerebral ischemia. Neuroscientist 2007; 14:78-90. [PMID: 17914086 DOI: 10.1177/1073858407301681] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Patients surviving ischemic stroke often express delayed epileptic syndromes. Late poststroke seizures occur after a latency period lasting from several months to years after the insult. These seizures might result from ischemia-induced neuronal death and associated morphological and physiological changes that are only partly elucidated. This review summarizes the long-term morphofunctional alterations observed in animal models of both focal and global ischemia that could explain late-onset seizures and epileptogenesis. In particular, this review emphasizes the change in GABAergic and glutamatergic signaling leading to hyperexcitability and seizure genesis.
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Affiliation(s)
- Jérôme Epsztein
- Institut de Neurobiologie de la Méditerranée, Institut National de la Santé et de la Recherche Médicale Unité 29, and Université de La Méditerranée, Marseille Cedex, France
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28
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Moreira T, Cebers G, Pickering C, Ostenson CG, Efendic S, Liljequist S. Diabetic Goto-Kakizaki rats display pronounced hyperglycemia and longer-lasting cognitive impairments following ischemia induced by cortical compression. Neuroscience 2006; 144:1169-85. [PMID: 17175109 DOI: 10.1016/j.neuroscience.2006.10.054] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2006] [Revised: 09/07/2006] [Accepted: 10/27/2006] [Indexed: 01/04/2023]
Abstract
Hyperglycemia has been shown to worsen the outcome of brain ischemia in several animal models but few experimental studies have investigated impairments in cognition induced by ischemic brain lesions in hyperglycemic animals. The Goto-Kakizaki (GK) rat naturally develops type 2 diabetes characterized by mild hyperglycemia and insulin resistance. We hypothesized that GK rats would display more severe cerebral damage due to hyperglycemia-aggravated brain injury and, accordingly, more severe cognitive impairments. In this study, recovery of motor and cognitive functions of GK and healthy Wistar rats was examined following extradural compression (EC) of the sensorimotor cortex. For this purpose, tests of vestibulomotor function (beam-walking) and combined tests of motor function and learning (locomotor activity from day (D) 1 to D5, operant lever-pressing from D14 to D25) were used. EC consistently reduced cerebral blood flow in both strains. Anesthesia-challenge and EC resulted in pronounced hyperglycemia in GK but not in Wistar rats. Lower beam-walking scores, increased locomotor activity, impairments in long-term habituation and learning of operant lever-pressing were more pronounced and observed at later time-points in GK rats. Fluoro-Jade, a marker of irreversible neuronal degeneration, revealed consistent degeneration in the ipsilateral cortex, hippocampus and thalamus at 2, 7 and 14 days post-compression. The amount of degeneration in these structures was considerably higher in GK rats. Thus, GK rats exhibited marked hyperglycemia during EC, as well as longer-lasting behavioral deficits and increased neurodegeneration during recovery. The GK rat is thus an attractive model for neuropathologic and cognitive studies after ischemic brain injury in hyperglycemic rats.
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Affiliation(s)
- T Moreira
- Department of Clinical Neuroscience, Division of Drug Dependence Research Building L4a:00, Karolinska Institutet, SE-17177 Stockholm, Sweden.
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Frahm C, Siegel G, Grass S, Witte OW. Stable expression of the vesicular GABA transporter following photothrombotic infarct in rat brain. Neuroscience 2006; 140:865-77. [PMID: 16616431 DOI: 10.1016/j.neuroscience.2006.02.045] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2005] [Revised: 02/22/2006] [Accepted: 02/22/2006] [Indexed: 11/20/2022]
Abstract
Before exocytotic release of the inhibitory neurotransmitter GABA, this amino acid has to be stored in synaptic vesicles. Accumulation of GABA in vesicles is achieved by a specific membrane-integrated transporter termed vesicular GABA transporter. This vesicular protein is mainly located at presynaptic terminals of GABAergic interneurons. In the present study we investigated the effects of focal ischemia on the expression of the vesicular GABA transporter. Vesicular GABA transporter mRNA and protein expression was examined after photothrombosis in different cortical and hippocampal brain regions of Wistar rats. In situ hybridization and quantitative real-time RT-PCR were performed to analyze vesicular GABA transporter mRNA. Both vesicular GABA transporter mRNA-stained perikarya and mRNA expression levels remained unaffected. Vesicular GABA transporter protein-containing synaptic terminals and somata were visualized by immunohistochemistry. The pattern of vesicular GABA transporter immunoreactivity as well as the protein expression level revealed by semiquantitative image analysis and by Western blot remained stable after stroke. The steady expression of vesicular GABA transporter mRNA and protein after photothrombosis indicates that the exocytotic release mechanism of GABA is not affected by ischemia.
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Affiliation(s)
- C Frahm
- Department of Neurology, Friedrich-Schiller-University, Erlanger Allee 101, 07747 Jena, Germany.
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30
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Moreira T, Cebers G, Salehi M, Wägner A, Liljequist S. Impaired long-term habituation is dissociated from increased locomotor activity after sensorimotor cortex compression. Behav Brain Res 2006; 167:9-22. [PMID: 16337698 DOI: 10.1016/j.bbr.2005.06.048] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2005] [Revised: 06/14/2005] [Accepted: 06/14/2005] [Indexed: 11/24/2022]
Abstract
Behavioural habituation to a novel environment is a simple form of learning in rodents. We studied the habituation and locomotor activity (LMA) of Wistar rats subjected to unilateral, transient (30min) extradural compression (EC) of the right sensorimotor cortex. One group of rats was tested every 24h during the first 5 days (D1-D5) post-EC. Two other groups were tested for the first time in the LMA boxes on D3 and D6 post-EC and their performance was compared with the group tested on D1 (activity in a novel environment). Total and center locomotion, vertical activity and time spent in the center of the LMA box were reduced on D1 post-EC and normalized by D2. The EC-induced motor paresis was undetectable on the rotarod by D2 and on the beam-walking by D3. Total locomotion, vertical activity and time spent in the center of EC-rats significantly increased from D1 to D3. EC caused neurodegeneration in the cortex, caudate putamen and thalamus as detected by Fluoro-Jade staining. The size of the cortical damage decreased from D2 to D5 in the medial and caudal regions of the compressed hemisphere, in accordance with recovery of motor function. LMA provided additional information in the follow-up of recovery from brain injury and habituation to the environment. Thus, long-term, inter-session habituation was impaired from D1 to D3 but dissociated from increased LMA intra-session on D3, when the motor deficits provoked by EC were already undetectable in the rotarod and beam-walking tests.
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Affiliation(s)
- Tiago Moreira
- Department of Clinical Neuroscience, Division of Drug Dependence Research, Karolinska University Hospital, Bldg. L4:00, SE-17176 Stockholm, Sweden
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31
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Setkowicz Z, Nowak B, Janeczko K. Neocortical injuries at different developmental stages determine different susceptibility to seizures induced in adulthood. Epilepsy Res 2006; 68:255-63. [PMID: 16387474 DOI: 10.1016/j.eplepsyres.2005.11.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2005] [Revised: 10/26/2005] [Accepted: 11/27/2005] [Indexed: 11/29/2022]
Abstract
Gliosis, axonal sprouting and remodelling of nerve connections in the injured brain have been regarded as epileptogenic processes dependent on the age when the injury was inflicted. The present study examines whether brains injured at different developmental stages may acquire different susceptibility to experimental status epilepticus induced in adulthood. In 6- and 30-day-old Wistar rats (P6s and P30s, respectively), a mechanical injury was performed in the left cerebral hemisphere. On postnatal day 60, all the animals and controls received single injections of kainic acid to evoke status epilepticus. During a 6-h period following the injection, the animals were observed continuously and motor symptoms of seizure activity were recorded and rated. P6s showed significantly lower intensity of kainic acid-induced epileptic symptoms and significantly longer survival than controls or P30s. In P30s, no significant change was detected. The data provide evidence that the developmental stage when the brain is injured determines epileptogenecity of the lesion. However, a considerable discrepancy between these data and those obtained previously following pilocarpine administration in the same experimental models of brain injury shows that each of the two models of epilepsy may display different aspects of the same age-dependent process triggered by the brain injury.
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Affiliation(s)
- Zuzanna Setkowicz
- Department of Neuroanatomy, Institute of Zoology, Jagiellonian University, 6 Ingardena St., 30 060 Kraków, Poland
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32
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Hayashi Y, Ishibashi H, Hashimoto K, Nakanishi H. Potentiation of the NMDA receptor-mediated responses through the activation of the glycine site by microglia secreting soluble factors. Glia 2006; 53:660-8. [PMID: 16498631 DOI: 10.1002/glia.20322] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
We have previously reported that both transferred microglia and microglia-conditioned medium (MCM) potentiated the N-methyl-D-aspatate (NMDA) receptor-mediated synaptic responses in cortical neurons. To elucidate the mechanism underlying the potentiation of NMDA receptor-mediated responses by microglia, we examined the effects of MCM on NMDA-induced inward currents in mechanically dissociated hippocampal CA1 neurons under whole-cell patch recordings. MCM potentiated the amplitude of NMDA-induced currents up to 10-fold in a dose-dependent manner, and this effect of MCM remained even after boiling or cutting off molecules with a molecular mass more than 3 kDa. In the presence of glycine with a concentration sufficient to saturate the NMDA receptor glycine site, MCM failed to further potentiate the NMDA-induced currents. The glycine site antagonist 5, 7-dichrolokynurenic acid, significantly inhibited the effects of MCM. The effect of MCM was still observed even after treatment with D-amino acid oxidase, a D-serine degrading enzyme. On the other hand, MCM had no significant effect on the voltage-dependent Mg(2+) blockade of NMDA receptors. Furthermore, MCM enhanced the formation of the long-term potentiation in the Schaffer collateral pathway-CA1 pyramidal cell synapses. Using a high performance liquid chromatography system, we found the levels of both glycine and L-serine in MCM to be significantly higher than those in the control medium. It was also noted that an increased glycine productivity of microglia was observed in the hippocampus in the acute phase of neuronal injury. These observations strongly suggest that glycine is a major causative molecule released from microglia that potentiates the NMDA-induced currents.
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MESH Headings
- Animals
- Animals, Newborn
- Cell Communication/drug effects
- Cell Communication/physiology
- Cells, Cultured
- Culture Media, Conditioned/pharmacology
- Dose-Response Relationship, Drug
- Excitatory Amino Acid Agonists/pharmacology
- Excitatory Amino Acid Antagonists/pharmacology
- Glutamic Acid/metabolism
- Glycine/metabolism
- Glycine/pharmacology
- Hippocampus/cytology
- Hippocampus/metabolism
- Long-Term Potentiation/drug effects
- Long-Term Potentiation/physiology
- Mice
- Mice, Inbred C57BL
- Microglia/drug effects
- Microglia/metabolism
- N-Methylaspartate/pharmacology
- Patch-Clamp Techniques
- Pyramidal Cells/drug effects
- Pyramidal Cells/metabolism
- Rats
- Rats, Wistar
- Receptors, Glycine/agonists
- Receptors, Glycine/antagonists & inhibitors
- Receptors, Glycine/metabolism
- Receptors, N-Methyl-D-Aspartate/drug effects
- Receptors, N-Methyl-D-Aspartate/metabolism
- Serine/antagonists & inhibitors
- Serine/metabolism
- Synaptic Transmission/drug effects
- Synaptic Transmission/physiology
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Affiliation(s)
- Yoshinori Hayashi
- Laboratory of Oral Aging Science, Faculty of Dental Sciences, Kyushu University, Fukuoka, Japan
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33
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Setkowicz Z, Janeczko K. A strong epileptogenic effect of mechanical injury can be reduced in the dysplastic rat brain. Epilepsy Res 2005; 66:165-72. [PMID: 16150574 DOI: 10.1016/j.eplepsyres.2005.08.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2005] [Revised: 08/04/2005] [Accepted: 08/08/2005] [Indexed: 11/23/2022]
Abstract
An exposure of rats to gamma-radiation at different stages of prenatal development produces brain dysplasias of different degree displaying also different susceptibility to pilocarpine-induced seizures. Following irradiation on prenatal day 13 (E13), the susceptibility is minimal and significantly lower even in relation to non-irradiated rats [Setkowicz, Z., Janeczko, K., 2003. Long-term changes in susceptibility to pilocarpine-induced status epilepticus following neocortical injuries in the rat at different developmental stages. Epilepsy Res. 53, 216-224]. On the other hand, the rat brain injured on postnatal day 30 presents very high susceptibility to seizures in the same pilocarpine model of epilepsy [Setkowicz, Z., Kluk, K., Janeczko, K., 2003. Long-term changes in postnatal susceptibility to pilocarpine-induced seizures in rats exposed to gamma radiation at different stages of prenatal development. Epilepsia 44, 1267-1273]. It could, therefore, be hypothesised that the congenital brain dysplasia produced by irradiation on E13 would minimize the highly increased susceptibility to seizures observed in the injured brain. Wistar rats were exposed to gamma-rays on E13 and they received a mechanical brain injury on postnatal day 30 (P30). On postnatal day 60, pilocarpine was injected to evoke status epilepticus. During a 6-h period following the injection, motor manifestations of seizure activity were recorded and rated. Seven days after pilocarpine injection, the animals were sacrificed and their brains were fixed. Pilocarpine injections in non-irradiated rats with brains injured on P30 evoked seizures of very high intensity and extremely high mortality in relation to non-injured controls. This high susceptibility to seizures following the brain injury was considerably decreased in rats irradiated on E13. The data provide evidence that the brain dysplasia in the rat acquired at this stage of prenatal development can significantly reduce the increased susceptibility to seizures evoked by the postnatal brain injury.
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Affiliation(s)
- Zuzanna Setkowicz
- Department of Neuroanatomy, Institute of Zoology, Jagiellonian University, 6 Ingardena St., 30 060 Kraków, Poland
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34
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Gan P, Cheng JS, Ng YK, Ling EA. Role of GABA in electro-acupuncture therapy on cerebral ischemia induced by occlusion of the middle cerebral artery in rats. Neurosci Lett 2005; 383:317-21. [PMID: 15955428 DOI: 10.1016/j.neulet.2005.04.032] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2005] [Revised: 04/04/2005] [Accepted: 04/12/2005] [Indexed: 11/30/2022]
Abstract
This study investigated the possible involvement of gamma-aminobutyric acid (GABA) in the therapeutic effect of cerebral ischemia by electro-acupuncture (EA) using the rat model with middle cerebral artery occlusion (MCAO). By immunohistochemistry, the changes of GABA expression level in the primary infarct area and its penumbral regions were examined. The changes in infarct area and survival neuron percentages were also assessed using haematoxylin and eosin stained sections after picrotoxin (PTX) injection, a GABA receptor's antagonist. Our results showed that EA markedly decreased the ischemic damaged areas in the cerebral cortex and hippocampus. Concomitant to this was an up-regulation of GABA immunoexpression in MCAO rats with EA treatment (P < 0.05). Furthermore, injection of PTX in rats subjected to MCAO or MCAO followed by EA treatment increased the infarct area and decreased survival cell percentage significantly when compared with those without PTX injection. In the light of these findings, it is suggested that EA on specific and established acupoints that are commonly used in clinical management of cerebral ischemia may have elicited an up-regulated expression of GABA that would have a neuroprotective effect.
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Affiliation(s)
- Ping Gan
- National Key Laboratory of Medical Neuroscience, Institute of Acupuncture Research, Shanghai Medical College, Fudan University, Shanghai 200032, PR China
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35
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Luhmann HJ, Huston JP, Hasenöhrl RU. Contralateral increase in thigmotactic scanning following unilateral barrel-cortex lesion in mice. Behav Brain Res 2005; 157:39-43. [PMID: 15617769 DOI: 10.1016/j.bbr.2004.06.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2004] [Revised: 06/08/2004] [Accepted: 06/08/2004] [Indexed: 11/24/2022]
Abstract
Adult C57BL/6 mice received uni- or bilateral cryogenic or sham-lesions over the barrel field and their exploratory behaviour was assessed in an open field between 1 and 7 days post-lesion. Bilateral cortical lesions produced a short-lasting increase in thigmotactic scanning with both sides of the face on the first day of testing. Mice with a unilateral barrel-cortex lesion showed more contralateral wall scanning with a recovery to behavioural symmetry after 5-7 days. Furthermore, the increase in contralateral thigmotaxis was most pronounced in animals with damage to the left barrel field, indicative of a lateralization of the lesion-induced behavioural changes. The cortical lesions did not influence locomotor activity and the rate of habituation to the open field (habituation 'learning'). Referring to recent electrophysiological findings, we hypothesize that the lesion established a lateralized source of increased neuronal excitability within the affected barrel-cortex, leading to more behaviour with its corresponding vibrissae. Alternatively, if the lesion results in contralateral 'neglect' in terms of input, the increased scanning with the affected vibrissae may reflect an attempt of the system to compensate for this with an increase in usage.
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Affiliation(s)
- Heiko J Luhmann
- Institute of Physiology and Pathophysiology, University of Mainz, Duesbergweg 6, 55128 Mainz, Germany
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36
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Conti F, Minelli A, Melone M. GABA transporters in the mammalian cerebral cortex: localization, development and pathological implications. ACTA ACUST UNITED AC 2004; 45:196-212. [PMID: 15210304 DOI: 10.1016/j.brainresrev.2004.03.003] [Citation(s) in RCA: 260] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/09/2004] [Indexed: 12/16/2022]
Abstract
The extracellular levels of gamma-aminobutyric acid (GABA), the main inhibitory neurotransmitter in the mammalian cerebral cortex, are regulated by specific high-affinity, Na+/Cl- dependent transporters. Four distinct genes encoding GABA transporters (GATs), named GAT-1, GAT-2, GAT-3, and BGT-1 have been identified using molecular cloning. Of these, GAT-1 and -3 are expressed in the cerebral cortex. Studies of the cortical distribution, cellular localization, ontogeny and relationships of GATs with GABA-releasing elements using a variety of light and electron microscopic immunocytochemical techniques have shown that: (i) a fraction of GATs is strategically placed to mediate GABA uptake at fast inhibitory synapses, terminating GABA's action and shaping inhibitory postsynaptic responses; (ii) another fraction may participate in functions such as the regulation of GABA's diffusion to neighboring synapses and of GABA levels in cerebrospinal fluid; (iii) GATs may play a role in the complex processes regulating cortical maturation; and (iv) GATs may contribute to the dysregulation of neuronal excitability that accompanies at least two major human diseases: epilepsy and ischemia.
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Affiliation(s)
- Fiorenzo Conti
- Dipartimento di Neuroscienze, Sezione di Fisiologia, Università Politecnica delle Marche, Via Tronto 10/A, Torrette di Ancona, I-60020 Ancona, Italy.
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37
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Huemmeke M, Eysel UT, Mittmann T. Lesion-induced enhancement of LTP in rat visual cortex is mediated by NMDA receptors containing the NR2B subunit. J Physiol 2004; 559:875-82. [PMID: 15284339 PMCID: PMC1665189 DOI: 10.1113/jphysiol.2004.069534] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
There is emerging evidence that injury of the cerebral cortex is followed by processes of enhanced neuroplasticity. In the present study, we investigate the functional properties of NMDA receptors (NMDARs) in the surround of focal lesions with recordings of extracellular field potentials (FPs) in acute slices of rat visual cortex at survival times of 2-6 days. FPs were recorded in cortical layer III lateral to the lesion, while long-term potentiation (LTP) was induced by theta-burst stimulation (TBS) in layer IV. The predominantly AMPA receptor-mediated FPs displayed a significantly enhanced LTP in the surround of the lesion at distances of 2-3.2 mm. The LTP was completely blocked by the NMDAR antagonist D-AP5. Ifenprodil, an antagonist of NMDARs containing the NR2B subunit, only slightly affected the LTP in slices from sham-operated animals, but significantly reduced the LTP in slices from lesioned rats. We quantitatively analysed the proportion of NMDARs containing the NR2B subunit after lesions by applying ifenprodil to pharmacologically isolated NMDAR-FPs. The NR2B antagonist reduced the NMDAR-FPs significantly more strongly at distances of 2.0-3.2 mm from the border of the lesion. This indicates that the early phase of increased synaptic long-term plasticity in the surround of cortical lesions is accompanied by an up-regulation of NMDARs containing the NR2B subunit.
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Affiliation(s)
- Markus Huemmeke
- Department of Neurophysiology, MA 4/149, Ruhr-University Bochum, D-44780, Germany
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38
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Koerner C, Meinck HM. Long-lasting motor cortex disinhibition after short transient ischemic attacks (TIAs) in humans. Neurosci Lett 2004; 361:21-4. [PMID: 15135883 DOI: 10.1016/j.neulet.2003.12.074] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Lesion-induced cortical hyperexcitability has been demonstrated in animal models of cerebral ischemia and after human stroke. We used transcranial magnetic stimulation to investigate motor cortex excitability in ten patients who suffered short transient ischemic attacks (TIAs; i.e. duration <60 min) in the week before examination. Intracortical inhibition (ICI) and facilitation (ICF) were assessed using paired-pulse stimulation. Single-pulse stimulation was applied to investigate cortical silent period and transcallosal inhibition. The side affected by the TIA was compared to the normal side of each patient. We found ICI significantly reduced, and a trend towards enhanced ICF on the affected side. All other parameters remained normal. Motor cortex disinhibition may occur after short TIAs in spite of morphologically intact brain tissue. Possibly, these functional changes correlate to the protective neurometabolic mechanisms elicited by short episodes of focal ischemia in animal models and in man.
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Affiliation(s)
- Claudia Koerner
- Department of Neurology, Ruprecht-Karls-Unversity, Heidelberg, Im Neuenheimer Feld 400, D-69120 Heidelberg, Germany.
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39
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Zepeda A, Sengpiel F, Guagnelli MA, Vaca L, Arias C. Functional reorganization of visual cortex maps after ischemic lesions is accompanied by changes in expression of cytoskeletal proteins and NMDA and GABA(A) receptor subunits. J Neurosci 2004; 24:1812-21. [PMID: 14985421 PMCID: PMC6730407 DOI: 10.1523/jneurosci.3213-03.2004] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Reorganization of cortical representations after focal visual cortex lesions has been documented. It has been suggested that functional reorganization may rely on cellular mechanisms involving modifications in the excitatory/inhibitory neurotransmission balance and on morphological changes of neurons peripheral to the lesion. We explored functional reorganization of cortical retinotopic maps after a focal ischemic lesion in primary visual cortex of kittens using optical imaging of intrinsic signals. After 1, 2, and 5 weeks postlesion (wPL), we addressed whether functional reorganization correlated in time with changes in the expression of MAP-2, GAP-43, GFAP, GABA(A) receptor subunit alpha1 (GABA(A)alpha1), subunit 1 of the NMDA receptor (NMDAR1), and in neurotransmitter levels at the border of the lesion. Our results show that: (1) retinotopic maps reorganize with time after an ischemic lesion; (2) MAP-2 levels increase gradually from 1wPL to 5wPL; (3) MAP-2 upregulation is associated with an increase in dendritic-like structures surrounding the lesion and a decrease in GFAP-positive cells; (4) GAP-43 levels reach the highest point at 2wPL; (5) NMDAR1 and glutamate contents increase in parallel from 1wPL to 5wPL; (6) GABA(A)alpha1 levels increase from 1wPL to 2wPL but do not change after this time point; and (7) GABA contents remain low from 1wPL to 5wPL. This is a comprehensive study showing for the first time that functional reorganization correlates in time with dendritic sprouting and with changes in the excitatory/inhibitory neurotransmission systems previously proposed to participate in cortical remodeling and suggests mechanisms by which plasticity of cortical representations may occur.
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Affiliation(s)
- Angelica Zepeda
- Departamento de Biología Celular y Fisiología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, 04510-México, Distrito Federal, México
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40
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Moriguchi S, Mizoguchi Y, Tomimatsu Y, Hayashi Y, Kadowaki T, Kagamiishi Y, Katsube N, Yamamoto K, Inoue K, Watanabe S, Nabekura J, Nakanishi H. Potentiation of NMDA receptor-mediated synaptic responses by microglia. ACTA ACUST UNITED AC 2004; 119:160-9. [PMID: 14625083 DOI: 10.1016/j.molbrainres.2003.09.007] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
To study the influence of microglia on glutamatergic synaptic transmission in the acute phase of neuronal injury, we first examined the effects of primary cultured microglia transferred onto the organotypic cortical slice cultures. In these microglia-transferred cortical slice cultures, stimulation of the subcortical white matter induced fast excitatory postsynaptic potentials followed by N-methyl-D-aspartate (NMDA) receptor-mediated plateau-like potentials that were never observed in control slice cultures. A similar potentiation of NMDA receptor-mediated postsynaptic responses was also observed by an application of a microglial-conditioned medium (MCM, 10% v/v) in acute cortical slices. These effects of MCM disappeared after boiling or incubation with proteinase K. After fractionation of MCM by anion-exchange chromatography, the enhancing activity of each fraction was quantitated electrophysiologically. When each fraction was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the fraction 24 which showed the most potent enhancing activity on NMDA receptor-mediated responses contained a relatively strong protein band with a molecular mass of approximately 70 kDa. MCM also enhanced both glutamate- and NMDA-induced inward currents recorded from acutely isolated cortical neurons. It was also noted that glutamate and NMDA induced transient large inward currents during an application of MCM, which were never observed in the control condition. These observations strongly suggest that NMDA receptor-mediated responses can be potentiated by both heat- and protease-labile (presumably 70-kDa proteins) molecules released from microglia.
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Affiliation(s)
- Shigeki Moriguchi
- Laboratory of Oral Aging Science, Faculty of Dental Sciences, Kyushu University, Maidashi 3-1-1, Fukuoka 812-8582, Japan
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41
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Cicinelli P, Pasqualetti P, Zaccagnini M, Traversa R, Oliveri M, Rossini PM. Interhemispheric Asymmetries of Motor Cortex Excitability in the Postacute Stroke Stage. Stroke 2003; 34:2653-8. [PMID: 14551397 DOI: 10.1161/01.str.0000092122.96722.72] [Citation(s) in RCA: 158] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Background and Purpose—
Changes in the intracortical inhibition (ICI) and facilitation (ICF) of motor cortex paired-pulse transcranial magnetic stimulation were reported in the affected (AH) and unaffected (UH) hemispheres of stroke patients and reflect some of the mechanisms related to motor cortex plasticity and different degrees of functional recovery. The interhemispheric differences of the ICI/ICF slopes have been found to have a nearly identical time course in the 2 hemispheres of healthy subjects, and whether such symmetry is modified after monohemispheric stroke has not yet been examined. Our goal was to investigate the interhemispheric asymmetries of the time course of ICI/ICF between the AH and UH of stroke patients in the postacute phase of recovery.
Methods—
ICI/ICF recovery curves to subthreshold-conditioning suprathreshold-test magnetic stimuli were recorded from the paretic and nonparetic hand muscles of 10 well-recovered stroke patients and compared with those of a population of 10 control subjects.
Results—
In the healthy subjects, ICI/ICF showed a symmetrical time evolution between the 2 hemispheres. In stroke patients, the ICI/ICF slopes were significantly different between the UH and AH; the intracortical inhibition was reduced in the AH and normal in the UH.
Conclusions—
The defective AH ICI associated with the effective UH ICI could represent a marker of poststroke cortical plasticity implicated as a mechanism relevant to functional recovery. Analysis of the interhemispheric asymmetries of the ICI/ICF recovery curves might provide a valuable neurophysiological parameter in the prognosis and follow-up of patients with monohemispheric stroke.
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Affiliation(s)
- Paola Cicinelli
- Fondazione Santa Lucia IRCCS, Via Ardeantina, 306, 00179, Rome, Italy.
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42
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Barmashenko G, Eysel UT, Mittmann T. Changes in intracellular calcium transients and LTP in the surround of visual cortex lesions in rats. Brain Res 2003; 990:120-8. [PMID: 14568336 DOI: 10.1016/s0006-8993(03)03447-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Injury and loss of neurons are observed in the center of a cerebral cortical lesion. Mechanisms of early functional reorganization post-lesion involve changes in the strength of synaptic coupling as measured in long-term potentiation (LTP). Since these changes in LTP may depend on the intraneuronal calcium concentration ([Ca2+]I), the present study analyzed the strength of synaptic LTP combined with measurements of the stimulus-induced peak calcium influx in slices from rat visual cortex in vitro. Slices were analyzed 1-7 days post-lesion by use of electrophysiological and calcium fluorescence imaging techniques. A theta-burst stimulus (TBS) was electrically applied to cortical layer IV, while changes in extracellular field potentials (FPs) and in the corresponding peak calcium influx were recorded in layers II/III. Both the strength of LTP and of the FP mediated peak calcium influx were significantly enhanced 1-6 days post-lesion at a distance of 4 mm from the lesion border. Pharmacological experiments revealed that the expression of LTP was dependent on the activation of NMDA receptors. The area of increased stimulus-evoked peak calcium influx correlated with the enhanced LTP, suggesting that changes in [Ca2+]I mediate the strength of long-term synaptic plasticity following a cortical lesion. This mechanism may support synaptic reorganization in the surround of the deafferented region in rat visual cortex.
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Affiliation(s)
- G Barmashenko
- Department of Neurobiology, Ruhr-University Bochum, D-44780, Bochum, Germany
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43
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Xerri C, Zennou-Azogui Y. Influence of the postlesion environment and chronic piracetam treatment on the organization of the somatotopic map in the rat primary somatosensory cortex after focal cortical injury. Neuroscience 2003; 118:161-77. [PMID: 12676147 DOI: 10.1016/s0306-4522(02)00911-9] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The influence of housing in an enriched or impoverished environment and anti-ischemic treatment (piracetam) on the organization of the intact regions of the somatosensory cortical maps adjacent to a focal cortical injury were investigated in adult rats. Response properties of small clusters of neurons were recorded in the area of the primary somatosensory cortex (SI) devoted to the contralateral forepaw representation. Electrophysiological maps were elaborated on the basis of the sensory "submodality" (cutaneous or noncutaneous) and the location of the receptive fields (RFs) of layer IV neurons. Recordings were made before, and 3 weeks after induction of a focal neurovascular lesion to the SI cortex. The main results were: 1) the focal ischemic injury induced a cellular loss which was less severe in the piracetam treated rats, regardless of the housing conditions; 2) the lesion resulted in a compression of the remaining forepaw map, a fragmentation of the representational zones serving the cutaneous surfaces (low-threshold inputs) and an enlargement of noncutaneous zones (high-threshold inputs) in the spared cortical sectors surrounding the lesion. These changes were found in all placebo rats, with the most detrimental effects in the animals exposed to an impoverished environment, and in the piracetam-plus-impoverished rats. In contrast, a limited compression of the forepaw map and a preservation of most representational sectors were observed in the piracetam-plus-enriched animals, 3) the size of the cutaneous RFs of the neurons within the intact cortical zones remained unchanged, regardless of environment or treatment; 4) consistent with the map changes, the skin surfaces lacking low-threshold cutaneous RFs increased after the lesion in all animal groups but the piracetam-plus-enriched rats; 5) cortical responsiveness as assessed with mechanical threshold evaluation was diminished in the placebo rats, whatever the environment, and in the piracetam-impoverished rats, but was not significantly affected in the piracetam-enriched animals. Our findings, based on the first double electrophysiological mapping in the rat SI cortex, highlight the protective effects of an environmental therapy associated with an anti-ischemic treatment on the neurophysiological properties of cortical neurons following a focal neurovascular injury to the neocortex.
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Affiliation(s)
- C Xerri
- Laboratoire Adaptation et Restauration Fonctionnelles, Université de Provence/CNRS, UMR 6149, Neurobiologie Intégrative et Adaptative, 52, Faculté des Sciences St Jérôme, case 361, 13397 Cedex 20, Marseille, France.
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44
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Farkas T, Racekova E, Kis Z, Horváth S, Burda J, Galik J, Toldi J. Peripheral nerve injury influences the disinhibition induced by focal ischaemia in the rat motor cortex. Neurosci Lett 2003; 342:49-52. [PMID: 12727315 DOI: 10.1016/s0304-3940(03)00230-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Photothrombotic lesions were produced in the rat primary motor cortex, and the brain excitability was assessed in a paired-pulse stimulation protocol by transcranial recording, in parallel at 16 points of the frontal cortex, including the insulted and the surrounding areas. The cortical lesion reduced the inhibition in the extended frontal cortex, with a delay of a few minutes. Unilateral facial nerve transection, however, accelerated the widespread disinhibition. Although the mechanism is not clear in detail, both peripheral and central injury-induced disinhibition may have a significant impact on the recovery of the function.
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Affiliation(s)
- Tamás Farkas
- Department of Comparative Physiology, University of Szeged, Közép fasor 52, H-6726, Szeged, Hungary
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45
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Abstract
There is accumulating evidence that intracellular and extracellular proteases of microglia contribute to various events in the central nervous system (CNS) through both nonspecific and limited proteolysis. Cathepsin E and cathepsin S, endosomal/lysosomal proteases, have been shown to play important roles in the major histocompatibility complex (MHC) class II-mediated antigen presentation of microglia by processing of exogenous antigens and degradation of the invariant chain associated with MHC class II molecules, respectively. Some members of cathepsins are also involved in neuronal death after secreted from microglia and clearance of phagocytosed amyloid- beta peptides. Tissue-type plasminogen activator, a serine protease, secreted from microglia participates in neuronal death, enhancement of N-methyl-D-aspartate receptor-mediated neuronal responses, and activation of microglia via either proteolytic or nonproteolytic activity. Calpain, a calcium-dependent cysteine protease, has been shown to play a pivotal role in the pathogenesis of multiple sclerosis by degrading myelin proteins extracellulary. Furthermore, matrix metalloproteases secreted from microglia also receive great attention as mediators of inflammation and tissue degradation through processing of pro-inflammatory cytokines and damage to the blood-brain barrier. The growing knowledge about proteolytic events mediated by microglial proteases will not only contribute to better understanding of microglial functions in the CNS but also may aid in the development of protease inhibitors as novel neuroprotective agents.
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Affiliation(s)
- Hiroshi Nakanishi
- Laboratory of Oral Aging Science, Faculty of Dental Sciences, Kyushu University, Fukuoka 812-8582, Japan.
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46
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Setkowicz Z, Janeczko K. Long-term changes in susceptibility to pilocarpine-induced status epilepticus following neocortical injuries in the rat at different developmental stages. Epilepsy Res 2003; 53:216-24. [PMID: 12694930 DOI: 10.1016/s0920-1211(03)00029-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
In the brain, injury-induced gliosis and axonal sprouting have been regarded as age-dependent repairing processes with, unfortunately, epileptogenic effects. The present study examines whether brains injured at different developmental stages become more or less susceptible to experimentally-induced status epilepticus. In 6- and 30-day-old Wistar rats (P6s and P30s, respectively), a mechanical injury was performed in the cortex of the left cerebral hemisphere. On postnatal day 60, all the animals and naïve controls received single intraperitoneally pilocarpine injections to evoke status epilepticus. During a 6-h period following the injection, the animals were observed continuously and motor manifestations of seizure activity were recorded and rated. Seven days after pilocarpine injection, the animals were perfused and their body and brain weights recorded. When compared to controls, P6s showed neither significant variations in their epileptic behavior nor in brain and body weights. In relation to controls and to P6s, P30s presented an extremely high mortality, a significant loss of body weight and much longer-lasting seizures of much higher intensity. The data provide evidence that the long-term variations in susceptibility to experimentally-induced status epilepticus are determined by differences in the brain response to injury at different stages of postnatal development.
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Affiliation(s)
- Zuzanna Setkowicz
- Department of Neuroanatomy, Institute of Zoology, Jagiellonian University, Ingardena 6, 30 060 Kraków, Poland
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Manganotti P, Patuzzo S, Cortese F, Palermo A, Smania N, Fiaschi A. Motor disinhibition in affected and unaffected hemisphere in the early period of recovery after stroke. Clin Neurophysiol 2002; 113:936-43. [PMID: 12048054 DOI: 10.1016/s1388-2457(02)00062-7] [Citation(s) in RCA: 179] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
OBJECTIVES To investigate motor disinhibition in affected and unaffected motor areas in the acute stage after stroke and during the early period of recovery. METHODS Fifteen patients with moderate to severe hemiparesis after acute unilateral stroke were compared with 10 healthy age-matched controls. We used paired transcranial magnetic stimulation to study intracortical inhibition and facilitation from the thenar eminence muscles on both sides. F-wave from the median nerve on both sides were recorded. The recordings were performed 5-7 days (T1) and 30 days after stroke. RESULTS In 10 patients who showed the presence of reliable motor evoked potentials on the affected side, intracortical inhibition was significantly reduced. On the unaffected side intracortical inhibition (ICI) was significantly reduced in all patients. Patients who presented significant motor recovery after 30 days showed persistence of abnormal disinhibition in the affected hemisphere but a return to normal ICI in the unaffected hemisphere. Patients with poor motor recovery showed persistence of abnormal disinhibition on both sides. No significant changes were observed in F-wave amplitude. CONCLUSIONS Motor disinhibition occurs on both sides after stroke in all acute stage patients. Changes in motor disinhibition on unaffected side also are related to motor recovery.
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Affiliation(s)
- P Manganotti
- Sezione di Neurologia Riabilitativa, Dipartimento di Scienze Neurologiche e della Visione, Policlinico 'Gianbattista Rossi', Universita' di Verona, Via delle Menegone, Verona, Italy.
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48
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Schweigart G, Eysel UT. Activity-dependent receptive field changes in the surround of adult cat visual cortex lesions. Eur J Neurosci 2002; 15:1585-96. [PMID: 12059966 DOI: 10.1046/j.1460-9568.2002.01996.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Extracellular single cell spike activity was recorded in the visual cortex of anaesthetized adult cats at identical sites before and 2 days after focal excitotoxic lesions induced by injections of ibotenic acid. In the surround of the lesions (up to 5 mm from the border of the lesion), the average postlesion receptive field (RF) sizes were not different from the prelesion RFs. However, RFs of neurons with increased postlesion excitability were slightly enlarged; such neurons were mainly found close to the anterior border of the lesion (< or = 1 mm). After applying a visual training procedure for 1 h to the postlesion RFs (repetitive, synchronous stimulation of a part of the RF and the neighbouring unresponsive part of the visual field), there was a small (0.4-0.8 degrees ) but significant and specific increase of RF size in about half of the tested neurons. This RF enlargement was similar to that observed with the same training procedure in the visual cortex of normal cats. Thus, small RF changes can be induced by visual stimulation within one hour in normal cells as well as in cells at the border of cortical lesions. Any differences between normal and lesioned animals appear to be related to lesion-induced changes of excitability.
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Affiliation(s)
- Georg Schweigart
- Abteilung für Neurophysiologie, Medizinische Fakultät, Ruhr-Universität Bochum, Germany
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Huemmeke M, Eysel UT, Mittmann T. Metabotropic glutamate receptors mediate expression of LTP in slices of rat visual cortex. Eur J Neurosci 2002; 15:1641-5. [PMID: 12059971 DOI: 10.1046/j.1460-9568.2002.02002.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Long-term-potentiation (LTP) can be induced by application of a standard theta-burst stimulation protocol in slice preparations of the neocortex. This type of LTP is known to be dependent on the activation of NMDA receptors. The present study used specific experimental conditions to evoke a non-NMDA receptor mediated type of LTP. By use of weak theta-burst stimulation (wTBS) we describe a non-NMDA receptor dependent LTP in rat visual cortex in vitro, which is sensitive to an antagonist of metabotropic glutamate receptors (mGluR). In slices of the visual cortex we stimulated ascending inputs in cortical layer IV and recorded extracellular field potentials (FPs) from cortical layers II/III. In disinhibited slices (with 1 microm picrotoxin), a wTBS induced LTP to 138% of control. The expression of this potentiation was insensitive to the NMDA-receptor antagonist, D-AP5, but could be abolished by application of the mGluR antagonist MCPG. These data suggest an NMDA-independent mechanism for LTP induction in the visual cortex which can be observed in layer II/III neurons.
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Affiliation(s)
- Markus Huemmeke
- Department of Neurophysiology, Ruhr-University Bochum, Germany
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50
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Abstract
Lesion-induced functional loss is reduced when new synaptic connections are established in the surround of a cortical lesion. For this, long-term synaptic plasticity can play a key role. We studied long-term potentiation (LTP) and long-term depression (LTD) in slices of rat visual cortex with small cortical lesions. Surprisingly, the normal balance between LTP and LTD was significantly altered in the first week following cortical injury. Theta-burst induced LTP was increased, whereas LTD evoked by low frequency stimulation was not affected. The increased potentiation of subcortical inputs after cortical lesions opens a window for facilitated early functional reorganization by repetitive visual training.
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Affiliation(s)
- T Mittmann
- Department of Neurophysiology, Ruhr-University Bochum, D-44780 Bochum, Germany
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