Regionally Selective Blockade of GABAergic Inhibition by Zinc in the Thalamocortical System: Functional Significance

The thalamocortical (TC) system is a tightly coupled synaptic circuit in which GABAergic inhibition originating from the nucleus reticularis thalami (NRT) serves to synchronize oscillatory TC rhythmic behavior. Zinc is colocalized within nerve terminals throughout the TC system with dense staining for zinc observed in NRT, neocortex, and thalamus. Whole cell voltage-clamp recordings of GABA-evoked responses were conducted in neurons isolated from ventrobasal thalamus, NRT, and somatosensory cortex to investigate modulation of the GABA-mediated chloride conductance by zinc. Zinc blocked GABA responses in a regionally specific, noncompetitive manner within the TC system. The regional levels of GABA blockade efficacy by zinc were: thalamus > NRT > cortex. The relationship between clonazepam and zinc sensitivity of GABAA-mediated responses was examined to investigate possible presence or absence of specific GABAAreceptor (GABAR) subunits. These properties of GABARs have been hypothesized previously to be dependent on presence or absence of the γ2 subunit and seem to display an inverse relationship. In cross-correlation plots, thalamic and NRT neurons did not show a statistically significant relationship between clonazepam and zinc sensitivity; however, a statistically significant correlation was observed in cortical neurons. Spontaneous epileptic TC oscillations can be induced in vitro by perfusion of TC slices with an extracellular medium containing no added Mg2+. Multiple varieties of oscillations are generated, including simple TC burst complexes (sTBCs), which resemble spike-wave discharge activity. A second variant was termed a complex TC burst complex (cTBC), which resembled generalized tonic clonic seizure activity. sTBCs were exacerbated by zinc, whereas cTBCs were blocked completely by zinc. This supported the concept that zinc release may modulate TC rhythms in vivo. Zinc interacts with a variety of ionic conductances, including GABAR currents, N-methyl-d-aspartate (NMDA) receptor currents, and transient potassium (A) currents.d−2-amino-5-phosphonovaleric acid and 4-aminopyridine blocked both s- and cTBCs in TC slices. Therefore NMDA and A current-blocking effects of zinc are insufficient to explain differential zinc sensitivity of these rhythms. This supports a significant role of zinc-induced GABAR modulation in differential TC rhythm effects. Zinc is localized in high levels within the TC system and appears to be released during TC activity. Furthermore application of exogenous zinc modulates TC rhythms and differentially blocks GABARs within the TC system. These data are consistent with the hypothesis that endogenously released zinc may have important neuromodulatory actions impacting generation of TC rhythms, mediated at least in part by effects on GABARs.

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Glycine Tranporter-1 Blockade Potentiates NMDA-Mediated Responses in Rat Prefrontal Cortical Neurons In Vitro and In Vivo

Journal of Neurophysiology ◽

10.1152/jn.00680.2002 ◽

2003 ◽

Vol 89 (2) ◽

pp. 691-703 ◽

Cited By ~ 170

Author(s):

Long Chen ◽

Mark Muhlhauser ◽

Charles R. Yang

Keyword(s):

Neural Development ◽

Cortical Neurons ◽

Critical Role ◽

Cell Voltage ◽

Prefrontal Cortical ◽

Glycine Transporter ◽

Excitatory Responses ◽

Site Stimulation

The N-methyl-d-aspartate (NMDA) receptor (NMDA-R) has pivotal roles in neural development, learning, memory, and synaptic plasticity. Functional impairment of NMDA-R has been implicated in schizophrenia. NMDA-R activation requires glycine to act on the glycine-B (GlyB) site of the NMDA-R as an obligatory co-agonist with glutamate. Extracellular glycine near NMDA-R is regulated effectively by a glial glycine transporter (GlyT1). Using whole-cell voltage-clamp recordings in prefrontal cortex (PFC) slices, we have shown that exogenous GlyB site agonists glycine and d-serine, or a specific GlyT1 inhibitor N[3-(4′-fluorophenyl)-3-(4′-phenylphenoxy)propyl]sarcosine (NFPS) in the presence of exogenous glycine (10 μM), potentiated synaptically evoked NMDA excitatory postsynaptic currents (EPSCs) in vitro. Furthermore, in urethan-anesthetized rats, microiontophoretic NMDA pulses excite single PFC neurons. When these responses were blocked by approximately 50% to approximately 90% on continuous iontophoretic application of the GlyB site, antagonist (+)HA-966, intravenous NFPS (5 mg/kg), or a GlyB site agonist d-serine (50 mg/kg iv) reversed this (+)HA-966 block. NFPS may elevate endogenous glycine levels sufficiently to displace (+)HA-966 from the GlyB sites of the NMDA-R, thus enabling reactivation of the NMDA-Rs by iontophoretic NMDA applications. d-Serine (50–100 mg/kg iv) or NFPS (1–2 mg/kg iv) alone also augmented NMDA-evoked excitatory responses. These data suggest that direct GlyB site stimulation byd-serine, or blockade of GLYT1 to elevate endogenous glycine to act on unsaturated GlyB sites on NMDA-Rs, potentiated NMDA-R-mediated firing responses in rat PFC. Hence, blockade of GlyT1 to elevate glycine near the NMDA-R may activate hypofunctional NMDA-R, which has been implicated to play a critical role in the pathophysiology of schizophrenia.

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TRAF3 mediates neuronal apoptosis in early brain injury following subarachnoid hemorrhage via targeting TAK1-dependent MAPKs and NF-κB pathways

Cell Death and Disease ◽

10.1038/s41419-020-03278-z ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Yan Zhou ◽

Tao Tao ◽

Guangjie Liu ◽

Xuan Gao ◽

Yongyue Gao ◽

...

Keyword(s):

Subarachnoid Hemorrhage ◽

Brain Injury ◽

Therapeutic Target ◽

Cortical Neurons ◽

Neuronal Apoptosis ◽

Early Brain Injury ◽

Neurological Deficits ◽

Human Brain Tissue

AbstractNeuronal apoptosis has an important role in early brain injury (EBI) following subarachnoid hemorrhage (SAH). TRAF3 was reported as a promising therapeutic target for stroke management, which covered several neuronal apoptosis signaling cascades. Hence, the present study is aimed to determine whether downregulation of TRAF3 could be neuroprotective in SAH-induced EBI. An in vivo SAH model in mice was established by endovascular perforation. Meanwhile, primary cultured cortical neurons of mice treated with oxygen hemoglobin were applied to mimic SAH in vitro. Our results demonstrated that TRAF3 protein expression increased and expressed in neurons both in vivo and in vitro SAH models. TRAF3 siRNA reversed neuronal loss and improved neurological deficits in SAH mice, and reduced cell death in SAH primary neurons. Mechanistically, we found that TRAF3 directly binds to TAK1 and potentiates phosphorylation and activation of TAK1, which further enhances the activation of NF-κB and MAPKs pathways to induce neuronal apoptosis. Importantly, TRAF3 expression was elevated following SAH in human brain tissue and was mainly expressed in neurons. Taken together, our study demonstrates that TRAF3 is an upstream regulator of MAPKs and NF-κB pathways in SAH-induced EBI via its interaction with and activation of TAK1. Furthermore, the TRAF3 may serve as a novel therapeutic target in SAH-induced EBI.

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Machine learning-based classification of mitochondrial morphology in primary neurons and brain

Scientific Reports ◽

10.1038/s41598-021-84528-8 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Garrett M. Fogo ◽

Anthony R. Anzell ◽

Kathleen J. Maheras ◽

Sarita Raghunayakula ◽

Joseph M. Wider ◽

...

Keyword(s):

Image Analysis ◽

Cortical Neurons ◽

Mitochondrial Dynamics ◽

Automated Image Analysis ◽

Mitochondrial Morphology ◽

Analysis Pipeline ◽

Genetic Ablation ◽

Block Face

AbstractThe mitochondrial network continually undergoes events of fission and fusion. Under physiologic conditions, the network is in equilibrium and is characterized by the presence of both elongated and punctate mitochondria. However, this balanced, homeostatic mitochondrial profile can change morphologic distribution in response to various stressors. Therefore, it is imperative to develop a method that robustly measures mitochondrial morphology with high accuracy. Here, we developed a semi-automated image analysis pipeline for the quantitation of mitochondrial morphology for both in vitro and in vivo applications. The image analysis pipeline was generated and validated utilizing images of primary cortical neurons from transgenic mice, allowing genetic ablation of key components of mitochondrial dynamics. This analysis pipeline was further extended to evaluate mitochondrial morphology in vivo through immunolabeling of brain sections as well as serial block-face scanning electron microscopy. These data demonstrate a highly specific and sensitive method that accurately classifies distinct physiological and pathological mitochondrial morphologies. Furthermore, this workflow employs the use of readily available, free open-source software designed for high throughput image processing, segmentation, and analysis that is customizable to various biological models.

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Kir6.2-containing ATP-sensitive potassium channels protect cortical neurons from ischemic/anoxic injury in vitro and in vivo

Neuroscience ◽

10.1016/j.neuroscience.2006.10.043 ◽

2007 ◽

Vol 144 (4) ◽

pp. 1509-1515 ◽

Cited By ~ 31

Author(s):

H.-S. Sun ◽

Z.-P. Feng ◽

P.A. Barber ◽

A.M. Buchan ◽

R.J. French

Keyword(s):

Potassium Channels ◽

Cortical Neurons ◽

Anoxic Injury

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KBP interacts with SCG10, linking Goldberg–Shprintzen syndrome to microtubule dynamics and neuronal differentiation

Human Molecular Genetics ◽

10.1093/hmg/ddq280 ◽

2010 ◽

Vol 19 (18) ◽

pp. 3642-3651 ◽

Cited By ~ 30

Author(s):

Maria M. Alves ◽

Grzegorz Burzynski ◽

Jean-Marie Delalande ◽

Jan Osinga ◽

Annemieke van der Goot ◽

...

Keyword(s):

Nervous System ◽

Enteric Nervous System ◽

Neuronal Differentiation ◽

Cortical Neurons ◽

Neuronal Development ◽

Direct Interaction ◽

Clinical Disorder ◽

Neurite Development

Abstract Goldberg–Shprintzen syndrome (GOSHS) is a rare clinical disorder characterized by central and enteric nervous system defects. This syndrome is caused by inactivating mutations in the Kinesin Binding Protein (KBP) gene, which encodes a protein of which the precise function is largely unclear. We show that KBP expression is up-regulated during neuronal development in mouse cortical neurons. Moreover, KBP-depleted PC12 cells were defective in nerve growth factor-induced differentiation and neurite outgrowth, suggesting that KBP is required for cell differentiation and neurite development. To identify KBP interacting proteins, we performed a yeast two-hybrid screen and found that KBP binds almost exclusively to microtubule associated or related proteins, specifically SCG10 and several kinesins. We confirmed these results by validating KBP interaction with one of these proteins: SCG10, a microtubule destabilizing protein. Zebrafish studies further demonstrated an epistatic interaction between KBP and SCG10 in vivo . To investigate the possibility of direct interaction between KBP and microtubules, we undertook co-localization and in vitro binding assays, but found no evidence of direct binding. Thus, our data indicate that KBP is involved in neuronal differentiation and that the central and enteric nervous system defects seen in GOSHS are likely caused by microtubule-related defects.

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A MICROCALORIMETRIC STUDY OF TURTLE CORTICAL SLICES: INSIGHTS INTO BRAIN METABOLIC DEPRESSION

Journal of Experimental Biology ◽

10.1242/jeb.191.1.141 ◽

1994 ◽

Vol 191 (1) ◽

pp. 141-153 ◽

Cited By ~ 1

Author(s):

C Doll ◽

P Hochachka ◽

S Hand

Keyword(s):

Cortical Neurons ◽

Heat Dissipation ◽

Energy Charge ◽

Utilization Rate ◽

Rapid Decline ◽

Metabolic Depression ◽

Slice Preparation ◽

Cortical Slices

In previous papers, we have examined turtle cortical neurons in vitro for mechanisms of anoxic metabolic depression ('channel arrest' and changes in electrical parameters). Negative results prompted the current study with the aim of examining more closely the energy profile and metabolism of turtle cortical slices. Calorimetry is used to measure heat dissipation during normoxia and nitrogen perfusion (120 min) and the results are converted into an ATP utilization rate. These indicate that the control rate of ATP utilization (1.72 µmol ATP g-1 min-1) agrees closely with in vivo whole-brain metabolic measurements. Both nitrogen perfusion and pharmacologically induced anoxic (cyanide+N2) groups depressed heat dissipation considerably compared with the control value (nitrogen 37 %; pharmacological anoxia 49 %). The resulting ATP utilization estimates indicate metabolic depressions of 30 % (nitrogen) and 42 % (pharmacological anoxia). The slice preparation did not exhibit a change in any measured adenylate parameter for up to 120 min of anoxia or pharmacological anoxia. Significant changes did occur in [ADP], ATP/ADP ratio and energy charge after 240 min of exposure to anoxic conditions. These results support the idea that the turtle cortical slice preparation has a profound resistance to anoxia, with both nitrogen perfusion and pharmacological anoxia causing a rapid decline in heat dissipation and metabolism.

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Ephrin-B3 controls excitatory synapse density through cell-cell competition for EphBs

eLife ◽

10.7554/elife.41563 ◽

2019 ◽

Vol 8 ◽

Cited By ~ 3

Author(s):

Nathan T Henderson ◽

Sylvain J Le Marchand ◽

Martin Hruska ◽

Simon Hippenmeyer ◽

Liqun Luo ◽

...

Keyword(s):

Cortical Neurons ◽

Spine Density ◽

Cell Competition ◽

Intrinsic Factors ◽

Genetic Mouse Model ◽

Synapse Density ◽

A Cell ◽

Cell Cell

Cortical networks are characterized by sparse connectivity, with synapses found at only a subset of axo-dendritic contacts. Yet within these networks, neurons can exhibit high connection probabilities, suggesting that cell-intrinsic factors, not proximity, determine connectivity. Here, we identify ephrin-B3 (eB3) as a factor that determines synapse density by mediating a cell-cell competition that requires ephrin-B-EphB signaling. In a microisland culture system designed to isolate cell-cell competition, we find that eB3 determines winning and losing neurons in a contest for synapses. In a Mosaic Analysis with Double Markers (MADM) genetic mouse model system in vivo the relative levels of eB3 control spine density in layer 5 and 6 neurons. MADM cortical neurons in vitro reveal that eB3 controls synapse density independently of action potential-driven activity. Our findings illustrate a new class of competitive mechanism mediated by trans-synaptic organizing proteins which control the number of synapses neurons receive relative to neighboring neurons.

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Modulator of apoptosis-1 is a potential therapeutic target in acute ischemic injury

Journal of Cerebral Blood Flow & Metabolism ◽

10.1177/0271678x18794839 ◽

2018 ◽

Vol 39 (12) ◽

pp. 2406-2418 ◽

Cited By ~ 3

Author(s):

Su Jing Chan ◽

Hui Zhao ◽

Kazuhide Hayakawa ◽

Chou Chai ◽

Chong Teik Tan ◽

...

Keyword(s):

Cortical Neurons ◽

Infarct Volume ◽

Neuronal Loss ◽

Ischemic Injury ◽

Glucose Deprivation ◽

Artery Occlusion ◽

In Vivo Models ◽

The Brain

Modulator of apoptosis 1 (MOAP-1) is a Bax-associating protein highly enriched in the brain. In this study, we examined the role of MOAP-1 in promoting ischemic injuries following a stroke by investigating the consequences of MOAP-1 overexpression or deficiency in in vitro and in vivo models of ischemic stroke. MOAP-1 overexpressing SH-SY5Y cells showed significantly lower cell viability following oxygen and glucose deprivation (OGD) treatment when compared to control cells. Consistently, MOAP-1−/− primary cortical neurons were observed to be more resistant against OGD treatment than the MOAP-1+/+ primary neurons. In the mouse transient middle cerebral artery occlusion (tMCAO) model, ischemia triggered MOAP-1/Bax association, suggested activation of the MOAP-1-dependent apoptotic cascade. MOAP-1−/− mice were found to exhibit reduced neuronal loss and smaller infarct volume 24 h after tMCAO when compared to MOAP-1+/+ mice. Correspondingly, MOAP-1−/− mice also showed better integrity of neurological functions as demonstrated by their performance in the rotarod test. Therefore, both in vitro and in vivo data presented strongly support the conclusion that MOAP-1 is an important apoptotic modulator in ischemic injury. These results may suggest that a reduction of MOAP-1 function in the brain could be a potential therapeutic approach in the treatment of acute stroke.

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Possible Effects of Depolarizing GABAA Conductance on the Neuronal Input–Output Relationship: A Modeling Study

Journal of Neurophysiology ◽

10.1152/jn.00988.2004 ◽

2005 ◽

Vol 93 (6) ◽

pp. 3504-3523 ◽

Cited By ~ 9

Author(s):

Kenji Morita ◽

Kunichika Tsumoto ◽

Kazuyuki Aihara

Keyword(s):

Firing Rate ◽

Cortical Neurons ◽

Reversal Potential ◽

Pyramidal Cells ◽

Resting Potential ◽

Input Output ◽

Wide Range ◽

The Relationship

Recent in vitro experiments revealed that the GABAA reversal potential is about 10 mV higher than the resting potential in mature mammalian neocortical pyramidal cells; thus GABAergic inputs could have facilitatory, rather than inhibitory, effects on action potential generation under certain conditions. However, how the relationship between excitatory input conductances and the output firing rate is modulated by such depolarizing GABAergic inputs under in vivo circumstances has not yet been understood. We examine herewith the input–output relationship in a simple conductance-based model of cortical neurons with the depolarized GABAA reversal potential, and show that a tonic depolarizing GABAergic conductance up to a certain amount does not change the relationship between a tonic glutamatergic driving conductance and the output firing rate, whereas a higher GABAergic conductance prevents spike generation. When the tonic glutamatergic and GABAergic conductances are replaced by in vivo–like highly fluctuating inputs, on the other hand, the effect of depolarizing GABAergic inputs on the input–output relationship critically depends on the degree of coincidence between glutamatergic input events and GABAergic ones. Although a wide range of depolarizing GABAergic inputs hardly changes the firing rate of a neuron driven by noncoincident glutamatergic inputs, a certain range of these inputs considerably decreases the firing rate if a large number of driving glutamatergic inputs are coincident with them. These results raise the possibility that the depolarized GABAA reversal potential is not a paradoxical mystery, but is instead a sophisticated device for discriminative firing rate modulation.

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