Spreading Depression and Related Events Are Significant Sources of Neuronal Zn2+ Release and Accumulation

Spreading depression (SD) involves coordinated depolarizations of neurons and glia that propagate through the brain tissue. Repetitive SD-like events are common following human ischemic strokes, and are believed to contribute to the enlargement of infarct volume. Accumulation of Zn2+ is also implicated in ischemic neuronal injury. Synaptic glutamate release contributes to SD propagation, and because Zn2+ is costored with glutamate in some synaptic vesicles, we examined whether Zn2+ is released by SD and may therefore provide a significant source of Zn2+ in the postischemic period. Spreading depression-like events were generated in acutely prepared murine hippocampal slices by deprivation of oxygen and glucose (OGD), and Zn2+ release was detected extracellularly by a Zn2+-selective indicator FluoZin-3. Deprivation of oxygen and glucose-SD produced large FluoZin-3 increases that propagated with the event, and signals were abolished in tissues from ZnT3 knockout animals lacking synaptic Zn2+. Synaptic Zn2+ release was also maintained with repetitive SDs generated by microinjections of KCl under normoxic conditions. Intracellular Zn2+ accumulation in CA1 neurons, assessed using microinjection of FluoZin-3, showed significant increases following SD that was attributed to synaptic Zn2+ release. These results suggest that Zn2+ is released during SDs and could provide a significant source of Zn2+ that contributes to neurodegeneration in the postischemic period.

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Mitochondrial Inhibition Prior to Oxygen-Withdrawal Facilitates the Occurrence of Hypoxia-Induced Spreading Depression in Rat Hippocampal Slices

Journal of Neurophysiology ◽

10.1152/jn.01015.2005 ◽

2006 ◽

Vol 96 (1) ◽

pp. 492-504 ◽

Cited By ~ 38

Author(s):

Florian J. Gerich ◽

Sebastian Hepp ◽

Irmelin Probst ◽

Michael Müller

Keyword(s):

Mitochondrial Respiration ◽

Spreading Depression ◽

Hippocampal Slices ◽

Atp Synthesis ◽

Atp Depletion ◽

Mitochondrial Uncoupling ◽

Ca1 Neurons ◽

Optical Signals ◽

Nitropropionic Acid ◽

Carbonyl Cyanide

Oxygen withdrawal blocks mitochondrial respiration. In rat hippocampal slices, this triggers a massive depolarization of CA1 neurons and a negative shift of the extracellular DC potential, the characteristic sign of hypoxia-induced spreading depression (HSD). To unveil the contribution of mitochondria to the sensing of hypoxia and the ignition of HSD, we modified mitochondrial function. Mitochondrial uncoupling by carbonyl cyanide 4-(trifluoromethoxy) phenylhydrazone (FCCP, 1 μM) prior to hypoxia hastened the onset and shortened the duration of HSD. Blocking mitochondrial ATP synthesis by oligomycin (10 μg/ml) was without effect. Inhibition of mitochondrial respiration by rotenone (20 μM), diphenyleneiodonium (25 μM), or antimycin A (20 μM) also hastened HSD onset and shortened HSD duration. 3-nitropropionic acid (1 mM) increased HSD duration. Cyanide (100 μM) hastened HSD onset and increased HSD duration. At higher concentrations, cyanide (1 mM), azide (2 mM), and FCCP (10 μM) triggered SD episodes on their own. Compared with control HSD, the spatial extent of the intrinsic optical signals of cyanide- and azide-induced SDs was more pronounced. Monitoring NADH (nicotinamide adenine dinucleotide) and FAD (flavin adenine dinucleotide) autofluorescence and mitochondrial membrane potential verified the mitochondrial targeting by the drugs used. Except 1 mM cyanide, no treatment reduced cellular ATP levels severely and no correlation was found between ATP, NADH, or FAD levels and the time to HSD onset. Therefore ATP depletion or a cytosolic reducing shift due to NADH/FADH2 accumulation cannot serve as a general explanation for the hastening of HSD onset on mitochondrial inhibition. Additional redox couples (glutathione) or events downstream of the mitochondrial depolarization need to be considered.

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Platelet Glutamate Uptake and Release in Migraine With and Without Aura

Cephalalgia ◽

10.1111/j.1468-2982.2006.01234.x ◽

2007 ◽

Vol 27 (1) ◽

pp. 35-40 ◽

Cited By ~ 30

Author(s):

M Vaccaro ◽

C Riva ◽

L Tremolizzo ◽

M Longoni ◽

A Aliprandi ◽

...

Keyword(s):

Amino Acid ◽

High Performance ◽

Spreading Depression ◽

Glutamate Uptake ◽

Glutamate Release ◽

Plasma Concentrations ◽

Control Group ◽

Therapeutic Approaches ◽

The Brain ◽

Uptake And Release

Glutamate may play an important role in the pathogenesis of migraine: glutamate release in the brain may be involved in the development of spreading depression and increased concentrations of this amino acid have been reported in plasma and platelets from migraine patients. Here we assessed platelet glutamate uptake and release in 25 patients affected by migraine with aura (MA) and 25 patients affected by migraine without aura (MoA), comparing the results with a group of 20 healthy matched controls. Both glutamate release from stimulated platelets and plasma concentrations of the amino acid were assessed by high-performance liquid chromatography, and were increased in both types of migraine, although more markedly in MA. Platelet glutamate uptake, assessed as 3H-glutamate intake, was increased in MA, while it was reduced in MoA with respect to the control group. These results support the view that MA might involve different pathophysiological mechanisms from MoA and, specifically, up-regulation of the glutamatergic metabolism. Understanding these dysfunctional pathways could lead to new, possibly more successful therapeutic approaches to the management of migraine.

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Early anoxia-induced vesicular glutamate release results from mobilization of calcium from intracellular stores

Journal of Neurophysiology ◽

10.1152/jn.1993.70.1.1 ◽

1993 ◽

Vol 70 (1) ◽

pp. 1-7 ◽

Cited By ~ 69

Author(s):

A. N. Katchman ◽

N. Hershkowitz

Keyword(s):

Calcium Influx ◽

Glutamate Release ◽

Hippocampal Slices ◽

Calcium Currents ◽

Patch Clamp Recording ◽

Ca1 Neurons ◽

Whole Cell Patch Clamp ◽

Mepsc Frequency ◽

Synaptic Changes

1. The cause of the increased frequency of glutamatergic miniature excitatory postsynaptic currents (mEPSCs) resulting from anoxia was investigated in CA1 neurons of the in vitro rat hippocampal slice. These neurons were examined by whole-cell patch-clamp recording, and hypoxia was induced by switching the perfusion of the slice from oxygenated artificial cerebral spinal fluid (ACSF) to ACSF saturated with 95% N2-5% O2. Except where noted, experiments were carried out in ACSF containing 1 microM tetrodotoxin (TTX). 2. Although anoxia resulted in a significant increase in the frequency of mEPSCs, the amplitude, rise time, and half-decay time of the mEPSCs were unchanged. This increase in frequency indicates that there is a change in presynaptic neurotransmitter release mechanisms, probably an increase in calcium concentration, soon after the onset of anoxia. The unchanged kinetics and amplitude of the mEPSCs indicate that anoxic-induced synaptic changes are not a result of changes in the postsynaptic glutamate receptor. 3. When hippocampal slices were exposed to anoxic conditions in ACSF with calcium excluded, an increase in mEPSC frequency equal to that in normal ACSF was observed. When 0.2 mM of CdCl2 was added to the zero-calcium ACSF, anoxia still resulted in increases in mEPSC frequency equal to those of normal ACSF. It is therefore concluded that the anoxia-induced increase in mEPSC frequency does not result from an increase in a transmembrane calcium influx. The zero-calcium plus 0.2 mM CdCl2 ACSF solution completely abolished orthodromically elicited synaptic potential (in the absence of TTX), indicating that calcium currents that mediate normal orthodromic transmitter release were completely abolished in the latter experiments.(ABSTRACT TRUNCATED AT 250 WORDS)

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Glutamate Does Not Mediate Acute Neuronal Damage after Spreading Depression Induced by O2/Glucose Deprivation in the Hippocampal Slice

Journal of Cerebral Blood Flow & Metabolism ◽

10.1097/00004647-200002000-00024 ◽

2000 ◽

Vol 20 (2) ◽

pp. 412-422 ◽

Cited By ~ 58

Author(s):

Akef S. Obeidat ◽

Cathryn R. Jarvis ◽

R. David Andrew

Keyword(s):

Spreading Depression ◽

Neuronal Damage ◽

Lucifer Yellow ◽

Hippocampal Slices ◽

Field Potential ◽

Glucose Deprivation ◽

Light Transmittance ◽

Irreversible Damage ◽

Glutamate Antagonists ◽

Ca1 Neurons

This study argues that, in contrast to accepted excitotoxicity theory, O2/glucose deprivation damages neurons acutely by eliciting ischemic spreading depression (SD), a process not blocked by glutamate antagonists. In live rat hippocampal slices, the initiation, propagation, and resolution of SD can be imaged by monitoring wide-band changes in light transmittance (i.e., intrinsic optical signals). Oxygen/glucose deprivation for 10 minutes at 37.5°C evokes a propagating wave of elevated light transmittance across the slice, representing the SD front. Within minutes, CA1 neurons in regions undergoing SD display irreversible damage in the form of field potential inactivation, swollen cell bodies, and extensively beaded dendrites, the latter revealed by single-cell injection of lucifer yellow. Importantly, glutamate receptor antagonists do not block SD induced by O2/glucose deprivation, nor do they prevent the resultant dendritic beading of CA1 neurons. However, CA1 neurons are spared if SD is suppressed by reducing the temperature to 35°C during O2/glucose deprivation. This supports previous electrophysiologic evidence in vivo that SD during ischemia promotes acute neuronal damage and that glutamate antagonists are not protective of the metabolically stressed tissue. The authors propose that the inhibition of ischemic SD should be targeted as an important therapeutic strategy against stroke damage.

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Sulfhydryl Oxidation Reduces Hippocampal Susceptibility to Hypoxia-Induced Spreading Depression by Activating BK Channels

Journal of Neurophysiology ◽

10.1152/jn.00291.2005 ◽

2005 ◽

Vol 94 (2) ◽

pp. 1091-1103 ◽

Cited By ~ 28

Author(s):

Sebastian Hepp ◽

Florian J. Gerich ◽

Michael Müller

Keyword(s):

Spreading Depression ◽

Hippocampal Slices ◽

Underlying Mechanism ◽

Redox Status ◽

Bk Channels ◽

Tissue Slices ◽

Ca1 Neurons ◽

Sh Groups ◽

Nitrobenzoic Acid ◽

Sulfhydryl Oxidation

The cytosolic redox status modulates ion channels and receptors by oxidizing/reducing their sulfhydryl (SH) groups. We therefore analyzed to what degree SH modulation affects hippocampal susceptibility to hypoxia. In rat hippocampal slices, severe hypoxia caused a massive depolarization of CA1 neurons and a negative shift of the extracellular DC potential, the characteristic sign of hypoxia-induced spreading depression (HSD). Oxidizing SH groups by 5,5′-dithiobis 2-nitrobenzoic acid (DTNB, 2 mM) postponed HSD by 30%, whereas their reduction by 1,4-dithio-dl-threitol (DTT, 2 mM) or alkylation by N-ethylmaleimide (500 μM) hastened HSD onset. The DTNB-induced postponement of HSD was not affected by tolbutamide (200 μM), dl-2-amino-5-phosphonovaleric acid (150 μM), or 6-cyano-7-nitroquinoxaline-2,3-dione (25 μM). It was abolished, however, by Ni2+ (2 mM), withdrawal of extracellular Ca2+, charybdotoxin (25 nM), and iberiotoxin (50 nM). In CA1 neurons DTNB induced a moderate hyperpolarization, blocked spontaneous spike discharges and postponed the massive hypoxic depolarization. DTT induced burst firing, depolarized glial cells, and hastened the onset of the massive hypoxic depolarization. Schaffer-collateral/CA1 synapses were blocked by DTT but not by DTNB; axonal conduction remained intact. Mitochondria did not markedly respond to DTNB or DTT. While the targets of DTT are less clear, the postponement of HSD by DTNB indicates that sulfhydryl oxidation increases the tolerance of hippocampal tissue slices against hypoxia. We identified as the underlying mechanism the activation of BK channels in a Ca2+-sensitive manner. Accordingly, ionic disregulation and the loss of membrane potential occur later or might even be prevented during short-term insults. Therefore well-directed oxidation of SH groups could mediate neuroprotection.

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Hypoxia-tolerant neonatal CA1 neurons: relationship of survival to evoked glutamate release and glutamate receptor-mediated calcium changes in hippocampal slices

Developmental Brain Research ◽

10.1016/s0165-3806(97)00189-2 ◽

1998 ◽

Vol 106 (1-2) ◽

pp. 57-69 ◽

Cited By ~ 32

Author(s):

Philip E Bickler ◽

Bonnie M Hansen

Keyword(s):

Glutamate Receptor ◽

Glutamate Release ◽

Hippocampal Slices ◽

Ca1 Neurons ◽

Relationship Of

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L-α-Aminoadipate Reduces Glutamate Release from Brain Tissue Exposed to Combined Oxygen and Glucose Deprivation

Journal of Cerebral Blood Flow & Metabolism ◽

10.1097/00004647-199705000-00011 ◽

1997 ◽

Vol 17 (5) ◽

pp. 567-570 ◽

Cited By ~ 8

Author(s):

Tor S. Haugstad ◽

Iver A. Langmoen

Keyword(s):

Glutamate Release ◽

Hippocampal Slices ◽

Glucose Deprivation ◽

Gaba Release ◽

Dependent Manner ◽

Oxygen And Glucose Deprivation ◽

Energy Deprivation ◽

Dose Dependent ◽

The Brain

The effect of the glutamate analogue L- α-aminoadipate ( αAA) on the release of glutamate and γ-aminobutyric acid (GABA) from rat hippocampal slices was investigated in vitro. Oxygen/glucose deprivation caused a large release of glutamate and GABA. αAA added during energy deprivation reduced the glutamate release in a dose-dependent manner (56% reduction at 5 m M), whereas GABA release was unchanged. We speculate that ischemic glutamate release from the brain is mediated by a low affinity transport mechanism that is blocked by αAA.

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Activity-dependent regulation of synaptic strength by PSD-95 in CA1 neurons

Journal of Neurophysiology ◽

10.1152/jn.00526.2011 ◽

2012 ◽

Vol 107 (4) ◽

pp. 1058-1066 ◽

Cited By ~ 26

Author(s):

Peng Zhang ◽

John E. Lisman

Keyword(s):

Glutamate Receptors ◽

Metabotropic Glutamate Receptors ◽

Hippocampal Slices ◽

Long Term Potentiation ◽

Synaptic Strength ◽

Ca1 Neurons ◽

Metabotropic Glutamate ◽

Group I ◽

Term Potentiation ◽

Activity Dependent

CaMKII and PSD-95 are the two most abundant postsynaptic proteins in the postsynaptic density (PSD). Overexpression of either can dramatically increase synaptic strength and saturate long-term potentiation (LTP). To do so, CaMKII must be activated, but the same is not true for PSD-95; expressing wild-type PSD-95 is sufficient. This raises the question of whether PSD-95's effects are simply an equilibrium process [increasing the number of AMPA receptor (AMPAR) slots] or whether activity is somehow involved. To examine this question, we blocked activity in cultured hippocampal slices with TTX and found that the effects of PSD-95 overexpression were greatly reduced. We next studied the type of receptors involved. The effects of PSD-95 were prevented by antagonists of group I metabotropic glutamate receptors (mGluRs) but not by antagonists of ionotropic glutamate receptors. The inhibition of PSD-95-induced strengthening was not simply a result of inhibition of PSD-95 synthesis. To understand the mechanisms involved, we tested the role of CaMKII. Overexpression of a CaMKII inhibitor, CN19, greatly reduced the effect of PSD-95. We conclude that PSD-95 cannot itself increase synaptic strength simply by increasing the number of AMPAR slots; rather, PSD-95's effects on synaptic strength require an activity-dependent process involving mGluR and CaMKII.

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