A microdialysis study in rat brain of dihydrokainate, a glutamate uptake inhibitor

Fallgren, Åsa B.; Paulsen, Ragnhild E.

doi:10.1007/bf02527667

Cited by 24 publications

(14 citation statements)

References 18 publications

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“…This effect has been shown both ex vivo (Robinson et al, 1991) and in vivo (Fallgren and Paulsen, 1996). DHK does not bind to AMPA/kainite or other glutamate receptors with significant affinity (Johnston et al, 1979), indicating selectivity for GLT-1.…”

Section: Drugsmentioning

confidence: 72%

“…However, previous work has shown that infusion of DHK directly into a specific brain region increases extracellular glutamate levels in the same region (eg, Fallgren and Paulsen, 1996) and that other mood-related effects of DHK infused into the amygdala are blocked by AP5, an N-methyl-D-aspartate receptor antagonist (Lee et al, 2007). It has also been reported that site-specific DHK infusion can have effects other than increasing glutamate.…”

Section: Discussionmentioning

confidence: 99%

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Blockade of the GLT-1 Transporter in the Central Nucleus of the Amygdala Induces both Anxiety and Depressive-Like Symptoms

John

Sypek

Carlezon

et al. 2015

Neuropsychopharmacol

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Depression has been associated with abnormalities in glutamatergic neurotransmission and decreased astrocyte number in limbic areas. We previously demonstrated that global and prefrontal cortical blockade of the astrocytic glutamate transporter (GLT-1) induces anhedonia and c-Fos expression in areas that regulate anxiety, including the central amygdala (CEA). Given the role of the amygdala in anxiety and the high degree of comorbidity between anxiety and depression, we hypothesized that GLT-1 blockade in the CEA would induce symptoms of anhedonia and anxiety in rats. We microinjected the GLT-1 inhibitor, dihydrokainic acid (DHK), into the CEA and examined effects on intracranial self-stimulation (ICSS) as an index of hedonic state, and on behavior in two anxiety paradigms, elevated plus maze (EPM) and fear conditioning. At lower doses, intra-CEA DHK produced modest increases in ICSS responding (T0). Higher doses resulted in complete cessation of responding for 15 min, suggesting an anhedonic or depressive-like effect. Intra-CEA DHK also increased anxiety-like behavior such that percent time in the open arms and total entries were decreased in the EPM and acquisition of freezing behavior to the tone was increased in a fear-conditioning paradigm. These effects did not appear to be explained by non-specific changes in activity, because effects on fear conditioning were assessed in a drug-free state, and a separate activity test showed no significant effects of intra-CEA DHK on locomotion. Taken together, these studies suggest that blockade of GLT-1 in the CEA is sufficient to induce both anhedonia and anxiety and therefore that a lack of glutamate uptake resulting from glial deficits may contribute to the comorbidity of depression and anxiety.

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Section: Drugsmentioning

confidence: 72%

Section: Discussionmentioning

confidence: 99%

Blockade of the GLT-1 Transporter in the Central Nucleus of the Amygdala Induces both Anxiety and Depressive-Like Symptoms

John

Sypek

Carlezon

et al. 2015

Neuropsychopharmacol

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“…This effect is difficult to explain, but the lack of an increase in taurine with DHK administered prior to ischemia indicates that DHK itself does not inhibit taurine uptake or cause its release. The persistent taurine elevation may be a secondary response to the increase in glutamate with ischemia, as suggested by Fallgren et al 30 …”

Section: Eaa Release Via Vracsmentioning

confidence: 83%

Volume-Regulated Anion Channels Are the Predominant Contributors to Release of Excitatory Amino Acids in the Ischemic Cortical Penumbra

Feustel

Jin

Kimelberg

2004

Stroke

110

106

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Background and Purpose-Release of excitatory amino acids (EAA) is considered a cause of neuronal damage in ischemia. We investigated the sources and mechanisms of EAA release using microdialysis in regions of incomplete ischemia where perfusion was reduced by 50% to 80%, by applying inhibitors of volume-regulated anion channels (VRACs) and the GLT-1 glutamate transporter. Methods-Reversible middle cerebral artery occlusion (rMCAo) was induced in anesthetized rats using the intraluminal suture technique. Microdialysate concentrations of glutamate, aspartate, and taurine were measured before, during 2 hours of rMCAo, and for 2 hours after rMCAo. Vehicle, dihydrokainate (DHK, 1 mmol/L), a GLT-1 inhibitor, or tamoxifen (50 mol/L), a VRAC inhibitor, were administered continuously via the dialysis probes starting one hour prior to ischemia. Results-During incomplete ischemia, dialysate glutamate levels averaged 1.74Ϯ0.31 mol/L (SEM) in the control group (nϭ8), 2.08Ϯ0.33 mol/L in the DHK group (nϭ7), and were significantly lower at 0.88Ϯ0.30 mol/L in the tamoxifen group (nϭ9; PϽ0.05). As perfusion returned toward baseline levels, EAA levels declined in the vehicle and tamoxifen-treated animals but they remained elevated in the DHK-treated animals. Conclusion-In contrast to previous results in severely ischemic regions, DHK did not reduce EAA release in less severely ischemic brain, suggesting a diminished role for transporter reversal in these areas. These findings also support the hypothesis that in regions of incomplete ischemia, release of EAAs via VRACs may play a larger role than reversal of the GLT-1 transporter. Another potential source is through volume-regulated anion channels (VRACs). Although the molecular identity of the channel is unknown, pharmacologic agents known to block VRACs lead to reduced EAA release in vitro 7 and in vivo. 2,9,10 VRACs are also known as volume-sensitive organic anion channels (VSOACs) and, electrophysiologically, as I cl-swell channels. 11,12 In vivo work has primarily been in severely ischemic brain regions; there have been few studies on the mechanisms of EAA release in the less severely affected brain regions. We hypothesize that transporter reversal may make a decreased contribution to EAA release in less severely affected ischemic brain where energy depletion and ionic disruptions are less severe. The normal operation of these transporters in the penumbra would decrease rather than increase EAA release. We used microdialysis, in an area where cerebral blood flow (CBF) is less affected by reversible middle cerebral artery occlusion (rMCAo) to investigate the relative contributions of reversal of the glutamate transporter (GLT-1) and VRACmediated release to EAA increases by studying the effects of inhibitors of the GLT-1 transporter (dihydrokainate, DHK) and VRACs (tamoxifen) on ischemia-induced EAA increases. MethodsAll animal procedures were in accordance with the guidelines for care and use of laboratory animals and were approved by the institutional animal care and use comm...

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“…The concentration of glutamate in the cytoplasm and synaptic vesicles in neurons has been estimated by measurements of the amino acid in extracts (4). Extracellular glutamate concentrations have been measured by in vivo microdialysis techniques (5,6). However, these techniques are limited in spatial and temporal resolution and are not suitable for detecting rapid local concentration changes around single synapses.…”

mentioning

confidence: 99%

Detection of glutamate release from neurons by genetically encoded surface-displayed FRET nanosensors

Okumoto

Looger

Micheva

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

367

312

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Glutamate is the predominant excitatory neurotransmitter in the mammalian brain. Once released, its rapid removal from the synaptic cleft is critical for preventing excitotoxicity and spillover to neighboring synapses. Despite consensus on the role of glutamate in normal and disease physiology, technical issues limit our understanding of its metabolism in intact cells. To monitor glutamate levels inside and at the surface of living cells, genetically encoded nanosensors were developed. The fluorescent indicator protein for glutamate (FLIPE) consists of the glutamate͞aspartate binding protein ybeJ from Escherichia coli fused to two variants of the green fluorescent protein. Three sensors with lower affinities for glutamate were created by mutation of residues peristeric to the ybeJ binding pocket. In the presence of ligands, FLIPEs show a concentration-dependent decrease in FRET efficiency. When expressed on the surface of rat hippocampal neurons or PC12 cells, the sensors respond to extracellular glutamate with a reversible concentration-dependent decrease in FRET efficiency. Depolarization of neurons leads to a reduction in FRET efficiency corresponding to 300 nM glutamate at the cell surface. No change in FRET was observed when cells expressing sensors in the cytosol were superfused with up to 20 mM glutamate, consistent with a minimal contribution of glutamate uptake to cytosolic glutamate levels. The results demonstrate that FLIPE sensors can be used for real-time monitoring of glutamate metabolism in living cells, in tissues, or in intact organisms, providing tools for studying metabolism or for drug discovery.aspartate ͉ hippocampal neuron ͉ neurotransmitter ͉ secretion ͉ transport I n addition to being an intermediate of primary metabolism in all biological cells, glutamate serves as the major excitatory amino acid neurotransmitter in the vertebrate central nervous system (1). As such, glutamate influences essentially all forms of behavior, including consciousness, sensory perception, motor control, and mood. Changes in the strength of connectivity at glutamatergic synapses in the form of long-term potentiation and long-term depression are considered to be the cellular mechanisms underlying learning and memory (2). In addition to its role in normal nervous system physiology, glutamate is also thought to be directly involved in neurologic damage occurring in stroke and neurodegenerative disorders, including AIDS-dementia complex, motor neuron disease, and Alzheimer's and Parkinson's diseases, through receptormediated toxicity (3).Despite its prominent role in normal and disease physiology, accurate and precise measurements of glutamate in living tissue are lacking. The concentration of glutamate in the cytoplasm and synaptic vesicles in neurons has been estimated by measurements of the amino acid in extracts (4). Extracellular glutamate concentrations have been measured by in vivo microdialysis techniques (5, 6). However, these techniques are limited in spatial and temporal resolution and are not suitable ...

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A microdialysis study in rat brain of dihydrokainate, a glutamate uptake inhibitor

Cited by 24 publications

References 18 publications

Blockade of the GLT-1 Transporter in the Central Nucleus of the Amygdala Induces both Anxiety and Depressive-Like Symptoms

Blockade of the GLT-1 Transporter in the Central Nucleus of the Amygdala Induces both Anxiety and Depressive-Like Symptoms

Volume-Regulated Anion Channels Are the Predominant Contributors to Release of Excitatory Amino Acids in the Ischemic Cortical Penumbra

Detection of glutamate release from neurons by genetically encoded surface-displayed FRET nanosensors

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