Direct demonstration by [13C]NMR spectroscopy that glutamine from astrocytes is a precursor for GABA synthesis in neurons

Sonnewald, Ursula; Westergaard, Niels; Schousboe, Arne; Svendsen, John S.; Unsgård, G.; Petersen, Steffen B.

doi:10.1016/0197-0186(93)90064-c

Cited by 227 publications

(242 citation statements)

References 35 publications

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“…Seizure severity was graded according to a modified Racine scale. 4,14 Fifteen minutes after kainate injection, the mice were injected intraperitoneally with a combination of [1-13 C]glucose (543 mg/kg) and [1,[2][3][4][5][6][7][8][9][10][11][12][13] C]acetate (504 mg/kg) and after another 15 minutes, the brains of the mice were subjected to microwave fixation at 4 kW for 1.7 seconds (model GA5013, Gerling Applied Engineering, Modesto, CA, USA). This is the most humane euthanization method instantly inactivating proteins in the brain.…”

Section: Metabolic Studiesmentioning

confidence: 99%

“…For proton decoupled 13 C-NMR spectra of cortical extracts, a 301 pulse angle and 30 kHz spectral width with 64 K data points were employed. An acquisition time of 1.08 seconds and a relaxation delay of 0.5 seconds were used and the number of scans needed to obtain an appropriate signal-tonoise ratio was typically 30,000.…”

Section: Nuclear Magnetic Resonance Spectroscopymentioning

confidence: 99%

“…Factors for the nuclear Overhauser and relaxation effects, obtained from several sets of spectra, i.e., one set obtained with decoupling, NOE, and short repetition time (the parameters used for all samples) and another set with 1 H decoupling, no NOE, and 20 seconds delay time to allow for full relaxation of the relevant peaks, were applied to all 13 C spectra. Singlets obtained in the 13 C spectrum were corrected for naturally abundant 13 C and amounts calculated from 1 H spectra were corrected for 13 C containing metabolites and number of protons. 13 [4,[5][6][7][8][9][10][11][12][13] C]a-ketoglutarate is in rapid equilibrium with [4,[5][6][7][8][9][10][11][12][13] C]glutamate, which is a precursor for [4,[5][6][7][8][9][10][11][12][13] C]glutamine.…”

Section: Nuclear Magnetic Resonance Spectroscopymentioning

confidence: 99%

“…The onset of seizure activity was investigated using a subconvulsive and a convulsive dose of kainate and brain metabolism was mapped 15 minutes after kainate treatment by injecting the mice with a combination of [1-13 C]glucose and the astrocyte-specific substrate [1,2-13 C]acetate. 13 Subsequently, changes in the metabolic pathways were revealed by nuclear magnetic resonance (NMR) spectroscopic analyses of cortical tissue extracts. …”

Section: Introductionmentioning

confidence: 99%

“…A combination of [1,2-13 C]acetate and [1-13 C]glucose was injected and subsequent nuclear magnetic resonance spectroscopy of cortical extracts was employed to distinctively map astrocytic and neuronal metabolism. The subconvulsive dose of kainate led to an instantaneous increase in the cortical lactate content, a subsequent reduction in the amount of [4,[5][6][7][8][9][10][11][12][13] C]glutamine and an increase in the calculated astrocytic TCA cycle activity. In contrast, the convulsive dose led to decrements in the cortical content and 13 C labeling of glutamate, glutamine, GABA, and aspartate.…”

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confidence: 98%

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A Subconvulsive Dose of Kainate Selectively Compromises Astrocytic Metabolism in the Mouse Brain In Vivo

Walls

Eyjolfsson

Schousboe

et al. 2014

J Cereb Blood Flow Metab

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Despite the well-established use of kainate as a model for seizure activity and temporal lobe epilepsy, most studies have been performed at doses giving rise to general limbic seizures and have mainly focused on neuronal function. Little is known about the effect of lower doses of kainate on cerebral metabolism and particularly that associated with astrocytes. We investigated astrocytic and neuronal metabolism in the cerebral cortex of adult mice after treatment with saline (controls), a subconvulsive or a mildly convulsive dose of kainate. A combination of [1,2-13 C]acetate and [1-13 C]glucose was injected and subsequent nuclear magnetic resonance spectroscopy of cortical extracts was employed to distinctively map astrocytic and neuronal metabolism. The subconvulsive dose of kainate led to an instantaneous increase in the cortical lactate content, a subsequent reduction in the amount of [4,[5][6][7][8][9][10][11][12][13] C]glutamine and an increase in the calculated astrocytic TCA cycle activity. In contrast, the convulsive dose led to decrements in the cortical content and 13 C labeling of glutamate, glutamine, GABA, and aspartate. Evidence is provided that astrocytic metabolism is affected by a subconvulsive dose of kainate, whereas a higher dose is required to affect neuronal metabolism. The cerebral glycogen content was dose-dependently reduced by kainate supporting a role for glycogen during seizure activity.

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Section: Metabolic Studiesmentioning

confidence: 99%

Section: Nuclear Magnetic Resonance Spectroscopymentioning

confidence: 99%

Section: Nuclear Magnetic Resonance Spectroscopymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 98%

See 3 more Smart Citations

A Subconvulsive Dose of Kainate Selectively Compromises Astrocytic Metabolism in the Mouse Brain In Vivo

Walls

Eyjolfsson

Schousboe

et al. 2014

J Cereb Blood Flow Metab

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Synthesis of vesicular GABA from glutamine involves TCA cycle metabolism in neocortical neurons

Waagepetersen¹,

Sonnewald

Larsson³

et al. 1999

J. Neurosci. Res.

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In contrast to the classic concept of direct conversion of glutamine to gamma-aminobutyric acid (GABA; via glutamate), this process may involve alpha-ketoglutarate as an intermediary metabolite and tricarboxylic acid (TCA) cycle activity. To obtain information about a possible differential role of these pathways for the synthesis of cytosolic and vesicular GABA, cultured neocortical neurons were incubated in medium containing [U-(13)C]glucose (0.5 mM) and in some cases unlabeled glutamine (0.5 mM). Subsequently, the cells were "superfused" for investigation of the effect of depolarization by 55 mM K+. To make sure that depolarization by 55 mM K+ released only vesicular GABA, tiagabin, a nontransportable inhibitor of the plasma membrane GABA carriers, was included in the medium to prevent GABA release from the cytoplasmic pool by reversal of the carriers. The importance of the TCA cycle for conversion of the carbon skeleton of glutamine to GABA was evident from the effect of glutamine on the labeling pattern of GABA. Percentage of labeling by GABA released into the depolarizing medium was the same as that in the corresponding cell extracts and was unaffected by the presence of glutamine during incubation. Despite the existence of multiple forms of glutamate decarboxylase, compartmentation of glutamate pools, and functionally different compartments within neurons, there appears to be full equilibration between the vesicular and cytosolic pools of GABA. However, during depolarization, the newly synthesized pool of GABA from glutamine does not rapidly equilibrate with the vesicular pool.

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Evaluation of the importance of transamination versus deamination in astrocytic metabolism of [U-13C] glutamate

Westergaard¹,

Drejer²,

Schousboe³

et al. 1996

Glia

104

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Direct demonstration by [13C]NMR spectroscopy that glutamine from astrocytes is a precursor for GABA synthesis in neurons

Cited by 227 publications

References 35 publications

A Subconvulsive Dose of Kainate Selectively Compromises Astrocytic Metabolism in the Mouse Brain In Vivo

A Subconvulsive Dose of Kainate Selectively Compromises Astrocytic Metabolism in the Mouse Brain In Vivo

Synthesis of vesicular GABA from glutamine involves TCA cycle metabolism in neocortical neurons

Evaluation of the importance of transamination versus deamination in astrocytic metabolism of [U-13C] glutamate

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