Neuroglial metabolism in the awake rat brain: CO2 fixation increases with brain activity.

Details

Serval ID
serval:BIB_1F8CFEEF785E
Type
Article: article from journal or magazin.
Collection
Publications
Title
Neuroglial metabolism in the awake rat brain: CO2 fixation increases with brain activity.
Journal
Journal of Neuroscience
Author(s)
Oz G., Berkich D.A., Henry P.G., Xu Y., LaNoue K., Hutson S.M., Gruetter R.
ISSN
1529-2401 (Electronic)
ISSN-L
0270-6474
Publication state
Published
Issued date
2004
Volume
24
Number
50
Pages
11273-11279
Language
english
Notes
Publication types: Journal Article ; Research Support, N.I.H., Extramural ; Research Support, Non-U.S. Gov't ; Research Support, U.S. Gov't, Non-P.H.S. ; Research Support, U.S. Gov't, P.H.S.Publication Status: ppublish
Abstract
Glial cells are thought to supply energy for neurotransmission by increasing nonoxidative glycolysis; however, oxidative metabolism in glia may also contribute to increased brain activity. To study glial contribution to cerebral energy metabolism in the unanesthetized state, we measured neuronal and glial metabolic fluxes in the awake rat brain by using a double isotopic-labeling technique and a two-compartment mathematical model of neurotransmitter metabolism. Rats (n = 23) were infused simultaneously with 14C-bicarbonate and [1-13C]glucose for up to 1 hr. The 14C and 13C labeling of glutamate, glutamine, and aspartate was measured at five time points in tissue extracts using scintillation counting and 13C nuclear magnetic resonance of the chromatographically separated amino acids. The isotopic 13C enrichment of glutamate and glutamine was different, suggesting significant rates of glial metabolism compared with the glutamate-glutamine cycle. Modeling the 13C-labeling time courses alone and with 14C confirmed significant glial TCA cycle activity (V(PDH)((g)), approximately 0.5 micromol x gm(-1) x min(-1)) relative to the glutamate-glutamine cycle (V(NT)) (approximately 0.5-0.6 micromol x gm(-1) x min(-1)). The glial TCA cycle rate was approximately 30% of total TCA cycle activity. A high pyruvate carboxylase rate (V(PC), approximately 0.14-0.18 micromol x gm(-1) x min(-1)) contributed to the glial TCA cycle flux. This anaplerotic rate in the awake rat brain was severalfold higher than under deep pentobarbital anesthesia, measured previously in our laboratory using the same 13C-labeling technique. We postulate that the high rate of anaplerosis in awake brain is linked to brain activity by maintaining glial glutamine concentrations during increased neurotransmission.
Keywords
Adenosine Triphosphate/biosynthesis, Animals, Aspartic Acid/metabolism, Brain/metabolism, Carbon Dioxide/metabolism, Carbon Isotopes/diagnostic use, Carbon Radioisotopes/diagnostic use, Energy Metabolism/physiology, Glucose/metabolism, Glutamic Acid/metabolism, Glutamine/metabolism, Male, Models, Biological, Neuroglia/metabolism, Neurons/metabolism, Oxidation-Reduction, Rats, Rats, Sprague-Dawley, Wakefulness/physiology
Pubmed
Web of science
Open Access
Yes
Create date
04/08/2010 15:28
Last modification date
20/08/2019 12:55
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