Energy metabolism in the rat cortex under thiopental anaesthesia measured In Vivo by 13C MRS. Issue 11 (19th March 2017)

• Record Type: Journal Article
• Authors: Sonnay, Sarah; Duarte, João M. N.; Just, Nathalie; Gruetter, Rolf
• Other Names: Schousboe Arne guestEditor.; Yu Albert C. H. guestEditor.; McKenna Mary C. guestEditor.
• Is Part Of: Journal of neuroscience research. Volume 95:Issue 11(2017)
• Page Start: 2297
• Page End: 2306
• Publication Date: 2017-03-19
• Subjects: glucose -- metabolism -- MRS -- thiopental -- α‐chloralose -- neuron‐glia interaction; Neurobiology -- Periodicals; 612
• DOI: 10.1002/jnr.24032
• Languages: English
• ISSNs: 0360-4012

Abstract

Abstract : Barbiturates, commonly used as general anaesthetics, depress neuronal activity and thus cerebral metabolism. Moreover, they are likely to disrupt the metabolic support of astrocytes to neurons, as well as the uptake of nutrients from circulation. By employing 13 C magnetic resonance spectroscopy (MRS) in vivo at high magnetic field, we characterized neuronal and astrocytic pathways of energy metabolism in the rat cortex under thiopental anaesthesia. The neuronal tricarboxylic acid (TCA) cycle rate was 0.46 ± 0.02 µmol/g/min, and the rate of the glutamate‐glutamine cycle was 0.09 ± 0.02 µmol/g/min. In astrocytes, the TCA cycle rate was 0.16 ± 0.02 µmol/g/min, accounting for a quarter of whole brain glucose oxidation, pyruvate carboxylase rate was 0.02 ± 0.01 µmol/g/min, and glutamine synthetase was 0.12 ± 0.01 µmol/g/min. Relative to previous experiments under light α‐chloralose anaesthesia, thiopental reduced oxidative metabolism in neurons and even more so in astrocytes. Interestingly, total oxidative metabolism in the cortex under thiopental anaesthesia surpassed the rate of pyruvate production by glycolysis, indicating substantial utilisation of substrates other than glucose, likely plasma lactate. © 2017 Wiley Periodicals, Inc. Abstract : By quantifying neuronal and glial oxidative metabolism in the living brain under thiopental anaesthesia, we verified a general metabolic depression and further identified that there is an alteration of the relative fraction of glucose oxidation in each cell type. This is relative to experiments under other anaesthesia protocols and that substrates, other than glucose, are substantially used as source of pyruvate for oxidative metabolism.