Sustained neuronal activation raises oxidative metabolism to a new steady-state level: evidence from 1H NMR spectroscopy in the human visual cortex.
To date, functional 1H NMR spectroscopy has been utilized to report the time courses of few metabolites, primarily lactate. Benefiting from the sensitivity offered by ultra-high magnetic field (7 T), the concentrations of 17 metabolites were measured in the human visual cortex during two paradigms of visual stimulation lasting 5.3 and 10.6 mins. Significant concentration changes of approximately 0.2 micromol/g were observed for several metabolites: lactate increased by 23%+/-5% (P<0.0005), glutamate increased by 3%+/-1% (P<0.01), whereas aspartate decreased by 15%+/-6% (P<0.05). Glucose concentration also manifested a tendency to decrease during activation periods. The lactate concentration reached the new steady-state level within the first minute of activation and came back to baseline only after the stimulus ended. The changes of the concentration of metabolites implied a rise in oxidative metabolism to a new steady-state level during activation and indicated that amino-acid homeostasis is affected by physiological stimulation, likely because of an increased flux through the malate-aspartate shuttle.
Mangia
Silvia
S
Department of Radiology, Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota 55455, USA. mangia@cmrr.umn.edu
Tkác
Ivan
I
Gruetter
Rolf
R
Van de Moortele
Pierre-Francois
PF
Maraviglia
Bruno
B
Uğurbil
Kâmil
K
D000328:Adult; D000596:Amino Acids / Q000378:metabolism; D001224:Aspartic Acid / Q000378:metabolism; D005260:Female; D006801:Humans; D019344:Lactic Acid / Q000378:metabolism; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D008293:Malates / Q000378:metabolism; D008297:Male; D009474:Neurons / Q000378:metabolism* / Q000502:physiology*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000097:blood; D014793:Visual Cortex / Q000378:metabolism* / Q000502:physiology*
D000596:Amino Acids; D008293:Malates; D001224:Aspartic Acid; D019344:Lactic Acid; D010100:Oxygen