Ex vivo analysis of lactate and glucose metabolism in the rat brain under different states of depressed activity.
Brain metabolism of glucose and lactate was analyzed by ex vivo NMR spectroscopy in rats presenting different cerebral activities induced after the administration of pentobarbital, alpha-chloralose, or morphine. The animals were infused with a solution of either [1-(13)C]glucose plus lactate or glucose plus [3-(13)C]lactate for 20 min. Brain metabolite contents and enrichments were determined from analyses of brain tissue perchloric acid extracts according to their post-mortem evolution kinetics. When amino acid enrichments were compared, both the brain metabolic activity and the contribution of blood glucose relative to that of blood lactate to brain metabolism were linked with cerebral activity. The data also indicated the production in the brain of lactate from glycolysis in a compartment other than the neurons, presumably the astrocytes, and its subsequent oxidative metabolism in neurons. Therefore, a brain electrical activity-dependent increase in the relative contribution of blood glucose to brain metabolism occurred via the increase in the metabolism of lactate generated from brain glycolysis at the expense of that of blood lactate. This result strengthens the hypothesis that brain lactate is involved in the coupling between neuronal activation and metabolism.
Serres
Sébastien
S
Unité de Résonance Magnétique des Systèmes Biologiques, Unité Mixte de Recherche 5536, CNRS-Université Victor Segalen, 146 Rue Léo-Saignat, 33076 Bordeaux, France.
Bezancon
Eric
E
Franconi
Jean-Michel
JM
Merle
Michel
M
D000409:Alanine / Q000737:chemistry / Q000378:metabolism; D000701:Analgesics, Opioid / Q000494:pharmacology; D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D001923:Brain Chemistry; D002545:Brain Ischemia / Q000378:metabolism; D002560:Cerebrovascular Circulation; D002698:Chloralose / Q000494:pharmacology; D005260:Female; D005947:Glucose / Q000378:metabolism*; D006993:Hypnotics and Sedatives / Q000494:pharmacology; D019344:Lactic Acid / Q000378:metabolism*; D009020:Morphine / Q000494:pharmacology; D019906:Nuclear Magnetic Resonance, Biomolecular; D010424:Pentobarbital / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D014020:Tissue Extracts / Q000737:chemistry / Q000378:metabolism
D000701:Analgesics, Opioid; D006993:Hypnotics and Sedatives; D014020:Tissue Extracts; D002698:Chloralose; D019344:Lactic Acid; D009020:Morphine; D010424:Pentobarbital; D005947:Glucose; D000409:Alanine