Impaired glutamine metabolism in NMDA receptor hypofunction induced by MK801.
Paradoxically, glutamate receptor antagonists have neurotoxic and psychotogenic properties in addition to their neuroprotective potential during excessive glutamate release. In the present study the non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist MK801 was used to examine glial-neuronal interactions in NMDA receptor hypofunction. Rats were given a subanesthetic dose of MK801 together with [1-13C]glucose and [1,2-13C]acetate, and brains were removed 20 min later. Analyses of extracts from cingulate, retrosplenial plus middle frontal cortices (CRFC) and temporal lobe were performed using HPLC and 13C and 1H nuclear magnetic resonance spectroscopy. Hypofunction of the NMDA receptor induced similar changes in both brain areas investigated; however, the changes were most pronounced in the temporal lobe. Generally, only labeling from [1-13C]glucose was affected by MK801. In CRFC and temporal lobe amounts of both labeled and unlabeled glutamine were increased, whereas those of aspartate were decreased. In the CRFC the decrease in labeling of aspartate was greater than the decrease in concentration, leading to decreased 13C enrichment. In temporal lobe, not in CRFC, increased concentrations of glutamate, GABA, succinate, glutathione and inositol were detected together with increased labeling of GABA and succinate from [1-13C]glucose. 13C Enrichment was decreased in glutamate and increased in succinate. The results point towards a disturbance in glutamate-glutamine cycling and thus interaction between neurons and glia, since labeling of glutamate and glutamine from glucose was affected differently.
Brenner
Eiliv
E
Department of Neuroscience, Norwegian University of Science and Technology (NTNU), Trondheim, Norway.
Kondziella
Daniel
D
Håberg
Asta
A
Sonnewald
Ursula
U
D000818:Animals; D001224:Aspartic Acid / Q000378:metabolism; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D002450:Cell Communication / Q000187:drug effects / Q000502:physiology; D016291:Dizocilpine Maleate / Q000494:pharmacology*; D015536:Down-Regulation / Q000187:drug effects / Q000502:physiology; D004734:Energy Metabolism / Q000187:drug effects / Q000502:physiology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005625:Frontal Lobe / Q000187:drug effects / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism*; D005973:Glutamine / Q000378:metabolism*; D005978:Glutathione / Q000378:metabolism; D007294:Inositol / Q000378:metabolism; D008297:Male; D009457:Neuroglia / Q000187:drug effects / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects / Q000378:metabolism*; D019802:Succinic Acid / Q000378:metabolism; D013702:Temporal Lobe / Q000187:drug effects / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D018691:Excitatory Amino Acid Antagonists; D016194:Receptors, N-Methyl-D-Aspartate; D005973:Glutamine; D001224:Aspartic Acid; D018698:Glutamic Acid; D007294:Inositol; D005680:gamma-Aminobutyric Acid; D016291:Dizocilpine Maleate; D019802:Succinic Acid; D005978:Glutathione; D005947:Glucose