Amino acid neurotransmitter metabolism in neurones and glia following kainate injection in rats

Limbic seizure was induced in rats by intraperitoneal injection of the glut amate receptor agonist kainic acid. After 14 days [1-C-13]glucose and [1,2- C-13]acetate were injected subcutaneously and the rats killed 15 min later. Analysis of brain extracts was performed using C-13-magnetic resonance spe ctroscopy and high performance liquid chromatography. No significant differ ences between the two groups of rats were found for label concentration in blood or total metabolite tissue levels. Only astrocytes are able to utiliz e acetate as a substrate, whereas glucose is thought to be metabolized pred ominantly in the neuronal tricarboxylic acid cycle. Thus information about neuronal and astrocytic metabolism could be obtained in the same animal. A significant increase in label derived from [1-C-13]glucose was observed in metabolites such as glutamate, gamma-aminobutyric acid, aspartate, and succ inate (all of which are mainly labelled in neurones). The increased labelli ng of glutamine in epileptic rats might be due to transfer of labelled glut amate from neurones to astrocytes. Astrocytic metabolism of acetate and tra nsfer of glutamine to neurones were not affected. The results suggest that increased neuronal activity 2 weeks following epileptic seizures produces i ncreased amino acid turnover in neurones. Changes in astrocytic metabolism were not detected. (C) 2000 Elsevier Science Ireland Ltd. All rights reserv ed.