Figure 2.

Total concentrations and percentage of ¹³C enrichment of glutamate, glutamine, and γ-aminobutyric acid (GABA), as measured by ¹H and ¹³C magnetic resonance spectroscopy (MRS). Total concentrations (μmol/g tissue) of glutamate, glutamine, and GABA, and their percentage of ¹³C enrichment, as measured by ¹H and ¹³C MRS. The MRS analyses were performed on brain extracts of the hippocampal formation, entorhinal/piriform cortex, and neocortex from animals injected with [1-¹³C]glucose and [1,2-¹³C]acetate 15 minutes before decapitation. The experimental groups comprised animals injected with either saline (controls; white bars) or kainate (KA; gray bars) 2 weeks earlier. Sample sizes for ¹³C and ¹H MRS, respectively: controls n=8 and 9, KA n=9 and 11 (hippocampal formation); controls n=3, KA n=8 and 11 (entorhinal/piriform cortex); and controls n=8 and 10, KA n=6 (neocortex). The labeling in [4-¹³C]glutamate, [4-¹³C]glutamine, and [2-¹³C]GABA mostly derives from neuronal metabolism of [1-¹³C]glucose, the labeling in [4,5-¹³C]glutamate, [4,5-¹³C]glutamine, and [1,2-¹³C]GABA exclusively derives from the metabolism of [1,2-¹³C]acetate in astrocytes. %, Enrichment is expressed as percentage of ¹³C-label measured by ¹³C MRS (nmol/g tissue) relative to the total concentration measured by ¹H MRS, signifying turnover of the metabolite. Values are given as mean±standard deviation. ^*Significantly different from control group using Student's t-test, P<0.05.