TEMPORAL CHANGES IN PROTON MRS METABOLITES AFTER KAINIC ACID-INDUCED SEIZURES IN RAT-BRAIN

Purpose: In situ H-1-magnetic resonance spectroscopy (MRS) was used to study temporal metabolic changes in a rat model of temporal lobe epil epsy (TLE) by using kainic acid (KA). Methods: Rat brains were scanned at the level of the hippocampal body for MRS measurements. Relative r atios of N-acetyl groups (NA: N-acetylaspartate and N-acetylaspartyl g lutamate), choline, and lactate (Lac) over creatine (Cr) were calculat ed. Results: NA/Cr ratios increased significantly during the ictal pha se. During the postictal and interictal phases, the NA/Cr ratio decrea sed. There was a significant and prolonged increase of the lactate/Cr ratio in the hippocampi of rats that started 1 h after the onset of KA -induced seizure activity and persisted up to 24 h after the injection . The prolonged lactate/Cr increase in an area susceptible to neuronal damage (e.g., hippocampus) correlated with the onset of seizure activ ity but remained elevated thereafter. Conclusions: The ictal and early postictal increase in lactate ratios may reflect increased cellular a ctivity and metabolism resulting from KA excitotoxicity. Assuming that the changes in NA/Cr ratios are due to NAA increase, we speculate tha t an activation of the N-acetylaspartylglutamate (NAAG) dipeptidase pa thway may explain the ictal increase in NA/Cr ratios. The late postict al decrease in NA/Cr ratios is a reflection of KA-induced neuronal cel l loss.