Excitatory amino acids are elevated in human epileptic cerebral cortex

Abstract

We used intraoperative electrocorticography to identify and compare specimens from two groups of patients undergoing temporal lobectomy: (1) spiking cortex (12 patients)—epileptic activity recorded over much of the temporal convexity; and (2) nonspiking cortex (9 patients)—temporal convexity free of interictal spiking, epileptic activity confined to the hippocampus and/or amygdala. Comparative amino acid levels were (μmol/g protein, mean ±: SEM): glutamate—spiking 109.8 ±: 1.8, nonspiking 87.4 ±: 2.0 (p < 0.001); aspartate—spiking 15.2 ±: 0.9, nonspiking 12.2 ±: 0.5 (p < 0.05); GABA—spiking 15.0 ±: 1.0, nonspiking 13.9 ±: 1.4 (NS); taurine—spiking 14.5 ±: 0.8, nonspiking 12.2 ±: 0.8 (NS); and glycine—spiking 11.5 ±: 0.8, nonspiking 7.4 ±: 0.6 (p < 0.01). Cortical epileptic activity appears to be associated with elevated concentrations of glutamate, aspartate, and glycine, but not GABA and taurine, perhaps indicating a relative imbalance between putative excitatory and inhibitory amino acid neurotransmitters.