Bilateral seizure-related changes of extracellular glutamate concentration in hippocampi during development of amygdaloid kindling.

To monitor the seizure-related changes of extracellular hippocampal glutamate (Glu) concentration during the development of amygdaloid kindling, we used brain dialysates and an enzymatic cycling technique for Glu determination with a highly sensitive assay and high time resolution (1 min). The extracellular Glu level was transiently (for 3 min) enhanced after stimulus and returned rapidly to baseline. In partially kindled rats (stage 3), the extracellular Glu level during the first minute post stimulus was 2.5-3.5-fold that of baseline, while fully kindled rats exhibited about a 5-fold increase in Glu level. Amygdaloid kindling is accompanied by a progressive, transient, stimulus-induced enhancement of extracellular Glu levels during the first minute post stimulus in both hippocampi.