[Sequential changes in content of excitatory amino acids in the epileptic focus during seizure]

Recently much attention has been paid to excitatory amino acids in seizure susceptibility and induction. In order to examine the relationship between epilepsy, especially seizure induction, and excitatory amino acids, we examined sequential change in content of excitatory amino acids in the epileptic focus by microdialysis system in a cat amygdaloid kindling model. Fifteen crossbred adult cats divided into three groups: a sham operation group (Sh) as the control, just after stage 4 group (S4), and just after stage 6 seizure group (S6). Under halothane anesthesia, Microdialysis probe was inserted to the kindled focus, the right amygdala, and glutamate and aspartate contents of extracellular fluid were measured from 15 minutes prior to 30 minutes after seizure by high performance liquid chromatography (HPLC). The probe was perfused with artificial cerebrospinal fluid at a flow rate of 2 microliters/min for 5 minutes. Before seizure, glutamate and aspartate concentration showed no significant changes in the S4 and S6 group compared with the Sh group. But after seizure, glutamate concentration was significantly higher in the S4 and S6 group temporally, while aspartate concentration was higher only in the S6 group temporally. Based on the results that the release of glutamate and aspartate do not change in seizure susceptibility, that glutamate is released in partial seizure, and that glutamate and aspartate are released in generalized seizure from the epileptic focus, excitatory amino acids are involved in seizure induction in a cat amygdaloid kindling.