Longitudinal changes of brain amino acid content occurring before, during and after epileptic activity.

In cats affected with cortical epileptogenic foci induced by penicillin application to and cobalt implantation into the pericruciate area, the brain amino acids contents were determined in the focus as well as in extrafocal areas. In different groups of animals, brain removal for biochemical determinations was performed at different times before, during and after epilepsy and the values compared to controls. The only amino acid to show a significant change before appearance of spikes in both types of epilepsy was taurine, which decreased. Cobalt epilepsy was accompanied by changes in a larger number of amino acids than penicillin epilepsy: in the former the brain content of taurine, GABA, aspartate, glutamate, serine, threonine, glycine and alanine was altered. The changes were proportional to the severity of epilepsy and more prominent in the focus area. After disappearance of spikes the levels of most amino acids returned to normal except for some amino acids, previously unaffected by penicillin epilepsy, which were decreased. It is proposed that the decrease in brain taurine, occurring before the appearance of penicillin and cobalt epilepsy, could increase the excitability of a certain neuronal population and thus, by potentiating the effects on neurons of penicillin and cobalt, contribute to the initiation of epilepsy.