[Amino acids in human epileptogenic foci]

The functional status of GABA synapses together with tissue levels of other putative neurotransmitter amino acids was studied in epileptogenic foci (identified by stereo-EEG) removed neurosurgically from 14 epileptic patients unresponsive to anti-epileptic medication. L. glutamic acid decarboxylase was lower than normal in epileptogenic cortical tissue from 10 to 12 patients. 3H-GABA-"A" receptor binding was low in all epileptogenic tissue examined. GABA levels were unchanged, whereas glutamate was increased in 7 patients. These studies confirm previous observations that there is a decreased functional activity of GABA synapses in a high proportion of epileptogenic foci. Therefore these data indicate that there is indeed an imbalance between excitatory and inhibitory neurotransmitter systems.