A GABA-EEG Test of the Blood-Brain Barrier near Epileptic Foci

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Abstract
The permeability of the blood-brain barrier (BBB) to y-aminobutyric acid (GABA) in the region of an epileptic focus may be assessed by infusing GABA and measuring a change in epileptic spike activity on the EEG. GABA does not cross the normal BBB but will suppress epileptic spike activity when it does cross where the BBB is damaged. 9 alumina-cobalt experimental epileptic foci were all initially suppressible, but 7 then became unsuppressible. When the foci were irradiated to lower the BBB, all 7 be-came temporarily suppressible. The experiments demonstrate that (1) epileptic foci can be equally active both with the BBB ''open'' and ''closed''; (2) the intravenous GABA-EEG test can detect whether the BBB near the epileptic focus is open to GABA, and (3) anatomie tests of BBB integrity (in these experiments intravenous trypan blue) cannot deter-mine if whether BBB near the focus is ''open'' to GABA. Since the intravenous GABA-EEG test reveals the permeability of the BBB in the immediate environment of the epileptic focus, it may be very useful in the selection of a susceptible therapeutic group for inhibitory amino acid therapy.