Spreading Depression and Epileptic Activity in Living Human Neocortical Tissues

The close kinship between spreading depression (SD) and experimental epileptic activity has stimulated extensive investigation into the mutual relationship of these two phenomena. Despite the many studies into the simultaneous occurrence of SD and epileptiform burst discharges in animal neuronal tissues, the interaction of these phenomena in human neuronal tissues is not clear. Therefore, the effect of SD on the bioelectrical activity of human neocortical tissues was tested in neocortical slice preparations from 15 patients who underwent surgery for the treatment of refractory epilepsy. Synchronous rhythmic sharp field potentials appeared spontaneously in 12 slices obtained from 8 patients. SD significantly enhanced the repetition rate and amplitude of these rhythmic potentials in all tested slices. In 4 slices obtained from one patient suffering from partial seizure with aura, induction of SD elicited ictal-form epileptic activity. In 16 slices obtained from another 6 patients SD did not change the bioelectrical activity. However, initiation of SD after superfusion with gamma-aminobutyric acid (GABAA) receptor antagonist bicuculline (5 microM) for 60min induced ictal-form epileptic activity in all tested slices. The results indicate that SD may increase the neuronal excitability in human brain tissue and trigger the seizure attacks in some epileptic patients.