Figure 4.

Partial EFP failure associated with the glutamine synthetase inhibition is reversed by exogenous glutamine. A, Sample tracings (top) and time course of evoked field potential area (bottom) demonstrate, that after addition of GBZ/CGP to a neocortical slice preincubated with the glutamine synthetase inhibitor MSO, intermittent epileptiform field potentials are elicited at an ISI of 5 s with approximately half of the stimuli leading to polyphasic activity. Within ∼6 min after the subsequent addition of 500 μm glutamine to the perfusate, every stimulus leads to an epileptiform field potential. The percentage of stimuli leading to epileptiform field potentials for the different conditions is noted next to sample tracings. B, Paired analysis of the probability of evoking an epileptiform field potential (P_EFP) at baseline (10 min after addition of GBZ/CGP) and 15 min after the addition of 500 μm glutamine indicates the consistency of this finding (n = 7; p < 0.0001). Slices were preincubated with 5 mm MSO for 20–60 min before recording.