Figure 5.

Epileptiform-like activity is synchronous within the whole hippocampus and is blocked by TTX. A, Extracellular recording from four different electrodes positioned in the CA1 and CA3 pyramidal cell layers as shown in the inset [left, CA1 proximal (CA1 prox); CA1 distal (CA1 dist)]. The electrodes were separated by >150 μm. Inset, Right, A typical ictal-like event seen at an expanded timescale reveals synchronization of neuronal activity in the whole hippocampus. B, Average values of the delay between the onset of the signal in the electrode positioned in the CA3b region and the ones positioned in the other areas of the hippocampus (n = 9). C, Ictal-like activity is blocked by TTX. D, Normalized histograms for the signals recorded from CA1 distal (top) and CA3c (bottom) under control conditions (gray), 0 Mg²⁺ and picrotoxin (picro; black), and 0 Mg²⁺, picrotoxin, and TTX (gray; picrotoxin at 100 μm, TTX at 1 μm). E, F, Same as in C and D for a representative experiment showing interictal-like activity. G, Average frequency of ictal-like (n = 8) and interictal-like (n = 3) events in control conditions, in the presence of picrotoxin and 0 extracellular Mg²⁺, and in the presence of picrotoxin, 0 extracellular Mg²⁺, and TTX (1 μm).