Fig. 2. Application of 4-AP in a solution containing 1.6 mM Mg²⁺ and 2.0 mM Ca²⁺ induced ictal-like epileptiform activity in entorhinal cortex which did not persist after washing out the 4-AP.

4-AP (100 μM) caused ictal-like activity in the entorhinal cortex in 1.6 mM Mg²⁺/2.0 mM Ca²⁺ solution in 10 of 22 slices; however, the ictal-like activity did not persist upon washout of the 4-AP (n = 5 of 5). A: In this slice the ictal-like activity was replaced with interictal-like activity at approximately 12 min of 4-AP washout. Trace filtered after digitization using a 0.5 Hz high-pass RC filter. B: Expanded traces from early (a) and late (b) in the washout showing an ictal-like event from point a in A and interictal-like events from point b in A. Traces in B were not filtered after digitization. C: Summary of 5 slices which had ictal-like activity in 4-AP, comparing percent time spent in ictal-like activity before and after 4-AP washout (Wilcoxon).