Hippocampal CA1 evoked response and radial 8-arm maze performance after hippocampal kindling.

Rats with chronically implanted electrodes in the hippocampal CA1 region were trained in the open radial 8-arm maze and then subjected to kindling (afterdischarges, ADs) or 0.17 Hz low-frequency stimulations (LFSs) as controls. Partial kindling (21 ADs) induced a general increase of AD threshold but no motor convulsions. The commissurally evoked average evoked potentials (AEPs) in CA1 were enhanced above the pre-AD baseline or the AEPs in LFS control rats at 1 day after the 1st, 6th, 11th and 16th AD and for at least 25 days after 21 ADs. Similarly, maze performance was significantly worse in kindled than LFS rats for about 4 weeks after 21 ADs/LFSs. The study confirms the long-lasting behavioral effect of partial kindling and suggests that synaptic enhancement may underlie the behavioral disruption.