Chronic electrode implantation entails epileptiform field potentials in rat hippocampal slices, similarly to amygdala kindling.

Evoked field potentials were recorded in the CA3, CA1 and dentate gyrus (DG) of hippocampal slices from amygdala kindled, non-stimulated amygdala electrode-implanted, and non-implanted age-matched rats to evaluate the consequences on hippocampal neuronal networks of kindling stimulation versus electrode implantation. No overt modification of field potentials was detected in either the CA1 or the DG areas. In contrast, a very significant increase in the occurrence of repetitive population spikes evoked by single stimuli was detected in the CA3 area in slices from both amygdala kindled and non-stimulated amygdala implanted rats. The epileptiform pattern of CA3 field potentials was at least as well expressed in implanted non-stimulated, as in kindled rats, suggesting that electrode implantation has a major contribution to this marker of epileptogenesis.