The effects of interictal spikes on single neuron firing patterns in the hippocampus during the development of temporal lobe epilepsy

The interictal spikes (IS) are characteristic signatures of epileptic tissue, and relevant in presurgical evaluation of epilepsy. However, the mechanism and effects of IS remain unclear. In this study, we examined the relationship between IS and single neuron firing patterns, using an epileptic rat with temporal lobe epilepsy (TLE). We investigated the firing of interneurons and pyramidal cells in the CA3 region of the hippocampus. The results show that IS are associated with decreased single neuron firing rates compared with IS-free epochs. Furthermore, the paroxysmal interictal-spiking patterns are associated with sustained decrease in single neuron firing rates. We also found that IS stopped as approaching to seizures. These results demonstrate that IS might be responsible for the development of TLE and ictal events by changing the firing patterns of hippocampal neurons.