Hippocampal slices from long-term streptozotocin-injected rats are prone to epileptiform responses

Evoked field potentials were recorded in the CA3, CA1 and dentate gyrus (DG) regions of hippocampal slices from rats injected with streptozotocin (STZ; 60 mg/kg i.p.), to detect whether STZ-induced diabetes entails changes in hippocampal excitability. No change in hippocampal responsiveness was observed in slices from diabetic rats, up to 3 weeks post-STZ. Repetitive population spikes (PSs) reminiscent of an epileptiform hyperexcitability were, however, recorded in CA3 > CA1 > DG areas after more than 4 weeks ('long-term') post-STZ, although the maximal amplitudes were not different in STZ-diabetic versus control rats. Intracellular recordings on CA3 pyramidal neurons confirmed that fimbrial stimulation evokes significantly more action potentials in neurons from 'long-term' STZ-diabetic versus control rats. This is the first report of the appearance of repetitive hippocampal responses, particularly in the seizure-prone CA3 area, as a long-term consequence of hyperglycemic STZ treatment in rat.