Hypoxic-ischemic encephalopathy sustained in early postnatal life may result in permanent epileptic activity and an altered cortical convulsive threshold in rat.

The aim of this study was to investigate whether the rat cerebral cortex, damaged by hypoxia-ischemia in early postnatal life, would show an increased seizure susceptibility and/or spontaneous epileptic discharges in adulthood. To that end 12-13-day-old Wistar rat pups were unilaterally exposed to hypoxic-ischemic conditions. After a recovery period of about 2.5 months, recording and stimulation electrodes were permanently implanted over the left and right fronto-parietal neocortex. Long-term recording of baseline electrocortical activity showed that only those animals that had incurred severe brain damage, as was reflected by the presence of a cortical infarction, ran a high risk of developing permanent epileptic activity. With the aid of the stimulation electrodes the initial threshold for localized seizure activity was found to be the same for the experimental and non-treated groups. However, when the kindling-like decline of this threshold was assessed by repeated testing over a 2-week period, the infarcted animals tended to a more rapid decline but a higher stabilization level than the non-infarcted and control animals.