QUANTITATIVE-ANALYSIS OF THE ELECTROCORTICOGRAM AFTER FOREBRAIN ISCHEMIA IN THE RAT

The purpose of the study was to test the hypothesis that the postischemic neuronal damage is accompanied by changes of the electrocorticogram (ECoG) of freely moving rats during long-term recovery after forebrain ischemia. Ten minutes forebrain ischemia was induced in male Wistar rats. ECoG was recorded 1 day before as well as 1 h, 1 day and 7 days after ischemia. The ECoG power was calculated and for characterizing postischemic ECoG development the percentage of preischemic ECoG power was evaluated. The awake state of the rats was considered for analysis only. Furthermore, the neuroprotective effect of phencyclidine (PCP, 5 mg/kg i.v., 15 min prior to ischemia) was demonstrated in the ECoG changes. One hour after ischemia the ECoG power of the theta (4.75-6.75 Hz), alpha (7.00-12.50 Hz) and beta (12.75-18.50 Hz) band was decreased compared with sham-operated controls and PCP did not influence these changes. However, I day after ischemia ECoG power of the saline-treated ischemic rats was completely restored and no longer different from that of the sham-operated group. PCP-treated ischemic animals showed significantly elevated ECoG power in comparison with saline-treated animals. Seven days after ischemia ECoG power of the saline-treated ischemic rats again decreased. In comparison with the ischemic controls, the ECoG activity of the PCP-treated ischemic rats was significantly higher. PCP maintained postischemic ECoG power at the non-ischemic control level. It is suggested that the decrease in the ECoG activity several days after ischemia is related to the delayed neuronal damage. PCP is known to protect neurons against this ischemic damage and, therefore, ECoG activity in PCP-treated rats is less reduced than in untreated controls.