Electro-cortical signs of early neuronal damage following transient global cerebral ischemia in rat

During recovery after a transient global cerebral ischemia (TGCI), rat electrocorticogam (ECoG) shows epochs of synchronized activity (SA) alternating with epochs of low amplitude background activity (BA). The aim of this study was to compare the changes in these electrical activities during a 30-min recovery period that followed either a non-injuring (3 minutes, N=10) or an injuring (10 minutes, N=10) TGCI. During TGCI there was a 3 fold reduction n amplitudes of both SA and BA but no changes in frequency. During reperfusion following a 3 minutes TGCI, the amplitudes of both SA and BA recovered to about 70%. During the reperfusion that followed a 10 minutes TGCI, BA showed no recovery, whereas SA recovered to about 40%. During the 30 min reperfusion, there was a time-dependent decrease in the frequency of SA, but independent on the duration of TGCI. In contrast, the frequency of the BA did not change during reperfusion. Our data indicate that following cerebral ischemia the recovery of SA cm take place independently of BA. The lack of recovery in BA may indicate early subcortical neuronal damage.