Somatosensory evoked potentials in cerebral ischemia of rabbits

Twenty-one rabbits were used in the ischemic group and six in the control group. Cerebral ischemia of variable degree was induced by Fe particle injection method. Somatosensory evoked potentials (SEPs) and cerebral blood flow (CBF) were compared when the CBF levels decreased to their minimum. The latency of the SEPs increased along with the decrease of the CBF when it was lower than 20 ml/100 g/min (68% of the pre-ischemic control level). This may be related to the ischemic change of the white matter. The amplitude showed diphasic changes. When the CBF decreased below 20 ml/100 g/min, the amplitude increased; when the CBF was lower than 11 ml/100 g/min (38% of the pre-ischemic level), it decreased. These results indicate that the functions of the cerebral cortex might be excited in mild ischemia, and be suppressed in severe ischemia.