Effects of repeated short versus single long episodes of focal ischemia on somatosensory evoked potentials and development of cerebral infarction in cats.

The effects of repeated short episodes of focal ischemia at 30-minute intervals or a single equivalent long episode of focal ischemia on neuronal function and development of cerebral infarction were compared using somatosensory evoked potential (SEP) recording and 2,3,5-triphenyltetrazolium chloride staining in a cat model. Seventeen cats underwent transorbital occlusion of the middle cerebral artery (MCA), using one of three procedures: sham-operation; single 1-hour occlusion of the MCA, followed by 3 hours of recirculation; or three 20-minute occlusions of the MCA at 30-minute intervals, followed by 3 hours of recirculation. Two of six cats in the single long-term occlusion group showed recovery of SEP, whereas all six cats in the repeated short-term occlusion group showed recovery of SEP at 3 hours after recirculation. All six cats in the single long-term occlusion group had cerebral infarction of various sizes, but only one cat in the repeated short-term occlusion group developed infarction. Repeated short episodes of focal ischemia are relatively less damaging than a single equivalent long episode of focal ischemia, even if the reperfusion interval is extended to 30 minutes.