Induction of tolerance against traumatic brain injury by ischemic preconditioning.

We tested the hypothesis that a transient non-lethal ischemic insult lasting 2 min would protect against subsequent moderate traumatic brain injury. Sprague-Dawley rats were randomized into three experimental groups, including sham ischemia procedures and ischemic preconditioning (IPC) followed 48 h later by moderate traumatic brain injury (TBI) provoked by parasagittal fluid percussion injury (1.8-2.1 atm) and IPC followed by 48 h sham TBI. Seven days after the secondary insult, animals were perfusion-fixed for quantitative histopathological analysis. The CA3 necrotic cell count was decreased by 63% in TBI animals that had undergone IPC as compared to TBI animals that underwent sham IPC. TBI animals that had undergone IPC demonstrated significantly smaller contusion volumes than the TBI alone group (6.44 +/- 1.51 vs 1.37 +/- 0.63 mm3, mean +/- s.e.m.) These data indicate that IPC applied 2 days before moderate fluid percussion brain injury increases the brain resistance to traumatic brain damage.