Neuroprotective Effect of Focal Ischemic Preconditioning in Transient Focal Ischemia Animal Model

ABSTRACT

BACKGROUND: The term 'ischemic preconditioning', which implies the first, brief, sublethal ischemia before the next ischemia, is widely accepted to have protective effect in the myocardium, and recently with a specified circumstances, in the brain also. However, the existence of this 'ischemic tolerance' phenomenon is not yet clarified in the repeated transient focal cerebral ischemia model. This study was performed to test whether the ischemic preconditiong has protective effect also in this TIA-mimicking condition. METHODS: Using intraluminar suture technique, initial transient focal ischemia was maintained for 30 minutes in the rat brain. After this ischemic preconditioning, second ischemia of 120 minutes duration was performed using the same method at 1, 3, 5, and 7 days after the 1st ischemia (n=20). The resulting brain infarct volume was assessed and compared to that of previously sham-operated paired controls(n=20). RESULTS: Using the infarct volume as parameters, there was no significant difference between the ischemia and control group in all pairs. But when the percent of infarct volume compared to the hemispheric volume was used instead, neocortical infarct percent was significantly smaller at day 3 after preconditiong (p<0.05). But such difference was not found at 1, 5, and 7th day in the neocotex. Neither the percent of total infarct nor the subcortical infarct showed any statistical difference. CONCLUSION: It could be concluded that transient focal cerebral ischemic preconditioning have neuroprotective effect. The optimal interval between ischemia for this 'ischemic tolerance' to happen is 3 days, and this phenomenon seems to be the function of cerebral cortex, but not the subcortex.