The primary objective of this proposal is to assess the efficacy and mechanism of action of clinically relevant neuronal protective pharmacotherapies aimed at preventing disturbances in calcium activated enzyme systems after reversible cerebral ischemia. Despite promising results in animal stroke models there is still no clinically proven effective therapy for acute stroke, the third most common cause of death in the U.S. This dilemma may be explained in part by a poor correlation between the design of preclinical and clinical efficacy studies. In this proposal, we hope to reconcile some of these differences by trying as much as possible to model important components of clinical stroke, in particular reperfusion, its occurrence, timing, and consequences. In order to carry out this work, we have developed a particularly rigorous and clinically relevant model of stroke in rats, and determined the temporal thresholds before which neuronal protective therapies must be started to be effective. We will address the first specific aim by establishing a duration of ischemia vs severity of damage """"""""dose-response"""""""" curve and s ee if it can be shifted favorably by therapy. Both histologic and functional outcome will be measured. We will address the second specific aim by producing a severe and predictable amount of edema during reperfusion and see if it can be limited by therapy. The therapies we will evaluate are based on preliminary data indicating efficacy at doses tolerated in man, and a mechanism of action thought to ameliorate disturbances in calcium metabolism by impacting specific steps in the cascade of post-ischemic glutamate excitotoxicity. The proposed work should help identify pharmacotherapies and therapeutic strategies most likely to lead to success in clinical trials for hyperacute stroke. The second major objective of this work is to explore the relationship of Cam-K-II to ischemic injury. Cam-K-II is the most abundant protein kinase in the brain, and is activated by increases in intracellular calcium after ischemia caused, in part, by increased extracellular glutamate and activation of the NMDA receptor. We have shown that persistent downregulation of Cam-K-II activity due to enzyme translocation is associated with irreversible neuronal damage. We will study the nature and reversibility of this translocation which may lead to new strategies for neuronal protective intervention.
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