Cerebal Ischemia During Anesthesia and Surgery

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DESCRIPTION (Verbatim from the applicant's abstract) There is a considerable risk of cerebral ischemia during anesthesia and cardiac, neurovascular and carotid artery surgery. This has fostered an interest in identifying agents that might protect the brain against ischemic injury. Anesthetics are logical candidate neuroprotective agents because they reduce excitotoxic injury. A number of studies have shown that anesthetics are neuroprotective. In these studies, the injury was evaluated after only a short recovery period. Recent data indicate that post-ischemic brain injury is a dynamic process in which neurons continue to die for a long period after the initial ischemia. Much of this delayed neuronal death is caused by apoptosis. Whether anesthetics can provide long-term permanent neuroprotection is not known. In the present proposal, the long term neuroprotective efficacy of anesthetics will be determined. The hypothesis that will be tested is that anesthetics reduce early neuronal injury caused by excitotoxicity but they do not prevent delayed neuronal death caused by apoptosis and that the combination of anesthetics and anti-apoptotic agents might produce robust and permanent neuroprotection. In the first phase, the dose-related neuroprotective efficacy of the barbiturate pentobarbital and of the volatile anesthetic isoflurane will be evaluated in a model of focal cerebral ischemia. Injury will be evaluated after both short (2 days) and long (2 weeks to 3 months) recovery periods to determine whether neuroprotection is transient or permanent. In the second phase, the effect of anesthetics on the processes that lead to apoptosis in the post-ischemic brain will be determined. Specifically, the temporal profile of cytochrome c release, activation of caspases 9, 8 and 3 and of c-Jun-N-terminal kinase (JNK) in the post-ischemic brain will be determined by immunohistochemistry, Western blotting and the measurement of the activities of the caspases and (JNK. Morphologic injury will be evaluated by light and electron microscopy and by TUNEL staining. In this phase, the relative contribution of each of the processes that lead to apoptosis and the impact of anesthetic agents on these processes will be determined. In the third phase, the neuroprotective efficacy of a combination of anesthetics (anti-excitotoxic) and anti-apoptotic agents will be evaluated in a model of focal ischemia. Specifically, the effect of inhibition of caspases 9, 3, 8 and JNK in combination with anesthetic agents on ischemic brain injury will be determined after short and long recovery periods. The proposed experiments will provide insight into the mechanisms by which anesthetic agents influence the pathophysiology of ischemic cerebral injury and may identify agents that should be considered as potentially protective in the clinical setting. The long term goals of the research are to prevent the occurrence of isehemic brain injury in patients undergoing anesthesia and surgery.