Deciphering the complex metabolic and molecular basis of cerebral ischemia and using this knowledge to develop therapeutic strategies for the treatment of stroke is the theme of this competitive renewal application from the Interdepartmental Stroke Program Project at the MGH. To this end, 3 projects plus one Scientific Core are proposed. Project by Paul L. Huang will develop and characterize genetic mutant mice in which neuronal and endothelial isoforms of brain nitric oxide synthase have been deleted [KN (neuronal knockout) and KV (endothelial knockout)], and proposes to build on existing preliminary data suggesting the feasibility of this approach for studies in Project. Project by Michael A. Moskowitz proposed to use these animals to examine the consequences of selectively deleting neuronal and endothelial isoforms of brain nitric oxide synthase on the hemodynamic, structural and biochemical events characterizing focal and global ischemia. Project by Joe Bonventre, Walter Koroshetz will examine and characterize the structure and function of phospholipase A2 in normal and ischemic brain to extend their data documenting activation of PLA2's with ischemia/reperfusion and excitotoxicity. Project by Seth Finklestein, Flint Beal) investigates the phenomenon and underlying mechanism of growth factor neuroprotection in models of cerebral ischemia. Each of the projects will utilize the Scientific-Imaging Core (Bruce Rosen, Michael A. Moskowitz) both as a source for focal and global ischemic animals and as a resource for imaging and spectroscopy. The approach taken is multidisciplinary, interdepartmental, represents a logical extension of work accomplished during the previous 4 year funding period, incorporates new and exciting developments in molecular biology and genetics, introduces a young promising scientist to the field of stroke, and incorporates state-of- the-art imaging tools to examine the consequences of ischemia on brain metabolism, blood flow and tissue survival.