The aim of this project is to study the treatment of stroke with hemodilution using basic research techniques. Currently the use of hemodilution with low molecular weight dextran (LMWD) is being evaluated in clinical trials. Hemodilution and hemoconcentration will be evaluated in acute stroke using an animal model of focal cerebral ischemia and the double label autoradiographic technique for determining local cerebral blood flow (LCBF) and local cerebral pH (LCpH) in the same brain section. Data analysis will focus on the measurement of LCBF, LCpH and their ratio in anatomical regions. The border zone of the ischemic area will be evaluated as an area where hemodilution could effect stroke outcome. Hemodilution and hemoconcentration will be used in a chronic model of stroke and evaluated using both neuropathological and autoradiographic criteria. Animals will be studied at various hematocrits to find the optimal hematocrit level. Both plasma and LMWD will be used as hemodilutants to uncover any specific, beneficial effect of LMWD on stroke outcome due to its properties as an inhibitor of red cell and platelet aggregation.