Photochemically induced, graded cerebral infarction in the mouse by laser irradiation evolution of brain edema.

Cerebral infarction was produced in mice by intravenous injection of a photosensitive dye, rose bengal (10 mg/kg), and by focal illumination of the intact skull surface for 3 min with a laser source, operating at 570 nm with power levels of 2, 5, 10, and 20 mW. Location of infarction was made using 2,3,5-triphenyltetrazolium chloride and the time course of edema in the irradiated cerebral hemisphere was evaluated by measuring water, sodium, and potassium content 4, 24, and 72 hr after irradiation. With power levels of 2 and 5 mW, the infarct was restricted to the cortex, whereas with power levels of 10 and 20 mW, it extended to subcortical regions. Increases in water and sodium and decrease in potassium content were maximal 24 hr after irradiation and depended on the power level. Highly significant correlations were found, 24 hr after irradiation, between the power level and the changes in water and ion concentrations. With reproducible, incremental grades of damage being desirable for pharmacological trials, the model may be suited for the testing of therapeutic agents.