Controlling the Volume of the Focal Cerebral Ischemic Lesion through

Stroke is the third leading cause of human death. Various models have been used to study the mechanisms of tissue damage and neuronal protection. Each model has its advantages and disadvantages. Middle cerebral artery occlusion (MCAo), has been widely used, but produces large ischemic lesions of varying size, which is a disadvantage in the study of neuronal protective mechanisms. Photothrombosis provides an alternative model that can produce consistent lesion size. In this model, ischemia is induced by photo-activation of rose bengal in blood flow by green light illumination. Because ischemia can be induced while animals are kept in a stereotaxic device or on the stage of a microscope, this model has become widely used for in vivo study of cellular structure and function. In this study, photothrombosis was generated by using a wide-field epi-fluorescent microscope equipped with a metal halide lamp and ischemia was confirmed by blood flow reduction monitored by laser Doppler flowmetry. We demonstrated, by adjusting the intensity of output light and the size of irradiated area in the cortex, that the photothrombosis model can, with high reproducibility, be used to generate ischemic infarction of various sizes in mouse brains. Using immunostaining and histochemistry of brain sections, our data showed that photothrombosis induced neuronal death and that brain infarct volume was correlated with the power output and the size of irradiate