Photothrombotic middle cerebral artery occlusion and reperfusion laser system in spontaneously hypertensive rats

Background and Purpose-To establish a less invasive and reproducible focal ischemia model in the rat, we adopted a 2-laser system (ie, photothrombosis and YAG laser-induced reperfusion). Methods-The distal middle cerebral artery (MCA) of spontaneously hypertensive rats was occluded by 568-nm krypton laser and intravenous infusion of the photosensitizing dye rose bengal and was recanalized by 355-nm ultraviolet laser irradiation. Cerebral blood flow was determined by laser-Doppler flowmetry at the penumbral cortex. Infarct volume was determined at 3 days after distal MCA occlusion. Results-Brain temperature determined with infrared thermography was maintained within an acceptable range of approximately 1degreesC upper shift of the center of brain temperature distribution during krypton or YAG laser irradiation. The average of the values (23 experiments; n = 163) of coefficient of variation of infarct volume was 21+/-6%, indicating high reproducibility of this model. After distal MCA occlusion, cerebral blood flow was decreased to 32+/-16% of the control values and was increased to 98+/-21% after YAG laser-induced reperfusion. Infarct volume in these rats was 61+/-18 mm(3) (coefficient of variation=30%; n=6). Conclusions-We have characterized a highly reproducible focal ischemia model utilizing a 2-laser system, one to induce thrombotic MCA occlusion and the other to facilitate reperfusion.