Stroke model

Focal ischemia in the forelimb motor cortex was induced using the photothrombotic lesion model (44,45) resulting in infarcts covering 20% of the hemisphere (46). Briefly, mice were anesthetized with 2.5% isoflurane (halocarbon) in an oxygen/air mixture, respiration was monitored and rectal temperature was maintained at 37 ± 0.5°C using a heating plate (TCAT-2LV Controller, Physitemp Instruments, Clifton, NJ, USA). After fixation in a stereotactic frame (David Kopf Instruments, Tujunga, CA, USA), the skull was exposed by a 1 cm midline incision of the skin. An amount of 100 μl Rose Bengal (Sigma) at a concentration of 3 mg/ml saline was infused by tail vein injection. For illumination, a 2.4 mm laser beam with a wavelength of 565 nm (L4887-13, Hamamatsu Photonics, Japan) was focused on the motor cortex responsible for forelimb function (0.5 mm rostral, 1.8 mm lateral of bregma). Five seconds after Rose Bengal injection, the brain was illuminated though the intact skull for a total duration of 5 min. After illumination, the incision was sutured and 500 μl saline and 0.05 mg/kg Vetergesic (Ecuphar) was given to the animals subcutaneously. To recover, mice were placed in a separate cage with half of the cage placed under an ultraviolet lamp before returning to their home cage and housing facility. After stroke, mice were monitored on a daily basis during the first week and from then on animal health was checked weekly. To prevent unnecessary suffering of animals, mice were euthanized if they showed severe weakness or if they lost 20% of their body weight within 5 days.