We have established a new model of middle cerebral artery (MCA) occlusion in rats due to photochemically induced
thrombosis (PIT). This
thrombosis is caused by photochemical reaction between green light and systemic injection of
Rose Bengal (RB). Under
anesthesia, the left MCA was observed without cutting the dura mater via a subtemporal
craniotomy under an operation microscope. Photoillumination (wavelength, 540 nm; L4887, Hamamatsu Photonics, Japan) was applied to the MCA and then RB (20 mg/kg) was administered intravenously. The MCA was completely occluded by
thrombus about 6 min after the administration of RB with an operation microscope. Effects of
antithrombotic agents can be evaluated in this model, since this
thrombus is a typical arterial one caused by the injury of the endothelium, and this method is easy and the location and volume of
cerebral infarction are reproducible, since
thrombus is induced at the same portion of the MCA. Additionally the damage to animals is little, since
thrombosis in the MCA is induced without cutting the dura mater; furthermore, it is possible to do chronic experiments. In conclusion, this model is a useful one for investigation of
thrombolytic therapy in
cerebral thrombosis.