[A new model of middle cerebral artery thrombosis in rats].

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.