Targeted disruption of deep-lying neocortical microvessels in rat using ultrashort laser pulses

The study of neurovascular diseases such as vascular dementia and stroke require novel models of targeted vascular disruption in the brain. We describe a model of microvascular disruption in rat neocortex that uses ultrashort laser pulses to induce localized injury to specific targeted microvessels and uses two-photon microscopy to monitor and guide the photodisruption process. In our method, a train of high-intensity, 100-fs laser pulses is tightly focused into the lumen of a blood vessel within the upper 500 μm of cortex. Photodisruption induced by these laser pulses creates injury to a single vessel located at the focus of the laser, leaving the surrounding tissue intact. This photodisruption results in three modalities of localized vascular injury. At low power, blood plasma extravasation can be induced. The vessel itself remains intact, while serum is extravasated into the intercellular space. Localized ischemia caused by an intravascular clot results when the photodisruption leads to a brief disturbance of the vascular walls that initiates an endogenous clotting cascade. The formation of a localized thrombus stops the blood flow at the location of the photodisruption. A hemorrhage, defined as a large extravasation of blood including plasma and red blood cells, results when higher laser power is used. The targeted vessel does not remain intact.