Subacute hemorrhage and resolution of edema in Rose Bengal stroke model in rats coincides with improved sensorimotor functions.

The Rose Bengal model in rats is widely used to study brain plasticity, functional recovery and restorative therapies. The present study evaluated temporal profiles of hemorrhage and edema by magnetic resonance imaging (MRI) in rats in relation to sensorimotor impairment after photochemically induced cortical infarct. Adult, male Wistar rats were injected with Rose Bengal dye followed by illumination to produce a lesion over the sensorimotor cortex. Brain damage including infarct volume, edema, and bleeding was determined from postoperative days 1 to 10 by using MRI. Prussian blue staining was used to confirm hemorrhage in perfused brain sections. Functional outcome was assessed by limb-placing test during the follow-up. A consistent cortical lesion was detected in T(2) weighted MRI 24h after cortical photothrombosis without any signs of blood in T(2)(*) weighted images. However, from postoperative days 3 to 8, hemorrhage was indicated by almost complete signal void in T(2)(*) weighted gradient echo images and confirmed by Perls' Prussian blue staining on postoperative day 10 for presence of iron in corresponding lesion areas. The subacute appearance of hemorrhage on postoperative days 3-8 and resolution of edema coincides with improved performance in the limb-placing test. The results suggest that bleeding around cortical infarct is part of the wound healing process and may not impair functional outcome.