Photochemically induced ischemic stroke in rats

The photosensitive dye Bengal Rose is intravenously administered and a laser beam is stereotactically positioned onto the skull. Illumination through the intact skull leads to local activation of Bengal Rose, which results in free radical formation, disturbance of endothelial function and thrombus formation in illuminated small cortical vessels.Photochemically induced infarcts cause long-term sensorimotor deficits, allow long-term survival and are particularly suitable to assess the effectiveness of neuroregenerative therapies in chronic stroke studies.Stroke is the second most frequent cause of death and a leading cause of disability and cognitive impairment in developed countries [1,2]. Ischemic stroke, which accounts for approximately 80% of strokes, constitutes a huge socioeconomic burden. Experimental models of cerebral ischemia have been developed to mimic human stroke, gain a better understanding of underlying pathophysiological mechanisms and foster the development of new therapies. Common models of focal and multifocal cerebral ischemia include the intraluminal thread middle cerebral artery occlusion (MCAo) model, surgical MCAo models using ligation, clipping, electrocauterization etc., endothelin-1-induced MCAo, and embolization models using blood clots or other embolus material for vessel occlusion (for review see [3]).In 1985, Watson et al. introduced photothrombosis as a technique to induce focal cerebral infarction in the cortical vasculature of rats [4]. The key mechanism is a photochemical reaction triggered by systemic administration of Bengal Rose and focal illumination of the skull. Illumination leads to local activation of Bengal Rose, which results in free radical formation, disturbance of endothelial function and local thrombosis in small cortical vessels [3,5]. As compared to other animal models of stroke, animal preparation is simple because it does not require mechanical manipulation of cerebral blood vessels or parenchyma. Lesion size and l