Long term direct visualization of the photothrombotic cortical infarction through the intact skull of anesthetized mice

BACKGROUND: To assess post-stroke functional recovery and develop new treatments, numerous preclinical models have been developed, including the photothrombotic stroke model. This reproducible and simple method induces a targeted ischemic lesion in a chosen cortical area following intravenous rose bengal injection and controlled illumination with a 532 nm laser. However, identifying the infarct's location and extent in vivo requires sophisticated, time-consuming, and/or expensive tools such as MRI or advanced optical imaging techniques. Thus, we introduce here a simple and low-tech method. NEW METHOD: Our direct method takes advantage of the long-lasting fluorescence of rose bengal remaining in the damaged cortex and detectable through the intact skull using the same 532 nm laser. RESULT: At the lesion site, we observed an emission spot glowing through the skull for several weeks after stroke induction. Ex vivo immunohistochemical analysis showed that rose bengal fluorescence remains confined to the lesion, precisely delineating the infarct's boundaries. COMPARISON WITH EXISTING METHODS: This technique simplifies lesion localization and guides subsequent in vivo investigations, such as probe implantation, optogenetic fiber placement, or targeted tissue sampling in the perilesional cortex, where neuroplasticity and repair processes occur.