Background: Breakdown of the blood brain barrier (BBB) is an important contributor to injury after acute ischemic stroke in adults. Animal studies of ischemic stroke observed distinct differences in BBB permeability using Evans Blue (EB) between adult and neonatal rats. However, not much is known about BBB disruption in the juvenile rat. The aim of this study was to assess the evolution of in-vivo and ex-vivo BBB permeability in a photothrombotic juvenile rat stroke model. 
 
Methods: A photothrombotic stroke model was induced in 12 rats (37±1 days old) and BBB permeability was quantitatively assessed ex-vivo by measuring EB leakage on days 0, 1, 2, and 7. Three rats were used for every time point. Dynamic contrast-enhanced (DCE) MRI was performed in a subset of rats prior to sacrifice to measure BBB permeability in-vivo and compared to ex-vivo. 

Results: EB leakage was expressed as mean infarct to control hemispheric ratio and was 2.72 (day 0), 2.41 (day 1), 1.99 (day 2) and 2.16 (day 7). In-vivo BBB permeability results using MRI were 0.43 (day 0), 0.27 (day 2), and 0.31 (day 7) ml/100 g/min. These results correlated well with EB leakage (R2= 0.588, p<0.05).

Conclusion: We have characterized longitudinal BBB changes in juvenile rats using a photothrombotic ischemic stroke model. We have detected highest permeability on day 0 and confirmed persisting BBB disruption up to day 7. Future work will incorporate neuroprotective drugs stabilizing the BBB at different time points after childhood stroke.

LONGITUDINAL ASSESSMENT OF BLOOD-BRAIN BARRIER DISRUPTION IN A PHOTOTHROMBOTIC JUVENILE RODENT STROKE MODEL USING HISTOLOGY; PERMEABILITY MRI