Evaluating Minocycline as a Neuroprotective Agent in an Aged Female Rat MCAO Stroke Model

Abstract The middle cerebral artery occlusion (MCAO) suture model is widely accepted ischemic stroke model. However, researchers routinely use young male rats, ignoring that stroke risk is increased in older, post-menopausal women. To this end, we implemented (120-minute) transient- and permanent-occlusion MCAO models in female retired-breeder rats, examining the endpoint across 1-30 days to identify the optimal time course for the model. We found that in both groups the physical infarct (measured by triphenyltetrazolium chloride -TTC staining), which is present initially, was not detectable 30 days post-MCAO (even if some neurologic symptoms persist). Across shorter time-points (namely 24 hours and 7 days) we found that neurologic scores generally reach a plateau/maximum at ∽7 days, then infarct size gradually decreases over time for rats receiving a permanent MCAO. Across 3 transient occlusion times (60 minutes, 90 minutes, and 120 minutes), the longest gave the most robust result. Overall, the permeant and 120-minute transient MCAO evaluated at 7 days was optimal. Using these two models, we evaluated the neuroprotective qualities of the antibiotic, minocycline. We found that those in the treatment groups experienced a greater improvement in neurologic scores and a larger decrease in infarct size after daily treatment for seven days. This improvement was more prominent in the transiently occluded treatment group than in the permanently occluded group.