Tissue harvesting

Immediately following the second MRI scan (seven days post injection), animals were pre-anesthetized via an intramuscular injection of ketamine-xylazine solution (20 and 2 mg/kg, respectively), terminally anesthetized by propofol overdose, and, after arrest of respiratory activity, they were transcardially perfused with 10% sucrose followed by 4% PBS-buffered paraformaldehyde (PFA). Perfusion pressure was maintained at 120–140 mmHg. Brains were harvested and post-fixed in 4% PFA for 48 h at 4°C. Then, brains were subdivided into 8–10 blocks, cryo-protected in 30% sucrose until sank, frozen on dry ice powder for five minutes and kept until cryo-sectioning.