After decapitation, the mouse brain was removed and homogenized using a KIMBLE Dounce tissue grinder (Sigma-Aldrich, USA) in buffer A, containing 225 mM mannitol (Sigma-Aldrich), 75 mM sucrose (Dia-M, Russia), 5 mM Hepes (BioClot, Germany), 1 mM ethylene glycol tetraacetic acid (EGTA) (Sigma-Aldrich), pH 7.4 with the addition of 2 mg/mL fatty acid-free bovine serum albumin (BSA) (Dia-M). The wash buffer (buffer B) used in the centrifugation step had the same composition except BSA. The resulting homogenate was centrifuged using a Z 36 HK centrifuge (Hermle Labortechnik, Germany) for 5 min at 900 g. The supernatant was transferred into clean tubes and centrifuged for 10 min at 14 000 g. After that, the supernatant was removed, and the pellet was resuspended in 100 µL of buffer B and after addition of digitonin (Sigma-Aldrich) (0.02% final concentration) the susnepsion was incubated on ice for 2 min. The tubes were centrifuged for 15 min at 14 000 g. The supernatant was removed again, the pellet was resuspended in 100 µL of buffer B, and then centrifuged for 10 min at 14 000 g. The last step was repeated twice. The resulting pellet was resuspended in 20 µL of buffer B [22 (link)].