Intracisternal sampling of cerebrospinal fluid (CSF)

A dedicated CSF withdrawal system was used for POH experiments (Fig. 1). This system comprised of a 20 cm long polyethylene tubing (PE-10; inner diameter: 0.61 mm, outer diameter: 0.28 mm; Plastics One Inc., Roanoke, VA, USA); a 100 µL Hamilton syringe (inner diameter: 1.475 mm; Harvard Apparatus, Holliston, MA, USA), and a two-port shut-off valve assembly (PEEK, inner diameter: 0.5 mm; Idex Health and Science, Oak Harbor, WA, USA). Tubing was firmly secured at both ends of the valve assembly using NanoTight sleeves (FEP; inner diameter: 0.69 mm; Idex Health and Science, Oak Harbor, WA, USA); these sleeves flanked on either side of valve fittings. The valve fitting side that faced the cisternal space was connected to a different set of tubing assembly i.e. 1 cm PE-10 tubing sealed to a 1.27 mm long polyether ether ketone tubing (PEEK; 33 GA; Plastics One Inc., Roanoke, VA, USA). PE-10/PEEK tubing connections were sealed using molten wax and cyanoacrylate on the day of the experiment.