SARS-CoV-2 infection (intraventricular)

Animals were anaesthetized using a mixture of ketamine (50 mg/kg) and xylazine (5 mg/kg) injected i.p. After sterilization of the scalp with alcohol and betadine, a midline scalp incision was made to expose the coronal and sagittal sutures, and a burr holes were drilled 1 mm lateral to the sagittal suture and 0.5 mm posterior to the bregma. A 10-µl Hamilton syringe loaded with virus and inserted into the burr hole at a depth of 2 mm from the surface of the brain and left to equilibrate for 1 min before infusion. Once the infusion was finished, the syringe was left in place for another minute before removal. Bone wax was used to fill the burr hole, and skin was stapled and cleaned. Following intramuscular administration of analgesic (meloxicam and buprenorphine, 1 mg/kg), animals were placed in a heated cage until full recovery. For the high condition, 5 µl of SARS-CoV-2 (3 × 10⁷ PFU/ml) was used, and for the low condition, 5 µl of SARS-CoV-2 (3 × 10⁶ PFU/ml).