Permanent middle cerebral artery occlusion (pMCAO)

Permanent ischemic conditions were modeled after the same procedure in rats [19]. The base of the left proximal middle cerebral artery at the M1 segment [18,20,21] is permanently occluded, blocking flow to all MCA cortical branches. This is achieved by careful removal of the skull and dura from a 2x2mm ‘surgical window’ placed beyond the bottom left portion of the imaging window, directly over the M1 segment of MCA, just distal to MCA’s lenticulostriate branches and proximal to any cortical branching. The M1 occlusion therefore entails that only cortical ischemic damage is expected in this occlusion model. A half-curve reverse cutting suture needle is cut in half and threaded with two 4–0 silk threads and passed through the pial layer of the meninges, below MCA (the needle is kept above the cortical surface to the extent possible to minimize damage). Then the two threads (moved to ~1mm apart after being strung beneath the artery) are both tied and tightened around MCA and the vessel is transected (completely severed) between the two knots. Care is taken to avoid damaging the artery, and experiments are terminated if there are signs of bleeding from MCA (1 case).