Positive impact of pre-stroke surgery on survival following transient focal ischemia in hypertensive rats

► Methodological refinement improved survival from stroke in hypertensive rats. ► Post-stroke associated weight loss is reduced in animals with pre-stroke surgery. ► Surviving animals (±pre-stroke surgery) have equivalent infarct volumes. ► Surviving animals (±pre-stroke surgery) show same neurological deficit severity. ► Important implications for animal welfare/groups sizes required for stroke studies. We describe a positive influence of pre-stroke surgery on recovery and survival in a commonly used experimental stroke model. Two groups of male, stroke-prone spontaneously hypertensive rats (SHRSPs) underwent transient middle cerebral artery occlusion (tMCAO). Group 1 underwent the procedure without any prior intervention whilst group 2 had an additional general anaesthetic 6 days prior to tMCAO for a cranial burrhole and durotomy. Post-stroke recovery was assessed using a 32 point neurological deficit score and tapered beam walk and infarct volume determined from haematoxylin–eosin stained sections. In group 2 survival was 92% (n=12) versus 67% in group 1 (n=18). In addition, post-tMCAO associated weight loss was significantly reduced in group 2. There was no significant difference between the two groups in experimental outcomes: infarct volume (Group 1 317±18.6mm3 versus Group 2 332±20.4mm3), and serial (day 0–14 post-tMCAO) neurological deficit scores and tapered-beam walk test. Drilling a cranial burrhole under general anaesthesia prior to tMCAO in SHRSP reduced mortality and gave rise to infarct volumes and neurological deficits similar to those recorded in surviving Group 1 animals. This methodological refinement has significant implications for animal welfare and group sizes required for intervention studies.