Temporary middle cerebral artery occlusion in the rat: consistent protocol for a model of stroke and reperfusion

The intraluminal suture method of middle cerebral artery occlusion (MCAO) in the rat (the suture model) is a model of stroke which readily lends itself to studying the pathophysiology of post-ischaemic reperfusion. Unfortunately, variability of outcome has compromised the potential of the model, but systematic studies might characterize a consistent protocol. Therefore, the clinical and neuropathological outcome of temporary MCAO and reperfusion in the suture model were systematically investigated. Two hours or 4 h of MCAO were employed, measuring the extent of infarction at 24 h with triphenyltetrazolium chloride or at 72 h with histopathological techniques. Outcome was compared in three rat strains. Following 2 h of MCAO, motor function improved during reperfusion in Sprague-Dawley, but not in Wistar or Fischer-344 rats. All Sprague-Dawley and Wistar rats survived the protocol to 72 h, but 33% of Fischer-344 rats died. The extents of infarction and oedema were greater and less variable in Wistar and Fischer-344 than Sprague-Dawley rats, and in all three strains, the extent of infarction increased with reperfusion time. Following 4 h of MCAO, there was no improvement in motor function during reperfusion in Sprague-Dawley rats, and mortality was high at 24 h in Wistar (33%) and Fischer-344 rats (83%). Outcome was only pursued in Sprague-Dawley rats to 72 h, where the extent of infarction was quite variable. It was concluded that the extent and variability of outcome following temporary MCAO in the suture model is strain-dependent, and a consistent protocol with zero mortality was found in Wistar rats using 2 h of MCAO and 70 h of reperfusion.