The purpose of this study was to compare acute cerebral perfusion measured by computed tomography, stroke lesion volume measured by magnetic resonance imaging, and motor function in Sprague-Dawley rats supplied by Charles River (Charles River, Quebec, Canada) and Harlan (Harlan, Michigan, USA). During the acute stages of ischemia (<3 hours), Sprague-Dawley rats supplied by Harlan had a greater reduction in blood flow (67%) than rats supplied by Charles River (37%). MRI at days 1 and 6 after ischemia showed larger lesions in the Charles River animals compared to Harlan animals ( ) at both time points. Lesion volume decreased in both Charles River and Harlan rats at day 6 compared to day 1 ( ) and corresponded to lesion size on histology. The Harlan animals had significant functional deficits ( ) one day after surgery in postural hang reflex, forelimb placement, and tactile fraction first tests, whereas rats supplied by Charles River had no significant functional impairment as a result of surgery. The current study provides evidence that differences in response to ischemia between rats of the same strain supplied by different vendors should be an important consideration when animals are selected for the study of cerebral ischemia. 1. Introduction Various focal ischemia models can be used [1–7] to evaluate potential therapies for stroke. These models typically involve occlusion of the middle cerebral artery (MCA) and are subdivided into permanent and reversible. Permanent models include the Tamura approach [4, 6, 7] and its modifications involving the use of clips and threads [8–12], cauterization,  or reversible snare ligature . Cauterization of the MCA followed by permanent occlusion of the ipsilateral carotid artery and temporary occlusion of the contralateral carotid artery is one of the most frequently used models for focal and irreversible ischemia in rats [1–5]. This model of ischemia allows only partial reperfusion and results in a reproducible predominantly cortical insult in the primary somatosensory cortex (S1FL, S1BF) and the CA1 field of the hippocampus, without severe impairment of motor function . The temporary occlusion of the contralateral carotid artery reduces cerebral blood flow to ischemic ranges. This model is typically chosen because of its low mortality rate and is used for investigations of the biochemical changes during cerebral ischemia . When considering the animal model for ischemia studies, several criteria must be evaluated including the animal species and strain, as well as the animal supplier. Ischemia
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