Background and Purpose-It is unclear how genetic type 1 diabetes mellitus (DM) influences infarct size when blood glucose is tightly controlled. The aim of this study was to determine the effect of genetic type 1 DM, as occurs in BB rats, on infarct size after transient unilateral middle cerebral artery occlusion (MCAO) in male and female rats. In addition, studies suggest that male type 1 DM rats have a higher incidence of end-organ complications than do females. A second aim of this study was to determine the effect of chronic 17␤-estradiol (E 2 ) administration on infarct size in male BB rats. Methods-Diabetic male (MDiab, nϭ14) and female (FDiab, nϭ8) BB rats were studied and compared with background strain Wistar rats (MWist, nϭ16; FWist, nϭ14). Two additional male cohorts (MWistϩE 2 , nϭ15; MDiabϩE 2 , nϭ14) received subcutaneous 25 g E 2 implants 7 to 10 days before MCAO. Rats underwent 1 hour of MCAO followed by 22 hours of reperfusion. Physiological variables were controlled among groups, and the intraischemic laser Doppler flow signal was reduced similarly in all animals. Infarction volume was evaluated by 2,3,5-triphenyltetrazolium chloride staining and image analysis. Results-Preischemic blood glucose was 94Ϯ5, 127Ϯ13, 90Ϯ15, 63Ϯ18, 122Ϯ8, and 81Ϯ14 mg/dL in MWist, FWist, MDiab, FDiab, MWistϩE 2 , and MDiabϩE 2 rats, respectively (meanϮSE). Intraischemic laser Doppler flow was reduced to 20% to 25% of baseline in all groups. Striatal infarct size (percentage of ipsilateral caudate putamen) was increased in male diabetic rats relative to nondiabetic MWist rats (41Ϯ3% versus 28Ϯ3%). Striatal injury was not increased in FDiab rats, and infarction volume was smaller than that in FWist rats (23Ϯ4% in FWist versus 13Ϯ3% in FDiab). Chronic estrogen treatment reduced cortical and striatal infarction in MDiabϩE 2 rats compared with untreated MDiab rats. Conclusions-Type 1 DM is associated with increased infarct size after temporary MCAO, despite tight control of blood glucose. The deleterious effect of DM is evident only in males rats; female diabetic BB rats sustain small infarcts. Chronic E 2 treatment reduced injury in the male BB rat, providing neuroprotection even in the presence of DM. These data suggest that genetic diabetes even with mild glucose elevation plays a role in determining neuropathology in experimental stroke. However, factors such as reproductive steroids also determine outcome in DM stroke. (Stroke.

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Background Most ischemic strokes in humans are caused by ruptured arterial atheroma, which activate platelets and produce thrombi that occlude cerebral vessels. Methods To simulate these events, we threaded a catheter through the internal carotid artery toward the middle cerebral artery (MCA) orifice and injected collagen directly into the cerebral circulation of male C57Bl/6 mice and Wistar rats. Results Laser-Doppler flowmetry demonstrated reductions in cerebral blood flow (CBF) of ~80% in mice and ~60% in rats. CBF spontaneously increased but remained depressed after catheter withdrawal. Magnetic resonance imaging showed that ipsilateral CBF was reduced at 3 h after collagen injection and markedly improved at 48 h. Micro-computed tomography revealed reduced blood vessel density in the ipsilateral MCA territory at 3 h. Gross examination of excised brains revealed thrombi within ipsilateral cerebral arteries at 3 h, but not 24 h, after collagen injection. Immunofluorescence microscopy confirmed that platelets and fibrinogen/fibrin were major components of these thrombi at both macrovascular and microvascular levels. Cerebral infarcts comprising ~30% of hemispheric volume and neurobehavioral deficits were observed 48 h after ischemic injury in both mice and rats. Comparison with existing methods Collagen injection caused brain injury that was similar in magnitude and variability to mechanical MCA occlusion or injection of a pre-formed clot; however, alterations in CBF and the mechanism of vascular occlusion were more consistent with clinical ischemic stroke. Conclusion This novel rodent model of ischemic stroke has pathophysiologic characteristics consistent with clinical atherothrombotic stroke, is technically feasible, and creates reproducible brain injury.

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