Abstract
Glibenclamide improves outcomes in rat models of stroke, with treatment as late as 6 h after onset of ischemia shown to be beneficial. Because the molecular target of glibenclamide, the sulfonylurea receptor 1 (Sur1)-regulated NC(Ca-ATP) channel, is upregulated de novo by a complex transcriptional mechanism, and the principal pathophysiological target, brain swelling, requires hours to develop, we hypothesized that the treatment window would exceed 6 h. We studied a clinically relevant rat model of stroke in which middle cerebral artery occlusion (75% < reduction in LDF signal ≤90%) was produced using an intra-arterial occluder. Recanalization was obtained 4.5 h later by removing the occluder. At that time, we administered recombinant tissue plasminogen activator (rtPA; 0.9 mg/kg IV over 30 min). Immunolabeling showed modest expression of Sur1 5 h after onset of ischemia, with expression increasing 7- to 11-fold (P < 0.01) by 24 h. Rats were administered either vehicle or glibenclamide (10 μg/kg IP loading dose plus 200 ng/h by constant subcutaneous infusion) beginning 4.5 or 10 h after onset of ischemia. In rats treated at 4.5 or 10 h, glibenclamide significantly reduced hemispheric swelling at 24 h from (mean ± SEM) 14.7 ± 1.5% to 8.1 ± 1.6% or 8.8 ± 1.1% (both P < 0.01), respectively, and significantly reduced 48-h mortality from 53% to 17% or 12% (both P < 0.01), and improved Garcia scores at 48 h from 3.8 ± 0.62 to 7.6 ± 0.70 or 8.4 ± 0.74 (both P < 0.01). We conclude that, in a clinically relevant model of stroke, the treatment window for glibenclamide extends to 10 h after onset of ischemia.