Hyperglycemia increases infarct size in collaterally perfused but not end-arterial vascular territories

Abstract

Hyperglycemia exacerbates neuronal injury in the setting of reversible brain ischemia, but its effect on focal thrombotic infarction has been less extensively characterized. We investigated this problem in two rat models of focal vascular occlusion. In Model I, the right middle cerebral artery (MCA) was exposed via a subtemporal craniotomy in halothane- and nitrous oxide-anesthetized Wistar rats and was occluded photochemically by irradiation with an argon ion laser following the intravenous administration of the photosensitizing dye rose bengal. Permanent MCA occlusion was combined with temporary bilateral common carotid artery ligation. In Model II, similarly anesthetized Sprague-Dawley rats were subjected to permanent photochemical occlusion of the right MCA without common carotid occlusion. In both models, rats were food deprived for 24 h and were administered varying amounts of 50% dextrose (or saline) 15 min prior to vascular occlusion to produce a spectrum of plasma glucose values, ranging from 5 to 44 mumol/ml. Brains were examined histologically 7 days following vascular occlusion, and computer-assisted planimetry was used to compute infarct volumes. In Model I, the volume of neocortical infarction ranged from 30.3 to 108.4 mm3 and exhibited a strong linear correlation with increasing preischemic plasma glucose values (r = 0.70). In contrast, the size of the smaller striatal infarct in this model was not correlated with plasma glucose level. In Model II, there was a prominent striatal infarct, ranging in volume from 14.4 to 96.4 mm3, while neocortical infarction occurred inconstantly. As in Model I, striatal infarct volume in Model II showed no correlation with plasma glucose level.(ABSTRACT TRUNCATED AT 250 WORDS)