Hyperthermia Masks the Neuroprotective Effects of Tissue Plaminogen Activator

Background and Purpose— Previously, we have shown that hyperthermia significantly increased neuronal damage after ischemic injury in a focal embolic model of stroke in rats. In the present study, we examined the effects of hyperthermia on the efficacy of thrombolytic therapy in this stroke model. Methods— In part A, efficacy of tissue plaminogen activator (tPA) treatment was examined in normothermic and hyperthermic rats after embolization of preformed clots into middle cerebral artery (MCA). In part B, brain perfusion deficits were assessed in rats after MCA occlusion. In part C, blood–brain barrier (BBB) permeability was examined in rats after MCA occlusion. In part D, we examined the influence of hyperthermia on fibrinolytic activity of tPA in vitro. Results— Results showed that treatment with tPA significantly reduced infarct volume in normothermic and 38°C hyperthermic rats. When compared with normothermic rats, perfusion deficits in hyperthermic rats were significantly increased at both 3 hours and ...