Postischemic Administration of Idazoxan, an α-2 Adrenergic Receptor Antagonist, Decreases Neuronal Damage in the Rat Brain

The effect of an α-2 receptor antagonist, idazoxan, on ischemic neuronal damage in the hippocampus and neocortex was studied in rats following 10 min of forebrain ischemia. Idazoxan was given 0.1 mg/kg i. v. immediately after recirculation, followed by 48 h of continuous infusion at a rate of 10 μg/kg/min. A histopathological examination of the CA1 region of the dorsal hippocampus and neocortex from each hemisphere was made on paraffin-embedded sections following 7 days of survival. In ischemic animals receiving an infusion of saline, 71% of the neurons in the hippocampal CA1 region were degenerated. In contrast, in the idazoxan-treated animals only 31% of the neurons were irreversibly damaged (p < 0.01). We conclude that postischemic administration of the α-2 antagonist idazoxan protects neurons against damage following cerebral ischemia. Rapid postischemic administration of α-2 adrenergic receptor antagonists could be an effective treatment after stroke and cardiac arrest.