Pre-treatment with melatonin reduces volume of cerebral infarction in a permanent middle cerebral artery occlusion stroke model in the rat

We investigated whether pre-treatment with melatonin, a potent free radical scavenger and antioxidant, would protect against permanent focal cerebral ischemia without reperfusion in a rat middle cerebral artery occlusion (MCAO) model. A single dose of melatonin at 5, 15, or 50 mg/kg or the vehicle alone was given via an intraperitoneal injection at 0.5 h before permanent MCAO. Relative infarction volumes on day 3 were significantly reduced in the groups treated with melatonin at 5 (mean +/- SEM, 17.0 +/- 6.5%),15 (18.1 +/- 5.8%), or 50 (20.6 +/- 5.0%) mg/kg when compared with the vehicle-treated group (37.1 +/- 2.8%) and so melatonin treatment achieved a relative reduction in infarct volume by 54.2, 51.2 and 44.5%, respectively. Melatonin did not affect the hemodynamic parameters. Thus, pre-treatment with melatonin at a dose between 5 and 50 mg/kg protects against focal cerebral ischemia without reperfusion. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.