Focal cerebral ischemia in the cat: effect of naloxone on cortical blood flow and neurological deficit following middle cerebral artery occlusion.

The effect of the opiate antagonist naloxone on both the neurological deficit and regional cortical blood flow after middle cerebral artery occlusion in the cat was investigated. In animals with mild symptoms, naloxone did not consistently produce a significant behavioral effect. In all cats with neurological deficits, including hemiplegia or severe hemiparesis, 2 mg/kg naloxone administered intravenously 4 h after the ischemic lesion produced a reversal of neurological symptoms. This effect began within 2 min following naloxone injection and lasted for approximately 20 min. Animals were then anesthetized and cortical blood flow was measured by the hydrogen clearance method. Average cortical blood flow on the side of the occlusion was 50% that of the control side. Naloxone produced a significant additional decrease of 19.5% in cortical blood flow in the ischemic hemisphere, whereas no effect on blood flow on the control side was noted. Thus, although naloxone appears to temporarily reverse the severe neurological deficits resulting from middle cerebral artery occlusion in the cat, this effect appears to be accompanied by a decrease in local blood flow to the ischemic cortex.