Effect of the Opioid Antagonist Naloxone on the Regional Metabolic Rate for Glucose in the Conscious Rat Brain

Abstract

The effect of naloxone, a potent and specific opioid antagonist, on cerebral glucose utilization was investigated in conscious rat. For quantitative evaluation of the functional activity in brain, the regional cerebral metabolic rate for glucose (rCMR_glc) was measured by the double tracer technique, using [¹⁴C]2-deoxyglucose and [³H]3-O-methylglucose. Intravenous administration of naloxone significantly increased rCMR_glc in the medulla and thalamus at a dose of 1 or 10 mg/kg, and in the cerebral cortex, midbrain and cerebellum at a dose of 10 mg/kg. Our findings strongly suggest that naloxone by itself affects the cerebral functional activity within 10 min of administration.