Local cerebral glucose utilization during nitrous oxide and pentobarbital anesthesia in rats

Local cerebral glucose utilization was measured in rats during nitrous oxide and pentobarbital anesthesia, using the 2-[14C]-deoxyglucose method. During nitrous oxide anesthesia, 67%, marked heterogeneity of glucose utilization was observed. During pentobarbital anesthesia (30 mg/kg), glucose utilization decreased, the decrease being pronounced in the structures where glucose utilization was high during nitrous oxide anesthesia. During combined use of nitrous oxide and pentobarbital (30 mg/kg), with an electroencephalogram (EEG) consisting of 4-6 Hz wave super-imposed by 10-15 Hz wave, glucose utilization was higher in many brain structures, including the midbrain reticular formation, than that observed during pentobarbital (30 mg/kg) anesthesia alone. With pentobarbital, 125 mg/kg, the EEG became nearly flat and a dose-related decrease in glucose utilization was observed in the cerebral cortices and inferior colliculus but not observed in any other structures. During the combined use of nitrous oxide and pentobarbital (125 mg/kg), the EEG was nearly flat, and no statistically significant differences in glucose utilization were observed as compared with those during pentobarbital (125 mg/kg) anesthesia in any of the structures examined. The results suggest that nitrous oxide and pentobarbital affect local cerebral glucose metabolism differently and that nitrous oxide acts as cerebral metabolic stimulant in the presence of cortical function during pentobarbital anesthesia.