Local Cerebral Glucose Utilization during Nitrous Oxide and Pentobarbital Anesthesia in Rats

Abstract

Local cerebral glucose utilization was measured in rats during N2O and pentobarbital anesthesia, using the 2-[14C]-deoxyglucose method. During N2O 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 N2O anesthesia. During combined use of N2O and pentobarbital (30 mg/kg), with an EEG consisting of 4-5 Hz wave superimposed 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 in any other structures. During the combined use of N2O and pentobarbital (125 mg/kg), the EEG was nearly flat; 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. N2O and pentobarbital evidently affect local cerebral glucose metabolism differently. N2O acts as cerebral metabolic stimulant in the presence of cortical function during pentobarbital anesthesia.