Nitrous oxide alters oxidative metabolic activities of rat neocortex in situ

Nitrous oxide was shown by dual wavelength reflection spectrophotometry to decrease the ratio of reduction/oxidation of cytochrome a,a3 and to increase local blood volume in the cerebral cortex of rats in situ. These changes were in contrast to the decreased local blood volume and increased reduction of cytochrome a,a3 produced by pentobarbital. These effects of nitrous oxide were similar to those produced by respiration of 95% O2 with 5% CO2 except that such inspiration resulted in hemoglobin oxygenation while N2O produced some disoxygenation of hemoglobin. We conclude that the N2O effect on metabolism is likely due to increased energy demand. These results also provide some indication that changes in oxidative functioning in brain tissues may occur without alteration in the concentrations of high energy phosphate compounds.