Brain cyclic nucleotide responses to anesthesia with halothane delivered in air or purified oxygen

Inhalation of either 0.5% or 1.0% halothane in air caused a slight decrease in the cAMP concentration in rat cerebral cortex and cerebellum. During recovery, concentrations returned to normal in 3 h, or less. In contrast, cGMP decreased sixfold in cerebellum, but increased twofold in cortex. Recovery time for cerebellum was several hours. When oxygen was used as the carrier gas for halothane delivery, cAMP in the cortex doubled, in striking contrast to the case with halothane in air. Oxygen alone had no apparent effect. The cGMP effect of halothane delivered in oxygen appeared the same as for halothane in air. Thus, the cAMP effects of brain halothane are related to the enrichment of oxygen.