To elucidate the mechanism of general anesthesia, effects of sevoflurane anesthesia on dopamine metabolism in rat brain were studied. Sevoflurane 3% was administered for 20 minutes to Wistar male rats weighing 230-270 g under spontaneous respiration. The rats were sacrificed by decapitation and the brains were rapidly removed. They were dissected into nine discrete regions, locus coeruleus, pons plus, medulla oblongata, hypothalamus, thalamus, basal ganglia, midbrain, hippocampus, amygdala and cerebral cortex. The contents of dopamine (DA) and its major metabolites, 3, 4-dihydroxyphenyl acetic acid (DOPAC) and homovanillic acid (HVA) were measured by high performance liquid chromatography with the dual-cell coulometric detector before anesthesia, 20 minutes after the start of anesthesia and at the recovery from anesthesia. Significant increases in DA levels were observed in the pons, hypothalamus, thalamus and amygdala by sevoflurane anesthesia as compared with the control group. DOPAC levels increased significantly in the pons, hypothalamus, basal ganglia and cerebral cortex at the recovery from anesthesia. A significant increase in HVA levels was observed in amygdala by sevoflurane anesthesia, while an appreciable decrease in HVA levels was observed in hippocampus at recovery from anesthesia. It is concluded that DA metabolism is significantly suppressed in the pons, hypothalamus, thalamus, basal ganglia, midbrain and amygdala during sevoflurane anesthesia and this change in DA metabolism may be associated with the mechanism of sevoflurane anesthesia.