Effects of ethanol consumption and intake of low-carbohydrate (low-CHO) diet on noradrenaline (NA), dopamine (DA) and its metabolite, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), serotonin (5HT) and its metabolite, 5-hydroxyindoleacetic acid (5HIAA) contents in six brain regions of rats were investigated. 1) Change of DA neuron Ethanol-containing control diet (hypercaloric ethanol diet) did not affect DA content in any area of brain, but decreased HVA in cortex and hypothalamus and increased DOPAC and HVA in midbrain. Low-CHO diet increased DA content in striatum, DOPAC and HVA in midbrain, but decreased DOPAC in hippocampus and hypothalamus, and HVA in cortex, pons and medulla, hippocampus and hypothalamus. Ethanol-containing low-CHO diet (isocaloric ethanol diet) increased DA level in striatum, DOPAC and HVA in midbrain, but decreased HVA in cortex, hippocampus, striatum and hypothalamus. These results suggest that i) hypercaloric ethanol diet has an opposite effect to carbohydrate on DA metabolism: hypercaloric ethanol diet and lowered carbohydrate intake per se enhance DA metabolism in midbrain, whereas inhibit it in cortex and hypothalamus, ii) lowered carbohydrate intake also declines DA metabolism in pons and medulla and hippocampus, whereas enhances DA synthesis in striatum, iii) the combined effect of ethanol and carbohydrate intake on DA metabolism is inhibited each other in the rats of isocaloric ethanol diet feeding, and this diet decreased DA metabolism in striatum. 2) Change of 5HT neuron Hypercaloric ethanol diet did not affect the contents of 5HT and 5HIAA in any region of brain.(ABSTRACT TRUNCATED AT 250 WORDS)