Monoamine metabolism and its responses to food deprivation in the brain of Zucker rats.

Monoamines and their metabolites levels were simultaneously measured by high-performance liquid chromatography in brain regions of lean and fatty Zucker rats when fed ad lib and deprived of food for 72 hr to evaluate each monoamine metabolism. Metabolite/monoamine ratios were shown for brevity to represent its metabolism. 3-Methoxy-4-hydroxyphenylethyleneglycol/noradrenaline ratios were not affected by the phenotype factor but increased in the cortex of fatty rats and reduced in the midbrain of both phenotypes after fasting; the interaction between phenotype and feeding factors was observed in the cortex and hippocampus. 3,4-Dihydroxyphenylacetic acid/dopamine ratios were increased in the cortex of deprived fatty rats and in the medulla-pons of ad lib-fed fatties compared with lean counterparts and also increased in the striatum of lean rats after food deprivation; the interaction was observed in the cortex, midbrain and medulla-pons. Homovanillic acid/dopamine ratios were decreased in the striatum of deprived fatty rats and in the midbrain and medulla-pons of fatty rats whether deprived or not, but the ratios were not significantly changed by fasting; the interaction was observed in the striatum. 5-Hydroxyindoleacetic acid/5-hydroxytryptamine ratios were reduced in the cortex, striatum and medulla-pons of fatty rats in both feeding states and in the midbrain of deprived fatties, and after food deprivation increased in the cortex and midbrain of lean rats and in the hippocampus of both phenotypes; the interaction was observed in the midbrain.(ABSTRACT TRUNCATED AT 250 WORDS)