Effect of lithium on brain 5-hydroxytryptamine metabolism in mice.

Administration of lithium carbonate (2 mEq/kg) i.p., twice daily for 3 days to mice did not significantly after brain 5-hydroxytryptamine (5-HT) levels; however, brain 5-hydroxyindoleacetic acid (5-H1AA) accumulation after i.p. injection of probenecid (200 mg/kg) was significantly increased in lithium pretreated animals. Brain 5-hydroxytryptophan decarboxylase activity was enhanced by lithium pretreatment while brain monoamine oxidase (MAO) activity was unaltered. After i.p. injection of the monoamine oxidase inhibitor pargyline (100 mg/kg) the accumulation of brain 5-HT was greater in lithium treated than control mice, while the decrease in brain 5-HT levels after i.p. treatment with the 5-HT synthesis inhibitor para-chlorophenylalanine (PCPA 300 mg/kg) was significantly less in lithium pretreated mice.