Value of monoamine metabolite determinations in CSF as an index of their concentrations in rat brain following various pharmacological manipulations.

Using reversed-phase high performance liquid chromatography with electrochemical detection it is possible to measure concomitantly the concentration of several monoamines, their metabolites and aminoacid precursors in 100 microliters of rat cerebrospinal fluid. To study the quantitative relationship between CSF and brain, alterations in brain monoamines and monoamine metabolites were effected by treatment with L-DOPA or L-5HTP administered with or without concomitant inhibition of extracerebral aromatic amino acid decarboxylase and by treatment with alpha-monofluoromethyldopa, probenecid, haloperidol, or probenecid plus haloperidol. The concentrations of the monoamine metabolites, 5-hydroxyindoleacetic acid, 3,4-dihydroxyphenylacetic acid, and homovanillic acid as well as of the L-DOPA metabolite, 3-methoxy-4-hydroxyphenylalanine in the cerebrospinal fluid were linearly correlated with the concentrations of these metabolites in the brain. However, these correlations need to be interpreted cautiously, since the slopes of the individual regression lines obtained after different pharmacological treatments differed significantly.