Automated method to estimate catecholamine and indoleamine content and turnover rates

A double-label isotopic method for estimation of the rate of formation of serotonin (5-HT) and dopamine (DA) in mouse striatum, hippocampus and cortex was standardized. Mice received an intravenous pulse injection of [3H]tryptophan (TRP) and [3H]tyrosine (TYR) at 2.5, 5, 10 or 20 min before sacrifice by microwave irradiation. Compounds of interest were separated by automated high-performance liquid chromatography and their contents were determined by electrochemical detection. Programmed collection of the TYR, DA, 5-HT and TRP peaks allowed determination of their radioactivity by liquid scintillation. Conversion of [3H]TYR to [3H]DA was nearly ten times greater in striatum than cortex, whereas the formation of [3H]5-HT from [3H]TRP was similar in striatum, cortex and hippocampus.