Effects of L-dopa on dopamine and norepinephrine concentrations in rat brain assessed by gas chromatography.

A highly specific and sensitive gas chromatographic method has been developed which is capable of determining picogram amounts of dopamine (DA) and norepinephrine (NE) simultaneously. The catecholamines are converted to the N-2,6-dinitro-4-trifluoromethylphenyl, O-trimethylsilyl derivatives, which are analyzed by gas chromatography with electron-capture detection. The method has been applied to the assay of catecholamines in rat brain extracts. One hour after an acute dose (150 mg/kg i.p.) of L-3,4-dihydroxyphenylalanine, the rat brain concentration of DA increased by 130% while the concentration of NE was unchanged.