A method for concurrent measurement of picomole quantities of acetylcholine, choline, dopamine, norepinephrine, serotonin, 5-hydroxytryptophan, 5-hydroxyindoleacetic acid, tryptophan, tyrosine, glycine, aspartate, glutamate, alanine, and gamma-aminobutyric acid in single tissue samples from different areas of rat central nervous system

A rapid and sensitive method for separation and concurrent assay of 14 compounds at the picomole level in individual rat brain parts is described. The putative amino acid neurotransmitters (aspartate, γ-aminobutyric acid, glutamate, and glycine) are extracted from a 20-30 mg portion of the tissue with 5% TCA and assayed as their respective DNP-amino acid methyl ester derivatives by glc. Four other putative neurotransmitters (acetylcholine, dopamine, norepinephrine, and serotonin) and some of their precursors and metabolites (choline, tryptophan, 5-hydroxytryptophan, 5-hydroxyindoleacetic acid, and tyrosine) are extracted in 1 n formic acid-acetone ( v v: 15 85) from the remaining tissue. The lipids are removed with a heptane-chloroform ( v v: 8 1) wash and the aqueous phase is dried at 37°C under N₂. The dried extract is dissolved in water (pH 4). With one portion of this solution, acetylcholine and choline are assayed using a radioenzymatic method whereas with the rest, dopamine, norepinephrine, serotonin, 5-hydroxyindoleacetic acid, 5-hydroxytryptophan, tryptophan, and tyrosine are separated with three ion exchange resins arranged in tandem. These compounds are assayed fluorometrically with modified microadaptations of previously reported methods.