Mass chromatograms of a representative fraction (1 μL) collected from the striatum of an anesthetized through the Si probe. The trace for each of the 17 neurotransmitters and metabolites labeled were from a particular MS → MS transition monitored by LC-MS as described elsewhere.32 Abbreviations used are: acetylcholine (ACh), taurine, histamine (Hist), serine (Ser), aspartate (Asp), glycine (Gly), glutamate (Glu), γ-aminobutyric acid (GABA), adenosine, 5-hydroxyindoleacetic acid (5-HIAA), homovanillic acid (HVA), normetanephrine, 3,4-dihydroxyphenylacetic acid (DOPAC), serotonin (5-HT), 3-methoxytyramine (3-MT), norepinephrine (NE), dopamine (DA).