FIG. 2.

Examples of HPLC chromatograms of the amino acid neurotransmitters, glutamate (GLU), glycine (GLY), γ-aminobutyric acid (GABA), as well as dopamine (DA) during wakefulness and sleep. Behavioral states of wakefulness, nonrapid-eye-movement (NREM) sleep, rapid-eye-movement (REM) sleep, and awakening are indicated by 1.5-min continuous records of electroencephalographic (EEG), electrooculographic (EOG), pontogeniculooccipital (PGO), and electromyographic (EMG) activities (A). A relatively short 1.5-min time period is depicted to clearly illustrate the characteristic and marked differences in EEG, EOG, PGO, and EMG activities that were routinely used to score behavioral state when spinal dialysis samples for glutamate, glycine, GABA, and dopamine were collected. The chromatograms in B illustrate the change in glutamate, glycine, and GABA. There were marked increases in each of these neurotransmitters only during REM sleep. In contrast, there was a marked decrease in dopamine levels only during REM sleep compared with the other behavioral states (C).