ABSTRACT
Glutamate and glutamine are key amino acids in mammalian intermediary metabolism, intimately associated with aerobic metabolism via the tricarboxylic acid cycle and with ammonia metabolism. In addition they are involved in the synthetic pathways of numerous biologically important compounds. In the central nervous system (CNS), glutamate and its decarboxylation product, 4-aminobutyrate (GABA), may well function as important neurotransmitter substances. Thus superimposed on the "normal" role of glutamate and glutamine in cellular metabolism with its accompanying transport systems and enzymes is the further complication of specific membrane-associated receptor proteins and the associated ion-channel systems. Numerous studies have shown that when various CNS preparations are allowed to metabolize labeled glucose and/or acetate and then efflux of synaptic contents initiated by depolarization stimuli, there is a preferential efflux of glucose-labeled glutamate. The alkaloid veratridine was used to cause the efflux of synaptic glutamate and GABA.
