Stability of the amino acid content of nerve endings after administration of gamma-aminobutyrate agonists and antagonists.

The administration of GABA agonists or antagonists to mice resulted in unchanged levels of aspartate, glutamate, GABA and taurine in nerve endings (synaptosomes). On the other hand, agonist-induced increases in the levels of some of the amino acids occurred in locations other than the nerve endings. The GABA agonist SL75102 inhibited in vitro uptake of D-aspartate into synaptosomes, thereby raising the possibility that a similar phenomenon may cause an in vivo redistribution of glutamate and aspartate in brain tissue.