Calcium-dependent release of N-acetylaspartylglutamate from retinal neurons upon depolarization.

N-Acetylaspartylglutamate (NAAG) is present in high concentrations specifically in the nervous system. Its neuronal distribution, presence in synaptic vesicles and its excitatory actions support the hypothesis that this dipeptide participates in communication between neurons. Following the incorporation of [3H]glutamate by frog retinal cells in vivo, the release of radiolabeled glutamate, GABA and NAAG was studied during acute incubation of the retina in vitro. Release of the radiolabeled amino acids and dipeptide was stimulated by elevated extracellular potassium. The release required the presence of extracellular calcium. These data are the first which demonstrate the release of NAAG following biosynthesis from a radiolabeled precursor and are consistent with synaptic release of this dipeptide.