In vivo regulation of extracellular dopamine in the neostriatum: influence of impulse activity and local excitatory amino acids.

It has been suggested that dopamine release can be evoked by excitatory amino acids acting on dopaminergic terminals, as well as by the classical process of impulse-evoked exocytosis. We used in vivo microdialysis to examine whether endogenous excitatory amino acids locally evoked dopamine efflux under basal conditions. Infusion of N-methyl-d-aspartate (NMDA) or kainate into the neostriatum increased extracellular dopamine, and this effect was blocked by co-infusion of 2-amino-5-phosphonovalerate (APV) or 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), respectively. However, neither these antagonists nor kynurenate decreased extracellular dopamine when administered alone. In contrast, infusion of tetrodotoxin into the medial forebrain bundle reduced extracellular dopamine to below the limit of detection of our assay. These and other findings reviewed in this report suggest to us that extracellular dopamine in the neostriatum is not stimulated locally by endogenous excitatory amino acids.