INVIVO 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 excitator y amino acids acting on dopaminergic terminals, as well as by the clas sical process of impulse-evoked exocytosis. We used in vivo microdialy sis to examine whether endogenous excitatory amino acids locally evoke dopamine efflux under basal conditions. Infusion of N-methyl-d-aspart ate (NMDA) or kainate into the neostriatum increased extracellular dop amine, and this effect was blocked by co-infusion of 2-amino-5-phospho novalerate (APV) or 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), respe ctively. However, neither these antagonists nor kynurenate decreased e xtracellular dopamine when administered alone. In contrast, infusion o f 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 dop amine in the neostriatum is not stimulated locally by endogenous excit atory amino acids.