Dopaminergic modulation of glutamate release in striatum as measured by microdialysis.

Glutamate and aspartate are the primary neurotransmitters of projections from motor and premotor cortices to the striatum. Release of glutamate may be modulated by dopamine receptors located on corticostriatal terminals. The present study used microdialysis to investigate the dopaminergic modulation of in vivo striatal glutamate and aspartate release in the striatum of awake-behaving rats. Local perfusion with a depolarizing concentration of K+ through a dialysis probe into the rat striatum produced a significant increase in the release of glutamate, aspartate, and taurine. The D2 agonist LY171555 blocked the K(+)-induced release of glutamate and aspartate, but not taurine, in a concentration-dependent manner. The D1 agonist SKF 38393 did not alter K(+)-induced release of glutamate and taurine, but did significantly decrease aspartate release. Neither agonist had any effect on basal amino acid release. The D2 antagonist (-)-sulpiride reversed the inhibitory effects of LY 171555 on K(+)-induced glutamate release. These results provide in vivo evidence for a functional interaction between dopamine, the D2 receptor, and striatal glutamate release.