N-METHYL-D-ASPARTATE STIMULATES DOPAMINE RELEASE THROUGH NITRIC-OXIDE FORMATION IN THE NUCLEUS-ACCUMBENS OF RATS

Intracerebral microdialysis technique was utilized to study the effect of N-G-nitro-L-arginine, a nitric oxide (NO) synthase inhibitor, on N-methyl-D-aspartate (NMDA)-induced dopamine overflow in the nucleus accumbens of unanesthetized, freely moving rats. Perfusion of 1 and 3 mM NMDA through the microdialysis probe dose-dependently increased the extracellular dopamine level in the nucleus accumbens. Coapplication of 0.5 mM D-(-)-2-amino-5-phosphonovaleric acid (D-APS), a selective and competitive NMDA receptor antagonist, significantly reduced the dopamine overflow induced by 3 mM NMDA. Perfusion of 0.5 mM N-G-nitro-L-arginine alone did not affect the basal dopamine level, whereas it suppressed the NMDA-evoked dopamine overflow in the nucleus accumbens when concurrently applied with 3 mM NMDA. These results suggest that NO mediates, at least in part, dopamine release resulting from NMDA receptor activation in the nucleus accumbens of rats.