EFFECTS OF L-ENANTIOMER AND D-ENANTIOMER OF N-OMEGA-NITRO-ARGININE ONNMDA-EVOKED STRIATAL DOPAMINE OVERFLOW

The microdialysis method was utilized to study the effects of N-omega- nitro-L-arginine (L-NNA) and N-omega-nitro-D-arginine (D-NNA), an inhi bitor of nitric oxide (NO) synthesis from L-arginine and its D-enantio mer, on spontaneous and N-methyl-D-aspartate (NMDA)-evoked overflow of striatal extracellular dopamine (DA) in unanesthetized, freely moving rats. Perfusion of 3-10 mM NMDA through the microdialysis probe resul ted in a dose-dependent increase in striatal DA overflow. Perfusion of 500 mu M L-NNA alone did not change the DA level significantly, but w hen added to 3 mM NMDA, it substantially suppressed the NMDA-evoked in crease of DA. Perfusion of 500 mu M D-NNA altered neither the basal no r the NMDA-evoked DA level. Data suggest that the stimulatory effect o f NMDA in DA release involves activation of the L-arginine-NO pathway in the striatum.