ROLE OF THE L-ARGININE NITRIC-OXIDE PATHWAY IN THE BASAL HYDROXYL RADICAL PRODUCTION IN THE STRIATUM OF AWAKE RATS AS MEASURED BY BRAIN MICRODIALYSIS

In the present study, using the microdialysis technique, we provided e vidence of the existence of hydroxyl radicals ((OH)-O-.) in the striat um of awake rats under physiological conditions. This (OH)-O-. generat ion was virtually abolished by the N-methyl-D-aspartate (NMDA) recepto r antagonist dizocilpine. On the contrary, it was significantly enhanc ed by the (NO)-N-. synthase inhibitor N-G-nitro-L-arginine methyl este r (L-NAME). The effect of L-NAME was completely reversed by L-arginine . These results suggest that the basal (OH)-O-. production is largely the consequence of an NMDA receptor-mediated glutamatergic tone. Moreo ver, it is likely that endogenous (NO)-N-. exerts an antioxidant activ ity in brain by preventing the rise in (OH)-O-. levels.