L-ARGININE PRODUCES NO-INDEPENDENT INCREASES IN DOPAMINE EFFLUX IN RAT STRIATUM

THE effect of L-arginine (L-ARG; 10-100 mM) on dopamine efflux from ra t striatum was investigated using in vivo microdialysis. L-ARG (50 mM- 100 mM), but not D-arginine (100 mM) nor L-citrulline (100 mM), produc ed a biphasic effect on dopamine efflux with an initial small reductio n, followed by a large sustained increase. The effect of L-ARG was not prevented by nitric oxide synthase inhibition with N-G-nitro-L-argini ne methyl ester or 7-nitroindazole monosodium salt. Efflux of 3,4-dihy droxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) was reduced by L-ARG (10-100 mM), D-arginine (100 mM) and L-citrulline (100 mM). These data suggest that changes in dopamine, DOPAC and HVA efflux prod uced by high concentrations of L-ARG occur independently of NO, and th at the use of high L-ARG concentrations are inappropriate when investi gating the role of NO in striatum.