N(G)-Nitro-D-arginine methyl ester (D-NAME) is the less active enantiomer of the nitric oxide (NO) synthase inhibitor N(G)-nitro-L-arginine methyl ester . D-NAME was initially thought to be inactive and was often used as a negative control for L-NAME. Later studies showed that D-NAME (40 mg/kg/day in rats) can have similar but less pronounced effects as L-NAME (40 mg/kg/day in rats) in the cardiovascular system, particularly at long-term timepoints. D-NAME (3-10 µg/mouse) had no effect on nociception in mice assessed using the tail flick test.