L-arginine modulates morphine-induced changes in locomotion in mice

In mice opioids increase dopaminergic turnover in nucleus striatum and nucleus accumbens, causing behavioural changes such as increased locomotion. In this study we have shown that L-arginine administration increases morphine-induced locomotion in mice. D-Arginine had not effect, suggesting a stereospecific mechanism. Furthermore NG-nitro-L-arginine methyl ester, a specific inhibitor of nitric oxide synthase, reduced morphine-induced effect. These results suggest that endogenous nitric oxide could play a role in the modulation of dopaminergic effects elicited by morphine.