Effect of long-term L-dopa administration on striatal extracellular dopamine release.

When L-dopa was administered acutely to rats, the increase in the extracellular level of dopamine in the corpus striatum was attenuated by 43% in animals that had received L-dopa daily for 60 days as compared with animals receiving placebo. These findings indicate that chronic treatment with L-dopa impairs striatal dopamine formation or release.