Effects of Anonaine on Dopamine Biosynthesis and L-DOPA-Induced Cytotoxicity in PC12 Cells

The effects of anonaine, an aporphine isoquinoline alkaloid, on dopaminebiosynthesis and L-DOPA-induced cytotoxicity in PC12 cells were investigated. Anonaineat concentration ranges of 0.01-0.2 μM showed a significant inhibition of dopaminecontent at 24 h, with an IC50 value of 0.05 μM. Anonaine at 0.05 μM inhibited tyrosinehydroxylase (TH) and aromatic L-amino acid decarboxylase (AADC) activities to 38.4-40.2% and 78.4-90.2% of control levels at 12-24 h and 3-6 h, respectively. TH activity wasmore influenced than AADC activity. Anonaine also decreased intracellular cyclic AMPlevels, but not intracellular Ca2+ concentrations. In addition, anonaine (0.05 μM) reducedL-DOPA (50 μM and 100 μM)-induced increases in dopamine content at 24 h. However,anonaine (0.05 μM) did not enhance L-DOPA (50 μM and 100 μM)-induced cell death 476after 24 h. These results suggest that anonaine inhibits dopamine biosynthesis by mainlyreducing TH activity without aggravating L-DOPA-induced cytotoxicity in PC12 cells.