Amantadine increases L-DOPA-derived extracellular dopamine in the striatum of 6-hydroxydopamine-lesioned rats.

We investigated the effect of amantadine on L-DOPA-derived extracellular dopamine (DA) levels and aromatic L-amino acid decarboxylase (AADC) activity in the striatum of rats with nigrostriatal dopaminergic denervation by 6-hydroxydopamine (6-OHDA). Pretreatment with 30 mg/kg amantadine increased the cumulative amount of extracellular DA in the striatum of 6-OHDA-lesioned rats treated with 10 mg/kg benserazide and 50 mg/kg L-DOPA to 250% of that without amantadine (P<0.01). Under pretreatment with 10 mg/kg benserazide, AADC activity after 30 mg/kg amantadine administration was reduced to 43% of controls (P<0.01). Amantadine-induced increase in L-DOPA-derived extracellular DA provides the basis for the clinical usefulness of amantadine in combination with L-DOPA. However, the effect of amantadine on L-DOPA-derived extracellular DA may not be caused by changes in AADC activity.