Decarboxylation of exogenous L-DOPA in rat striatum after lesions of the dopaminergic nigrostriatal neurons: the role of striatal capillaries.

In rats with unilateral nigrostriatal lesions, L-DOPA-induced dopamine increases in ipsilateral striata were further enhanced after inhibition of DOPA decarboxylase in cerebral microvessels by carbidopa. DOPA levels were similar, but dopamine increases in lesioned striata were smaller, after carbidopa and DOPA (100 mg/kg) than after DOPA alone (500 mg/kg). These findings suggest that after degeneration of dopaminergic terminals, striatal decarboxylation of exogenous DOPA occurs partly, but not exclusively, in tbe capillaries.