Demonstration of L-dopa decarboxylating neurons specific to human striatum.

In the human striatum, we immunohistochemically demonstrated many neurons that were immunoreactive for aromatic L-amino acid decarboxylase (AADC; the second step dopamine-synthesizing enzyme) but not for tyrosine hydroxylase (TH; the first step dopamine-synthesizing enzyme). The number of AADC-positive neurons was especially large in the ventral striatum including the nucleus accumbens. The significance of AADC-positive neurons are discussed in relation to the acting sites of L-dopa and antipsychotic drugs.