Tyrosine hydroxylase and aromatic L-amino acid decarboxylase do not coexist in neurons in the human anterior cingulate cortex

Immunoreactivity for aromatic L-amino acid decarboxylase (AADC), the second step dopamine-synthesizing enzyme, was found immunohistochemically in neur ons of the human anterior cingulate cortex (ACC). Most of these neurons wer e located in layers V and VI and subcortical white matter; a small number w ere occasionally found in layer ill. Double immunohistochemistry for tyrosi ne hydroxylase (TH: the first step dopamine-synthesizing enzyme) and AADC r evealed that no neuronal cell bodies in the ACC were doubly immunostained f or TH and AADC, suggesting that these TH-only-or AADC-only-immunoreactive n eurons were not dopaminergic. AADC neurons in the human ACC might transform L-DOPA to dopamine, droxidopa to noradrenaline, and/or 5-hydraxytryptophan to serotonin. (C) 1999 Elsevier Science Ireland Ltd. All Fights reserved.