Do some tyrosine hydroxylase-immunoreactive neurons in the human ventrolateral arcuate nucleus and globus pallidus produce only l-DOPA?

Abstract The presence of ‘tyrosine hydroxylase (TH)-only’ -immunoreactive (IR) neurons is reported for the first time in the human hypothalamic region and basa ganglia, using immunohistochemical technique. ‘TH-only’-IR neurons were demonstrated in the ventrolateral part of the arcuate nucleus and medial segment of globus pallidus. These neurons lacked aromatic l -amino acid decarboxylase (AADC)-, dopamine-β-hydroxylase (DBH)-, and dopamine (DA)-immunoreactivity. The above results suggest that these ‘TH-only’-IR neurons are not dopaminergic, and possibly contain l -DOPA as an end-product.