Tyrosine hydroxylase gene expression in human ventral mesencephalon: detection of tyrosine hydroxylase messenger RNA in neurites.

The distribution of both tyrosine hydroxylase (TH) antigen and messenger RNA was investigated in the ventral mesencephalon from human brain using a 35S-labeled human TH cDNA probe and a polyclonal TH antibody. A hybridization signal was detected not only in the perikaryon but also in the neurites, most probably dendrites, of immunoreactive neurons. In cell bodies, the level of TH mRNA varies, revealing a regional heterogeneity. In the substantia nigra of patients with Parkinson's disease the number of labeled cells was markedly reduced as compared to controls.