Comparative studies on the distribution of protein-o-carboxylmethyltransferase and tyrosine hydroxylase in rat brain by immunocytochemistry

The distribution of protein-O-carboxylmethyltransferase and tyrosine hydroxylase immunoreactivity in brain was compared with the use of highly specific polyclonal antibodies prepared against the native form of each enzyme. Protein-O-carboxylmethyltransferase was found in brain areas rich in catecholamine neurons as identified by tyrosine hydroxylase immunoreactivity. Rabbit anti-protein-O-carboxylmethyltransferase labeled cell bodies in the locus coeruleus, substantia nigra, and paraventricular nucleus whereas rabbit anti-tyrosine hydroxylase prepared against highly purified, native tyrosine hydroxylase from cultured PC12 cells labelled cell bodies in the same brain regions. In addition, the antibody to tyrosine hydroxylase made possible the visualization of very fine cortical processes containing tyrosine hydroxylase and very dense neuronal networks throughout the nigrostriatal pathway. The coincidence of protein-O-carboxylmethyltransferase and tyrosine hydroxylase in catecholamine rich brain areas provide an anatomical basis for the possibility that protein-O-carboxylmethyltransferase could modulate catecholaminergic neurotransmission.