Detection of tyrosine hydroxylase and phenylethanolamine-N-methyltransferase messenger RNAs in the mouse adrenal gland and the brain by in situ hybridization.

To study the expression of tyrosine hydroxylase (TH) and phenylethanolamine-N-methyltransferase (PNMT) genes in the mouse adrenal gland and the brain, we performed in situ hybridization studies by using several types of complementary DNA probes recognizing coding regions of human TH (THc), the 3'-end of the human region of TH (TH3'), and the coding region of the human PNMT (PNMTc). THc mRNA was detected in the chromaffin cells of the mouse adrenal medulla and brain catecholaminergic neurons including the substantia nigra and ventral tegmental area. TH-immunopositive neurons were located in a similar pattern in adjacent sections. However no positive signals were detected by the TH3' probe. Using the PNMTc probe, the majority of cells in the adrenal medulla demonstrated positive labelling. Although the mouse TH and PNMT genes have not been fully isolated and sequenced, the present study strongly suggests that the sequence of the coding regions of TH and PNMT are similar in human and mouse. The THc and PNMTc probes are particularly useful in investigating the loci of gene transcription in mouse tissues.