The expression of catecholamine-synthesizing enzymes in the adrenal medulla is 
upregulated in parallel by stress and pharmacological treatments. In this study 
we examined whether a neuropeptide and its processing enzyme are regulated in 
parallel with catecholamine enzyme genes after drug treatment. Because the main 
effect of stress on the adrenal medulla is via splanchnic nerve stimulation of 
nicotinic receptors, we used nicotine to stimulate the medulla and visualized 
expression of catecholamine enzyme genes, the medullary peptide neuropeptide Y 
(NPY), and the neuropeptide-processing enzyme peptidylglycine alpha-amidating 
monooxygenase (PAM) by in situ hybridization quantified by image analysis of 
autoradiographic images. Rats received a single injection of nicotine (0, 1, or 
5 mg/kg sc). Six hours later, rats were transcardially perfused. Free-floating 
adrenal gland sections were hybridized with 35S-labeled cDNA probes for tyrosine 
hydroxylase (TH), dopamine beta-hydroxylase (DBH), phenylethanolamine 
N-methyltransferase (PNMT), PAM, and NPY. Nicotine treatment upregulated the 
expression of TH, PNMT, and NPY genes in a dose-dependent fashion. Small but 
nonsignificant increases were observed in DBH and PAM mRNA levels. These results 
suggest that common transcriptional activation mechanisms may upregulate both 
catecholamine and neuropeptide synthesis in the adrenal medulla after nicotinic 
stimulation.