Expression of catecholamine-synthesizing enzymes in paraganglionic and ganglionic cells in the laryngeal nerves of the rat

Summary The rat recurrent and superior laryngeal nerves with adjacent connective tissue were examined by immunohistochemical techniques for localization of the catecholamine-synthesizing enzymes tyrosine hydroxylase, dopamine--hydroxylase and phenylethanolamine-n-methyltransferase. Most of the cells in the paraganglia of the recurrent and superior laryngeal nerves showed an intense tyrosine hydroxylase-like immunoreactivity. A few paraganglionic cells exhibited dopamine--hydroxylase-like immunoreactivity while none of the cells displayed phenylethanolamine-n-methyltransferase-like immunoreactivity. Some of the ganglionic cells in the recurrent and superior laryngeal nerves showed dopamine--hydroxylase-like immunoreactivity whilst these cells never showed tyrosine hydroxylase- or phenylethanolamine-N-methyltransferase-like immunoreactivity. The arterioles were supplied with plexuses of nerve fibres showing tyrosine hydroxylase- and dopamine--hydroxylase-like immunoreactivity. The results indicate that dopamine is the major catecholamine located in the laryngeal nerve paraganglia and show that ganglionic cells in the recurrent and superior laryngeal nerves show immunolabelling for one of the enzymes in the catecholamine synthetic pathway, dopamine--hydroxylase.