Long-term hypoxia induces changes in the substance P immunoreactivity pattern in laryngeal nerve paraganglia.

We previously showed that long-term hypoxia increases the dopamine content in rat laryngeal nerve paraganglia. In the present study paraganglia of rats exposed to hypoxia (10 +/- 0.5% O2) for 14 days were examined immunohistochemically to detect changes in the expression of neuropeptides and catecholamine-synthesizing enzymes. Hypoxia induced an intense cellular substance P (SP)-like immunoreactivity (LI) in some paraganglia and an increase in the number of stromal nerve fibers showing SP-LI in others. The patterns of tyrosine hydroxylase-, dopamine-beta-hydroxylase-, phenylethanolamine-N-methyltransferase-, vasoactive intestinal polypeptide-, neuropeptide-Y and calcitonin gene-related peptide-LI were not changed in response to hypoxia. The results show that hypoxia induces changes in the pattern of SP immunoreactivity in laryngeal nerve paraganglia and may indicate that SP plays a role in the regulation of catecholamine metabolism in this tissue.

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

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-beta-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-beta-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-beta-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-beta-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-beta-hydroxylase.

Immunocytochemical localization of L-glutamate decarboxylase and catecholamine-synthesizing enzymes in the retroperitoneal sympathetic tissue of the newborn rat.

The localization of L-glutamate decarboxylase (GAD), the enzyme synthesizing gamma-aminobutyric acid, was studied in newborn rat retroperitoneal sympathetic tissue, i.e. the main retroperitoneal paraganglion, adrenal medullae and abdominal sympathetic ganglia using the indirect immunofluorescence method. The coexistence of GAD with the catecholamine-synthesizing enzymes tyrosine hydroxylase (TH) and phenylethanolamine N-methyltransferase (PNMT) was analyzed in consecutive sections or by staining one section consecutively with different antisera. GAD immunoreactivity was observed only in some cell types of each organ studied. In the main retroperitoneal paraganglion, the small, intensely TH-immunoreactive, paraganglion-type cells were GAD-immunoreactive, while the larger moderately TH-immunoreactive, neuron-like cells were non-reactive for GAD. In the adrenal medulla, GAD immunoreactivity was localized only in the adrenaline-synthesizing, PNMT-immunoreactive chromaffin cells. The noradrenaline-synthesizing, i.e. the TH-immunoreactive cells with no PNMT immunoreactivity, were non-reactive for GAD. In the abdominal sympathetic ganglia, some small intensely TH-immunoreactive cells were GAD-immunoreactive, while the principal neurons were non-reactive for GAD. These results provide immunohistochemical evidence that GAD is present and is colocalized with catecholamine-synthesizing enzymes in various sympathetic tissues of the newborn rat. The present results indicate that GAD is localized in adrenaline-synthesizing cells of all the sympathetic tissues studied. A fraction of noradrenaline-synthesizing cells of retroperitoneal sympathetic tissues, excluding the adrenal medulla, also contains GAD.