Long-term Hypoxia Induces Changes in the Substance P Immunoreactivity Pattern in Laryngeal Nerve Paraganglia

Abstract

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% 0₂) 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-β-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.

Key Words:

• paraganglia
• neuropeptides
• substance P
• hypoxia
• immunofluorescence
• rat