Networks of peptide-containing nerve fibres in laryngeal nerve paraganglia. An immunohistochemical study.

Sections of rat superior and recurrent laryngeal nerves (SLN and RLN) with enclosed paraganglia and ganglionic cells were incubated with antisera against five different neuropeptides. Vasoactive intestinal polypeptide-like immunoreactivity (VIP-LI) and neuropeptide Y (NPY)-LI was detected in a large number of varicose nerve fibres in the paraganglia. A few varicosities of the paraganglia showed substance P (SP)-LI or calcitonin gene-related peptide (CGRP)-LI, whereas there were no signs of enkephalin (ENK)-LI in these varicosities. The paraganglionic cells never exhibited immunoreactivity for any of the peptides tested, whereas some of the associated ganglionic cells showed NPY-LI, VIP-LI or ENK-LI. The study shows that the paraganglia of the SLN and RLN receive a significant peptidergic innervation and suggests that the peptide-containing nerve fibres in these structures originate from cells other than the paraganglionic cells. The findings imply that in further studies defining the function of laryngeal nerve paraganglia in larynx physiology, the role of neuropeptides should be examined.