Peptide-containing neurons projecting to the vocal cords of the rat: retrograde tracing and immunocytochemistry

The distribution and origin of neuropeptide Y-, vasoactive intestinal peptide- and calcitonin gene-related peptide-containing nerve fibers and adrenergic (dopamine-beta-hydroxylase-containing) fibers in the rat larynx were studied by retrograde tracing and selective denervations in combination with immunocytochemistry. An injection of the retrograde tracer True Blue to the right vocal cord resulted in the appearance of labelled nerve cell bodies in the ipsi- and contralateral superior cervical and stellate ganglia, the thyroid ganglia, the jugular-nodose ganglionic complexes, in the ipsilateral trigeminal and dorsal root ganglia at levels C2 and C3 and in local tracheal ganglia. Judging from the number of labelled nerve cell bodies, the jugular-nodose ganglionic complexes, dorsal root ganglia and superior cervical ganglia provide the greater part of the vocal cord innervation. Most of the True Blue-labelled nerve cell bodies in the superior cervical and stellate ganglia contained neuropeptide Y. In the thyroid ganglia the majority of labelled nerve cell bodies contained vasoactive intestinal peptide. In the jugular-nodose ganglionic complex and the dorsal root ganglia the majority of the labelled nerve cell bodies stored calcitonin gene-related peptide. Retrograde tracing and denervation studies revealed that all noradrenaline- and the majority of neuropeptide Y-containing nerve fibers emanate from the superior cervical and stellate ganglia. A minor population of neuropeptide Y-containing nerve fibers originate in local tracheal ganglia. The vasoactive intestinal peptide-containing nerve fibers originate in the thyroid ganglion and local tracheal ganglia, whereas calcitonin gene-related peptide-containing nerve fibres emanate from the dorsal root ganglia (C2-C3), the trigeminal ganglia and the jugular-nodose ganglia.