Medullary projections of vagal and related motor nuclei to the larynx as studied with WGA-HRP technique in the ferret (Mustela Putorius Furo).

ABSTRACT

The brain-stem origin of preganglionic parasympathetic nerve fibres in the superior laryngeal and recurrent laryngeal nerves of the ferret were determined using wheat germ aggutinin conjugated horseradish peroxidase (WGA-HRP). The two nerves were dissected in separate experiments and each nerve section very close to the larynx, and the central cut end of each nerve was then desheathed and inserted into polyethylene tubing filled with 10µl of WGA-HRP. Control ferrets had tracer injections into the nearby internal jugular vein. After 48-72 hours, each ferret was anaesthesized and perfused intracardially with normal saline, fixative and buffered sucrose. Transverse frozen sections of the brainstem were then taken from each ferret and examined for the presence of WGA- HRP labeled cells. In the superior laryngeal nerve (SLN) experiments, labeled cells were seen in the dorsal motor nucleus of the vagus nerve (DMNV) and the nucleus ambiguus (nA) while in the recurrent laryngeal nerve (RLN) experiments, labeled cells were seen only in the nA. An area of overlap of origins of superior laryngeal and recurrent laryngeal nerve fibres was observed in the intermediate part of the nA. No labeled cells were seen in any of the control experiments in which the tracer was injected into the internal jugular vein.