Connections of a vagal communicating branch in the ferret I. Pathways and cell body location

In contrast to most other species, ferrets possess a single communicating branch connecting the dorsal and ventral vagal trunks immediately rostral to the diaphragm. This branch is being used in physiological studies of gastrointestinal function and emesis. However, the fibre routes which pass through this branch are not known. In this study, the afferent and efferent pathways within this supradiaphragmatic vagal communicating branch of the ferret were studied through the use of the horseradish peroxidase (HRP) tracing technique. The region of the branch was exposed using a thoracotomy and HRP crystals were applied to one of the following: (A) the ventral end of the communicating branch, (B) the dorsal end of the communicating branch, (C) the distal end of the dorsal vagal trunk rostral to the communicating branch or (D) the distal end of the ventral vagal trunk rostral to the communicating branch. Following a 72 hour survival period, the animals were reanaesthetized and perfused. The superior cervical and nodose ganglia and the brain stem were processed using the tetramethylbenzidine method. Following application of HRP to the cut ventral end of the communicating branch, labelled cell bodies were found in the left and right nodose ganglia and in the left dorsal motor nucleus of the vagus. After HRP application to the cut dorsal end of the communicating branch, labelled cells were found in the left and right nodose ganglia. No HRP containing cell bodies were found following HRP application to the cut distal end of either the dorsal or the ventral vagal trunk. These results indicate that several afferent pathways exist within the branch, although only one consistently labelled efferent pathway was found.