Connections of a vagal communicating branch in the ferret II. Central projections

There is increasing interest in the central mechanisms involved in the regulation of gastrointestinal function. The ferret is becoming widely used for research in this area. However, knowledge of the brain stem organization of this species is inadequate. As part of an on-going study designed to provide information regarding the site of termination of abdominal afferents, the central connections of a supradiaphragmatic vagal communicating branch were determined in the ferret through the use of the horseradish peroxidase (HRP) tracing technique. The branch was exposed using a thoracotomy and HRP crystals were applied to the cut ventral end of the branch. Following a 72 hour survival period, the animals were reanesthetized and perfused. The brain stem was removed and processed using the tetramethylbenzidine method. Afferent terminals were found bilaterally in the nucleus of the solitary tract (nTS), area postrema (AP), the dorsal motor nucleus of the vagus (DMV), the external cuneate nucleus (ECN) and the principal subnucleus of the inferior olive (IOP). This is the first study of a brain stem projection of a specific vagal branch in this species, and demonstrates the similarities and differences which exist between the ferret and other species.