Medullary sites mediating some abdominal vagal reflexes in the ferret using [14C]2-deoxyglucose

The central projections of some abdominal visceral afferents passing through the vagal communicating branch were studied in anesthetized ferrets using [14C]2-deoxyglucose autoradiography. The reflex effects of electrical stimulation of the vagal communicating branch were studied while measurements of jejunal motor activity and transmural potential difference, a marker of electrogenic epithelial transport were made concurrently. The aim of this study was to examine brainstem projections of some afferent fibers in the communicating branch of the thoracic vagus nerve that are necessary for the reflex regulation of small intestinal motor activity and epithelial transport. In urethane-anesthetized ferrets, electrical stimulation of the cut central end of the vagal communicating branch increased jejunal motor activity and electrogenic epithelial transport. In addition, glucose utilization in the left medial sub-nucleus of the nucleus tractus solitarius and the dorsal motor nucleus of the vagus was significantly increased as compared with sham-operated non-stimulated control animals. Identical areas on the contralateral side of the brain showed no change in glucose utilization as compared with sham-operated non-stimulated controls. This functional brain-mapping study strongly suggests that the left medial sub-nucleus of the nucleus tractus solitarius and the dorsal motor nucleus of the vagus, in the ferret, are involved in processing alimentary afferent activity from both the small intestinal musculature and epithelium as well as the reflex changes in efferent vagal nerve activity to the same regions of the alimentary tract.