The vagal and spinal innervation of the gastro-duodenal junction of sheep.

This paper describes the distribution of vagal afferent, vagal preganglionic and thoraco-lumbar spinal afferent neurones to the gastro-duodenal junction of sheep which may form part of the structural basis for duodeno-gastric reflex mechanisms. After retrograde transport of cholera toxin-horseradish peroxidase (CT-HRP) from subserosal micro-injections into the gastro-duodenal junction, light-microscopic examination revealed CT-HRP-labelled cell bodies projecting from the medulla oblongata and the dorsal root ganglia. Medullary cell bodies were distributed bilaterally in the dorsal motor nucleus of the vagus (d.v.m.n.) 4.50 mm rostral and 2.52 mm caudal to a transverse plane through the obex. The sizes of brain-stem cell bodies, the extent of their dendritic arborization, axonal structure and orientation are described. Spinal sensory neurones were distributed to the thoraco-lumbar dorsal root ganglia T6-L3. Labelled cells and axons were found in the left and right vagal nodose ganglion. No labelled material was present in the lateral columns of the thoraco-lumbar spinal cord. A brain-stem map of medullary neurones was constructed from coronal sections of cresyl fast violet material. This enabled comparison between preparations and confirmed that all CT-HRP-labelled cell bodies and dendritic projections in the brain stem were confined to the d.v.m.n.