ABSTRACT
Since a major source of central nervous system innervation to the gut is provided by the vagus nerve, considerable study has been devoted to determining the brainstem organization of vagal projections from the alimentary tract. The topographical representation of the alimentary tract within the nucleus tractus solitarii (NTS) has been extensively studied by organ specific injections of neuroanatomical tracers. In the rat, direct intramuscular injections of horseradish peroxidase conjugates into different areas of the alimentary tract result in afferent terminal labeling confined to the NTS, paratrigeminal islands and the spinal trigeminal nucleus. The authors examined the ultrastructure of gastric vagal motoneurons and gastric vagal sensory afferents in the dorsal vagal complex of rats to determine whether monosynaptic contacts exist between them. Vagal motoneurons within the dorsal vagal complex have widespread dendrites which ramify rostrocaudally within both the dorsal motor nucleus and the NTS, enabling them to receive input from fibers of diverse origin.
