ABSTRACT
This chapter presents an overview of the organization of vagal nerve nuclei in a variety of vertebrate species at different grades of organization. Although the gross structure and organization of vagal nuclei is similar in amniote vertebrates, great variations can be found in vagal structures among the teleost fishes. Even in many percimorphs, however, vagal lobes are present rather than a diminutive nucleus of the solitary tract as occurs in most other vertebrates. Primary vagal sensory fibers terminate only in restricted layers of this structure with a large part of the vagal lobe being devoted to interneuron systems. Similarly, the nucleus of the solitary tract of rats is organized in an organotopic fashion. Similarly, in pigeons, the nucleus of the solitary tract has reflex connections to the nucleus ambiguus and the dorsal motor nucleus. In the amniote vertebrates, the projection from the nucleus of the solitary tract to these two targets is organized organotopically.
