ABSTRACT
The nucleus tractus solitarii (NTS), located in the dorsomedial medulla in most species, is a cylindrically shaped nucleus that extends from the level of the gracile and cuneate nuclei in the caudal medulla to the facial motor nucleus at the pontomedullary junction. A number of different techniques have been used to localize neurotransmitter/neuropeptides at the ultrastructural level. These include pre- and postembedding immunocytochemistry and autoradiography. The use of ultrastructural studies to localize a number of the neurotransmitters/neuromodulators within synaptic terminals has attempted to answer, if many of these neurochemicals are components of synaptic circuits within the NTS. Acetylcholine immunoreactive terminals in the NTS contain a single population of round, clear synaptic vesicles and asymmetrical junctions. The NTS contains a diverse population of neurotransmitters/neuropeptides that have a specific pattern within the different subdivisions of the nucleus. The presence of large numbers of neurotransmitters/neuropeptides in the NTS indicates the multiplicity of information processing the nucleus is responsible for.
