| Abstract: | The nucleus tractus solitarii (NTS), which receives visceralafferent information from the cardiovascular, respiratory, gastrointestinaland taste systems, contains multiple neurotrasmitters and neuropeptidesthroughout its rostral to caudal extent. The neurotransmittersand neuropeptides immunoreactivity is located predominatelyin varicose fibers and small puncta throughout the neuropil.In addition, immunoreactive NTS neurons for a variety of neurotransmittersand neuropeptides are present in subnuclear regions. The neuroactive substances localized immunohistochemically inthe NTS include acetylcholine, the neuropeptides, substanceP, methionine- and leucine-enkephalin, ß-endorphin,cholecystokinin, neurotensin, galanin, calcitonin gene-relatedpeptide, somatostatin, FMRMamide, neuropeptide Y, angiotensinII, vasoactive intestinal polypeptide, vasopressin, oxytocin,thyrotropin-releasing hormone, luteinizing hormone-releasinghormone, atrial natriuretic peptide, the catecholamines, dopamine,norepinephrine, epinephrine, serotonin, histamine and the aminoacids, GABA and glutamate. The pattern of innervation for eachneurotransmitter and neuropeptide is not homogeneously distributedthroughout the NTS. Each substance has a unique pattern withinthe NTS as each subnuclear region contains different immunohistochemicalstaining patterns and densities of fibers. At the ultrastructural level both neurotransmitters and neuropeptidesare present in synaptic terminals that are in contact with differentparts of the neuronal membranes. Typically, the labeled terminalscontain both small, clear vesicles and large, dense core vesicleswith the exception of synaptic terminals containing acetylcholine,GABA and glutamate which do not typically have the large, densecore vesicles. The most frequent post-synaptic target are dendritesand spinous processes. Less frequently, synaptic contacts arepresent on the cell soma. Chem. Senses 21: 367376, 1996. |
