Taste buds are situated at the junction of the external world and the alimentary canal. The sense of taste has been shown to play roles both in food selection and ingestion. This functional division corresponds to an anatomical division in terms of innervation of different groups of taste buds. Taste buds implicated in ingestive functions are situated closest to the esophagus and are innervated by the vagus nerve; taste buds involved in food selection are located closest to the external world and are innervated by the facial nerve. Our work has shown that taste inputs from these two gustatory nerves are procesed in different locations within the central nervous system. The disposition of glossopharyngeal nerve gustatory inputs is unknown and will be examined in the coming grant period. The proposed studies will compare and contrast the central organization of the different gustatory channels. Connections of the primary and secondary gustatory nuclei will be examined by means of horseradish peroxidase tracing techniques. The mode of termination of primary afferent fibers of the different gustatory nerves will be compared at light and electron microscopic levels. The synaptic organization of primary gustatory nuclei will be determined by means of combined degeneration and retrograde transport techniques. In addition, those areas of the CNS involved in regulation of digestion will be determined in order to delineate any areas of overlap between gustatory and digestive centers.
