Neurophysiological and morphological studies are planned to learn how developing peripheral and central nervous system taste neurons change functionally and structurally during normal development and how these processes are influenced by early environmental factors. Neurophysiological taste responses from single chorda tympani nerve fibers will be recorded in normal rats and in rats that have an attenuated taste response selectively to sodium salts as a result of being fed a sodium-deficient diet throughout development. In vivo voltage clamp experiments in combination with taste stimulation will be used to examine the response properties and the voltage sensitivity of these taste fibers and to determine the site of response alterations in taste receptor cells due to dietary sodium restriction (Specific Aim 1). Experiments are also planned to further our understanding of the relationship between taste bud size and number of neurons that innervate each taste bud during normal development and in sodium-restricted rats (Specific Aim 2). In addition to the studies that focus on the peripheral gustatory system, two specific aims are devoted to examine the structural and functional plasticity of the developing central gustatory system. Namely, the arborization pattern of single chorda tympani fibers in normal and sodium-restricted rats will be examined morphologically in the nucleus of the solitary tract (NST), the first central gustatory relay (Specific Aim 3), and the functional critical period for dietary effects on taste responses will be identified for neurons in the NST (Specific Aim 4). The proposed studies will provide new information on: 1) the chemical specificities of single chorda tympani fibers in control and sodium restricted rats, and localization and quantification of functional transduction elements for sodium taste, 2) how taste bud size and number of innervating taste fibers match each other during postnatal development and how early NaCl restriction affects such a match, 3) how the arborization and projection patterns of single neurons are affected by early NCI restriction, and 4) what the developmental endpoints are for the critical period in which early NaCl restriction affects central gustatory system function. The findings will provide new information on the development of peripheral and central nervous system taste responses and the neuroanatomical organization of the developing gustatory system. Such information will ultimately be used to better understand the biological basis for the development of taste preferences and aversions, and the role that prenatal diets have on shaping taste system structure and function.

National Institute of Health (NIH)
National Institute on Deafness and Other Communication Disorders (NIDCD)
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Special Emphasis Panel (ZRG1-HAR (01))
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University of Virginia
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Collins, L N; Hill, D L; Brunjes, P C (2018) Myelination of the developing lateral olfactory tract and anterior commissure. J Comp Neurol 526:1843-1858
Sun, Chengsan; Krimm, Robin; Hill, David L (2018) Maintenance of Mouse Gustatory Terminal Field Organization is Dependent on BDNF at Adulthood. J Neurosci :
Sun, Chengsan; Hummler, Edith; Hill, David L (2017) Selective Deletion of Sodium Salt Taste during Development Leads to Expanded Terminal Fields of Gustatory Nerves in the Adult Mouse Nucleus of the Solitary Tract. J Neurosci 37:660-672
Skyberg, Rolf; Sun, Chengsan; Hill, David L (2017) Maintenance of Mouse Gustatory Terminal Field Organization Is Disrupted following Selective Removal of Peripheral Sodium Salt Taste Activity at Adulthood. J Neurosci 37:7619-7630
Dvoryanchikov, Gennady; Hernandez, Damian; Roebber, Jennifer K et al. (2017) Transcriptomes and neurotransmitter profiles of classes of gustatory and somatosensory neurons in the geniculate ganglion. Nat Commun 8:760
Meng, Lingbin; Huang, Tao; Sun, Chengsan et al. (2017) BDNF is required for taste axon regeneration following unilateral chorda tympani nerve section. Exp Neurol 293:27-42
Meng, Lingbin; Ohman-Gault, Lisa; Ma, Liqun et al. (2015) Taste Bud-Derived BDNF Is Required to Maintain Normal Amounts of Innervation to Adult Taste Buds. eNeuro 2:
Sun, Chengsan; Dayal, Arjun; Hill, David L (2015) Expanded terminal fields of gustatory nerves accompany embryonic BDNF overexpression in mouse oral epithelia. J Neurosci 35:409-21
Graham, Dustin M; Sun, Chengsan; Hill, David L (2014) Temporal signatures of taste quality driven by active sensing. J Neurosci 34:7398-411
Wang, Siting; Corson, James; Hill, David et al. (2012) Postnatal development of chorda tympani axons in the rat nucleus of the solitary tract. J Comp Neurol 520:3217-35

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