. Taste stimuli interact with taste-sensitive cells in taste buds, the majority of which are located in papillae on the upper surface of the tongue. Substances with appetitive tastes (e.g., sweet stimuli) are normally ingested; those that are aversive (e.g., bitter stimuli) are rejected, although these tendencies can be modified by experience. Some of the changes that occur in taste preferences appear to be age related and this has been well-documented in rodent models. Changes in taste sensitivity to sodium chloride with early postnatal development are especially clear. Some sensitivity to sodium chloride is present at birth, but much develops later, particularly when the animals are weaned. There are two modes of salt-taste sensing, which appear to reside in different regions of the taste bud. One sensor, on the apical microvilli of taste cells, makes direct contact with the mouth fluid. The other is sequestered on the basolateral membrane of the cells so that some stimuli must diffuse through the tight junctions separating the apical and basolateral domains of the cells to reach the receptor sites. Data suggest that access to these basolateral sites can be blocked by calcium, and that the tight junction permeability to taste stimuli changes during development. In vivo recordings of taste nerve responses, with the receptive field under voltage-clamp, will be used to screen for candidate stimuli of the basolateral receptor sites in developing and mature rats. In parallel, a newly developed in vitro technique will be used to make direct measurements of fluxes of various stimuli across the paracellular regions of single fungiform papillae. Both fluorescent dyes and ion selective microelectrodes will be used to measure fluxes of hydrogen ions due to several acids, various salts of sodium and potassium, calcium ions, and ammonium ion derivatives. Calcium is especially important because it is expected to reduce its own paracellular permeability as well as that of other stimuli. These experiments will determine the actual range of stimulating concentrations of stimuli on the basolateral side of the taste buds, which preliminary results indicate are far lower than the concentrations placed on the tongue. Methods will also be developed to determine the buffering properties of the lateral intercellular spaces for hydrogen and calcium.

Agency
National Institute of Health (NIH)
Institute
National Institute on Deafness and Other Communication Disorders (NIDCD)
Type
Research Project (R01)
Project #
5R01DC002422-08
Application #
6516140
Study Section
Special Emphasis Panel (ZRG1-IFCN-4 (01))
Program Officer
Davis, Barry
Project Start
1994-08-01
Project End
2004-06-30
Budget Start
2002-07-01
Budget End
2003-06-30
Support Year
8
Fiscal Year
2002
Total Cost
$310,238
Indirect Cost
Name
Virginia Commonwealth University
Department
Physiology
Type
Schools of Medicine
DUNS #
City
Richmond
State
VA
Country
United States
Zip Code
23298
Lyall, Vijay; Heck, Gerard L; Vinnikova, Anna K et al. (2005) A novel vanilloid receptor-1 (VR-1) variant mammalian salt taste receptor. Chem Senses 30 Suppl 1:i42-3
Lyall, Vijay; Heck, Gerard L; Phan, Tam-Hao T et al. (2005) Ethanol modulates the VR-1 variant amiloride-insensitive salt taste receptor. II. Effect on chorda tympani salt responses. J Gen Physiol 125:587-600
Lyall, Vijay; Heck, Gerard L; Phan, Tam-Hao T et al. (2005) Ethanol modulates the VR-1 variant amiloride-insensitive salt taste receptor. I. Effect on TRC volume and Na+ flux. J Gen Physiol 125:569-85
Lyall, Vijay; Heck, Gerard L; Vinnikova, Anna K et al. (2004) The mammalian amiloride-insensitive non-specific salt taste receptor is a vanilloid receptor-1 variant. J Physiol 558:147-59
Lyall, Vijay; Alam, Rammy I; Malik, Shahbaz A et al. (2004) Basolateral Na+-H+ exchanger-1 in rat taste receptor cells is involved in neural adaptation to acidic stimuli. J Physiol 556:159-73
Vinnikova, Anna K; Alam, Rammy I; Malik, Shahbaz A et al. (2004) Na+-H+ exchange activity in taste receptor cells. J Neurophysiol 91:1297-313
Lyall, Vijay; Alam, Rammy I; Phan, Tam-Hao T et al. (2002) Modulation of rat chorda tympani NaCl responses and intracellular Na+ activity in polarized taste receptor cells by pH. J Gen Physiol 120:793-815
Lyall, Vijay; Alam, Rammy I; Phan, Tam-Hao T et al. (2002) Excitation and adaptation in the detection of hydrogen ions by taste receptor cells: a role for cAMP and Ca(2+). J Neurophysiol 87:399-408
DeSimone, J A; Lyall, V; Heck, G L et al. (2001) Acid detection by taste receptor cells. Respir Physiol 129:231-45
Lyall, V; Alam, R I; Phan, D Q et al. (2001) Decrease in rat taste receptor cell intracellular pH is the proximate stimulus in sour taste transduction. Am J Physiol Cell Physiol 281:C1005-13

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