Taste is a major factor in food selection and preference. Foods containing high levels of saccharides and sodium are usually preferred over bland- tasting foods. The hedonic impact of saccharides (sweet-tasting) and sodium (salty-tasting) plays a role in the selection of foods normally regarded as nutritious. However, in some individuals the drive to satisfy these tastes results in poor food selection and abnormal eating habits having serious health consequences. The latter include obesity, bulimia, and hypertension. To understand the role of taste in feeding behavior, it is essential to have an appreciation of the physiological and biophysical processes that underlie excitation of taste sensory cells on the tongue. To help accomplish this, we have developed a method that permits recordings from taste nerves (chorda tympani) with a circumscribed portion of the dorsal lingual receptive field under voltage-clamp. The method takes advantage of the polar epithelial topology of the taste sensory mucosa to probe both the transcellular and paracellular ion pathways in taste buds. It will be used to apply voltage-perturbations (VPs) across the apical membranes of taste cells and their tight junctional barriers and to record the effects of such perturbations on the neural response. Transduction mechanisms that rely on ion flow across taste cell apical membranes can be detected under voltage-perturbation. Sodium ion is detected in this way. We shall use VPs to follow the postnatal development of the sodium-detecting taste system in rats and hamsters, two species in which changes in sensitivity to sodium approaches maturity from opposite poles, i.e. hyposensitivity in young rats and hypersensitivity in young hamsters. With VP methods, changes in ion channel density and/or sodium- channel affinity will be followed in developing rats and hamsters. VP methods are freely reversible, do not rely on pharmacological agents, and because they are assayed in the neural response, there is assurance that the applied perturbations have consequences for taste reception. VP methods will also be used to probe changes in potassium salt sensitivity with development in rats and changes in saccharide sensitivity in developing hamsters.
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