Neurophysiological recordings from taste nerves of golden hamsters (Mesocricetus auratus) will define the functional organization of a mammalian peripheral gustatory nervous system, which is composed of several distinct chemoreceptive systems. Recent data suggest that ionic taste stimuli are transduced by two fundamentally different mechanisms, which activate parallel neural pathways, the N fibers and H fibers of the chorda tympani nerve. One mechanism, involving transport of sodium ions through ion channels in apical membranes of taste-bud cells, is supported by several lines of evidence. The other mechanism, involving transepithelial ionic currents to nerve endings at the base of the taste bud, has less direct support. """"""""Sweet"""""""" taste stimuli are likely transduced by taste-bud cells that are innervated by S fibers of the chorda tympani nerve, but many lines of evidence suggest that numerous receptors and several coding channels are involved. These hypotheses will be tested by recording neural activity from single N, H and S fibers while stimulating the anterior tongue or single fungiform papillae with selected taste stimuli. Effects of treating the tongue with pharmacological agents that affect apical membrane channels or currents at the base of taste-bud cells will be monitored. Functional specificity of individual taste buds will be established by recording from several single nerve fibers connected to one fungiform papillae. Functional homogeneity of the taste buds connected to one single fiber will be established by recording effects of single or binary stimuli applied to several different papillae in the receptive field of a single fiber. These experiments will advance understanding of how the gustatory system processes information about taste stimuli, which will provide means for controlling the intake of purified prototypic taste stimuli such as sucrose and sodium chloride. Excess intake of these chemicals leads to common health problems in modern society.
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