PERIPHERAL GUSTATORY PROCESSING

University Of Connecticut Sch Of Med/Dnt, Farmington CT

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Abstract

Processing of taste information for complex stimuli by the peripheral nervous system is poorly understood. The studies address the peripheral gustatory system of the golden hamster (Mesocricetus auratus) with neurophysiological recordings from the chorda tympani (CT) and glossopharyngeal (GL) nerves. Hamster CT and GL nerve fibers respond to sucrose, sodium chloride, hydrochloric acid and quinine. HCl (QHCl) but greater than 75 percent of CT fibers are sucrose-best (S) or NaCl-best (N) and greater than 75 percent of GL fibers are HCl-best (H) or QHC1-best (Q) neurons. CT and GL neurons gather information about taste stimuli subsequent to transduction and processing by taste receptor cells within taste buds. Responses of CT neurons to taste mixtures suggest that transduction mechanisms for appetitive and aversive stimuli interact at the level of the taste bud. For example, QHC1 stimulates CT H neurons but inhibits sucrose responses of CT S neurons in mixtures. Recordings of responses of CT neurons to mixtures of a sugar (sucrose) or non-sugar sweetener (dulcin (4-ethoxyphenyl urea) with QHC1 or one of two ionic (denatonium benzoate, KC1) or non-ionic (caffeine, sucrose octa-acetate) aversive substances address mechanisms of the interaction. Results bear on hypotheses that the inhibition is dependent on (a) activation of enzymes that break down cyclic AMP, (b) stimulation of taste receptors within the same taste bud, (c) chemical features of the substances, and (d) perceptual quality of the substances. Recordings of responses of GL neurons to binary mixtures of sucrose, NaC1 and QHCl address whether interactions similar to those seen for fungiform taste buds occur in vallate and foliate taste buds. With the behaving hamster, functional consequences of mixture effects are addressed by measuring patterns of generalization of conditioned taste aversions. It is hypothesized that taste intensities of sucrose in quinine-sucrose mixtures, and quinine in NaC1-quinine mixtures will be decreased. Taste information processing within taste buds and its effect on taste perception may provide mechanisms to control excess intake of appetitive stimuli.