Chemical Senses Advance Access originally published online on August 24, 2009
Chemical Senses 2009 34(8):653-666; doi:10.1093/chemse/bjp047
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Taste Coding after Selective Inhibition by Chlorhexidine
1 John B. Pierce Laboratory, 290 Congress Avenue and Yale University School of Medicine, New Haven, CT 06519, USA 2 Department of Oral Health and Diagnostic Sciences, Division of Periodontology, Center for Chemosensory Sciences, School of Dental Medicine, University of Connecticut Health Center, 263 Farmington Avenue, Farmington, CT 06030-1715, USA
Correspondence to be sent to: Marion E. Frank, Department of Oral Health and Diagnostic Sciences, Division of Periodontology, Center for Chemosensory Sciences, School of Dental Medicine, University of Connecticut Health Center, Farmington, CT 06030-1715, USA. e-mail: mfrank{at}neuron.uchc.edu
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Abstract |
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Coding of the complex tastes of ionic stimuli in humans was studied by combining taste confusion matrix (TCM) methodology and treatment with chlorhexidine gluconate. The TCM evaluates discrimination of multiple stimuli simultaneously. Chlorhexidine, a bis-biguanide antiseptic, reversibly inhibits salty taste and tastes of a subset of bitter stimuli, including quinine hydrochloride. Identifications of salty (NaCl, "salt"), bitter (quinine·HCl, "quinine"), sweet (sucrose, "sugar"), and sour (citric acid, "acid") prototypes, alone and as components of binary mixtures, were measured under 4 conditions. One was a water-rinse control and the others had the salt and quinine tastes progressively reduced by treatment with 1 mM chlorhexidine, 3 mM chlorhexidine, and ultimately to zero by elimination of NaCl and quinine·HCl. Treatment with chlorhexidine perturbed identification of salt more than quinine; both were thereafter more often confused with "water" and unidentified when mixed with sucrose or citric acid. All pairwise discriminations that depended on the tastes of NaCl and quinine·HCl deteriorated, and although H2O was mistakenly identified as quinine after chlorhexidine, this may have been a decisional bias. Other confusions reflected "unprompted mixture analysis" and an obscuring of salt taste by a less-inhibited stronger quinine or sugar or acid tastes in mixtures. Partial inhibition of the tastes of NaCl and quinine·HCl by chlorhexidine was considered in the context of multiple receptors for the 2 compounds. Discrimination among prototypic stimuli with varying strengths was consistent with a gustatory system that evaluates a small number of independent tastes.
Key words: binary mixtures, dynamic mixture analysis, mixture suppression, quinine inhibition, salt inhibition, taste confusion matrix
Accepted 2 July 2009