ABSTRACT
Threshold and suprathreshold sensitivities to 13 bitter compounds were determined for 16 young adults (mean age = 27.4 years) and 18 elderly persons (mean age = 81.3 years). Half of the subjects in each age group were tasters of the bitter compound phenylthiocarbamide (PTC) and half were nontasters. Both detection and recognition thresholds, determined by a forced-choice ascending detection method, were elevated in older subjects; there were no significant differences in threshold values between tasters and nontasters of PTC. A strong relationship between bitter threshold values and the logarithm of the octanol/water partition coefficient was found for both young and elderly subjects. For young subjects, suprathreshold bitterness ratings were more intense for tasters of PTC compared with nontasters. Significant losses in suprathreshold sensitivity to bitter tastants with age were also found. However, unlike threshold sensitivity, no relationship was found between suprathreshold bitter taste intensity and lipophilicity.
Subject(s)
Aging/psychology , Taste Threshold/physiology , Adult , Aged , Aged, 80 and over , Caffeine , Chemical Phenomena , Chemistry, Physical , Humans , Lipids , Phenylthiourea , Quaternary Ammonium CompoundsABSTRACT
Taste sensitivity to five glutamate salts (sodium glutamate, potassium glutamate, ammonium glutamate, calcium diglutamate, and magnesium diglutamate) were determined in sixteen young (mean age 25.58 years) and eighteen elderly (mean age 86.89 years) subjects. The effect of inosine 5'-monophosphate (IMP) and ions on taste perception of glutamate compounds was also investigated. The detection thresholds for glutamate salts were 5.04 times higher in elderly subjects than in young subjects; the recognition thresholds were 3.84 times higher. For young subjects, 0.1 mM IMP lowered detection and recognition thresholds for all 5 salts. A stronger concentration of IMP (1 mM) had this effect in both young and elderly groups. Elderly subjects perceived suprathreshold concentrations as less intense than young subjects. Chloride and acetate salts of sodium, potassium, and calcium reduced the detection and recognition thresholds of L-glutamic acid but had no effect sodium glutamate thresholds.
Subject(s)
Aging/physiology , Electrolytes/metabolism , Glutamates , Inosine Monophosphate/physiology , Taste/physiology , Adult , Aged , Aged, 80 and over , Female , Humans , Ion Channels/physiology , Male , Receptors, Glutamate , Receptors, Neurotransmitter/physiology , Taste Buds/physiology , Taste Threshold/physiologyABSTRACT
Amiloride analogs that were designed to inhibit three types of Na+ transport systems (the epithelial Na+ channel, the Na+/H+ antiporter, and the Na+/Ca++ exchanger) were applied to the tongue of the gerbil to determine their effects of electrophysiological taste responses to NaCl, CaCl2, sucrose, and glutamic acid. The pattern of responses from the chorda tympani nerve indicates that the taste of NaCl is almost totally accounted for by the epithelial Na+ channel. Phenamil, an amiloride analog which specifically blocks the epithelial Na+ channel at low concentrations, suppressed the taste responses to 0.03 M NaCl by 97%. The pattern of responses also indicates that the Na+/H+ antiporter and the Na+/Ca2+ exchanger do not mediate salt taste in the gerbil. None of the amiloride analogs blocked taste responses to CaCl2, sucrose, or glutamic acid. It is concluded that the salty taste of NaCl in the gerbil is almost totally mediated by the epithelial Na+ channel, and the kinetics of this channel are identical to amiloride-sensitive sodium channels in other systems.
