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PubMed2005

Activity-guided identification of (S)-malic acid 1-O-D-glucopyranoside (morelid) and gamma-aminobutyric acid as contributors to umami taste and mouth-drying oral sensation of morel mushrooms (Morchella deliciosa Fr.).

Although morel mushrooms are widely used as tasty ingredients in savory dishes, knowledge of the key compounds evoking their attractive taste is still very fragmentary. In the present study, taste activity-guided fractionation of an aqueous morel extract by means of the recently developed taste dilution analysis (TDA) enabled the localization of several umami-like-tasting fractions as well as a fraction imparting an intense mouth-drying sensation to the oral cavity. Hydrophilic interaction liquid chromatography (HILIC), LC-MS, and amino acid analysis led to the successful identification of gamma-aminobutyric acid as the chemical inducer of the mouth-drying and mouth-coating oral sensations imparted by the morel extract. Besides the well-known umami-like taste contributors L-glutamic acid, L-aspartic acid, and succinic acid, an additional HILIC fraction was isolated and evaluated as tasting umami-like. LC-MS and NMR studies revealed that this fraction consisted of a mixture of (S)-malic acid 1-O-alpha-D-glucopyranoside and (S)-malic acid 1-O-beta-D-glucopyranoside, the structure of which could be successfully confirmed by independent synthesis. To the best of our knowledge, this morel-derived glycoside, which we named (S)-morelid, has previously not been reported in any food products. Sensory analysis of aqueous solutions of the compounds identified revealed threshold concentrations of 0.02 mmol/L for the mouth-drying effect of gamma-aminobutyric acid and 6.0 mmol/L for the umami-like, slightly sour taste of (S)-morelid.

Ascomycota↗
PubMed1977

Illness-alone exposure as a source of interference with the acquisition and retention of a taste aversion.

Four studies were conducted to explore the effects of unpaired lithium chloride (LiCl) injections, the unconditioned stimulus (US), on the acquisition and retention of a taste aversion. In Experiment 1, subjects were preexposed to a US; for one group the US was paired with a distinctive taste, whereas for a second group it was not. Following this preparation, both groups received the US paired with a novel taste. Only the US-alone group showed a retardation of subsequent taste-aversion conditioning. Experiment 2 indicated that an exposure to LiCl without a specific gustatory cue will interfere with the avoidance of a specific taste, regardless of whether the US experience occurs before or after a single taste-LiCl pairing. Following sucrose-LiCl pairings in Experiment 3A, LiCl-alone exposures retroactively interfered with the retention of the prior aversion to sucrose, with the level of post-US interference becoming an increasing function of the number of US-alone experiences. In Experiment 3B, the association of sucrose with LiCl did not interfere with the development of an almond aversion, whereas LiCl-alone exposures following the acquisition of a sucrose aversion proactively interfered with the development of a second taste aversion (almond). It is suggested that a physiological explanation will not adequately account for the present results of these experiments. The results are discussed within the framework of alternative associative models.

Animals↗
PubMed2006

Effects of brain lesions on taste-potentiated odor aversion in rats.

Rats failed to acquire aversions to odor stimulus, which was followed 30 min later by an unconditioned stimulus (US). However, when the odor stimulus was accompanied by a taste stimulus, they acquired odor aversions as well as taste aversions. In this phenomenon, referred to as a taste-potentiated odor aversion, lesions of the amygdala disrupted both taste and odor aversions, whereas lesions of the parvicellular part of ventroposteromedial thalamic nucleus (VPMpc) or insular cortex (IC) disrupted taste aversion but attenuated only odor aversion. These results suggest that both taste and odor stimuli are associated with US in the amygdala and that taste inputs delivered to the amygdala through the IC and/or VPMpc play an important role in potentiation of odor aversion.

Amygdala↗
PubMed1979

Taste aversions to mother's milk: the age-related role of nursing in acquisition and expression of a learned association.

The development of taste aversion learning to novel cues contained in mother's milk was examined in rat pups. Pups receiving distinctive mild by experimenter-delivered oral infusions followed by toxicosis formed an aversion to the dam's diet. Robust aversions were learned as early as Day 10 and were retained for at least 11 days. When the same distinctive milk was obtained directly from a foster mother through nursing, however, only weanling-age pups (over 20 days) formed an aversion. X-ray analysis of nipple location in the mouths of suckling pups suggested that pups between the ages of 10 and 21 days receive milk at a similar tongue locus. Flavored milk was then delivered at specific time intervals in controlled quantities through tongue cannulas implanted at loci corresponding to the nipple position shown by the X-rays. Cannulated preweanling pups that were attached to a nipple during milk delivery failed to associate the taste cue with illness, whereas both preweanlings off the nipple and weanlings on the nipple acquired aversions to the taste cue in the milk. The evidence obtained in these experiments suggests that pups of all ages are incapable of expressing a taste aversion in a nursing situation and that preweanling pups in particular are also dificient in acquiring aversions within a suckling context. The inability of preweanling pups to acquire taste aversions in a nursing situation appears to result from a failure to associate taste cues with illness rather than a failure to detect taste cues obtained from a nipple.

Age Factors↗
PubMed2006

A TAS1R receptor-based explanation of sweet 'water-taste'.

'Water-tastes' are gustatory after-impressions elicited by water following the removal of a chemical solution from the mouth, akin to colour after-images appearing on 'white' paper after fixation on coloured images. Unlike colour after-images, gustatory after-effects are poorly understood. One theory posits that 'water-tastes' are adaptation phenomena, in which adaptation to one taste solution causes the water presented subsequently to act as a taste stimulus. An alternative hypothesis is that removal of the stimulus upon rinsing generates a receptor-based, positive, off-response in taste-receptor cells, ultimately inducing a gustatory perception. Here we show that a sweet 'water-taste' is elicited when sweet-taste inhibitors are rinsed away. Responses of cultured cells expressing the human sweetener receptor directly parallel the psychophysical responses-water rinses remove the inhibitor from the heteromeric sweetener receptor TAS1R2-TAS1R3, which activates cells and results in the perception of strong sweetness from pure water. This 'rebound' activity occurs when equilibrium forces on the two-state allosteric sweet receptors result in their coordinated shift to the activated state upon being released from inhibition by rinsing.

Adaptation, Physiological↗
PubMed2005

Zinc status and taste acuity in older Europeans: the ZENITH study.

BACKGROUND: Age-related decline in taste acuity may be both a cause and an effect of depleted zinc and/or increased zinc requirement. OBJECTIVE: The aim of this study was to explore associations between zinc status and taste acuity in healthy older European adults aged 55-90 y. SAMPLE: Volunteers were recruited within Italy (n = 108 aged 70-90 y), the United Kingdom (UK) (n = 93 aged 55-70) and two regions of France (n = 186), Grenoble (aged 70-90 y) and Clermont-Ferrand (aged 55-70 y). METHODS: A signal detection theory approach was adopted, employing a three-alternative, forced-choice procedure. The data were converted to R-indices and bivariate correlations were computed to explore relationships between serum zinc, erythrocyte zinc and taste acuity. ANOVA was undertaken to determine regional differences in zinc status. RESULTS: Higher erythrocyte zinc status was associated with better acuity for salt (sodium chloride) taste in the sample as a whole (P = 0.012) (n = 385). Higher serum zinc levels were associated with greater sensitivity to sour taste (citric acid) (P = 0.015) only in the older groups (aged 70-90 y). There were no apparent associations between serum or erythrocyte zinc status and acuity for bitter (quinine) or sweet (sucrose) tastes irrespective of age. CONCLUSION: These results agree with those previously suggesting that age-related detriment in sensitivity for salt taste may be associated with depleted zinc.

Age Factors↗
PubMed2000

Leptin as a modulator of sweet taste sensitivities in mice.

Leptin acts as a potent inhibitory factor against obesity by regulating energy expenditure, food intake, and adiposity. The obese diabetic db/db mouse, which has defects in leptin receptor, displays enhanced neural responses and elevated behavioral preference to sweet stimuli. Here, we show the effects of leptin on the peripheral taste system. An administration of leptin into lean mice suppressed responses of peripheral taste nerves (chorda tympani and glossopharyngeal) to sweet substances (sucrose and saccharin) without affecting responses to sour, salty, and bitter substances. Whole-cell patch-clamp recordings of activities of taste receptor cells isolated from circumvallate papillae (innervated by the glossopharyngeal nerve) demonstrated that leptin activated outward K(+) currents, which resulted in hyperpolarization of taste cells. The db/db mouse with impaired leptin receptors showed no such leptin suppression. Taste tissue (circumvallate papilla) of lean mice expressed leptin-receptor mRNA and some of the taste cells exhibited immunoreactivities to antibodies of the leptin receptor. Taken together, these observations suggest that the taste organ is a peripheral target for leptin, and that leptin may be a sweet-sensing modulator (suppressor) that may take part in regulation of food intake. Defects in this leptin suppression system in db/db mice may lead to their enhanced peripheral neural responses and enhanced behavioral preferences for sweet substances.

Animals↗
PubMed1999

Blocking taste receptor activation of gustducin inhibits gustatory responses to bitter compounds.

Gustducin, a transducin-like guanine nucleotide-binding regulatory protein (G protein), and transducin are expressed in taste receptor cells where they are thought to mediate taste transduction. Gustducin and transducin are activated in the presence of bovine taste membranes by several compounds that humans perceive to be bitter. We have monitored this activation with an in vitro assay to identify compounds that inhibited taste receptor activation of transducin by bitter tastants: AMP and chemically related compounds inhibited in vitro responses to several bitter compounds (e.g., denatonium, quinine, strychnine, and atropine). AMP also inhibited behavioral and electrophysiological responses of mice to bitter tastants, but not to NaCl, HCl, or sucrose. GMP, although chemically similar to AMP, inhibited neither the bitter-responsive taste receptor activation of transducin nor the gustatory responses of mice to bitter compounds. AMP and certain related compounds may bind to bitter-responsive taste receptors or interfere with receptor-G protein coupling to serve as naturally occurring taste modifiers.

Adenosine Monophosphate↗
PubMed2002

Secretory function of the salivary gland in patients with taste disorders or xerostomia: correlation with zinc deficiency.

A notable proportion of patients with taste disorders complain of xerostomia and when zinc is prescribed the xerostomia is often improved in conjunction with the taste disorder. To study the relationship between taste disorders, zinc deficiency and xerostomia, we measured salivary gland function and zinc levels in 93 patients with hypogeusia and/or xerostomia and 60 patients with unilateral acute peripheral facial palsy who served as controls. We then prescribed zinc for patients with low serum zinc levels and evaluated xerostomia and taste sensation after 6 months of this treatment. The salivary gland secretory ratio (SGSR), determined by dynamic salivary 99mTc scintigraphy, was found to be an objective measure of salivary gland function and was reduced in patients with xerostomia. Patients with salivary gland dysfunction also had abnormal morphology of the papillae of the tongue. No significant relation was found between the severity of taste disorders and SGSR values, but low SGSR values were found in patients with zinc deficiency. Patients with taste disorders and/or xerostomia who were treated with zinc had relief of symptoms at 6 months, indicating that both taste disorders and xerostomia are among the symptoms of zinc deficiency.

Adult↗
PubMed2004

Hypogeusia as a complication of uvulopalatopharyngoplasty and use of taste strips as a practical tool for quantifying hypogeusia.

Hypogeusia is an uncommon complication of uvulopalatopharyngoplasty (UPPP) and few reports in the literature have documented it. Excision of part of the soft palate and damage to the glossopharyngeal nerve or its lingual branch as a result of diathermy or surgery are the possible causes. The case of a 45-year-old male who suffered hypogeusia following UPPP is reported herein. He reported no improvement over a 6-month period. Quantitative assessment of his taste threshold for the 4 basic tastes using taste strips showed a score of 7/18, indicating hypogeusia. The possibility of taste disorder as a postoperative complication should be discussed before patients consent to UPPP Postoperative taste threshold assessment should be done using taste strips if the patient complains of taste disorders.

Ageusia↗
PubMedDate not supplied

Age-associated increases in intensity discrimination for taste.

Impaired taste sensation in the aging person may affect the appreciation of food and beverages and compromise nutritional status. Changes in flavor perception may be due to altered ability to discriminate between intensities of suprathreshold taste stimuli. An interesting question is whether all taste qualities (sweet, salty, sour, bitter) show similar age-associated decline in intensity discrimination. Taste intensity discrimination has been shown to be significantly poorer in elderly than in young women for the bitter stimulus caffeine, but not for the sweet stimulus sucrose. The present experiment investigated effects of taste substance and age on taste intensity discrimination by assessing Weber ratios (WRs) for citric acid and sodium chloride (NaCl) in 60 people, half elderly, and half women. Results indicate a significant effect of age on WRs for citric acid and NaCl, suggesting the importance of suprathreshold intensity discrimination for taste perception in the elderly.

Adult↗
PubMed1996

Influence of zinc supplementation to diets at graded levels of protein on taste sensitivity, morphological changes of tongue epithelia and serum zinc concentration in growing rats.

OBJECTIVE: We previously reported dietary protein was needed to maintain normal taste function and low serum zinc concentration led due to protein insufficiency [1], but generally zinc has been known to improve taste dysfunction. The present study was designed to determine whether zinc supplementation is effective in maintaining normal taste function at different levels of dietary protein. METHODS: Sixty weanling rats were given free access to one of six diets: protein-free, 2.5% and 8% purified egg protein (PEP), and 10 ppm zinc supplementation at each protein level for 28 days. Preference tests between aqueous solution of 1, 2, 5 or 10 mmol/L NaCl vs. deionized water were conducted on days 14, 17, 20 and 23, respectively. Blood was collected for the measurements of serum zinc concentration, and the tongue of each rat was excised for observation by electron microscopic scanning. The number of fungiform papillae with normal taste pores and also the number of rats with abnormal morphological changes on tongue epithelia were recorded. RESULTS: In basal diet groups, the rats fed 8% and 2.5% PEP diets discriminated 2 mmol/L NaCl liquid, while those fed the protein-free diet discriminated only the highest concentration of 10 mmol/L in this experiment. Serum zinc concentration and the ratio of fungiform papillae with normal taste pores increased with increasing dietary protein level. Abnormal morphological changes of tongue epithelia were observed in the protein-free diet group whether or not it contained additional zinc. No significant differences were observed between the basal and zinc supplemented diets at the other protein levels in the other parameters. CONCLUSION: These results suggest that adequate dietary protein is more important in maintaining normal taste function and zinc supplementation did not improve taste function when dietary protein was suboptimal.

Animals↗
PubMed1978

Intracellular characteristics and responses of taste bud and lingual cells of the mudpuppy.

Intracellular recordings of membrane potentials of mudpuppy lingual cells were made with micropipette electrodes. Three types of cells were distinguished by their responses to chemical stimulation. Surface epithelial (SE) cells outside of taste buds responded with large membrane potential and resistance changes to a variety of stimuli representing the four taste qualities. Salts and acids evoked particularly large potential changes, and MgCl2, acids, and quinine greatly increased the membrane resistance. One type of taste bud cell (TB-1) was characterized by large depolarizations to K salts, and the other type of taste bud cell (TB-2) characteristically hyperpolarized to MgCl2, acid, and sugar solutions. Membrane resistance changes accompanying TB-1 and TB-2 cell responses were relatively small compared to those of SE cells. Electrotonic coupling was observed between pairs of SE and TB-2 cells but not for pairs of TB-1 cells nor cells of different types. After recording cell responses, dye-marking allowed verification of results in situ and histologically. From the identification of cells in section, it is hypothesized the TB-1 and TB-2 cells correspond to light and dark cells, respectively. Responses of TB-1 cells imply a taste receptive function; wheras TB 2-cell responses suggest secretory, supportive, and (or) receptive functions. Factors affecting cellular characteristics, non-taste bud cell responsiveness, response mechanisms, and function of electrotonic coupling are discussed in relation to taste reception.

Acids↗
PubMed1988

The organization of taste sensibilities in hamster chorda tympani nerve fibers.

Electrophysiological measurements of nerve impulse frequencies were used to explore the organization of taste sensibilities in single fibers of the hamster chorda tympani nerve. Moderately intense taste solutions that are either very similar or easily discriminated were applied to the anterior lingual surface. 40 response profiles or 13 stimulus activation patterns were considered variables and examined with multivariate statistical techniques. Three kinds of response profiles were seen in fibers that varied in their overall sensitivity to taste solutions. One profile (S) showed selectivity for sweeteners, a second (N) showed selectivity for sodium salts, and a third (H) showed sensitivity to salts, acids, and other compounds. Hierarchical cluster analysis indicated that profiles fell into discrete classes. Responses to many pairs of effective stimuli were covariant across profiles within a class, but some acidic stimuli had more idiosyncratic effects. Factor analysis of profiles identified two common factors, accounting for 77% of the variance. A unipolar factor was identified with the N profile, and a bipolar factor was identified with the S profile and its opposite, the H profile. Three stimulus activation patterns were elicited by taste solutions that varied in intensity of effect. Hierarchical cluster analysis indicated that the patterns fell into discrete classes. Factor analysis of patterns identified three common unipolar factors accounting for 82% of the variance. Eight stimuli (MgSO4, NH4Cl, KCl, citric acid, acetic acid, urea, quinine HCl, HCl) selectively activated fibers with H profiles, three stimuli (fructose, Na saccharin, sucrose) selectively activated fibers with S profiles, and two stimuli (NaNO3, NaCl) activated fibers with N profiles more strongly than fibers with H profiles. Stimuli that evoke different patterns taste distinct to hamsters. Stimuli that evoke the same pattern taste more similar. It was concluded that the hundreds of peripheral taste neurons that innervate the anterior tongue play one of three functional roles, providing information about one of three features that are shared by different chemical solutions.

Animals↗
PubMed1988

Sugar-activated ion transport in canine lingual epithelium. Implications for sugar taste transduction.

There is good evidence indicating that ion-transport pathways in the apical regions of lingual epithelial cells, including taste bud cells, may play a role in salt taste reception. In this article, we present evidence that, in the case of the dog, there also exists a sugar-activated ion-transport pathway that is linked to sugar taste transduction. Evidence was drawn from two parallel lines of experiments: (a) ion-transport studies on the isolated canine lingual epithelium, and (b) recordings from the canine chorda tympani. The results in vitro showed that both mono- and disaccharides in the mucosal bath stimulate a dose-dependent increase in the short-circuit current over the concentration range coincident with mammalian sugar taste responses. Transepithelial current evoked by glucose, fructose, or sucrose in either 30 mM NaCl or in Krebs-Henseleit buffer (K-H) was partially blocked by amiloride. Among current carriers activated by saccharides, the current response was greater with Na than with K. Ion flux measurements in K-H during stimulation with 3-O-methylglucose showed that the sugar-evoked current was due to an increase in the Na influx. Ouabain or amiloride reduced the sugar-evoked Na influx without effect on sugar transport as measured with tritiated 3-O-methylglucose. Amiloride inhibited the canine chorda tympani response to 0.5 M NaCl by 70-80% and the response to 0.5 M KCl by approximately 40%. This agreed with the percent inhibition by amiloride of the short-circuit current supported in vitro by NaCl and KCl. Amiloride also partially inhibited the chorda tympani responses to sucrose and to fructose. The results indicate that in the dog: (a) the ion transporter subserving Na taste also subserves part of the response to K, and (b) a sugar-activated, Na-preferring ion-transport system is one mechanism mediating sugar taste transduction. Results in the literature indicate a similar sweet taste mechanism for humans.

Amiloride↗
PubMed1999

Regions of the human brain affected during a liquid-meal taste perception in the fasting state: a positron emission tomography study.

BACKGROUND: The sensation of taste provides reinforcement for eating and is of possible relevance to the clinical problem of obesity. OBJECTIVE: Positron emission tomography (PET) was used to explore regions of the brain that were preferentially affected during the taste perception of a liquid meal by 11 right-handed, lean men in the fasting state. DESIGN: After subjects had fasted for 36 h, 2 measurements of regional cerebral blood flow (rCBF) obtained immediately after subjects retained and swallowed 2 mL of a flavored liquid meal (the taste condition) were compared with 2 measurements of rCBF obtained immediately after subjects retained and swallowed 2 mL of water (the baseline condition). RESULTS: Compared with the baseline condition, taste was associated with increased rCBF (P < 0.005) in the left dorsolateral prefrontal cortex and superior temporal gyrus; the right ventrolateral prefrontal cortex, supramarginal gyrus, and anterior thalamus; and bilaterally in the hippocampal formation, posterior cingulate, midbrain, occipital cortex, and cerebellum. Taste was also associated with decreased rCBF (P < 0.005) in the right dorsolateral prefrontal cortex, superior temporal gyrus, and supplementary motor area, and bilaterally in the medial prefrontal cortex and inferior parietal lobule. CONCLUSIONS: This exploratory study provides additional evidence that the temporal cortex, thalamus, cingulate cortex, caudate, and hippocampal formation are preferentially affected by taste stimulation. The asymmetric pattern of activity in the dorsolateral prefrontal cortex and superior temporal gyrus may contribute to the taste perception of a liquid meal perceived as pleasant. Additional studies are required to determine how these regions are affected in patients with obesity or anorexia.

Adult↗
PubMed2001

Increased intensity perception of aversive taste following right anteromedial temporal lobe removal in humans.

We used a modified version of the Spatial Taste Test to assess taste intensity perception in patients with either left or right temporal resection from the anteromedial temporal lobe (AMTL), and a group of control subjects. Sweet, sour, salty and bitter solutions were applied onto discrete locations of the tongue to stimulate either left or right fungiform, or left or right foliate papillae. Intensity ratings were assessed with the Labeled Magnitude Scale. Subjects also sipped 5 ml of each solution for whole mouth stimulation. Genetically based determinants of taste sensitivity were assessed with ratings of 6-n-propylthiouracil, and covaried from all analyses. As in previous studies, analysis of covariance indicated that the subjects in the right temporal group rated an aversive bitter taste as more intense than did subjects in the control group. In contrast, there were no group differences for sucrose ratings, suggesting that the AMTL may be involved preferentially in processing aversive compared with hedonic tastes. No group x side, or group x location effects were present. These results confirm that removal of the right AMTL in humans results in increased taste intensity/aversiveness perception. This finding complements existing literature indicating that the AMTL is important for processing aversive taste, and suggests that inhibitory mechanisms may play an important role in such processing.

Adult↗
PubMed1995

Propylthiouracil tasting: determination of underlying threshold distributions using maximum likelihood.

The ability to taste low concentrations of propylthiouracil (PROP) and related bitter compounds is heritable. The current analysis determines whether the distribution of PROP taste thresholds is consistent with an additive or a dominant mode of Mendelian transmission. To that end, the lowest concentration of PROP detectable was determined for 1015 subjects and models of bi- or tri-modal distributions of PROP taste thresholds were tested. The model with the greatest likelihood had three distributions and followed an additive model of PROP taste sensitivity if the variances associated with the distributions were assumed to be equal. However, if the taste thresholds were transformed to remove skewness, or if the variances were unequal, then three- or two-distribution models were equally likely. Resolution of the mode of inheritance for bitter taste perception awaits additional family studies and the characterization of the molecular basis of taste perception for these bitter compounds.

Adolescent↗