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PubMed1985

The taste and mechanical response properties of neurons in the parvicellular part of the thalamic posteromedial ventral nucleus of the rat.

A total of 41 taste and 17 mechanoreceptive neurons were recorded in the parvicellular part of the posteromedial ventral nucleus of the thalamus (VPMpc) of amobarbital-anesthetized rats. Most of the taste neurons were located in the rostral part, while most of the mechanoreceptive neurons were located in the middle part of the VPMpc. Stimulation of the whole oral cavity with four basic taste stimuli produced smaller mean response magnitudes in these thalamic taste neurons than in the parabrachio-thalamic (P-T) taste relay neurons. Receptive fields (RFs) for most of the 21 taste neurons examined were located on the tongue or on the tongue and palate, as with P-T relay neurons. Some neurons had RFs ipsilaterally in the oral cavity, as do P-T relay neurons; but others had RFs contralaterally or bilaterally. Several neurons had large RFs in comparison with those of P-T relay neurons. A majority of the thalamic taste neurons were also mechanosensitive, and their RFs were larger for mechanical stimulation than for taste stimulation. Many (12/17) of the mechanoreceptive neurons had a low response threshold, activated by stroking the tissue with a glass rod; and others had a high response threshold, activated by a pinch with a pair of non-serrated forceps. Their RFs were contralaterally or bilaterally located on either the tongue, or palate or on both regions. One taste neuron and some mechanoreceptive neurons were also excited by mechanical stimulation on the cheek or lip. These observations may represent integrative processes for taste and mechanical oral information at the thalamic level.

Action Potentials↗
PubMed1994

Changes in properties of neuronal responses in two cortical taste areas in rats of various ages.

Changes in the features of responses of cortical taste neurons were studied in granular insular (GI) and dysgranular insular (DI) areas of urethane-anesthetized SD rats of four age groups (4-10, 14-20, 25-35 and > 90 days). Stimuli included four basic taste stimuli, 0.1 M NH4Cl, and the water extract of a food pellet, applied to the entire oral cavity. At the age of 4-10 days, taste neurons showed no spontaneous discharge, and most responded to NH4Cl in a phasic fashion. In older age groups, however, there was a spontaneous discharge, and tonic taste responses were evident; some responded better to the four basic stimuli and to the food than to NH4Cl. With only a few days' difference in age, inhibitory responses were also noted in both areas. Average taste responses increased or decreased at different ages, depending on the type of taste stimulus and recording area. When taste responses were plotted against the four basic taste stimuli in the order of sucrose, NaCl, HCl and quinine along the abscissa, some neurons showed double-peaked response profiles. This suggests the convergence and mutual inhibition of afferents at single cortical neurons. The fraction of neurons with double-peaked response profiles increased at the age of 25-35 days in both areas. Neurons in rats aged 25-35 days were predominantly sensitive to either NH4Cl or NaCl, or to either food or sucrose. Neurons in rats of other ages, during the preweanling and the adult stages, tended to respond to both these stimuli. Our observations suggest that cortical taste neurons develop in the rat brain in accordance with the maturation of both the taste receptors and the neural networks.

Aging↗
PubMed1994

Human taste cells express the G protein alpha-gustducin and neuron-specific enolase.

Expression of the alpha-subunit of the taste-specific G protein alpha-gustducin and the glycolytic enzyme neuron-specific enolase (NSE) was investigated immunohistochemically in human circumvallate and foliate taste papillae. Immunofluorescence for alpha-gustducin was observed in taste cells of both types of papillae and exhibited two patterns of immunofluorescence, plasmalemmal and cytosolic. The plasmalemmal pattern showed intense immunofluorescence localized to the apical region, and was exhibited by most immunoreactive taste cells. In contrast, the cytosolic pattern, observed in one or two immunoreactive cells in a taste bud per section, showed immunofluorescence distributed throughout the cytoplasm. A subpopulation of alpha-gustducin-immunoreactive taste receptor cells, most of which exhibited the cytosolic pattern, also expressed NSE. Optical sectioning, using confocal laser scanning microscopy, demonstrated the highest level of expression of alpha-gustducin in the apical microvillar region of the taste cells in close apposition to the taste pore. These studies indicate conservation of epitopes of alpha-gustducin in humans and rats, and suggest that this G protein is associated with taste transduction in both rats and humans. The patterns of expression of alpha-gustducin, and coexpression with NSE, may correlate with specialized subtypes or developmental stages of taste receptor cells.

Aged↗
PubMedDate not supplied

Effect of umami taste stimulations on vagal efferent activity in the rat.

Effects of umami taste stimulation with monosodium glutamate (MSG) on the efferent discharges in the pancreatic, gastric and hepatic branch of the vagus nerve were observed in the anesthetized rat, in comparison with those of sweet and salty taste stimulation. Umami taste stimulation with 2.8% MSG solution caused an enhancement of vagal activities in pancreatic, gastric and hepatic branches. Sweet taste stimulation with 5% glucose or 10% sucrose increased efferent activity of hepatic and pancreatic branches and inhibited in gastric branch of the vagus nerve. Salty taste stimulation with 5% NaCl resulted in an increase in vagal gastric nerve activity and a decrease in that of vagal pancreatic and hepatic nerve; however, weak salty taste stimulation with 0.9% NaCl solution caused no remarkable change in efferent activity. It was assumed that umami taste stimulation, strong salty taste stimulation and sweet taste stimulation revealed different patterns of vagal responses which play some role on different anticipatory changes in hepatic, pancreatic and gastric functions following ingestion of food with different taste.

Animals↗
PubMed2004

Effect of age and disease on taste perception.

Abnormalities in taste function may contribute to poor dietary intake in the elderly, and in patients with renal failure or cancer. This study examined the effect of age on taste thresholds, and taste thresholds adjusted for age, in patients with renal failure with and without dialysis, and patients with cancer receiving chemotherapy and/or radiotherapy. Three groups of healthy volunteers aged 21-34 (n=26), 36-61 (n=13), and 69-94 (n=24), were recruited for the study on the effect of age. Nineteen patients with chronic renal failure on chronic ambulatory peritoneal dialysis (CAPD) and 11 age-matched chronic renal failure patients not yet requiring dialysis were recruited to examine the effect of chronic renal failure on taste function. Twenty-four inpatients with various types of cancer were recruited from a clinical oncology ward. Taste threshold was measured using commercial flavors supplied by Firmenich (pork, beef) and the ascending forced-choice method. Results showed that taste threshold increased with age. No abnormality in taste threshold was observed in patients with chronic renal failure with and without dialysis, and in patients with cancer. However, altered taste occurred in a large number of these patients. Abnormal taste function is present in healthy elderly people, and in patients with chronic renal failure and cancer. The nature of the abnormality differs among these groups, consisting of elevation of taste threshold in the elderly, and dysgeusia in those with disease.

Adult↗
PubMed2006

Transgenic labeling of taste receptor cells in model fish under the control of the 5'-upstream region of medaka phospholipase C-beta 2 gene.

Vertebrate taste receptor cells express signaling molecules such as taste receptors and effectors to convert taste stimuli to inner cellular signals. Phospholipase C-beta2 (PLC-beta2) is an effector enzyme that is necessary to transduce taste signals in the mouse. It was shown that a subset of the plc-beta2 expressing cells also express taste receptor molecules, T1Rs or T2Rs, in mammals and fish. To label plc-beta2 expressing cells in the model fish species, we constructed a transgene by linking the 5'-upstream region of the medaka plc-beta2 gene to a green fluorescent protein (GFP) gene. The resulting transgenic medaka exhibited GFP signals in taste buds of the lips and the pharyngeal region. Detailed observation revealed that the GFP signals were in a subpopulation of taste bud cells, and co-localized with the transcript of endogenous plc-beta2 gene. Zebrafish introduced with the same transgene showed GFP signals in a subpopulation of taste bud cells of the lips and the pharyngeal region as in the case of medaka. This is the first report of successful labeling of taste receptor cells in two model fish species under the control of the plc-beta2 promoter. This promoter will be a useful genetic tool to study the vertebrate taste system in general.

Animals↗
PubMed2004

Sweet and bitter tastes of alcoholic beverages mediate alcohol intake in of-age undergraduates.

Alcoholic beverages are complex stimuli, giving rise to sensations that promote or inhibit intake. Previous research has shown associations between 6-n-propylthiouracil (PROP) bitterness, one marker of genetic variation in taste, and alcohol behaviors. We tested the PROP bitterness and alcohol intake relationship as mediated by tastes of sampled alcoholic beverages. Forty-nine undergraduates (mean age=22 years) participated. According to the Alcohol Use Disorders Identification Test (AUDIT), only 3 of 49 subjects reported patterns indicating problematic drinking. Participants used the general Labeled Magnitude Scale to rate PROP bitterness and tastes from and preference for Pilsner beer, blended scotch whiskey, instant espresso and unsweetened grapefruit juice. Alcohol intake was reported over a typical week. Regression analysis tested the hypothesis that PROP bitterness influenced alcohol bitterness and sweetness, which in turn predicted alcohol intake. Those who tasted less PROP bitterness tasted all beverages as less bitter and more preferred. Sweetness of scotch was significantly greater in those who tasted PROP as least bitter. For scotch, greater sweetness and less bitterness from sampled scotch were direct predictors of greater alcohol intake. For beer, preference ratings were better predictors of alcohol intake than the bitter or sweet tastes of the sampled beer. These findings support that PROP bitterness predicts both positive and negative tastes from alcoholic beverages and that those tastes may predict alcohol intake. The college environment may attenuate direct effects of PROP bitterness and intake. Here, PROP bitterness does not predict alcohol intake directly, but acts instead through sweet and bitter tastes of alcoholic beverages.

Adult↗
PubMed2005

Bitter taste markers explain variability in vegetable sweetness, bitterness, and intake.

Intake of vegetables falls short of recommendations to lower risk of chronic diseases. Most research addresses bitterness as a sensory deterrent to consuming vegetables. We examined bitter and sweet sensations from vegetables as mediators of vegetable preference and intake as well as how these tastes vary with markers of genetic variation in taste (3.2 mM 6-n-propylthiouracil bitterness) and taste pathology (1.0 mM quinine bitterness, chorda tympani nerve relative to whole mouth). Seventy-one females and 39 males (18-60 years) reported prototypical tastes from and preference for Brussels sprouts, kale and asparagus as well as servings of vegetables consumed, excluding salad and potatoes. Intensity and hedonic ratings were made with the general Labeled Magnitude Scale. Data were analyzed with multiple linear regression and structural equation modeling. Vegetable sweetness and bitterness were independent predictors of more or less preference for sampled vegetables and vegetable intake, respectively. Those who taste PROP as most bitter also tasted the vegetables as most bitter and least sweet. The spatial pattern of quinine bitterness, suggestive of insult to chorda tympani taste fibers, was associated with less bitterness and sweetness from vegetables. Via structural equation modeling, PROP best explained variability in vegetable preference and intake via vegetable bitterness whereas the quinine marker explained variability in vegetable preference and intake via vegetable bitterness and sweetness. In summary, bitterness and sweetness of sampled vegetables varied by taste genetic and taste function markers, which explained differences in preference for vegetables tasted in the laboratory as well as overall vegetable intake outside the laboratory.

Adolescent↗
PubMed2003

Gustatory neurons derived from epibranchial placodes are attracted to, and trophically supported by, taste bud-bearing endoderm in vitro.

Taste buds are multicellular receptor organs innervated by the VIIth, IXth, and Xth cranial nerves. In most vertebrates, taste buds differentiate after nerve fibers have reached the lingual epithelium, suggesting that nerves induce taste buds. However, under experimental conditions, taste buds of amphibians develop independently of innervation. Thus, rather than being induced by nerves, the developing taste periphery likely regulates ingrowing nerve fibers. To test this idea, we devised a culture approach using axolotl embryos. Gustatory neurons were generated from cultured epibranchial placodes, and when cultured alone, axon outgrowth was random over 4 days, a time period coincident with axon growth to the periphery in vivo. In contrast, cocultures of placodal neurons with oropharyngeal endoderm (OPE), the normal taste bud-containing target for these neurons, resulted in neurite growth toward the target tissue. Unexpectedly, placodal neurons also grew toward flank ectoderm (FE), which these neurons do not encounter in vivo. To compare further the impact of OPE and FE explants on gustatory neurons, cocultures were extended and examined at 6, 8, and 10 days, when, in vivo, placodal fibers have innervated the epithelium but prior to taste bud formation, when taste buds have differentiated and are innervated, and when the mouth has opened and larvae have begun to feed, respectively. The behavior of placodal axons with respect to target type did not differ between OPE and FE cocultures at 6 days. However, by 8 days, differences in axonal outgrowth were observed with respect to target type, and these differences were enhanced by 10 days in vitro. Most clearly, exuberant placodal fibers grew in 10-day OPE cocultures, and numerous neurites had invaded OPE explants by this time, whereas gustatory neurites were sparse in FE cocultures, and rarely approached and almost never contacted FE explants. Thus, embryonic endoderm destined to give rise to taste buds specifically attracts its innervation early in development, as placodal neurons send out axons. Later, when gustatory axons synapse with differentiated taste buds in vivo, the OPE provides trophic support for cultured gustatory neurons.

Ambystoma mexicanum↗
PubMed2000

Food acceptance and genetic variation in taste.

OBJECTIVE: To determine if individuals who taste 6-n-propylthiouracil (PROP), one marker of genetic variation in taste, as exceptionally bitter can also perceive sugars as sweeter, other bitters as more intense, and dietary fats as more creamy and/or viscous than do individuals who taste PROP as weakly bitter. This study examined the association between genetic variation in taste and acceptance for sweet, high-fat, and bitter foods and beverages. DESIGN: Genetic variation was measured by perceived bitterness of PROP (influenced by genetic, hormonal, and pathologic factors) and density of fungiform papillae on the anterior portion of the tongue (influenced primarily by genetic factors). Four sweet, 3 fat, and 3 bitter groups were derived from principal components analyses of questionnaire items. SUBJECTS: Convenience sample of healthy adults (24 women, 22 men; mean age +/- standard deviation = 21 +/- 6 years) who did not report high dietary restraint. STATISTICAL ANALYSES: Pearson product moment correlations between genetic taste measures and food and beverage groups. RESULTS: The sample showed diversity in genetic taste measures: perceived bitterness of 0.0032 mol/L PROP ranged from "weak" to well above "very strong"; fungiform papillae densities ranged from 33 to 156 papillae per square centimeter. Distribution of perceived bitterness of PROP and fungiform papillae density differed in women and men. The association between genetic taste measures and acceptance of sweet and high-fat groups differed in women and men. In women, liking of sweet and high-fat food and beverage groups decreased with increasing perceived bitterness of PROP. In men, liking of these foods and beverages increased but with increasing papillae densities. Genetic taste measures were not associated with a dislike of bitter food and beverage groups. APPLICATIONS: The influence of genetic variation in taste on food intake depends on how perceptible sweet, fat, or bitter components are in foods and beverages, as well as the value of sensory factors vs other factors (e.g., health, convenience) on personal dietary choices. Female supertasters of PROP bitterness may avoid high-fat or sweet foods because these oral sensations are too intense and thus less pleasant. Supertasters may taste more bitterness in vegetables but still enjoy eating them because of their healthfulness and because condiments (especially those that are salt based) can block bitterness.

Adolescent↗
PubMed1983

Flavor-illness aversions: potentiation of odor by taste is disrupted by application of novocaine into amygdala.

Taste and odor have different properties in toxiphobic conditioning. When each is used alone, taste becomes aversive when followed by immediate or delayed poison, while odor becomes aversive only if followed by immediate poison. However, if odor and taste are presented as a compound and followed by delayed poison, then odor does become aversive when tested alone. It is as if taste has potentiated the odor signal. Several experiments assessed the role of the amygdala in this potentiation effect by anesthetizing the amygdala with 10% novocaine. Novocaine applied 30 min before presentation (Pre-CS) of an odor-taste compound disrupted the potentiated odor aversion but not the taste aversion. In contrast, novocaine applied 1 min after the compound odor-taste or 1 min prior to LiCl poison did not dissociate odor and taste aversions; both odor and taste aversions were facilitated. Novocaine applied 30 min before an odor alone also disrupted an odor aversion induced by immediate LiCl. But identical treatment did not disrupt odor avoidance conditioned by immediate foot-shock, suggesting that amygdala anesthesia does not simply produce anosmia. Pre-CS novocaine treatment also disrupted flavor neophobia prior to conditioning. The results suggest that novocaine applied to the amygdala disrupts the integration of odor with taste and illness during toxiphobic conditioning.

Amygdala↗
PubMed1997

GABAergic neurotransmission in rat taste buds: immunocytochemical study for GABA and GABA transporter subtypes.

Gamma-aminobutyric acid (GABA) is known to be a candidate for the neurotransmitter involved in the sense of taste. We hereby studied GABA and its termination system, GABA transporters, in rat taste buds by immunocytochemical approaches. Immunoblot analysis of three GABA transporter subtypes (GAT1, GAT2 and GAT3) revealed that the immunoreactive bands of GAT2 and GAT3, but not GAT1, were detected in the tongue. GAT3-immunoreactive band was recognized only in the circumvallate papilla containing a large number of taste buds while GAT2-immunoreactive bands were seen in all areas of the tongue. GAT2 immunoreactivity appeared to be specifically in the nerve fibers beneath the lingual epithelium. Both GAT3 and GABA immunoreactivities were detected only in taste buds. A few GAT3-immunoreactive cells were found in a cross-section of each taste bud but most GAT3-immunoreactive cells were localized in the margin of the taste bud. GAT3 was predominantly concentrated in the distal portion of the GAT3-immunoreactive cells. In contrast, GABA-immunoreactive cells were seen more frequently within each taste bud and the immunoreactivity was distributed throughout the perikarya of the cells. These results suggest that the GABA-uptake system is present in the taste buds and the GABAergic neurotransmission involved in the sensation of taste is terminated by the uptake of GABA into certain taste cells via GAT3.

Animals↗
PubMed1986

Dissociated taste disorder.

Dissociated taste disorder is a special symptom occurring when only one or two taste qualities of the four primary taste are disturbed. Eleven % of all cases of taste disorders complain of this symptom. The subjects of this investigation were 46 patients due to be examined. We used our filter-paper disc method invented for clinical qualitative and quantitative gustometry by taste examination. True dissociated taste disorder was confirmed in 12 patients only with respect to sweetness. No dissociated taste disorder was found for the other types of taste. Sweetness differs from the other three primary tastes in that it is brought about by a protein acting as a receptor. In patients suffering from true dissociated taste disorders, the predominant cause of the condition is zinc deficiency. When zinc is not available in adequate quantities, the synthesis of the protein at the sweet-sensitive receptor site can no longer be achieved smoothly, and this may lead to the development of the complaint.

Aged↗
PubMed2002

Quality of life, taste, olfactory and oral function following high-dose chemotherapy and allogeneic hematopoietic cell transplantation.

Multiple oral complaints develop following high-dose chemo/radiotherapy and hematopoietic cell transplantation (HCT) which can influence quality of life. The purpose of this investigation was to assess quality of life, oral function, taste and smell in a cohort of patients following HCT. A general quality of life survey (the European Organization for Research and Treatment of Cancer (EORTC)) Quality of Life (QOL) questionnaire (QLQ-C30), with an added oral symptom and function scale and assessment of taste and smell was administered to a consecutive series of patients at day 90-100 post HCT. General QOL was impacted by fatigue, affecting physical, social emotional and cognitive function. While oral function scales appeared to be little affected at day 90-100 post HCT, abnormalities of taste were reported. Reports of changes in taste and smell appeared to parallel each other and changes remained at the time of the survey post-HCT. Change in taste appeared to be closely associated with dry mouth. Patients appeared to have difficulty in differentiating sour and bitter, which had been more affected than salt and sweet taste. Females appeared to report greater changes in taste than males. Increased smell sensitivity and taste change resulted in changes in food preparation in some cases, as did reported increase in sensitivity to sour and bitter taste. Acute complications are well known to affect QOL during the early period following HCT, but little assessment of long-term changes in oral QOL and taste has been conducted following transplant. The EORTC QLQ C-30 questionnaire with the oral addendum provides a measure of the quality of life and oral function, and may provide useful outcome measures for assessment of oral care prevention and management in HCT patients.

Adult↗
PubMed2004

Detection and recognition thresholds to the 4 basic tastes in Mexican patients with primary Sjögren's syndrome.

BACKGROUND: Primary Sjögren's syndrome (pSS) is a chronic autoimmune disease characterized by inflammatory lymphocytic infiltration of the salivary glands, leading to dryness of the mouth (xerostomia). It has been postulated that xerostomia is the preceding stage for the development of alterations in taste acuity (dysgeusia) in this type of patients. OBJECTIVES: To determine detection and recognition thresholds to the 4 basic tastes (sweet, salty, sour and bitter) in pSS patients and compare them to a control group. To determine if the long-term consumption of chile peppers and spicy Mexican diets had an effect on the taste perception and acuity of the pSS patients. SETTING: This study was done in the Department of Food Science and Technology of the Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán (INCMNSZ), a third-level hospital in Mexico City. SUBJECTS: The patient group consisted of 21 Mexican females (mean +/- s.d., age: 53.1 +/- 9.8 y) diagnosed with pSS (time of duration of the disease, 8.6 +/- 6.6 y, median 7 y, range 1-25 y) who were recruited at the outpatient service of the Department of Immunology and Rheumatology of the INCMNSZ. The control group consisted of 20 healthy nonsmokers age-matched Mexican women (50.3 +/- 11.9 y) most of them personnel of the INCMNSZ, and some friends and nonblood relatives to the patients (sisters-in-law) who volunteered to participate in the study. INTERVENTIONS: Detection and recognition thresholds were determined by the method of least noticeable differences on three occasions during three nonconsecutive days. Saliva production was determined by Saxon's test on two separate occasions. RESULTS: Although saliva production was severely reduced in pSS patients (1.35 +/- 0.55 ml/2 min, P<0.001) compared to controls (6.26 +/- 2.41 ml/2 min), all subjects recognized the 4 basic tastes when these were tested at suprathreshold concentrations. The detection thresholds for the sweet, sour and bitter tastes were higher in pSS patients, as well as the recognition thresholds for the salty, sour and bitter tastes. A relationship between time of evolution of the disease and saliva production with individual thresholds could not be established. CONCLUSIONS: pSS patients exhibited different degrees of dysgeusia depending on the taste being studied, that is, they were mildly dysgeusic for the sweet and salty tastes and clearly dysgeusic for the sour and bitter tastes. Although both pSS patients and controls had consumed 'typical Mexican diets' their entire lives, our results showed that the consumption of chile peppers and spicy foods did not have any effect on the taste perception and acuity of the pSS patients.

Capsicum↗
PubMed2003

Blockade of cortical muscarinic but not NMDA receptors prevents a novel taste from becoming familiar.

Exposure to a novel taste solution in the rat is followed by a decrease in its intake known as neophobia. This effect gradually disappears, and consumption increases from the second presentation of the taste (attenuation of neophobia), reflecting that the animal learned that it is safe to drink it. Conversely, if gastric malaise is induced after first intake, the rat will develop a long-lasting aversion (conditioned taste aversion). Previous attempts to elucidate the physiological nature of taste memory trace stems only from procedures that require malaise to measure taste memory. Here we assess the relevance of both muscarinic and N-methyl-d-aspartate receptors, known to be involved in conditioned taste aversion, on taste memory using a nonaversive procedure (attenuation of neophobia learning). Attenuation of neophobia was impaired by the muscarinic receptor antagonist, scopolamine, microinjected 20 min before, immediately after or up to 2 h after the first taste experience, suggesting that muscarinic receptors are involved in the acquisition and consolidation of attenuation of neophobia learning. However, the N-methyl-d-aspartate receptor antagonist, d,l-2-amino-5-phosphonovaleric acid, did not affect attenuation of neophobia even when the same dose of the drug was able to disrupt conditioned taste aversion learning, which suggests that attenuation of neophobia learning would be independent of N-methyl-d-aspartate receptors activity in the insular cortex. The neophobic response induced by strong saccharin presentation was not affected by either of the treatments given, which rules out any impairment in taste perception. These results indicate that while cortical muscarinic receptors are important in the formation and consolidation of safe memory trace, N-methyl-d-aspartate receptor activity appears to be noncritical.

2-Amino-5-phosphonovalerate↗
PubMed1996

Changes in taste perception following mental or physical stress.

Taste perception depends not only on the chemical and physical properties of tastants, but may also depend on the physiological and psychological conditions of those who do the tasting. In this study, the effects of mood state on taste sensitivity was evaluated in humans who were exposed to conditions of mental or physical fatigue and tension. Taste responses to quinine sulfate (bitter), citric acid (sour) and sucrose (sweet) were tested. The intensity of the taste sensations were recorded by a computerized time-intensity (Tl) on-line system. Subjects performed mental tasks by personal computer or physical tasks by ergometer for 10-40 min. Before and after these sessions, the duration of the after-taste and the intensity of the sensation of taste were recorded by the Tl system, and in addition, psychological mood states were evaluated with POMS (Profile of Mood State). Tl evaluation showed that after the mental tasks, the perceived duration of bitter, sour and sweet taste sensations was shortened relative to the control. Total amount of bitterness, sourness and sweetness was also significantly reduced. Furthermore, the maximum intensity of bitterness was significantly reduced. There were no significant differences in bitterness and sweetness sensations following physical tasks. However, relative to before the physical task, the duration of the after-taste of sourness was significantly shortened by the physical task. After the physical task, the buffering capacity of saliva was significantly increased. Thus mental and physical tasks alter taste perception in different ways; the mechanisms underlying these changes remain to be determined.

Adult↗
PubMed1996

Multiple human taste receptor sites: a molecular modeling approach.

Numerous experimental data on the human peripheral taste system suggest the existence of multiple low-affinity and low-specificity receptor sites which are responsible for the detection and the complete discrimination of a very large number of organic molecules. According to this hypothesis, a given molecule interacts with numerous taste receptors and vice versa. Statistical analysis of taste intensities estimated by 58 human subjects for various molecules enables the calculation of taste intermolecular distances. For the present modeling study, we hypothesized that a short taste distance (i.e. taste similarity) between two distinct molecules indicates that they bind with similar distributions of affinities to the taste receptors, and hence display similar binding motifs. In order to find common molecular binding motifs among 14 selected organic tastants, hydrogen-bonding and hydrophobic interaction properties were mapped onto their molecular surfaces. The 14 surfaces were then cut in 240 fragments, most of which were made up of 2-4 potentially interacting zones. A correspondence index was defined to measure the analogy between two optimally superimposed fragments. The 75 most representative fragments were all matched pairwise. Twelve distinct clusters of fragments were isolated from the 2775 calculated comparisons. These 12 fragment types were used to calculate structural similarity distances. We then performed a combinatorial analysis to identify which fragment combination best reconciled structural and taste distances. We finally identified an optimal subset of seven fragment types out of the 12, which significantly and best accounted for the 91 pairwise taste distances between all 14 modeled tastants. These seven validated fragment types are therefore presented as good candidates to be recognized by the same number of distinct taste receptor sites. Potential applications of these identified binding motifs to tastant design are suggested.

Binding Sites↗