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At least 199 records · Page 11Linked to original sources
PubMed1992

Conditioned taste and taste-potentiated odor aversions in the Syracuse high- and low-avoidance (SHA/Bru and SLA/Bru) strains of rats (Rattus norvegicus).

Syracuse high- and low-avoidance Long-Evans rats (Rattus norvegicus; SHA/Bru and SLA/Bru) were selectively bred for good and poor active-avoidance learning. However, SLA/Bru animals are superior to SHA/Bru rats in conditioned suppression and passive avoidance learning. In this experiment, saccharin taste and almond odor were the components of a compound conditioned stimulus (flavor) in an illness-induced aversive conditioning paradigm. SLA/Bru rats (n = 17) showed stronger conditioned flavor, taste, and odor aversion than did SHA/Bru animals (n = 18). Unselected Long-Evans rats (n = 18) were intermediate between the selected strains. SLA/Bru and Long-Evans rats showed taste-potentiated odor aversions in this experiment, whereas SHA/Bru animals did not. The results provide evidence that genetic factors, as exemplified by the different strains, are importantly involved in the mechanisms underlying interoceptive and exteroceptive aversive conditioning.

Animals↗
PubMed2005

Psychophysical investigations of cetylpyridinium chloride in rats: its inherent taste and modifying effects on salt taste.

Salts are transduced by at least 2 mechanisms: (a) antagonized by amiloride and (b) antagonized by cetylpyridinium chloride (CPC). The authors report on 4 behavioral experiments in rats that characterize the orosensory properties of CPC itself as well as its effect in suppressing the intensity of NaCl and KCl taste. Experiments 1 and 2 indicated that CPC has a quinine-like taste quality. Experiments 3 and 4 demonstrated that the recognition of KCl, but not NaCl, is modestly reduced by mixture with CPC. However, control experiments call into question the mechanism of the salt suppression of CPC, because both CPC-salt and quinine-salt mixtures had similar effects. The relevance of these studies for understanding salt and bitter taste coding is discussed.

Animals↗
PubMed1984

Salt taste sensitivity and stimulus volume: sips and drops. Some implications for the Henkin taste test.

Various presentation procedures and stimulus volumes were compared in their effect on salt taste sensitivity. For sodium chloride (NaCl) stimuli pipetted onto the tongue, subjects had comparable measured sensitivity to 10 ml and 1 ml volumes but a reduced sensitivity to 0.1 ml volumes. The greatest sensitivity was achieved with 10 ml sipped volumes. Modification of the Henkin dropwise triangular taste test, by increasing the stimulus volumes, increased subjects' sensitivity. Only the 1 ml pipette presentation increased the sensitivity of the Henkin procedure, albeit slightly, to the detection of changes in taste sensitivity, the purpose for which the procedure was actually designed. Such modification did not perturb salivary NaCl levels more than the regular Henkin procedure, so it would not be expected to introduce sensitivity drift.

Adolescent↗
PubMed2002

Electrophysiological studies of salty taste modification by organic acids in the labellar taste cell of the blowfly.

Using the labellar salt receptor cells of the blowfly, Phormia regina, we electrophysiologically showed that the response to NaCl and KCl aqueous solutions was enhanced and depressed by acetic, succinic and citric acids. The organic acid concentrations at which the most enhanced salt response (MESR) was obtained were found to be different: 0.05-1 mM citric acid, 0.5-2 mM succinic acid and 5-50 mM acetic acid. Moreover, the degree of the salt response was not always dependent on the pH values of the stimulating solutions. The salt response was also enhanced by HCl (pH 3.5-3.0) only when the NaCl concentration was greater than the threshold, indicating that the salty taste would be enhanced by the comparatively lower concentrations of hydrogen ions. Another explanation for the enhancement is that the salty taste may also be enhanced by undissociated molecules of the organic acids, because the MESRs were obtained at the pH values lower than the pKa(1) or pKa(2) values of these organic acids. On the other hand, the salty taste could be depressed by both the lower pH range (pH 2.5-2.0) and the dissociated organic anions from organic acid molecules with at least two carboxyl groups.

Animals↗
PubMed2006

Extracellular production of neoculin, a sweet-tasting heterodimeric protein with taste-modifying activity, by Aspergillus oryzae.

Neoculin (NCL), a protein with sweetness approximately 500-fold that of sugar, can be utilized as a nonglycemic sweetener. It also has taste-modifying activity to convert sourness to sweetness. NCL is a heterodimer composed of an N-glycosylated acidic subunit (NAS) and a basic subunit (NBS), which are conjugated by disulfide bonds. For the production of recombinant NCL (rNCL) by Aspergillus oryzae, alpha-amylase with a KEX2 cleavage site, -K-R-, was fused upstream of each of NAS and NBS and the resulting fusion proteins were simultaneously expressed. For accurate and efficient cleavage of the fusion construct by KEX2-like protease, a triglycine motif was inserted after the KEX2 cleavage site. As NBS showed lower production efficiency than did NAS, a larger amount of the NBS expression plasmid than of NAS expression plasmid was introduced during cotransformation, resulting in successful production of rNCL in the culture medium. Moreover, to obtain a higher production yield of rNCL, the active form of hacA cDNA encoding a transcription factor that induces an unfolded protein response was cloned and expressed constitutively. This resulted in a 1.5-fold increase in the level of rNCL production (2.0 mg/liter). rNCL was purified by chromatography, and its NAS was found to be N-glycosylated as expected. The original sweetness and taste-modifying activity of rNCL were comparable to those of native NCL when confirmed by calcium imaging with human embryonic kidney cells expressing the human sweet taste receptor and by sensory tests.

Aspergillus oryzae↗
PubMed2004

The gastrointestinal tract "tastes" nutrients: evidence from the intestinal taste aversion paradigm.

To develop and use a behavioral paradigm for assessments of what nutrient properties are detected by intestinal chemoreceptors, we combined features of the "electronic esophagus" preparation (Elizalde G and Sclafani A. Physiol Behav 47: 63-77, 1990) and the conditioned taste aversion protocol (Garcia J and Koelling RA. Psychon Sci 4: 123-124, 1966). In four experiments, separate groups of food-deprived rats with gastric (experiments 1-4) or duodenal (experiment 4) catheters were infused with either carbohydrates (maltodextrin) or fats (corn oil) into their stomachs or small intestines, either while they consumed nonnutritive flavored solutions (experiments 1 and 2) or in the absence of any intake (experiments 3 and 4). For some animals, one of the macronutrient infusions was paired with lithium chloride injections shown to support conventional conditioned aversions. After training, in various oral preference test trials, animals were given opportunities to taste and consume the nonnutritive solutions that had served as oropharyngeal conditioned stimuli as well as the nutrients that had been infused intragastrically, with or without poisoning, but never sampled by mouth. As previously established, preferences for the nonnutritive flavors were enhanced by association with intragastric infusions of macronutrients, with carbohydrates producing the greater preference. On first exposure to the two macronutrients for oral consumption, animals reduced their intake of the nutrient that had been previously poisoned when it was infused into the gastrointestinal tract. These results, along with additional controls, suggest that nutrient tastes detected in the intestines can be recognized centrally based on oropharyngeal gustatory stimulation.

Animals↗
PubMed1993

Sweet taste transduction in hamster taste cells: evidence for the role of cyclic nucleotides.

1. Physiological and behavioral responses to artificial sweeteners, natural sweeteners, and cyclic nucleotides were assessed using two techniques. An extracellular "in situ" technique recorded action potentials from fungiform taste buds and the two-bottle preference test measured behavioral preferences for the different sweeteners. 2. Two high-potency sweeteners, NC-00274-01 (NC01) and NC-00044-AA (NCAA), were preferred over water at micromolar concentrations. Saccharin and sucrose were likewise preferred, but at millimolar concentrations. 3. Bursts of action currents were elicited by sucrose at 200 mM, saccharin at 20 mM, and NCAA at 0.1 mM. A concentration-response curve for the high-potency sweetener NC01 revealed a threshold concentration of 1 microM and a saturation concentration of 100 microM. No responses were elicited by aspartame. 4. The responses to different sweeteners adapted rapidly at saturating concentrations. With NC01, adaptation was concentration dependent: at threshold the response adapted very slowly if at all. Adaptation increased with increasing concentration. 5. Membrane-permeant analogues of adenosine 3',5'-cyclic monophosphate and guanosine 3',5'-cyclic monophosphate mimicked sweeteners in their ability to elicit a response. This occurred with high fidelity: nearly every taste bud that responded to sweeteners also responded to the nucleotides and every sweet-unresponsive taste bud was nucleotide unresponsive. 6. The sweet responses and nucleotide responses occurred in the absence of permeant apical cations and were not enhanced nor diminished by the presence of such cations. Amiloride had no effect on the sweet response.

Animals↗
PubMedDate not supplied

Taste preferences for nutritional supplements: comparison of cancer patients and healthy controls using a wine-tasting scale.

Thirty-nine cancer patients (Ca) and 37 age-and sex-matched healthy controls (Co) evaluated 11 commercially available enteral supplements using a modified wine-tasting scale. The cancer patients were 19 males with lung cancer and 20 females with breast cancer, and their controls consisted of 17 males and 20 females, respectively. Mean evaluation scores for the individual supplements revealed no significant differences (NS) between lung cancer patients and controls. Ensure Plus (strawberry) received the highest score from both groups (Ca 16.0 +/- 3.0 vs Co 17.1 +/- 2.6, N.S.) while Vital received the lowest (Ca 6.3 +/- 4.8 vs Co 4.9 +/- 4.2, NS). Similar results were obtained for breast cancer patients and their controls except that chocolate Sustacal was rated significantly higher by breast cancer patients than by controls (16.6 +/- 2.6 vs 13.3 +/- 4.3, p less than 0.01). Again, Ensure Plus (strawberry) received the highest score from both groups (Ca 17.0 +/- 3.5 vs Co 17.8 +/- 2.3, NS), while Vital was rated lowest by both groups (Ca 5.6 +/- 4.7 vs Co 4.3 +/- 5.0, NS). The modified wine-tasting scale provides a method for quantitating taste preference for various dietary supplements. We report here the numerical rating of 11 supplements by patients with lung cancer and patients with breast cancer as well as their age- and sex-matched controls.

Breast Neoplasms↗
PubMedDate not supplied

[The neural bases of taste aversion learning: the formation of acquired hedonic taste representations].

INTRODUCTION: Taste aversion conditioning is a form of associative learning in which certain qualities of a food (mainly its taste) are associated to specific negative visceral consequences that derive from eating it. Establishing this learning depends on gustatory-visceral integration processes carried out in the central nervous system. DEVELOPMENT: In this manuscript our aim is to offer a global view of the centres and connections that play the most significant roles in the formation of taste aversion learning (TAL). CONCLUSIONS: Many researchers consider that the initial level of integration is situated within the parabrachial nuclei. A priori and given the basic vital nature of TAL, its formation and completion could be thought to take place at this brain stem level, without requiring the intervention of the higher processing structures. Nevertheless, in the literature on TAL there is a large body of both neuroanatomical and neurobehavioural evidence that seems to indicate that the formation of TAL requires complex interactions between the parabrachial nuclei and certain prosencephalic structures, such as the insular cortex or the amygdala, among others.

Amygdala↗
PubMed1997

Gustatory functions, sodium appetite, and conditioned taste aversion survive excitotoxic lesions of the thalamic taste area.

Rats with bilateral, electrophysiologically guided, ibotenic acid lesions of the gustatory thalamus (THLX) were tested for their ability to perform a variety of taste-guided behaviors. First, in daily 30-min sessions, the rats were given repeated 10-s access periods to a range of concentrations of sucrose, NaCl, or QHCl, plus water. Both the control and the THLX rats exhibited similar concentration-response functions, regardless of hydrational state. Next, on 3 trials, the rats were given 15 min access to 0.3 M l-alanine and then injected with LiCl (0.15 M, 1.33 ml/100 g body weight ip). All rats learned a taste aversion following 1 pairing with LiCl. Finally, on 3 separate occasions, the rats were injected with furosemide, and Na(+)-appetite was evaluated 24 hr later. All rats expressed an equivalent sodium appetite after the first furosemide injection, but only the control rats increased intake of 0.51 M NaCl with repeated sodium depletions. These observations reinforce prior data implying that an intact gustatory thalamus is not necessary for the expression of some taste-guided behaviors.

Animals↗
PubMed2006

Bitter taste receptors and human bitter taste perception.

A vast number of structurally diverse bitter compounds need to be detected by a subfamily of only approximately 25 human bitter receptors. Failure in detecting them might be lethal, since some naturally occurring bitter compounds, such as strychnine, are very toxic. This review presents an overview about the enormous progress in the field of mammalian bitter taste research with special emphasis on humans, if data were available. It summarizes the current knowledge about the anatomical basis for bitter taste perception, intracellular signal transduction, evolution, expression and polymorphisms of hTAS2R genes, and the molecular basis for the recognition of bitter compounds.

Animals↗
PubMed1995

Quinine-HCl-induced modification of receptor potentials for taste stimuli in frog taste cells.

After frog taste cells were adapted to 1 mM quinine-HCl (Q-HCl) for 10 sec, modification of receptor potentials in the taste cells induced by salt, acid, sugar and bitter stimuli was studied with microelectrodes. The phasic component of receptor potentials induced by 0.1 M NaCl, KCl, NH4Cl and MgCl2 was enhanced following adaptation to Q-HCl. The rate of rise of receptor potentials in response to the salts was increased after Q-HCl adaptation. The amplitude and the rate of rise of receptor potentials induced by 1 mM acetic acid were larger after Q-HCl adaptation than after water adaptation. The amplitude of phasic component and rate of rise of receptor potentials for 0.5 M sucrose after Q-HCl were the same as those after water. The amplitudes of tonic receptor potentials for 1 mM Q-H2SO4, brucine and picric acid after Q-HCl adaptation were the same as those after 1 mM NaCl adaptation. Correlation coefficient between taste cell responses induced by 1 mM Q-HCl and 1 mM Q-H2SO4 was very high, but those between 1 mM Q-HCl and 1 mM brucine responses and between 1 mM Q-HCl and 1 mM picric acid responses were low. This indicates that Q-HCl and Q-H2SO4 bind to the same receptor site, but brucine and picric acid bind to different receptor sites to which Q-HCl does not bind.

Animals↗
PubMed1978

Change in taste preference related to aging of taste cells in rat.

Following the suppression of renewal of rat taste cells by vinblastine sulphate, the preference for sucrose decreased markedly while the aversion to quinine did not change. The results suggest that the sensitivity of taste cells to sucrose decreases with their aging, but the sensitivity to quinine increases.

Aging↗
PubMed1981

Molecular mechanism of sweet taste: relationship of hydrogen bonding to taste sensitivity for both young and elderly.

Taste detection thresholds for 11 sweeteners varying widely in chemical structure were determined for young and elderly subjects. The rank orders of the thresholds for young and elderly were highly correlated (Spearman's rho=0.976) although the thresholds were 2.72 times higher on the average for the elderly when compared with the young. This decreased sensitivity was statistically highly significant, p=0.000266. Sweeteners with the lowest detection thresholds tended to have the greatest number of units (AH-B systems) capable of intermolecular hydrogen bonding. In addition, use of the method of magnitude estimation with 10 sweeteners revealed that the elderly perceived less growth in intensity with increasing concentration than young subjects. The slopes of the psychophysical functions relating concentration and perceived intensity were flatter in all cases for elderly subjects; the mean ratio, slope(young)/slope(elderly), was 2.06. The largest relative decline in slope was found for those stimuli with the greatest number of possible AH-B types, suggesting that the possibilities for concerted intermolecular hydrogen bonding may decline with age. If the elderly compensate for their diminished taste acuity with increased consumption, they may constitute a population with higher than average risk of any adverse dose-related biological effects of artificial sweeteners.

Adult↗
PubMed1996

Detection of tastes in mixture with other tastes: issues of masking and aging.

When one taste (masker) is strong enough, it can completely mask another task (target) of different quality. How strong the masker must be to do this depends on how strong the target is. As the target concentration is increased, the masking concentration must be increased, too, but in ever-increasing proportion. To quantify the conditions for such complete masking, the target's detection threshold was measured as a function of the masker's concentration, from zero to strong. This was done for 12 binary combinations of sucrose, sodium chloride, citric acid and quinine hydrochloride. The 12 functions generated show that some tastants mask each other much more efficiently than others. Masking gives new insight into the role of aging in taste: older (66-90 years) subjects' thresholds, regardless of masking concentration, always measured a constant factor higher than younger (18-29 years) subjects' thresholds (about two to seven times higher, depending on target tastant). Thus, with increasing level of the masker, the thresholds of young and elderly go up in parallel. Thresholds of tastants in water alone are false predictors of elderly persons' ability to perceive ingredients like salt and sugar condiments in foods, where, because of masking, their thresholds can be several times higher than in water. Age manifested itself relatively mildly in sucrose and citric acid, moderately in sodium chloride, and strongly in quinine hydrochloride.

Adolescent↗
PubMed2003

Taste perception with age: generic or specific losses in supra-threshold intensities of five taste qualities?

The influence of ageing on supra-threshold intensity perception of NaCl, KCl, sucrose, aspartame, acetic acid, citric acid, caffeine, quinine HCl, monosodium glutamate (MSG) and inosine 5'-monophosphate (IMP) dissolved in water and in 'regular' product was studied in 21 young (19-33 years) and 21 elderly (60-75 years) persons. While the relative perception (intensity discrimination) seems to be remarkably resistant to the effect of ageing, the absolute perception (intensity rating) decreased with age for all tastants in water, but only for the salty and sweet tastants in product. When assessed while wearing a nose clip, only the perception of salty tastants was diminished with age. The slopes of the psychophysical functions were flatter in the elderly than in the young for the sweet, bitter and umami tastants in water, and for the sour tastants in product only. The age effects found were almost exclusively generic and never compound-specific within a taste. This study indicates that the relevance of determining intensities of tastants dissolved in water for the 'real life' perception of taste in complex food is rather limited.

Adult↗
PubMed1998

Self-inhibition in Ca2+ -evoked taste responses: a novel tool for functional dissection of salt taste transduction mechanisms.

Rat chorda tympani (CT) responses to CaCl2 were obtained during simultaneous current and voltage clamping of the lingual receptive field. Unlike most other salts, CaCl2 induced negatively directed transepithelial potentials and gave CT responses that were auto-inhibitory beyond a critical concentration. CT responses increased in a dose-dependent manner to approximately 0.3 M, whereafter they decreased with increasing concentration. At concentrations where Ca2+ was self-inhibitory, it also inhibited responses to NaCl, KCl, and NH4Cl present in mixtures with CaCl2. Ca2+ completely blocked the amiloride-insensitive component of the NaCl CT response, the entire KCl-evoked CT response, and the high-concentration-domain CT responses of NH4Cl (>/=0.3 M). The overlapping Ca2+-sensitivity between the responses of the three Cl- salts (Na+, K+, and NH+4) suggests a common, Ca2+-sensitive, transduction pathway. Extracellular Ca2+ has been shown to modulate the paracellular pathways in different epithelial cell lines by decreasing the water permeability and cation conductance of tight junctions. Ca2+-induced modulation of tight junctions is associated with Ca2+ binding to fixed negative sites. This results in a conversion of ion selectivity from cationic to anionic, which we also observed in our system through simultaneous monitoring of the transepithelial potential during CT recording. The data indicate the paracellular pathway as the stimulatory and modulatory site of CaCl2 taste responses. In addition, they indicate that important transduction sites for NaCl, KCl, and NH4Cl taste reception are accessible only through the paracellular pathways. More generally, they show that modulation of paracellular transport by Ca2+ in an intact epithelium has functional consequences at a systemic level.

Amiloride↗