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PubMed1995

Effects of capsaicin desensitization on taste in humans.

The desensitization effects on taste resulting from application of 100 or 10 ppm capsaicin, accompanied by daily testing of a capsaicin series (1-1000 ppm, in log steps), or the desensitization resulting from application of 100 ppm capsaicin without the daily capsaicin testing, were investigated. The taste stimuli were three concentrations each of NaCl, sucrose, citric acid, quinine and 6-n-propylthiouracil. Following either type of 100 ppm desensitization, the magnitude estimates of the two bitter tastes, in particular, and citric acid showed significant decrements. Following 10 ppm capsaicin or an ethanol control procedure, there were no such effects. Recovery was complete in 1-3 days. It seems possible that the taste decrements are due to effects on both the taste and tactile components of taste, though there is a stronger case for effects on the tactile component.

Adolescent↗
PubMed1996

Retention of conditioned taste aversion to NaCl after chorda tympani transection in Fischer 344 and Wistar rats.

Fischer 344 (F344) rats fail to prefer sodium chloride (NaCl) solution to water, and this behavior is dramatically altered by bilateral transection of the chorda tympani nerve (CTX). Tests of retention and generalization of a conditioned taste aversion (CTA) to 0.15 M NaCl were used to assess alterations in salt taste perception after CTX. A CTA was established to 0.15 M NaCl in groups of F344 and Wistar rats after two pairings with LiCl (IP, 2% body weight; 0.15 M). After conditioning, animals received bilateral CTX or sham operations. Approximately 2 weeks after surgery animals were tested for retention of the CTA. Aversion to 0.15 M NaCl was evident in CTX and SHAM rats that had been conditioned prior to surgery, with no apparent difference in magnitude as a function of surgical condition. Thus, although CTX profoundly alters F344 rats' hedonic response to NaCl, it does not alter perceptual characteristics so markedly that NaCl is no longer recognized as the stimulus presented during aversion conditioning. Rather these studies suggest that in both the F344 and Wistar strains the chorda tympani nerve is not necessary for retention of a presurgical CTA to NaCl. These studies, therefore, do not provide evidence of changes in NaCl perceptual "quality" as a consequence of CTX either in F344 rats, where such changes were indicated by the preference data, or in the Wistar rat, where they were not.

Afferent Pathways↗
PubMed1996

Sweet taste and diet in type II diabetes.

The relationship between sweet taste function and dietary intake was studied in 21 patients with type II diabetes mellitus and 16 age-, weight-, and sex-matched controls. Subjects rated the sweetness intensity and pleasantness of a series of beverage samples sweetened with sucrose: 1.5-24%, fructose: 1-18%, or aspartame: 0.25-4%. They also kept 7-day food records. No group differences were found in sweet taste perception, pleasantness ratings, daily energy intakes, or macronutrient composition of the diets. However, subjects with diabetes consumed less sucrose but 3.5 times more alternative sweeteners than did controls. Peak pleasantness ratings for the beverage samples were positively correlated with dietary sweetness content in the subjects with diabetes but not the controls. These findings suggest that in diabetes, hedonic ratings for a sweetened beverage were related to dietary sweetness intake rather than changes in sweet taste perception.

Adult↗
PubMed1995

Effect of anesthesia of the chorda tympani nerve on taste perception in humans.

Individuals who have sustained considerable damage to parts of the taste system often fail to experience changes in everyday taste experience. The two halves of the tongue are independently innervated: the chorda tympani (branch of the facial or VIIth cranial nerve) innervating the anterior two-thirds and the glossopharyngeal (IXth cranial nerve) innervating the posterior one-third. Anesthesia of the chorda tympani nerve on one side produced increased taste intensities for some stimuli on the area innervated by the glossopharyngeal nerve on the other side. Because this effect occurs across the midline and taste projects ipsilaterally, the effect must occur in the central nervous system (CNS). This supports Halpern and Nelson's release-of-inhibition hypothesis that the area to which the chorda tympani projects in the CNS must normally inhibit that of the glossopharyngeal nerve. Anesthesia of the chorda tympani abolishes that inhibition and leads to perception of increased taste intensities from areas innervated by the glossopharyngeal nerve.

Afferent Pathways↗
PubMed1986

Constraints imposed on taste physiology by human taste reaction time data.

The speed with which an organism responds to stimulus events is reaction time (RT): the minimum time interval between stimulus arrival at a receptor organ, and an overt response by the organism. This time interval specifies maximum duration of all processes necessary for the RT sequence. Responses to any change in taste have RT less than 1 sec for suprathreshold concentrations. Therefore, constituent events at taste receptors, in the central nervous system (CNS), and at the response organ, must have sufficient durations less than 1 sec (Constraint 1). Taste stimulus durations of 50 msec, and therefore taste receptor events of approximately 50 msec, are sufficient for these responses (Constraint 2), as well as for taste quality identification responses (Constraint 3). Taste receptor latencies, neural conduction times, and RT response organ events are even briefer. Thus, 60% to 90% of human taste RT is CNS events. Taste receptor events remain crucial, but CNS processing is important, and apparently time limiting, in all human taste judgments.

Afferent Pathways↗
PubMed1987

Effects of haemodialysis on taste and thirst.

Fifteen patients undergoing haemodialysis tasted soup varying in salt concentration and apple puree varying in sucrose concentration, immediately before and after dialysis. Matched controls tasted the same foods with a similar interval between tastings. The samples were rated for intensity, and on a relative-to-ideal scale. For the salt, the slopes of the functions plotted against log (concentration) were higher after dialysis than before, whilst the most preferred concentration was lower. There were no effects found for the sweetness ratings or for the controls. Likewise there were no overall differences in the ratings between the patients and controls. Thirst was found to increase on dialysis, and there was a trend of this being higher for the patients than for the controls. The reduction in preferences for salt by dialysis would make compliance with a reduced salt diet easier, but the increase in thirst would make compliance with reduced fluid intake more difficult.

Adolescent↗
PubMed1980

Magnitude estimates of amino acids for young and elderly subjects.

Serial dilutions of twenty-three amino acids were presented to young and elderly subjects who rated the relative intensities of the dilutions using the magnitude estimation procedure. In each case the slope of the psychophysical function relating concentration and perceived intensity was flatter for the elderly subjects: the mean ratio (slope (young)/slope (elderly)) was 2.55. This result could be due to an age-related decline in gustatory apparatus or associated central areas as well as memory loss and decline in performance often found in the elderly. No conclusive relationships between the slopes of the psychophysical functions were found with chemical structure, taste quality, or solubility.

Adolescent↗
PubMed1981

Age and sex effects on taste of sucrose, NaCl, citric acid and caffeine.

A procedure combining forced choice discrimination with intensity scaling served to evaluate taste perception of sucrose, NaCl, citric acid and caffeine in 24 young and 24 geriatric subjects. Each group was divided equally by sex. No overall sex differences occurred for taste discrimination, and suprathreshold taste intensity scaling for sucrose and NaCl did not differ by sex or age. However, young adults generally discriminated lower concentrations of citric acid and caffeine from water blanks than did geriatric subjects. Younger subjects judged suprathreshold concentrations of caffeine significantly more intense, as did young females compared to young males; similarly, young females judged citric acid as stronger than did older males. The present suggest that age and gender are major factors in sour and bitter perception.

Adult↗
PubMed1992

The effect of injury on the properties of afferent fibres in the lingual nerve.

The receptor properties of mechanosensitive afferent fibres in the lingual nerve have been studied using electrophysiological techniques in cats. In normal animals some fibres responded only to mechanical stimulation of filiform or fungiform papillae but others also responded when a cold stimulus was applied to the receptive field. Twelve weeks after crushing the lingual nerve, the regenerated fibres had slower conduction velocities but the receptor properties were not significantly different from normal. Twelve weeks after sectioning the lingual nerve, there was a greater reduction in conduction velocities and in addition the mechanoreceptive fields were smaller, force thresholds were higher, adaptation times longer and a smaller proportion of fibres responded to a cold stimulus. These results suggest that section injuries are more likely to result in persistent sensory abnormalities than crush injuries.

Action Potentials↗
PubMed1982

Gustatory functions of the nucleus tractus solitarius in the rabbit.

Multiunit analysis revealed a rostral region of NTS containing cells responsive to taste stimulation of rostral tongue. Using representative stimuli for the 4 basic types of taste, maximal incidence and magnitude of response was found to NaCl, followed by HCl, sucrose and QHCl. Further analysis of temporal patterns of response to the tastants revealed differences among stimuli in latency and time course. A principal components analysis indicated that time course, apart from magnitude of response, could contribute to neural differentiation of tastants. Information was also derived on neural intensity functions for these basic types of tastants. Additional observations with sodium saccharin revealed minimal neuronal responsivity despite reported evidence of behavioral preference for this tastant by rabbits.

Animals↗
PubMedDate not supplied

Ethanol preference following the sucrose-fading initiation procedure.

Lever responding maintained with ethanol reinforcement at concentrations up to 20% (v/v) was initiated in non-food and -water deprived rats via a sucrose-fading procedure. Home cage two-bottle preference tests between water and 10% ethanol were conducted before (pre) and after (post) the ethanol initiation procedure to determine the effect of initial ethanol preference on ethanol initiation and of initiation on later ethanol preference. Initial preference testing found that the rats could be divided into two groups, animals with low ethanol preference scores (preference below 25%) and those with moderate ethanol preference scores (preference between 25% and 50%). All animals were successfully initiated with the sucrose-fading procedure to lever press with ethanol reinforcement. Following initiation, home cage preference was markedly increased for the initially low-preferring rats (from 12% to 43%), while moderate-preferring rats showed only slight increases (from 37% to 47%). The shift in ethanol preference was discussed in terms of the relation between ethanol preference and behavioral history.

Alcohol Drinking↗
PubMed2006

The sweet tooth hypothesis: how fruit consumption relates to snack consumption.

Building on prior work related to taste preferences of fruit lovers, we investigate the "sweet tooth" hypothesis. First, using CSFII survey data, we show that fruit consumption is more highly related to sweet snack consumption than it is to salty snack consumption. Second, a follow-up study with a different population supports the relationship by showing that sweet snack consumption is more related to fruit consumption than it is to vegetable consumption. Knowing that people who frequently eat sweet snacks may be predisposed to increasing their fruit consumption will enable better targeting and tailoring of educational efforts, such as those used in the 5-a-Day for Better Health campaign.

Adult↗
PubMed2005

Fruit consumption of boys (8--11 years) is related to preferences for sour taste.

The present study investigated whether the most preferred balance between sweet and sour taste of children (n=50, 9.2+/-0.9 yrs of age) are related to their consumption of fruit. Taste preferences were measured with a rank-by-elimination procedure with seven sweet orangeades that differed in added citric acid (i.e. 0.009-0.065 M). Fruit consumption was assessed with a questionnaire that was completed by the children's parents. Results showed that boys' but not girls' most preferred balance between sweet and sour taste was positively correlated with their consumption of fruit: that is, the more added citric acid was preferred the more fruit was consumed. We conclude that preference for high concentrations of citric acid in a sweet context may be associated with the consumption of fruit in boys. In girls, the optimal balance between sweet and sour taste seems to be of less importance; their consumption of fruit may be more influenced by their parents, availability and health related motives.

Child↗
PubMed2006

Sensory correlation of glucose levels in a starch-based semi-solid model system before and after alpha-amylase breakdown.

In this study a diabetic glucose monitor was used to measure the glucose content of 40 model vanilla custard desserts, these were compared with sensory ratings from a trained quantitative descriptive analysis panel. Stimuli varied in starch type, concentration and homogenisation but had identical sugar, flavour and fat contents. Despite this, mean sensory ratings of sweetness varied from 21 to 43 on a 100-point scale. Glucose levels in the stimuli were measured, in vitro, before and after the addition of 0.1% whole human saliva to the product. In all cases glucose concentration increased after the addition of saliva as starch was converted to glucose. There were highly significant correlations of some odour, flavour, mouth feel and after-feel attributes with glucose concentration. The correlation of sweet flavour with glucose concentration was higher in unmodified stimuli than in stimuli with added saliva, suggesting that sweetness is perceived soon after ingestion. Additional glucose produced through starch breakdown appeared to have a relatively small impact on the sensory scores of the stimuli.

Adult↗
PubMed2005

Validation of a rat behavioral avoidance model from a drug delivery perspective.

Conventional taste-masking strategies are used to overcome the bitter taste perception of pharmaceuticals by coating the drug particles and/or adding flavoring agents. However, for certain product categories such as rapid dissolve sublingual tablets, taste-masking is challenging. Programs exploring such formulation strategies in the LO-CS phase or post CS phase possess very little toxicological information available in order to conduct human taste panel studies. The potential of a bitter taste perception can present a significant business risk. The objective of the study was to validate a rat behavioral avoidance model that identifies bitter-tasting compounds. Most classic bitter substances elicit a response in the micromolar concentration range while most drugs elicit a response in the millimolar range, hence a validation exercise was conducted to examine if the existing biological model was sensitive enough to identify known bitter tasting drugs as such. Five compounds: ergotamine tartrate, fluoxetine, sucrose, sumatriptan and povidone were chosen to represent a spectrum of compounds. The bitter tasting compounds were identified as such in the model. Based on these results, the assay may serve as a useful surrogate test to identify compounds that may have bitter taste issues.

Animals↗