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PubMed1988

Temperature dependence of amiloride-sensitive and -insensitive components of rat taste nerve response to NaCl.

The temperature dependence of the rat taste response to NaCl was examined by measuring the chorda tympani activities in response to NaCl solution of varying temperatures before and after amiloride treatment. The response to NaCl was composed of 3 components: component I which was not suppressed by amiloride and components II and III which were suppressed by amiloride. Components I, II and III show maximal responses around 30, 30 and 10 degrees C, respectively. The response to NaCl at 10 degrees C was composed mostly of amiloride-sensitive component (component III). Magnitude of the amiloride-insensitive component (I) was greatly affected by variation of anion species. The amiloride-sensitive component II also showed anion influence but the influence was different from that for component I. Another amiloride-sensitive component (III) showed practically no anion influence. Threshold concentrations of the components were 0.1 mM for component I, 3 mM for component II and 0.3 mM for component III. Equilibrium potentials of Na+ at the threshold concentrations across the apical membrane of taste cells were calculated to be -120.2 mV for component I, -31.4 mV for component II and -85.4 mV for components III. Thus the equilibrium potentials of Na+ at the thresholds for components I and III were more negative than the resting potentials reported, which suggested that an increase in permeabilities of Na+ through receptor sites (or channels) for these components will lead to hyperpolarization, not depolarization of taste cells.

Amiloride↗
PubMed2005

Taste disturbance after tonsillectomy and laryngomicrosurgery.

OBJECTIVE: To investigate the incidence of taste disturbance after tonsillectomy and laryngomicrosurgery. STUDY DESIGN: A prospective study. METHODS: Thirty-five consecutive patients underwent tonsillectomy with electric coagulator at Kanebo Memorial Hospital from September 2002 to May 2004. Another 35 consecutive patients underwent laryngomicrosurgery in a routine way during the same period. Both procedures were performed by two experienced doctors. The postoperative taste function was evaluated with questionnaire, electrogustometry (EGM), and serum levels of Zn, Cu and Fe. RESULTS: After tonsillectomy, 3/35 patients (8.6%) complained of taste disturbance, due to the pressure on the tongue in two, and Zn deficiency after lack of intake in one. All three patients recovered taste within 1.5 months. None of our patients had taste disturbance due to surgical insult of the lingual branch of the glossopharyngeal nerve. After laryngomicrosurgery, only one patient (2.9%) complained of taste disturbance with elevation of the EGM threshold that resulted from the pressure on the tongue. In addition, abnormal sensation in the tongue occurred in 9 cases (25.7%) after tonsillectomy and in 2 cases (5.7%) after laryngomicrosurgery, and feeling of thirst occurred in 12 cases (34.3%) and in 8 cases (22.9%), respectively. CONCLUSION: Taste disturbance occurs in few cases when experienced surgeons perform tonsillectomy or laryngomicrosurgery. However, it is recommended to inform the patients of the potential postoperative complications such as taste disturbance and abnormal sensation of the tongue.

Adolescent↗
PubMed2004

Bitter receptor gene (TAS2R38), 6-n-propylthiouracil (PROP) bitterness and alcohol intake.

BACKGROUND: Phenylthiocarbamide (PTC) and 6-n-propylthiouracil (PROP), chemically related compounds, are probes for genetic variation in bitter taste, although PROP is safer with less sulfurous odor. Threshold for PROP distinguishes nontasters (increased threshold) from tasters (lower threshold); perceived intensity subdivides tasters into medium tasters (PROP is bitter) and supertasters (PROP is very bitter). Compared with supertasters, nontasters have fewer taste papillae on the anterior tongue (fungiform papillae) and experience less negative (e.g., bitterness) and more positive (eg, sweetness) sensations from alcohol. We determined whether the TAS2R38 gene at 7q36 predicted PROP bitterness, alcohol sensation and use. METHODS: Healthy adults (53 women, 31 men; mean age 36 years)--primarily light and moderate drinkers--reported the bitterness of five PROP concentrations (0.032-3.2 mM) and intensity of 50% ethanol on the general Labeled Magnitude Scale. PROP threshold and density of fungiform papillae were also measured. Subjects had common TAS2R38 gene haplotypes [alanine-valine-isoleucine (AVI) and proline-alanine-valine (PAV)]. RESULTS: PROP bitterness varied significantly across genotypes with repeated measures ANOVA: 26 AVI/AVI homozygotes tasted less bitterness than either 37 PAV/AVI heterozygotes or 21 PAV/PAV homozygotes. The PAV/PAV group exceeded the PAV/AVI group for bitterness only for the top PROP concentrations. The elevated bitterness was musch less than if we defined the groups using psychophysical criteria. With multiple regression analyses, greater bitterness from 3.2 mM PROP was a significant predictor of greater ethanol intensity and less alcohol intake--effects separate from age and sex. Genotype was a significant predictor of alcohol intake, but not ethanol intensity. With ANOVA, AVI/AVI homozygotes reported higher alcohol use than either PAV/AVI heterozygotes or PAV/PAV homozygotes. When age effects were minimized, PROP bitterness explained more variance in alcohol intake than did the TAS2R38 genotype. CONCLUSIONS: These results support taste genetic effects on alcohol intake. PROP bitterness serves as a marker of these effects.

Adult↗
PubMed2005

Taste disorders after tonsillectomy: case report and literature review.

The authors describe a case of dysgeusia that occurred during the recovery period after a tonsillectomy. The cause was thought to be a lesion to the lingual branch of the glossopharyngeal nerve because of the location of the symptoms at the posterior region of the buccal cavity and because of the raised electrogustometric thresholds in the posterior region of one half of the tongue. Clarification of this type of case was made by a review of the literature from 1966 to June 2004, carried out with the aid of Medline. From a medicolegal standpoint, it is important to inform the patient of the risk of dysgeusia after tonsillectomy, especially if that patient has a profession in which taste plays an essential role.

Adult↗
PubMed1982

Amino acids as taste stimuli. I. Neural and behavioral attributes.

The physiological importance of L-amino acids implies that the gustatory system should be sensitive to their presence in the environment. This notion is reinforced by research showing that rats are able to self-regulate their dietary consumption of amino acids and other important nutrients. This paper describes two studies which begin a systematic evaluation of the neural and behavioral effects of L-amino acids on gustation in the rat. The first experiment defined the neural thresholds, intensity-response functions and time courses of whole chorda tympani nerve responses to 12 stimuli. Thresholds varied from 10(-4) M (arginine) to 8 X 10(-2) M (proline), with pH-related amino acids being low and those reported by humans to be sweet being high. Maximum neural effectiveness, relative to the resting level of neural activity, ranged from 108% (2.0 M lysine-hydrochloride) to 8% (0.1 M leucine), with pH-related stimuli evoking the greatest activity. Neural time courses were varied, and often did not include well-defined phasic and tonic components. The second experiment measured the rat's preferences in 24-h two-bottle tests. Preference thresholds were typically lower than neural thresholds, presumably due to extra-chorda tympani input involved in the perception of flavor. They ranged from 2 X 10(-6) M (methionine) to 6 X 10(-2) m (leucine) and were in good agreement with psychophysically defined humar thresholds. Seven stimuli were preferred at low concentrations, but only two (alanine, leucine) continued to be appetitive as intensity increased. Preferences were predictable for 10 of the 12 stimuli from psychophysical reports. Rats also rejected amino acids in direct proportion to their toxicity, demonstrating the protective function of the taste-hedonic system.

Amino Acids↗
PubMed1999

An automated regional taste-testing system.

A fully programmable and portable automated regional taste-testing system is described. This system utilizes a glass stimulator held to the surface of the tongue by a mild vacuum. Temporally and spatially discrete trains of stimuli, delivered from a bank of glass reservoirs through microprocessor-controlled Teflon solenoid valves and both glass and Tygon tubing, can be delivered to the lingual surface at millisecond durations. Rinses between stimuli are similarly programmed. The stimulus delivery is monitored at the surface of the tongue, using a capacitance sensor to alert the subject of stimulus delivery. An example of the application of this system is shown, in which we demonstrate that the detection threshold for NaCl is inversely related to stimulus duration by a power function.

Adult↗
PubMed1975

Phenylthiocarbamide tasting in a sample of twins.

1. Twenty-eight pairs of monozygotic and eighteen pairs of dizygotic twins were tested for their ability to taste phenylthiocarbamide (P.T.C.) by the method of Harris & Kalmus (1949). 2. Much greater variance in threshold levels was detected within the DZ than within the MZ pairs and this confirms the genetic origin of most variation in ability to taste this substance. 3. Variance in threshold levels within MZ pairs is of the same magnitude as the variance of reported duplicate measurements on the same individuals. 4. DZ twin pairs were classified as either concordant or discordant in their tasting ability. Variance within concordant DZ pairs is significantly greater than within the MZ pairs and it is shown that this difference can be accounted for in terms of the incomplete dominance of the T allele reported by Kalmus (1958). However, the data do not exclude the possiblity that this greater variation in threshold levels is partly due to multiple alleles or background genetic variation. 5. The frequency of the t allele in Australians of European descent in estimate at 0-52 plus or minus 0-06.

Adult↗
PubMed2004

Cloning, expression and characterization of recombinant sweet-protein thaumatin II using the methylotrophic yeast Pichia pastoris.

Thaumatin, an intensely sweet-tasting protein, was secreted by the methylotrophic yeast Pichia pastoris. The mature thaumatin II gene was directly cloned from Taq polymerase-amplified PCR products by using TA cloning methods and fused the pPIC9K expression vector that contains Saccharomyces cerevisiae prepro alpha-mating factor secretion signal. Several additional amino acid residues were introduced at both the N- and C-terminal ends by genetic modification to investigate the role of the terminal end region for elicitation of sweetness in the thaumatin molecule. The secondary and tertiary structures of purified recombinant thaumatin were almost identical to those of the plant thaumatin molecule. Recombinant thaumatin II elicited a sweet taste as native plant thaumatin II; its threshold value of sweetness to humans was around 50 nM, which is the same as that of plant thaumatin II. These results demonstrate that the functional expression of thaumatin II was attained by Pichia pastoris systems and that the N- and C-terminal regions of the thaumatin II molecule do not -play an important role in eliciting the sweet taste of thaumatin.

Amino Acid Substitution↗
PubMed2004

Public thresholds for chlorinous flavors in U.S. tap water.

Considering this rapid growth in the purchasing of bottled water and home filtration devices, utilities are increasingly concerned about consumer dissatisfaction with tap water quality. This project aimed to characterize public perceptions of chlorinous flavors in drinking water, and how these impact customers' choices with respect to consumption of tap water alternatives. On-site taste tests at seven water utilities with 30 to 40 panelists at each site, were conducted using a forced-choice triangle test method (ASTM method E679-91) to measure public sensitivity to chlorine and chloramine in drinking water. The chlor(am)ine concentration increased from set to set. The best-estimate sensitivity limit for each panelist was the geometric mean of that concentration at which the last miss occurred and the next (adjacent) higher concentration. The measured sensitivity limit of average American populations to free chlorine (159 persons tested) and chloramine (93 persons tested) in tap water were 0.8 and 3.7 mg/L Cl2, respectively. These thresholds are much higher than those previously reported in the literature using trained FPA panels. No significant differences were observed between tap water users and users of tap water alternatives or between the various markets tested with respect to average sensitivity, though individual sensitivity varied widely.

Community Participation↗
PubMed1987

Acetylcholine activates cerebral interneurons and feeding motor program in Limax maximus.

The cellular and network effects of acetylcholine (ACh) on the control system for feeding in Limax maximus were measured by intracellular recordings from feeding command-like interneurons and whole nerve recordings from buccal ganglion motor nerve roots that normally innervate the ingestive feeding muscles. The buccal ganglion motor nerve root discharge pattern that causes rhythmic feeding movements, termed the feeding motor program (FMP), was elicited either by attractive taste solutions applied to the lip chemoreceptors or by ACh applied to the cerebral ganglia. The ability of exogenous ACh applied to the cerebral ganglia to trigger FMP was blocked by the cholinergic antagonists curare and atropine. If the strength of the lip-applied taste stimulus was in the range of 1-2 times threshold, cerebral application of the cholinergic antagonists blocked or greatly decreased the ability of lip-applied taste solutions to trigger FMP (5 of 8 trials). The cerebral feeding interneurons, some of which activate FMP when stimulated intracellularly, are excited by small pulses of ACh applied directly to the cell body from an ACh-filled micropipette. A pulse of ACh that activates several of the feeding interneurons simultaneously triggers FMP. The data suggest that under certain stimulus conditions an obligatory set of cholinergic synapses onto the feedininterneurons must be activated for taste inputs to trigger ingestion. The determination of ACh's action within the feeding control system is necessary for understanding how enhanced cholinergic transmission leads to prolonged associative memory retention (Sahley, et al., 1986).

Acetylcholine↗
PubMed1977

[Behavioural and electrophysiological experiments on the sense of taste in Saguinus midas tamarin (Callitrichidae) (author's transl)].

The activity in the gustatory nerve from the anterior part of the tongue, the chorda tympani proper nerve, has been recorded during stimulation of the tongue of a New World monkey, Saguinus midas tamarin. A series of 0.3 M sugars and 0.07 M NaCl, 0.07 M sucrose, 0.004 M acetic acid and 0.00005 M quinine hydrochloride were used as taste stimuli. The concentrations of the last four stimuli were the same as those earlier found to be the lowest concentrations at which this monkey in behavioural experiments discriminates between them and water. The records showed that these threshold concentrations all elicited a neural response. Further, the neural activities during stimulation with the series of 0.3 M sugars were recorded. Using the amplitudes of the responses as a measure, the order between them was found to be fructose greater than glucose greater than lactose greater than arabinose greater than sucrose = galactose greater than raffinose. This order was discussed and related with the order found in behavioural experiments. With both methods, fructose seemed to be the strongest stimulus, but then the order among the sugars differed.

Acetates↗
PubMed1991

Preference of Old World monkeys for amino acids and other gustatory stimuli: the influence of monosodium glutamate.

Monosodium glutamate (MSG) is widely considered to enhance the flavor of beef, chicken, fish, and vegetables. This effect may be due to the interaction of glutamate with free amino acids or other basic taste stimuli present in these foods. A single-bottle test was used in order to test the preference of Old World monkeys for an extended array of gustatory stimuli individually and in combination with MSG. Six male cynomolgus monkeys, maintained on an 18-h water deprivation schedule, were given 30 min access daily to a sapid stimulus or distilled water. The following stimuli (selected on the basis of prior experimentation) were tested alone and in combination with 0.03 M MSG: sucrose, fructose, glucose, maltose, polycose, sodium saccharin, glycine, sodium chloride, hydrochloric acid, tartaric acid, malic acid, citric acid, quinine hydrochloride, urea, and beef broth. The L-isomers of the following free amino acids also were tested: alanine, histidine, phenylalanine, proline, serine, valine. The addition of MSG to the stimuli listed above had no significant effect upon the monkeys' preference or aversion thresholds. Most suprathreshold stimuli that the monkeys neither preferred nor avoided were unaffected by the addition of MSG. The monkeys' preference for sugars was adversely affected in mixtures containing MSG, but other stimuli that humans report to be sweet tasting (alanine, glycine, polycose) were unaffected. The data from the present experiment demonstrate that MSG was capable of altering the monkeys' preference for some but not all of the gustatory stimuli tested.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1998

Sensory responses to 6-n-propylthiouracil (PROP) or sucrose solutions and food preferences in young women.

Genetic sensitivity to the bitter taste of 6-n-propylthiouracil (PROP) has been linked with a greater number of food aversions and reported rejection of some bitter foods. Healthy young women (n = 121) were divided into nontasters, tasters and supertasters of PROP according to their PROP detection thresholds and the ratio of intensity ratings of PROP versus NaCl solutions. Hedonic response profiles to sucrose solutions distinguished between likers and dislikers of sweet. All subjects completed a 171-item food preference checklist. Food preference data were reduced by factor analyses, subscales of which were tested for reliability using Cronbach's alpha. Greater PROP sensitivity was associated with lower acceptance of coffee, cruciferous vegetables, tart citrus fruit, dark breads, and selected fats. In contrast, liking for sucrose solutions was linked to liking for sugar in tea and coffee, but not to any special pattern of food acceptance. Strategies aimed at increasing the consumption of grains, vegetables, and fruit should consider the role of inherited taste makers and their potential impact on dietary habits.

Adult↗
PubMed2001

Younger patients have a higher rate of recovery of taste function after middle ear surgery.

BACKGROUND: Although the chorda tympani nerve (CTN) is frequently damaged during tympanoplasty, little attention has been given to the patients' symptoms and taste function. OBJECTIVE: To investigate patients' symptoms and the functional recovery of taste after surgery using electrogustometry (EGM). DESIGN: Prospective study. PATIENTS: Analysis of 163 ears of 156 patients who underwent middle ear surgery from April 1997 through December 1999. There were 18 ears with noninflammatory diseases, 80 with chronic otitis media, and 65 with cholesteatoma. The patients' taste functions were examined 2 days before surgery and 2 weeks and 6 months after surgery. MAIN OUTCOME MEASURES: The taste disturbance before and after middle ear surgery and the relationship between age and the recovery rate of CTN function. RESULTS: Two weeks after surgery, the mean EGM threshold was elevated in all groups regardless of preservation or section of the CTN. Numbness in the tongue and taste disturbance were more frequently found in patients with preservation of CTN than in those with section of the CTN (P =.008 and P =.001, respectively). In patients with preservation of the CTN, 6 months after surgery, the recovery rate of EGM threshold was 83% in those aged 20 years or younger (P =.008 compared with the 2 older groups), 53% in the those aged 21 to 40 years, and 44% in those aged 41 to 60 years. CONCLUSION: Age is an important factor for recovery of taste function after middle ear surgery, which is useful information when explaining complications to patients.

Adolescent↗
PubMed1999

Gustatory changes associated with the menstrual cycle.

We studied changes in the palatability and gustatory functions as they correlate with the menstrual cycle in 30 healthy females with regular menstrual cycles. The gustatory function was investigated by conducting electrogustometry and by the filter-paper disk method with taste solutions in the follicular and luteal phases of the same subjects. The responses to a questionnaire revealed that appetite was enhanced prior to menstruation in 14 cases (46.7%). The results of electrogustometry showed that the threshold in the domain of the chorda tympani nerve was 0.3 +/- 3.4 dB in the follicular phase and -0.9 +/- 2.8 dB in the luteal phase. Although the threshold in the luteal phase indicated a statistically significant decrease (p < 0.05), the difference was so small that the change could not be subjectively discriminated. The threshold in the domain of the glossopharyngeal nerve was 2.6 +/- 4.0 dB in the follicular phase and 1.7 +/- 3.9 dB in the luteal phase, with no significant difference between the two values. Gustatory thresholds as obtained by the filter-paper disk testing were not significantly different between the follicular and luteal phases. Thus, although the taste function may change through the menstrual cycle, changes in gustatory thresholds are minimal and remain within the normal range.

Adult↗
PubMed2006

The relative effects of transection of the gustatory branches of the seventh and ninth cranial nerves on NaCl taste detection in rats.

Chorda tympani nerve (CT) transection in rats severely impairs NaCl taste detection. These rats can detect higher concentrations of NaCl, however, suggesting that remaining oral nerves maintain some salt sensibility. Rats were tested in a gustometer with a 2-response operant taste-detection task before and after sham surgery (n = 5), combined transection of the CT and the greater superficial petrosal nerves (GSP; 7x, n = 6), or transection of the glossopharyngeal nerve (GL; 9x, n = 4). Thresholds did not significantly change after sham surgery. Although the GL responds to NaCl and innervates nearly 60% of total taste buds, 9x surgery had no effect. However, 7x surgery increased NaCl detection threshold by approximately 2.5 log(10) units, greater than that reported for CT transection alone. These results suggest that the GSP contributes to NaCl sensitivity in rats and also demonstrate that the GL and perhaps the superior laryngeal and lingual nerve proper can maintain some NaCl detectability at high concentrations. These findings confirm the primacy of the 7th nerve relative to the 9th nerve in sensibility of NaCl in the rat model.

Analysis of Variance↗
PubMed1998

Gustatory responses to amino acids in the chorda tympani nerve of C3H mice.

Integrated neural responses to various amino acids were recorded from the chorda tympani (facial) nerve in C3H mice. The basic amino acids hydrochlorides L-Arg-HCl and L-Lys-HCl evoked large magnitude integrated taste responses, similar to that for NaCl, and had estimated electrophysiological thresholds of 0.0001 M. No significant difference was indicated between the response magnitudes for the L- and D-forms of the basic amino acid hydrochlorides; however, responses to the basic amino acid hydrochlorides cross-adapted with NaCl. Responses to neutral L-amino acids (Ser, Ala, Gly), which taste sweet to humans, showed higher thresholds (>0.0003 M), similar to that for sucrose, and did not cross-adapt with basic amino acid hydrochlorides or with NaCl. Responses to the neutral amino acids L-Ser and L-Ala were larger than those to their D-amino acid enantiomers. The acidic amino acids L-Asp and L-Glu showed concentration-response functions different from that for HCl. Both acidic amino acids were more stimulatory than HCl at the same pH, although the responses to them were cross-adapted by HCl, indicating a pH effect. A comparison of the stimulatory effectiveness among amino acid derivatives and analogues suggested that the alpha-amino group is essential for the stimulatory effectiveness of neutral amino acids.

Adaptation, Physiological↗