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PubMed1996

Effects of cerebroventricle administration of acidic fibroblast growth factor on conditioned taste aversion learning in rats.

Wistar strain rats were given acidic fibroblast growth factor (aFGF) or denatured aFGF into their cerebroventricle before taste aversion conditioning for saccharin solution. Animals administered with aFGF showed significantly lower aversion threshold for saccharin at the 1st day and preference ratios for saccharin vs distilled water at the 4th, 6th, and 7th day after the conditioning than those administered with denatured aFGF. These results suggests that aFGF in the cerebrospinal fluid facilitates acquisition of the conditioned taste aversion learning.

Animals↗
PubMed2002

Neurons in the cortical taste area receive nociceptive inputs from the whole body as well as the oral cavity in the rat.

Almost all mechanoreceptive neurons in the cortical taste area (CTA) of the rat had receptive fields (RFs) in the oral cavity, except for a few neurons at the border with the primary somatosensory area that had RFs on the contralateral rhinarium or upper lip. About one-third of the mechanoreceptive neurons with RFs in the oral cavity had additional RFs on the tips of limbs, earflaps or tail, i.e. the glabrous skin or skin with sparse hairs of the external surface of the body (whole body type). Most of these neurons received both innocuous and noxious inputs (wide dynamic range type), but some had either type of input (low threshold mechanoreceptive or nociceptive specific type). Some nociceptive neurons were responsive to taste, as previously found. Nociceptive neurons with the whole body type of RFs were diffusely distributed across the CTA without clustering. The corticocortical afferents, probably originating from the visceral part of the insula, may code body condition to modulate the taste responsiveness of the cortical taste neurons.

Animals↗
PubMed1975

[Differences in the responses of taste receptors to organic and inorganic acids with changes in the concentration of bicarbonate in the solution].

The thresholds of the pH for citric acid (pH=4.9) were found to exceed by 1.4 pH the thresholds for HC1 (3.5) at 1.2 mmol/1 bicarbonate in the solution. The reaction to citric acid was higher than to HC1 at equal pH. Decreasing of bicarbonate from 1.2 mmol/1 to 0 reduced pH threshold only for sitric acid from 4.90 to 3.15. pH threshold for HC1 remained 3.5 The chorda tympani response to stimulation with solutions containing bicarbonate (1.2 mmol/1) was higher than in absence of bicarbonate. The data obtained suggest two ranges of the acids in action.

Animals↗
PubMed2001

Parametric analysis of gastric distension responses in the parabrachial nucleus.

The parabrachial nucleus (PBN) is regarded as an important locus for the processing and integration of sensory inputs from oral, gastrointestinal, and postabsorptive receptor sites and is thus thought to play an important role in regulating food intake. Gastric distension is an important satiation cue; however, such responses have been qualitatively characterized only over a limited area of the PBN. To more fully characterize gastric distension responses throughout the PBN, the responses of single units to gastric distension were tested using computer-controlled balloon inflation (3-18 ml air) in pentobarbital sodium- and/or urethan-anesthetized male rats. Distension-responsive neurons were indeed distributed throughout the nucleus from rostral areas typically considered to be visceral to more caudal areas associated with gustatory function, providing further anatomical support for the hypothesis that the PBN integrates taste and visceral signals that control feeding. Most PBN neurons had thresholds of 6 ml or less, similar to vagal afferent fibers. However, in contrast to the periphery, there were both excitatory and inhibitory responses. Increases in volume were associated with two distinct effects. First, as volume increased, the response rate increased; second, the duration of the response increased. In fact, in a subset of cells, responses to gastric distension lasted well beyond the stimulation period, particularly at larger volumes. Prolonged gastric distension responses are not common in the periphery and may constitute a central mechanism that contributes to satiation processes.

Animals↗
PubMed1986

Gustatory responses in the nucleus tractus solitarius of the alert cynomolgus monkey.

Multiunit and single neuron responses to taste stimuli in the nucleus tractus solitarius (NTS) of alert cynomolgus monkeys were analyzed. Intensity-response functions, including neural thresholds to glucose and quinine HCl, agreed well with psychophysical reports, implying that the cynomolgus monkey and human share the same dynamic range of sensitivity to prototypical taste stimuli. The NTS is chemotopically organized: neurons most responsive to HCl are more common in the posterior gustatory area, whereas those most responsive to glucose and NaCl are located in the anterior NTS. Responsiveness to quinine is more widely distributed but tends toward the anterior. Efforts were made to determine if neurons could be divided into a discrete number of types, as determined by their sensitivities to the prototypical stimuli. The clearest distinction was between those that did or did not respond well to HCl. Beyond this, neuronal categories were not obvious. Individual neurons were quite broadly sensitive to our stimulus array, so that, for the typical NTS cell, no one of the four prototypes evoked a majority of the discharges. This extreme breadth of tuning suggests that taste-quality information in the monkey might be incorporated in relative discharge rates across the neuron population. Correlations among patterns of activity to the four prototypical stimuli indicated that only HCl and quinine HCl have closely related taste qualities.

Afferent Pathways↗
PubMed2000

Sodium detection during the water absorption response in Rana pipiens.

Although taste in vertebrates is typically associated with specialized receptors in the lingual epithelium, Hoff and Hillyard reported that the toad, Bufo punctatus, is able to "taste" sodium with the abdominal skin. This was reflected in a differential behavioral response to hypertonic NaCl. The present study tests for the presence of such abdominal chemoreceptors in the frog Rana pipiens. The experiment was a five-condition design in which frogs were placed on filter paper saturated with: deionized water, 250 mM NaCl, 350 mM NaCl, 12.9 microM amiloride, or 350 mM NaCl + 12.9 microM amiloride. The time that the frogs remained on the test substrate before moving to a surface of deionized water was recorded. It was necessary to dehydrate the frogs to 80% of their body weight to elicit a behavioral response to the NaCl whereas dehydration to 90% of their body weight has been reported effective in Bufo punctatus. The frogs displayed significantly shorter mean times to move on both concentrations of NaCl compared to deionized water, with the shortest times occurring when 350 mM NaCl was used. Amiloride alone did not have an effect upon times to move to deionized water, but did significantly reduce the response to 350 mM NaCl. Movement to amiloride + 350 mM NaCl did not differ significantly from that to deionized water. The results indicate that Rana pipiens, like Bufo punctatus, have epithelial chemoreceptors for the detection of NaCl on hydrated surfaces and that these receptors, like those of mammals, are amiloride sensitive.

Abdomen↗
PubMed1997

Taste responses to naringin, a flavonoid, and the acceptance of grapefruit juice are related to genetic sensitivity to 6-n-propylthiouracil.

Increased consumption of vegetables and fruit has long been the focus of dietary strategies for disease prevention. Some vegetables and fruit have bitter tastes, which can be aversive to consumers, particularly children. The present study tested the hypothesis that acceptance of grapefruit juice is influenced, in part, by sensitivity to the bitter taste of 6-n-propylthiouracil (Prop), a heritable trait. A sample of 123 women, mean age 28 y, was divided into nontasters (n = 39), tasters (n = 49), and supertasters (n = 35) of Prop by using procedures validated previously based on Prop detection thresholds and on intensity scaling of five suprathreshold solutions of Prop and sodium chloride. The subjects tasted and rated five solutions of the bioflavonoid naringin in 4% sucrose. Naringin, the principal bitter ingredient of grapefruit juice, has been implicated in the regulation of cytochrome P-450 enzymes. Increased taste acuity for both Prop and naringin was associated with greater dislike for each bitter compound. Prop supertasters disliked bitter naringin solutions significantly more than did either tasters or nontasters. Prop sensitivity was also associated with reduced acceptability of grapefruit juice. Acceptability of orange juice, which does not contain naringin, was unrelated to Prop taster status. Is the acceptability of other bitter vegetables and fruit also limited by inherited taste factors? If so, then genetic taste markers might limit dietary exposure to valuable dietary constituents and pose a barrier to current strategies for dietary change.

Adult↗
PubMed1989

Taste impairment and related factors in type I diabetes mellitus.

To study taste in type I (insulin-dependent) diabetes mellitus, 57 consecutive diabetic outpatients (mean +/- SE duration of diabetes 11.4 +/- 0.4 yr) and 38 control subjects were screened for taste disorders with electrogustometry and chemical gustometry. Both groups were comparable for all subject characteristics except body mass index, which was higher in the diabetic group (P less than .05). A taste impairment was found in the diabetic group relative to the control group with electrogustometry (mean threshold 184.3 +/- 15.8 vs. 58.7 +/- 9.2 microA; P less than .001) and chemical gustometry (mean score 13.2 +/- 0.7 vs. 17.1 +/- 0.8; P less than .001). Hypogeusia was found among 73% of the diabetic patients versus 16% of the control subjects (P less than .001). The four primary tastes were involved in taste impairment. With multivariate analysis, taste disorders were related to diabetic status and tobacco and alcohol consumption. In the diabetic group, taste impairment was significantly associated with complications and duration of disease. With multivariate analysis, peripheral neuropathy had the strongest association with taste disorders. These results suggest that taste is impaired during the course of type I diabetes mellitus and that taste impairment could be a complication of the disease. A mechanism of the neuropathic type could be involved.

Adult↗
PubMed1989

[Taste disorders and associated factors in type 1 diabetes].

In order to study taste in type 1 diabetes (insulin-dependent), 57 consecutive diabetic patients (mean duration of diabetes +/- SEM = 11.4 +/- 0.4 years) and 38 control subjects underwent electrogustometry and chemical gustometry. The diabetic and control group were comparable with the exception of the ponderal index which was significantly higher in diabetics (p less than 0.05). A deterioration in taste appreciation was confirmed in the diabetic group compared to the control group on electrogustometry (mean threshold: 184.3 +/- 15.8 vs 58.7 +/- 9.2 mu A; p less than 0.001) and chemical gustometry (mean score: 13.2 +/- 0.7 vs 17.1 +/- 0.8; p less than 0.001). Electrical hypogueusia was found in 73% of the diabetics compared to 16% of controls (p less than 0.001). The 4 primary tastes were involved in the deterioration. Multivariate analysis associated the taste disorder with the diabetic status of the subjects, their alcohol and tobacco consumption. In the diabetic group the deterioration in taste was associated with the complications and duration of diabetes. On multivariate analysis peripheral neuropathy had the strongest association with taste disorders. These results suggest that deterioration in taste occurs during the progression of type 1 diabetes and that the taste disorder could be a degenerative complication of the disease. A neuropathic type mechanism could be involved.

Adult↗
PubMed2004

Adolescent enrichment partially reverses the social isolation syndrome.

Early environmental experience produces profound neural and behavioural effects. For example, animals reared in isolation show increased anxiety, neophobia, and poorer performance in learning and spatial memory tasks. We investigated whether later enrichment reverses some or all of the deficits induced by isolation rearing. Eighty-four male Long-Evans rats (21 days old) were reared under different conditions: enriched (group housed with toys), isolated (one rat/cage), standard (two rats/cage), isolated-enriched, enriched-isolated, isolated-standard, or enriched-standard. In the latter four conditions, animals were housed in the first environment until adolescence (66 days). Following the 90-day rearing period, all animals were assessed in a battery of behavioural tests and cortical thickness was measured postmortem. Isolation rearing led to significant differences in behavioural tests measuring anxiety, spatial learning, and locomotor activity; switching the rearing condition partially reversed these changes. Rearing condition did not affect pain thresholds in the tail flick test or aversive associative learning in the conditioned taste aversion test. Enriched rats had the thickest cortex; isolated rats the thinnest. None of the switch groups differed significantly from standard-reared rats in this measure. Taken together, these results provide novel and interesting information regarding the effects of pre- or post-adolescent enrichment experience on behavioural and neural expression of the social isolation syndrome.

Adolescent↗
PubMed1995

Unawareness of smell loss in normal aging and Alzheimer's disease: discrepancy between self-reported and diagnosed smell sensitivity.

Awareness of loss in smell sensitivity was assessed in 80 normal elderly subjects, 80 patients with probable Alzheimer's disease (AD), and 80 patients with sinusitis by comparing measured smell sensitivity to questionnaire-based, self-reported sensitivity. Both AD patients and sinusitis patients had significantly poorer diagnosed smell sensitivity than the normal elderly. Both patient groups had thresholds which on average were about nine times more concentrated than those of the normal elderly. However, 74% of the AD patients and 77% of the normal elderly with smell loss reported normal smell sensitivity. In contrast, only 8% of the sinusitis patients with loss reported normal smell sensitivity.

Adolescent↗
PubMed2004

Methionine catabolism and production of volatile sulphur compounds by OEnococcus oeni.

AIMS: During malolactic fermentation (MLF), the secondary metabolisms of lactic acid bacteria (LAB) contribute to the organoleptic modification of wine. To understand the contribution of MLF, we evaluated the capacity of various wine LAB to metabolize methionine. METHODS AND RESULTS: Using gas chromatography (GC) coupled either with mass spectrometry (MS) or a flame photometry detector in sulphur mode (FPD), we studied this metabolism in laboratory media and wine. In laboratory media, several LAB isolated from wine were able to metabolize methionine. They formed methanethiol, dimethyl disulphide, 3-(methylsulphanyl)propan-1-ol and 3-(methylsulphanyl)propionic acid. These are known to have powerful characteristic odours and play a role in the aromatic complexity of wine. In various red wines, after MLF only the 3-(methylsulphanyl)propionic acid concentration increased significantly, as verified with several commercial starter cultures. This compound, which is characterized by chocolate and roasted odours, could contribute to the aromatic complexity produced by MLF. CONCLUSIONS: This study shows that LAB isolated from wine, especially OEnococcus oeni strains, the major species in MLF, are able to metabolize methionine to form volatile sulphur compounds. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first study to demonstrate the capacity of wine LAB to metabolize methionine.

Disulfides↗