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Anxiogenic and depressive-like effects, but no cognitive deficits, after repeated moderate tryptophan depletion in the rat.

The tryptophan (TRP) depletion method has been used as a tool to investigate the effects of acute lowered serotonin levels in the brain. In the present study, the effects of this treatment were investigated in rat models of anxiety (open field test, home cage emergence test), depression (forced swimming test, sucrose preference test) and cognition (spatial discrimination learning, sustained attention). It was found that the repeated TRP depletion increased anxiety-related behaviour in the open field test and increased immobility in the forced swimming test. The other behavioural tests did not reveal effects of treatment. TRP levels were decreased in plasma (34%) and hippocampus (33%) but not in the cortex. Stress-induced corticosterone levels were not affected after TRP depletion. The present findings indicate that repeated moderate TRP depletion leads to anxiogenic and depressive-like behaviour in the rat and corroborates the notion of the involvement of serotonin in these behaviours.

Animals↗

Effects of neophobia and habituation on the poison-induced avoidance of exteroceptive stimuli in the rat.

Two experiments on the role of neophobia in poison-induced aversions to exteroceptive stimuli are reported. In Experiment 1, rats were given either 10 or 25 days of habituation to the test situation prior to conditioning. Those animals with the longer habituation period avoided a complex of novel exteroceptive stimuli while those with the shorter habituation period did not. In Experiment 2 rats initially avoided the more novel of two containers, but gradually came to eat equal amounts from both. A single pairing of toxicosis with consumption from either the novel or the familiar container reinstated the avoidance of the novel container in both cases. The results were discussed in terms of an interaction between habituation and conditioning procedures. It was suggested that previously reported differences between interoceptive and exteroceptive conditioning effects may have been influenced by the differential novelty of the two classes of stimuli in the test situation. It was further suggested that non-contingently poisoned control groups should routinely be included in poison avoidance conditioning studies.

Animals↗

Social and biocultural determinants of food selection.

Health professionals concerned with improving the nutritional status of populations are facing numerous problems ranging from emaciation to overnutrition. This review article addresses the complexity, the relative significance and the interaction of factors leading to the nutritional profile of specific groups and individuals. When availability of food is threatened, the programs designed to reduce the incidence of malnutrition must balance the food supply with energy resources and population needs as well as encourage economic improvement of food distribution systems. For those persons having access to an abundant food supply, social forces and technological factors may affect food patterns, resulting in unbalanced diets associated with chronic diseases. Misinterpretation of reliable scientific findings is a major cause of abnormal nutrition behaviour. Overreaction to health messages may precipitate such conditions as anorexia nervosa or nutrient toxicity. Adverse food reactions, real or imagined, lead to restrictions in food selection. Excessive austerity in food use negates the pleasure of eating, a useful mechanism in food choice ensuring food diversity.

Attitude to Health↗

Taste modulation of nociception differently affects chronically stressed rats.

Stress responses cover a wide range of physiological changes, including alterations in the perception of and response to pain. Animals submitted to repeated stress present altered nociception and this effect is part of this process of adaptation; in addition pleasant and unpleasant experiences with tastes and odors have been shown to affect distinct behavioral aspects, such as pain perception. The aim of the present study is to verify the responses of repeatedly stressed rats (1 h of daily immobilization during 40 days) to pleasant and unpleasant tastes on nociception, when compared to control animals. An increase in the tail-flick latency (TFL) was observed 5 min after exposure to a sweet taste in the control group, whereas no effect was observed in chronically stressed animals. When submitted to an unpleasant taste (5% acetic acid), the chronically stressed group presented an increase in TFL, whereas no effect was observed in the control group. In conclusion, chronically stressed animals present different nociceptive responses to sweet and acid tastes; although control animals suitably respond to a sweet stimulus, stressed animals seem to be more apt to react to the unpleasant stimulus.

Adaptation, Physiological↗

Taste preferences and their relation to obesity in dogs and cats.

In the laboratory situation the preferences of dogs and cats for food seem to be relatively uniform. Cats prefer fish and commercial cat food to rats. Dogs prefer beef, pork and lamb to chicken, liver and horsemeat and strongly prefer meat to cereal diets. They prefer canned meat to fresh meat, ground meat to cubed meat and cooked meat to raw meat. Canned or semimoist preparations are preferred to dry ones. Pet dogs have much more variable preferences according to their owner's subjective evaluation. A variety of factors seem to be related in an as yet unknown way to some flavor preferences of pet dogs, i.e. the dog's sex/reproductive status, weight and relationship to owners and the content of the dog's meals. The complicated interaction between (a) a pet's taste, texture and olfactory sensation, (b) its owner's perception of the pet and its preferences and (c) its physical and social environment deserves further investigation. Obesity can result from endocrinological causes such as those following ovariohysterectomy, but most cases appear to be related to owner-induced variables. In a kennel situation most, but not all, dogs can be allowed free access to palatable food without becoming obese.

Animals↗

Gustatory responses to nongustatory stimuli.

Subjects were required to give taste responses to days of the week and states of the USA, as well as colour responses. Some consistency of response was obtained over three sessions held at two-week intervals. The implications of such consistency of response to nongustatory stimuli for psychophysical taste description are discussed.

Adult↗

Influence of sex, age and smoking status on patient comfort during gastroscopy with pharyngeal anesthesia by a new benzocaine-tetracaine preparation.

Thirty-seven patients underwent gastroscopy under pharyngeal anaesthesia with benzocaine-tetracaine (Endospray; Axcan Pharma). Patients recorded their perception of intubation, of the rest of the procedure, of taste and of throat well-being on visual analogue scales. Throat well-being and taste scores were better for men than for women. There was a strong trend for smokers to be more intolerant to intubation than nonsmokers. There was a weak but significant correlation for younger patients to be more intolerant to intubation. This study points to age and smoking status as possible factors influencing the perception of gastroscopy under pharyngeal anesthesia.

Adult↗

Effects of temperature on the perceived sweetness of sucrose.

The sweetness of sucrose depends on the temperature as well as the concentration of a solution. The main effect is that relatively low concentrations gain sweetness as temperature increases. This effect diminishes with progressively higher concentration and finally becomes negligible at about 0.5 M. At this concentration the various functions that relate perceived sweetness to concentration for various temperatures converge. The mechanism of the taste-temperature interaction is speculative, but the interaction is large enough to be of practical interest in the perception of common foods and beverages as well as a variable to be strictly controlled in taste experiments. An examination of method of tasting showed that swallowing stimuli did not substantially increase perceived sweetness.

Female↗

Taste and aging.

Taste thresholds are known to rise with age, but the status of suprathreshold sensations is less clear. The present study assessed the perceived intensities of sodium chloride, sucrose, citric acid, and quinine hydrochloride with the method of magnitude matching. This method takes advantage of participants' ability to judge sensations from two sensory continua (in this case taste intensity and loudness) on a common intensity scale, in effect, matching them. Elderly and young adults matched most of the moderate and strong tastes to the same loudnesses. If the sounds were equivalently loud to elderly and young adults, then these results would mean that moderate and strong tastes were also equivalently strong, that is, taste sensation had not faded for our elderly adults. Water and dilute taste solutions were matched to louder sounds by elderly than young participants. This may reflect the presence of a mild dysgeusia (background taste).

Acoustic Stimulation↗

De Gustibus: time scale of loss and recovery of tastes caused by radiotherapy.

PURPOSE: To quantify the prevalence and distress of taste loss at different intervals after radiotherapy (RT) for head and neck cancer. MATERIALS AND METHODS: In four different groups of head and neck cancer patients (73 patients in total), taste loss and distress due to taste loss were evaluated by taste acuity tests and taste questionnaires. Group 1 (n=17) was analyzed prior to RT. Groups 2 (n=17), 3 (n=17) and 4 (n=22) were at 2, 6 and 12-24 months after treatment, respectively. A cross-sectional analysis was performed between these four groups. RESULTS: Prior to initiation of RT (group 1), partial taste loss was observed in 35, 18 and 6% of patients for bitter, salt and sweet, respectively. At 2 months after RT (group 2), taste loss (partial or total) was seen in 88, 82, 76 and 53% for bitter, salt, sweet and sour, respectively. At 6 months (group 3), partial taste loss was seen in 71, 65, 41 and 41% (bitter, salt, sweet, sour) and after 1-2 years (group 4) in 41, 50, 27 and 27% (bitter, salt, sweet, sour). Distress caused by taste loss was most frequent in group 2 (82%). CONCLUSIONS: In this study, loss of taste after RT was found to be most pronounced after 2 months. Bitter and salt qualities were most impaired. Gradual recovery was seen during the first year after treatment. Partial taste loss still persisted 1-2 years after treatment and was responsible for slight to moderate discomfort.

Cross-Sectional Studies↗

Interaction of gustatory and lingual somatosensory perceptions at the cortical level in the human: a functional magnetic resonance imaging study.

The present study has investigated interaction at the cortical level in the human between two major components of flavor perception, pure chemical gustatory and lingual somatosensory perception. Twelve subjects participated in a functional magnetic resonance imaging study and tasted six stimuli, applied on the whole tongue, among which four were pure gustatory stimuli (NaCl, aspartame, quinine and HCl, pH 2.4 or 2.2) and two were both taste and lingual somatosensory stimuli, i.e. somato-gustatory stimuli (HCl, pH 1.6 or 1.5, and aluminum potassium sulfate). Functional images were acquired with an echo planar sequence on a 3 T system and were individually processed by correlation with the temporal perception profile. Both sets of stimuli showed activation in the same cortical areas, namely the insula, the rolandic operculum (base of the pre- and post-central gyri), the frontal operculum and the temporal operculum, confirming a wide overlap of taste and lingual somatosensory representations. However, the relative activation across areas and the analysis of co-activated areas across all runs for each set of stimuli allowed discrimination of taste and somatosensory modalities. Factor analysis of correspondences indicated different patterns of activation across the sub-insular and opercular regions, depending on the gustatory or somato-gustatory nature of the stimuli. For gustatory stimuli different activation patterns for the superior and inferior parts of the insula suggested a difference in function between these two insular sub-regions. Furthermore, the left inferior insula was co-activated with the left angular gyrus, a structure involved in semantic processing. In contrast, only somato-gustatory stimuli specifically produced a simultaneous and symmetrical activation of both the left and right rolandic opercula, which include a part of the sensory homunculus dedicated to the tactile representation of oral structures.

Adult↗

Olfactory dysfunction and related nutritional risk in free-living, elderly women.

OBJECTIVE/DESIGN: To determine the nutritional risk associated with measured olfactory dysfunction in free-living, elderly women through analytic observational methods. Olfactory perception was measured orthonasally (odor: butanol threshold and odor identification) and retronasally (flavor: orange flavor threshold in sweetened gelatin). SETTING/SUBJECTS: Elderly women were recruited from New Haven, Conn, through posters and direct contact. Screening of 120 elderly women identified 80 with high personal functioning to participate (mean age = 76 +/- 6 years, range = 65 to 93 years). All data were collected in subjects' homes. MAIN OUTCOME MEASURES: Nutritional risk was assessed in several ways: food behavior questionnaire; food preference questionnaire; interviews based on the National Cancer Institute food frequency questionnaire; five nonconsecutive, 24-hour food records; and weight, height, waist, and hip measurements. STATISTICAL ANALYSES: Correlation and regression analyses determined the separate association between olfactory perception and nutrition variables. RESULTS: Nearly half of the women (37 of 80) had olfactory dysfunction. The following nutritional risk pattern was associated with lower olfactory perception: lower interest in food-related activities (eg, enjoying cooking, eating a wide variety of foods); lower preference for foods with predominant sour/bitter taste (eg, citrus fruits) or pungency (eg, horseradish); higher intake of sweets; less intake of low-fat milk products; and nutrient intake profile indicative of higher risk for cardiac disease. APPLICATIONS: Olfactory dysfunction may make it more difficult for elderly women to maintain a diet to control risk for chronic disease. Practitioners should target nutrition intervention to elderly women with measured or self rated difficulty in preventing odors or olfactory flavor. Capitalizing on primary-taste quality and texture may help to compensate for the loss of olfactory flavor perception.

Aged↗

Oral health, taste, and olfaction.

Oral health, taste, and smell are critical components to an older person's overall sense of well-being and quality of life. Oral health problems can cause pain and discomfort and can hinder the maintenance of a satisfying and nutritious diet. Loss of taste and smell interferes with pleasure derived from food and food-related activities. Attention should be given to preserving teeth and optimizing oral function. Likewise, close evaluation of older adults' medications may identify the causes of taste and smell disorders. In instances in which nutrient intake is inadequate and chemosensory perception is considered a likely contributor, a trial of flavor enhancers or monosodium glutamate may improve both quality and quantity of intake. Much more information is needed to understand the interrelationship between chemosensory perception, food intake regulatory mechanisms, and nutritional status. Multidisciplinary studies will be required to understand how to improve nutrition through manipulation of oral characteristics, taste, and smell.

Aged↗

Taste reactivity to alcohol in rats.

Rats were infused intraorally with 4 concentrations of ethanol (3%, 6%, 9%, and 12%), and their subsequent oral, facial, and bodily responses were videotaped and analyzed. Naive rats did not display significant changes in ingestive-type responding over the concentrations tested. A significant increase in aversive responses was noted, with the largest number of aversive responses found with the 12% solution. Initial reactivity failed to predict subsequent consumption when rats were given free access to the same alcohol concentrations during 2-bottle tests. Reactivity testing after the period of alcohol access indicated that only the aversive responding changed significantly from the initial reactivity, with rats showing fewer aversive responses. The results indicated how the taste of alcohol is perceived by naive rats and how this perception is changed after consummatory experience with alcohol.

Alcohol Drinking↗

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↗