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PubMed1993

Taste receptors on the anterior tongue and nasoincisor ducts of rats contribute synergistically to behavioral responses to sucrose.

In four groups of rats, behavioral responsiveness to sucrose was tested by allowing them to lick solutions in a computer-controlled gustometer (10-s trials; 0.01-1.0 M). Rats with cautery lesions of the nasoincisor ducts (NID) behaved no differently from controls. After bilateral chorda tympani nerve (CT) section, which removes taste input from the anterior tongue (AT), rats demonstrated a marginal attenuation in their responsiveness to sucrose. Combining the two lesions, however, had the greatest effect on the concentration-response curve. By shifting the curve to the right and lowering the asymptotic licking rate, the combined lesion reduced the area under the curve by one third. The effects of the combined treatments were larger than would be predicted from the sum of either one alone. This presumably reflects the central convergence of primary afferent axons from the NID and AT. Neurophysiological data have demonstrated such convergence within the nucleus of the solitary tract.

Afferent Pathways↗
PubMed1994

Combined, but not single, gustatory nerve transection substantially alters taste-guided licking behavior to quinine in rats.

On the basis of electrophysiological studies, the glossopharyngeal nerve (GL) is far more responsive to quinine than the chorda tympani (CT) or greater superficial petrosal (GSP) nerves. The licking behavior of water-deprived rats to quinine (0.03-3.0 mM) and distilled water (10-s trails) was tested before and after various nerve transections. GL+CT section caused a substantial reduction in responsiveness. GSP+CT section had a moderate effect, and GL section alone produced only marginal impairments. Control, partially desalivated, and CT-sectioned rats were unaffected. Thus, the GL is not necessary for normal unconditioned taste-guided appetitive responsiveness to quinine, but the collective input from the GSP and CT is necessary and most likely sufficient. These data suggest that the quinine-evoked input of the GL and CT converge centrally.

Animals↗
PubMed1994

Lesions of the pontine parabrachial nuclei eliminate successive negative contrast effects in rats.

Rats shifted from a high to a low concentration of sucrose make fewer licks for the low concentration than rats that experience only the low concentration of sucrose. This phenomenon, referred to as successive negative contrast, is eliminated after bilateral electrolytic lesions of the amygdala. Because the amygdala receives direct projections from the gustatory zone of the parabrachial nuclei of the pons (PBN), this experiment was designed to examine this phenomenon in rats with electrophysiologically guided bilateral electrolytic lesions of the PBN. The results of this experiment showed that lesions of the PBN fully prevent contrast in rats shifted from the high to the low concentration of sucrose. Thus, an intact PBN is essential for the occurrence of successive negative contrast effects in rats.

Amygdala↗
PubMed1995

Gustatory parabrachial lesions disrupt taste-guided quinine responsiveness in rats.

This study examined the effects of electrophysiologically placed electrolytic lesions in the gustatory zone of the parabrachial nuclei (PBN) on the rat's taste-guided unconditioned licking of quinine hydrochloride during repeated 10-s trials. Concentration-response functions measured in water-deprived rats before and after surgery significantly shifted to the right as a result of the bilaterally placed lesions. These same rats were tested on their ability to acquire a lithium chloride (LiCl)-based conditioned taste aversion (CTA) to 0.1 M sucrose. Although the largest lesions severely affected performance in both tasks, there was only a modest correlation (r = -.447) between the extent of the lesion-induced shift in the quinine concentration-response curves and the degree of sucrose intake suppression after the first CTA conditioning trial. Thus, PBN lesions can disrupt performance on both tasks, but it appears that the neural processes governing unconditioned responsiveness to quinine may be to some extent dissociable from those subserving acquisition of a sucrose LiCl-based CTA.

Animals↗
PubMed1997

Chorda tympani nerve transection disrupts taste aversion learning to potassium chloride, but not sodium chloride.

In Experiment 1, rats with chorda tympani nerve transection (CTX) acquired a LiCl-conditioned taste aversion to 0.1 M NaCl at the same rate as controls. After 3 conditioning trials, the aversion generalized to 0.03 and 0.3 M NaCl, but did not generalize to KCI (0.03, 0.1, and 0.3 M), in either the sham or CTX group. In Experiment 2, the sham group, but not the CTX group, formed an aversion to 0.1 M KCI after 1 trial. The CTX rats did form a moderate aversion after 2 conditioning trials. Following the 3rd trial, the CTX group did not suppress licking to 0.03 or 0.3 M KCI or any concentration of NaCl in relation to controls. Although there is strong evidence that CTX affects NaCl taste perception, these findings indicate that, under certain conditions, rats can nonetheless distinguish NaCl from KCI after such neurotomy. Moreover, CTX appears to have a substantial effect on the perceived intensity of KCl.

Animals↗
PubMed1998

Taste responses in the greater superficial petrosal nerve: substantial sodium salt and amiloride sensitivities demonstrated in two rat strains.

A great quantity of research has focused on neural responses of the chorda tympani nerve (CT) to taste stimuli. This report examined salt and sugar sensitivity of the greater superficial petrosal nerve (GSP) and the effect of amiloride on these neural responses. In addition to Sprague-Dawley (SD) rats that have CT responses typical of most rat strains, we included Fischer 344 (F344) rats whose CT responses to sodium chloride (NaCl) are higher than those of other strains. After a stimulation series in which water served as the rinse, a series of stimuli was presented in 100 microM amiloride. The GSP was highly responsive to NaCl, sodium acetate (NaAc), ammonium chloride, and sucrose; NaCl and NaAc responses were strongly suppressed by amiloride. Relative responses to NaCl were significantly higher in F344 than in SD rats. In summary, the GSP is highly sensitive to salt and sugar stimulation, and palatal taste receptors have a considerable degree of amiloride sensitivity.

Afferent Pathways↗
PubMed1985

Adrenalectomy reduces peripheral neural responses to gustatory stimuli in the rat.

In the rat, sodium need leads to an increase in sodium intake, which depends on salt taste sensitivity. The adrenalectomized rat, because of excessive body sodium loss, has been an important animal model for studying the physiological mechanisms underlying salt ingestion. In order to investigate the mediation by peripheral taste responsivity of changes in salt intake, multiunit responses of the chorda tympani nerve to various concentrations of sodium chloride, potassium chloride, lithium chloride, hydrochloric acid, and quinine hydrochloride were recorded from adrenalectomized and control rats. In order to control for a generalized decrease in sensory sensitivity, recordings from the auriculotemporal nerve to tactile stimulation of the pinna were also performed. There were no group differences in amplitude of the integrated neural responses to tactile stimulation. The largest decrease in gustatory responsivity occurred for suprathreshold concentrations of sodium chloride and lithium chloride. The data are discussed with reference to possible mechanisms underlying this neural alteration and to the role that reductions in salt taste responsivity play in mediating increases in salt intake.

Adrenal Glands↗
PubMed2004

The easy to hard effect and perceptual learning in flavor aversion conditioning.

In experiments on the easy to hard effect, pretraining on an easy discrimination results in better performance on a harder version of the discrimination than pretraining on the hard discrimination itself. In addition, some theories posit that unreinforccd preexposure to the easy discrimination should be as effective as differentially reinforced easy pretraining in producing the easy to hard effect. Two experiments on flavor aversion conditioning in rats demonstrated the basic easy to hard effect. However, in neither experiment was easy preexposure more effective than hard preexposure in enhancing learning of the hard discrimination. Indeed, in Experiment 2, rats preexposed to an easy discrimination learned the hard discrimination significantly more slowly than those preexposed to the hard discrimination itself.

Animals↗
PubMed1981

The ontogeny of feeding in rats: IV. Taste development as measured by intake and behavioral responses to oral infusions of sucrose and quinine.

Infusions of sucrose or quinine were delivered through cannulas implanted in rat pup's mouths. Intake was measured, and behavioral responses were scored. Responsiveness to sweet and bitter tastes emerged over the first 2 wk of postnatal life. Pups showed discrimination between water and sucrose in their mouthing behavior and general activity from 3 days of age, but in their intake only from 6 days of age. Discrimination between water and quinine was not shown until 9 days of age in either behavior or intake. Even then, the stereotypic aversion reactions (paw treading, chin scraping) that characterize the adult response to quinine were not apparent until 12 days. By 15 days of age, preferences for sucrose and aversions to quinine were robust. They resembled those of adult rats and did not depend on previous experience with either solution.

Aging↗
PubMed2003

Evaluation of gustatory function in postmenopausal women.

OBJECTIVE: The aim of this study is to evaluate the gustatory function in postmenopausal women. SUBJECTS AND METHODS: Whole mouth taste test and spatial taste test were administered to 20 postmenopausal women (Group 1) and 20 age-matched male subjects (Group 2). Further investigations were carried out for subjective assessment of taste alteration and nutritional differences between premenopausal and postmenopausal periods. RESULTS: There was a significant reduction in sucrose perception and in palatal sensitivity in postmenopausal women (p<0.05). Only 7(35%) of the female patients noticed alteration in taste perception during the postmenopausal period. Alteration in dietary habits after menopause was reported by 9 (45%) patients. CONCLUSION: This study demonstrates that taste perception of the tongue does not change, but that there is a disorder in palatal perception in postmenopausal women. Furthermore, there is tendency to preference of sweeter foods during menopause.

Age Factors↗
PubMed2006

Simplifying the assessment of the recovery from surgical injury to the lingual nerve.

OBJECTIVE: To determine the sensitivity of conventional sensory assessment in monitoring lingual nerve recovery subsequent to third molar surgery and to evaluate if the assessment methods can be predictive of injury outcome. METHOD: A prospective case series of 94 patients presenting with lingual nerve injuries evaluated using objective mechanosensory and subjective methods during the recovery period of up to 12 months. RESULTS: The conventional tests were often unable to diagnose the presence of injury due to variability and they were not predictive of outcome. As a result of this study, we are able to identify patients more likely to have permanent rather than temporary lingual nerve injury at four to eight weeks post injury, using patient reported subjective function. The subjective function test also minimises the requirements for specialist training or equipment providing an ideal method for general dental practice. CONCLUSIONS: The development of these simple subjective tests may enable us to identify which patients are at risk of permanent lingual nerve injuries in the early post injury phase, thus allowing expeditious therapy when indicated.

Cranial Nerve Injuries↗
PubMed2006

Odour and taste sensitivity is associated with body weight and extent of misreporting of body weight.

BACKGROUND: Sensory factors are important determinants of appetite and food choices but little is known about the relationship between body weight and sensory capabilities. OBJECTIVE: To investigate the relationship between measured body weights, misreporting of body weight and sensory capabilities. DESIGN: In a cross-sectional sensory study, body weight was assessed by measured and self-reported body weight in healthy men (n=130) and women (n=181). Sensory capabilities were assessed as odour detection and identification, and detection for salty, sweet, sour and bitter taste. RESULTS: Odour detection, odour identification and taste perception scores were lower in subjects with a BMI >or=28 kg/m(2) than in subjects with a BMI <28 kg/m(2) in the age group <65 years whereas in subjects >or=65 years scores were higher in subjects with a BMI >or=28 kg/m(2) than in subjects with a BMI <28 kg/m(2) (BMI*age group: P=0.015, 0.053 and 0.015, respectively). Independent of age, scores were highest in under reporters of body weight (P=0.008, 0.001 and 0.017). Differences in taste perception could be attributed to sour (P=0.015) and bitter (P=0.026) perception, but not to salty or sweet perception. CONCLUSION: Relationship between sensory capabilities and body mass is age dependent. Compared to overweight subjects, the sensory capabilities of normal weight individuals appear to be higher (<65 years) and lower (>or=65 years). At any age, however, subjects who under reported their body weight show higher sensory capabilities.

Adult↗
PubMed2003

[Contact endoscopic quantification of fungiform papillae--correlation to taste ability?].

BACKGROUND: Besides anamnestic data and taste test, the clarification of epithelial taste disorders makes macroscopic evaluation of the surface of the tongue necessary. METHODS: In this article the contact endoscopy is evaluated for examination of the tongue epithelium and for quantification of the fungiforme papillae. These results are related to the results of the spatial taste test (1. chemical taste test with sodium chloride in 2 different suprathreshold concentrations and sucrose in also 2 different suprathreshold concentrations; 2. electrogustometry with a bipolar electrode). PATIENTS: In a prospective study we performed contact endoscopy in 16 healthy volunteers from ages 7 to 68 years. The subjects were divided into 2 age groups (< or = 45 years and > 45 years) and 2 papillae density groups. In 34 patients with either taste disorders of unknown cause or in patients with macroscopic changes at the tongue surface, the spatial and whole mouth taste tests and contact endoscopy were used to clarify the cause of the complaints. RESULTS: Density and shape of the fungiform papillae as well as the shape of the subepithelial vessels of the papillae vary among the investigated human subjects in the different age groups. No correlation between intensity ratings, papillae density und age was found after stimulation with 40 % sucrose at the tongue tip in the younger age group. Stimulation of the tongue edge with 15 % sodium chloride, however, showed a relationship between the two different density groups and the different age groups. CONCLUSIONS: The contact endoscopy allows the evaluation of the epithelium in the oral cavity. It is a nondestructive method and is additionally easy to handle, but the evaluation of the observed epithelia needs interdisciplinary co-operation with pathologists. No relevant informations are supplied in diagnostics of taste disorders.

Adolescent↗