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PubMed2004

Heavy particle irradiation, neurochemistry and behavior: thresholds, dose-response curves and recovery of function.

Exposure to heavy particles can affect the functioning of the central nervous system (CNS), particularly the dopaminergic system. In turn, the radiation-induced disruption of dopaminergic function affects a variety of behaviors that are dependent upon the integrity of this system, including motor behavior (upper body strength), amphetamine (dopamine)-mediated taste aversion learning, and operant conditioning (fixed-ratio bar pressing). Although the relationships between heavy particle irradiation and the effects of exposure depend, to some extent, upon the specific behavioral or neurochemical endpoint under consideration, a review of the available research leads to the hypothesis that the endpoints mediated by the CNS have certain characteristics in common. These include: (1) a threshold, below which there is no apparent effect; (2) the lack of a dose-response relationship, or an extremely steep dose-response curve, depending on the particular endpoint; and (3) the absence of recovery of function, such that the heavy particle-induced behavioral and neural changes are present when tested up to one year following exposure. The current report reviews the data relevant to the degree to which these characteristics are common to neurochemical and behavioral endpoints that are mediated by the effects of exposure to heavy particles on CNS activity.

Amphetamine↗
PubMed2002

Comparison of central and peripheral administration of C75 on food intake, body weight, and conditioned taste aversion.

Mice respond to fatty acid synthase (FAS) inhibitors by profoundly reducing their food intake and body weight. Evidence indicates that the central nervous system (CNS) may be the critical site of action; however, a peripheral contribution cannot be ruled out. We compared doses of the FAS inhibitor C75 in the CNS (third ventricle [i3vt]) and periphery (intraperitoneal [IP]) to reduce food intake and body weight in rats. Centrally, the threshold dose was 3 micro g, whereas a dose of 10 mg/kg was required peripherally. Such data argue for FAS activity in the CNS as a potent target for the actions of C75. To control for nonspecific effects of FAS inhibition, we compared C75 administration in two models of illness, conditioned taste aversion and need-induced sodium appetite. Our results suggest the anorexia produced by IP C75 is accompanied by visceral illness, whereas the anorexia produced by i3vt is not. In addition, we placed animals in an indirect calorimeter after an IP injection of C75. We found that consistent with behavioral measures of visceral illness, peripheral C75 reduced heat expenditure and resulted in animals losing less weight than fasted control animals, suggesting that peripherally administered C75 has aversive properties. Understanding the mechanisms by which FAS inhibition in the CNS reduces food intake could lead to specific targets for the manipulation of energy balance and the treatment of obesity.

4-Butyrolactone↗
PubMed1991

High dietary sodium enhances gustatory nerve activity and behavioral responses to NaCl.

Neural and behavioral taste responses to NaCl were studied in rats receiving a high-salt diet. Salt preferences and voluntary sodium intake were measured by the 24-h two-bottle choice method over a wide concentration range of NaCl solutions. As expected, the salt-loaded rats showed lower preference responses for all the solutions tested, which were presented in ascending order from 0.001 to 1.0 M NaCl. However, they freely ingested significantly greater amounts of sodium than the controls by drinking larger volumes of saline solution throughout the hypotonic concentration range, from 0.001 to 0.1 M NaCl. They showed lower voluntary intake of sodium only for isotonic and hypertonic solutions. Electrophysiological recordings from the chorda tympani nerve showed that the taste responses of the salt-loaded rats were greater in magnitude than those of the controls, and the neural stimulus-response function of the experimental group had a significantly steeper slope but no apparent difference in threshold. These experiments indicate that salt-loaded rats have enhanced appetitive responses to NaCl that may be mediated by increased sensory input.

Animals↗
PubMed1993

Smell and taste function in the visually impaired.

Surprisingly few quantitative studies have addressed the question of whether visually impaired individuals evidence, perhaps in compensation for their loss of vision, increased acuteness in their other senses. In this experiment we sought to determine whether blind subjects outperform sighted subjects on a number of basic tests of chemosensory function. Over 50 blind and 75 sighted subjects were administered the following olfactory and gustatory tests: the University of Pennsylvania Smell Identification Test (UPSIT); a 16-item odor discrimination test; and a suprathreshold taste test in which measures of taste-quality identification and ratings of the perceived intensity and pleasantness of sucrose, citric acid, sodium chloride, and caffeine were obtained. In addition, 39 blind subjects and 77 sighted subjects were administered a single staircase phenyl ethyl alcohol (PEA) odor detection threshold test. Twenty-three of the sighted subjects were employed by the Philadelphia Water Department and trained to serve on its water quality evaluation panel. The primary findings of the study were that (a) the blind subjects did not outperform sighted subjects on any test of chemosensory function and (b) the trained subjects significantly outperformed the other two groups on the odor detection, odor discrimination, and taste identification tests, and nearly outperformed the blind subjects on the UPSIT. The citric acid concentrations received larger pleasantness ratings from the trained panel members than from the blind subjects, whose ratings did not differ significantly from those of the untrained sighted subjects. Overall, the data imply that blindness, per se, has little influence on chemosensory function and add further support to the notion that specialized training enhances performance on a number of chemosensory tasks.

Blindness↗
PubMed1985

Effect of antidromic stimulation of the glossopharyngeal nerve on afferent discharges occurring with and without sensory stimulation of the frog tongue.

Repetitive stimulation of the bullfrog glossopharyngeal nerve at a rate of 100 Hz for 10 s and at a supra-maximal intensity resulted in little depression of the glossopharyngeal nerve responses to application of quinine and mechanical taps to the tongue, in a 30-40% decrease in the responses to salt, acid, water and warmed saline and in a 80% decrease in the number of spontaneous discharges from the tongue. Such a selective depression existed throughout changes in the frequency and the duration of the antidromic stimuli. The phenomena were attributed to antidromic impulses in high-threshold glossopharyngeal nerve afferents.

Animals↗
PubMed1975

The effect of signal probability, food intake, sex, and smoking on gustation, as measured by the theory of signal detection.

The possibility of applying Signal Detection Theory (SDT) to gustation was investigated by testing the effect of three variables--smoking, signal probability, and food intake (confounded with time of day)--on the taste sensitivity to sucrose of 24 male and 24 female Ss. No main effects or interactions were significant. The study indicated a "warm-up" effect, while adaptation was questionable. An analysis of false alarm (FA) reports was undertaken and discussed. Correlations were obtained between numerous variables and sensitivity. None of the correlations was statistically significant. It was concluded that although SDT is theoretically applicable to the gustatory modality, it is not practical for large-scale research.

Differential Threshold↗
PubMed1976

Dissociation of gustatory and weight regulatory responses to quinine following lateral hypothalamic lesions.

In a two-phase experiment, consummatory (Phase 1) and body weight regulation (Phase 2) responses to quinine adulteration of a wet mash diet were measured in rats recovered from bilateral lateral hypothalamic lesions (LH; n = 16) and in unoperated control rats (C; n = 18). In Phase 1, all rats were fed wet mash adulterated with increasing concentrations of quinine sulfate every other day, and fed unadulterated wet mash on the alternate days. Group LH consumed a significantly lower proportion of quinine-adulterated wet mash relative to unadulterated wet mash, displaying a steeper concentration-response function and a lower rejection threshold than did Group C. In Phase 2, Groups LH and C were maintained exclusively on quinine-adulterated mash for 20 days. This procedure caused equivalent weight loss in the two groups. Therefore, an apparent exaggerated aversion to quinine-adulterated food does not appear to contribute abnormally to the weight regulation exhibited by rats with lateral hypothalamic damage.

Animals↗
PubMed1990

Electrophysiological responses of the housefly, Musca domestica nebula (Fr), taste receptors to KCl.

This paper aims at studying the response of the housefly labellar chemoreceptor to stimulation by KCl. These studies are limited to testing various concentrations of KCl solutions (0.005-1 M), using the electrophysiological "tip recording" method and examining the various spike characteristics such as threshold, phasic and tonic response, spike amplitudes, frequency and adaptation; for the anion, cation and water receptors. The large, medium and small hairs all respond to salt. The frontal large, medium and small hairs show a higher frequency response to equimolar KCl than the distal hairs. There is a bilateral symmetry in response pattern. The results are compared with the reported work on Phormia and Calliphora species. The Biedler's hypothesis is also tested for the salt receptors of Musca.

Animals↗
PubMed1998

Sugar cell responses to lactose and sucrose in labellar and tarsal taste hairs of Musca domestica.

Receptor cell responses in the largest labellar (LL) and tarsal (D) taste hairs of the housefly Musca domestica were investigated electrophysiologically using the tip-recording technique. In LL hairs, test series with lactose in concentrations of 12.5-400 mmol.l-1 yielded a threshold concentration around 12 mmol.l-1 and a calculated concentration eliciting half-maximal response of around 40 mmol.l-1, the maximal response varying between 18 and 30 impulses/300 ms. D hairs are more sensitive towards lactose, indicated by a slightly lower threshold and a by 60% higher response to 400 mmol.l-1 lactose. The high variation in the relative stimulating effectiveness of lactose and sucrose and experiments with sugar mixtures imply that these sugars bind to different receptor sites without noticeable cross affinity. A comparison of the concentration response characteristics for sucrose and lactose in LL and D hairs suggests that sucrose can combine with more than one site type, expressed in different proportions in both hair types. Results obtained with p-nitrophenyl-beta-galactoside as stimulus indicate that a beta-galactoside link is not sufficient for a substance to interact specifically with the lactose binding site. The exceptional lactose sensitivity of the sugar cell in M. domestica is discussed in the context of food acquirement and digestion.

Animals↗
PubMed1989

A growth-limiting, mild zinc-deficiency syndrome in some southern Ontario boys with low height percentiles.

A double-blind, pair-matched 12-mo study examined the effects of a zinc supplement (10 mg Zn/d as ZnSO4) on linear growth, taste acuity, attention span, biochemical indices, and energy intakes of 60 boys (aged 5-7 y) with height less than or equal to 15th and midparent height greater than 25th percentiles. Boys with initial hair Zn less than 1.68 mumol/g (n = 16) had a lower mean (+/- SD) weight-for-age Z score (-0.44 +/- 0.59 vs -0.08 +/- 0.84), and a higher median recognition threshold for salt (15 vs 7.5 mmol; p = 0.02) than those with hair Zn greater than 1.68 mumol/g. Only boys with hair Zn less than 1.68 mumol/g responded to the Zn supplement with a higher mean change in height-for-age Z score (p less than 0.05); taste acuity, energy intakes, and attention span were unaffected. A growth-limiting Zn deficiency syndrome exists in boys with low height percentiles, hair Zn levels less than 1.68 mumol/g, and impaired taste acuity.

Body Height↗
PubMed1989

Food quality reports from noninstitutionalized aged.

Over several years, we have compared olfaction in elderly subjects with that in young subjects. The main tests have been 1) absolute threshold, 2) magnitude matching to assess whether aging impairs suprathreshold odor and trigeminal strength, and 3) odor identification. As have other laboratories, we have found impairment by all three measures. In one study, we devised a composite score of olfactory competence based on all three measures; the outcome suggests that it is uncommon for a person over 70 years to escape a degree of impairment, although the degree varies from person to person. We speak here of persons living at home and regularly attending senior citizens' centers in New Haven. After testing, we often gave a questionnaire having to do with the subjects' health and occupational history. Under the circumstances of our subject selection and testing, the questionnaires have revealed no striking correlations. Among the questions asked have been the following: 1) Do you have a problem tasting? 2) Do you have a problem smelling? 3) Have you noticed changes in tastes of foods? 4) Do you enjoy food? Of 276 elderly subjects, 17% answered yes to one or more of questions 1-3 and/or no to question 4. Only 5.8% of the total complained of weakened food enjoyment all or some of the time. Several were unable to say why. Some blamed a lifelong lack of interest in food; others, restricted diets, expense of foods, denture problems, etc. In contrast, the great majority (about 260 persons) rated the pleasure of eating with enthusiasm. Of 262 young subjects, 10% answered yes to one or more of questions 1-3 and/or no to question 4, and only four (1.5%) complained of food. Considering the losses involved, the rate of elderly complaining seems low, especially compared with much higher rates from institutionalized persons (for example, up to 33%). The reasons may or may not have to do with sensory factors, but the conclusion seems justified that a persons may profoundly enjoy the pleasures of food and drink despite a weakening of the nasal components involved.

Adolescent↗