Biomedical subjects

H P Weingarten

Publications and source records attributed to H P Weingarten.

At least 19 recordsLinked to original sources

PubMed1996

Flavor-postingestive consequence associations incorporate the behaviorally opposing effects of positive reinforcement and anticipated satiety: implications for interpreting two-bottle tests.

Rats consuming distinctively flavored solutions containing different numbers of calories learn to associate each flavor with the ensuing postingestive effects ("flavor-postingestive consequence learning"). The hallmark of such learning is preferential consumption of one of the flavors in two-bottle tests (both flavors presented in nutrient-identical solutions). Two experiments were conducted to characterize the relationship between the number of calories associated with flavors and subsequent preferences in two-bottle tests. In Experiment 1, three groups of rats each associated distinctive flavors with real-fed sugar and with sham-fed sugar. The groups differed in the concentration of sucrose (8%, 14%, 24%) with which they were trained. In two-bottle tests rats trained with 8% sucrose preferred the real-fed flavor, whereas rats trained with 24% sucrose preferred the sham-fed flavor. Rats trained with 14% sucrose were intermediate to the other groups. In Experiment 2, two groups of rats associated distinctive flavors with two concentrations of real-fed sucrose. In two-bottle tests, the group trained with 1% and 5% sucrose preferred the flavor paired with the higher concentration, whereas the group trained with 5% and 30% sucrose preferred the flavor paired with the lower concentration. These findings suggest that flavor-postingestive consequence learning incorporates both positive reinforcement, which has the behavioral effect of increasing intake of the associated flavor, and anticipated satiety, which has the behavioral effect of suppressing intake of the associated flavor. When a flavor is associated with relatively few calories, the positive reinforcing effect predominates over anticipated satiety. However, when a flavor is associated with a greater number of calories, anticipated satiety predominates over the positive reinforcing effect.

Animals↗

PubMed1996

Cytokines and food intake: the relevance of the immune system to the student of ingestive behavior.

The aims of this paper are to provide a selective review of the literature relating immune system mediators, especially cytokines, to the control of eating and to indicate why this literature is particularly relevant to the student of ingestive behavior. Four reasons are given. Firstly, many immune system mediators influence eating, providing excellent examples of neuroimmunological controls of behaviour. Secondly, the immune system appears to be involved in the profound eating pathology associated with several clinical conditions. Thirdly, cytokines affect both energy intake and energy expenditure. Fourthly, the anorexia typically associated with activation of the immune system provides an informative model for the analysis of gut-brain communication in the control of eating.

Body Weight↗

PubMed1996

Previous inflammation alters the response of the rat colon to stress.

BACKGROUND & AIMS: Patients with inflammatory bowel disease have symptoms of irritable bowel syndrome (IBS) with a higher than expected prevalence. Stress is an important factor in the pathogenesis of IBS. Thus, previous inflammation may predispose to IBS by rendering the bowel more susceptible to the impact of stress. The aim of this study was to examine the effect of previous colitis on stress-induced responses in rats. METHODS: Acute colitis was induced in rats by intrarectal administration of trinitrobenzene sulfonic acid (TNBS), and the rats were allowed to recover for 6 weeks before application of mild restraint stress for 3 consecutive days. In vitro measurements included myeloperoxidase activity, plasma corticosterone levels, interleukin 1 beta messenger RNA expression, and [3H]noradrenaline release from the myenteric plexus. RESULTS: Six weeks after administration of TNBS, stress caused a significant increase in myeloperoxidase activity in TNBS-treated rats but not in stressed controls; plasma corticosterone responses were similar. Stress also caused an exaggerated and significant suppression of [3H]noradrenaline release in TNBS-treated stressed rats compared with stressed controls. This was accompanied by a significant decrease in interleukin 1 beta messenger RNA expression in the colon. CONCLUSIONS: Previous colitis rendered the colon more susceptible to effects of stress on enteric nerve function and also increased some parameters of inflammation in response to stress.

Animals↗

PubMed1996

Interpretation of sham feeding data: curve-shift studies.

We explored the possibility that quantitative analysis of the relationship between sucrose concentration and sham intake differentiated how various treatments affected the intake of sweet solutions. Rats were sham fed sucrose solutions varying in concentration from 0.03125 to 1.5 M. Under different treatment conditions, intake concentration functions were generated that plotted amount sham fed against sucrose concentration. Sucrose concentration that yielded 50% maximal sham intake were calculated to indicate the position of the concentration-intake function on the x-axis. Quinine adulteration of sucrose solutions and injection of 0.5 mg/kg i.p. of the dopamine antagonist pimozide reduced sham intake and shifted the concentration-intake function to the right. Lithium chloride (60 mg/kg i.p.) injected 30 min before sham feeding, a reduction of food deprivation from 18 to 6 h before sham feeding, and 6 micrograms/kg cholecystokinin octapeptide reduced sham intake equivalent amounts but did not shift the concentration-intake functions along the x-axis. The data indicate that of several factors that reduce sham feeding, only some also shift the position of concentration-intake curves, and these curve shifts may identify intake changes mediated by alterations in the processing of the taste input.

Animals↗

PubMed1996

Dissociation of temperature changes and anorexia after experimental colitis and LPS administration in rats.

The acute phase of inflammation induces both anorexia and fever. Because several analyses suggest a linkage between the meal size and body temperature, we assessed whether temperature changes were causal to anorexia in situations involving acute inflammation. Specifically, we evaluated whether elevations of body temperature could account for the reduced food intake after induction of experimental colitis [via intrarectal infusions of trinitrobenzene sulfonic acid (TNB)] or injection of 100 micrograms/kg lipopolysaccharide (LPS). Temperature was monitored telemetrically in rats via implanted temperature transmitters. TNB-treated rats demonstrated a 5-day anorexia that resulted specifically from a decrease in meal size. Although TNB-treated rats were hypothermic on the day of treatment, no other body temperature changes were noted. LPS reduced food intake and elevated temperature, but these two effects were uncorrelated temporally. Although these results do not identify the mechanisms of anorexia, the findings indicate clearly that the anorexia associated with the acute inflammatory response is not secondary to fever.

Animals↗

PubMed1995

Fos-like immunoreactivity in vagal and hypoglossal nuclei in different feeding states: a quantitative study.

This study characterized the distribution of Fos-like immunoreactivity (FLI) in three hindbrain nuclei: dorsal motor nucleus of the vagus (DMN), nucleus of the solitary tract (NST) and hypoglossal nucleus (HG) in response to eating or activation of specific components of feeding behavior. The degree of FLI was quantified by automated image analysis software that provided an efficient and sensitive method for counting the number of cells labelled with Fos antibody. Ingestion, and anticipation, of a meal both increased FLI in the DMN and HG, but not in the NST. Sham feeding 1 M sucrose was a more potent stimulus for FLI activation in DMN and NST than combined oral plus gastric/postingestive stimulation provided by real feeding the same food. The results indicate that the physiological stimulus of eating is sufficient to elicit FLI in the hindbrain and that specific components of the feeding act, especially oral stimulation provided by sham feeding, can activate FLI. The results suggest further that, under specific experimental conditions, gastric and/or postgastric stimulation may decrease FLI in the NST and DMN.

Animals↗

PubMed1995

Determinants of high-fat diet hyperphagia: experimental dissection of orosensory and postingestive effects.

High-fat diets often promote greater caloric intake and/or weight gain than high-carbohydrate diets in both laboratory animals and humans. Because altering the fat content of a diet simultaneously changes both its sensory properties and postingestive effects, it is unclear whether high-fat hyperphagia is due to the diet's palatability, its postingestive effects, or both. The present studies isolated the independent capacity of the orosensory and postingestive effects of a liquid high-fat diet (High-Fat) to produce overeating relative to an isocaloric liquid high-carbohydrate (High-CHO) diet. Rats fed High-Fat orally ate more calories and gained more weight over 16 days than rats fed High-CHO orally. One-bottle sham-feeding intake of High-Fat and High-CHO did not differ, but in two-bottle sham-feeding tests High-Fat was clearly preferred. When orosensory influences on intake were equated via chronic self-regulated intragastric feeding, High-Fat still promoted greater intake than High-CHO, although absolute intake across both diets was lower during intragastric feeding relative to oral feeding. An analysis of short-term intake revealed that rats accustomed to infusion of High-CHO increased meal size immediately when switched to High-Fat. The present results, coupled with previous findings, suggest that the postingestive effects of fat enhance daily caloric intake in two ways: 1) during a meal, fat produces less suppression of intake per calorie than carbohydrate; and 2) after a meal, fat produces less suppression of intake per calorie during the intermeal interval than carbohydrate.

Animals↗

PubMed1994

Dissociation of palatability and calorie effects in learned flavor preferences.

Rats acquire a preference for a flavor paired with a caloric solution over a flavor paired with a solution providing fewer or no calories. Because the palatability and the caloric value of the solutions typically covary, it is unclear which property of the high-calorie solution reinforces the flavor preference. Two studies were conducted to assess the independent effects of palatability and calories in flavor preference conditioning. In Experiment 1, rats consumed two distinctively flavored solutions having equal palatability but different caloric value. The flavor paired with ingestion of more calories was subsequently preferred, indicating that a caloric advantage is sufficient to establish a flavor preference (flavor-calorie conditioning). In Experiment 2, rats consumed two distinctively flavored solutions having equal calories but different palatability. The flavor paired with the more palatable solution was subsequently preferred, indicating that a palatability advantage is sufficient to establish a flavor preference (flavor-flavor conditioning). This finding demonstrates flavor-flavor conditioning in the context of postingestive stimulation by calories. Taken together, these results demonstrate both flavor-calorie and flavor-flavor conditioning in the context of normal ingestion (i.e., self-paced oral intake of nutritive solutions).

Animals↗

PubMed1994

Dynamics of intake suppression after a preload: role of calories, volume, and macronutrients.

Twenty-four-hour cumulative food intake is the summation of repeated bouts of feeding, separated by intermeal intervals. Intake in a given meal influences subsequent feeding by modulating the duration of the intermeal interval, meal size, or both. Analysis of the time course of the effect of an individual meal on subsequent feeding may therefore clarify the controls of meal patterning and 24-h intake. In the present experiments, rats consumed a preload and then ate a test meal ad libitum. With the length of the preload-to-test meal interval varied from 10 to 180 min, the time course of the impact of various preloads on meal size was revealed. The main findings were the following: 1) caloric content, rather than volume, was the primary determinant of the intake-reducing effect of a glucose preload; 2) no differences in the time course of intake reduction were found after isocaloric preloads of fructose, glucose, and sucrose; 3) a fat preload attenuated subsequent intake less than an isocaloric sucrose preload; and 4) a short-lived (< 20 min) effect of sensory-specific satiety was evident. These findings are consistent with what is known about long-term effects of dietary manipulations on 24-h intake. Because daily intake reflects multiple iterations of feeding followed by an intermeal interval, a focused study of the duration of the impact of meals on subsequent ingestion may clarify the relationship between controls of individual meals and 24-h food intake.

Animal Feed↗

PubMed1994

Central interleukin-1 receptors contribute to suppression of feeding after acute colitis in the rat.

Experimental colitis, induced in rats by intrarectal administration of trinitrobenzenesulfonic acid (TNB), results in a suppression of eating for 3 days. Because interleukin-1 (IL-1) is elevated within 24 h after TNB treatment, and because chronic administration of IL-1 leads to a pattern of anorexia similar to that seen after TNB, we evaluated the role of endogenous IL-1 in the anorexia observed in the TNB model. Human recombinant IL-1 receptor antagonist (rhIL-1ra) was administered chronically via osmotic minipump either peripherally or centrally after TNB treatment. Peripheral delivery of 40 micrograms/h rhIL-1ra significantly attenuated TNB-induced anorexia. However, 24 micrograms/h rhIL-1ra attenuated TNB-induced anorexia only when delivered centrally, not peripherally. These findings implicate central IL-1 receptors in the suppression of eating during acute experimental colitis but leave open a possible involvement of peripheral IL-1 receptors.

Animals↗

PubMed1993

Dopamine antagonists act on central, but not peripheral, receptors to inhibit sham and real feeding.

We examined the relative contribution of dopamine (DA) receptors in the brain and periphery in the control of sham and real feeding of sucrose solutions. Intraperitoneal (IP) administration of pimozide, an antagonist of peripheral and brain DA receptors, suppressed both sham and real feeding in a dose-related manner. In contrast, IP injections of domperidone, a DA antagonist restricted to peripheral receptors, had no effect on either sham or real feeding. The inability of domperidone to influence sucrose intake did not result from a lack of biological activity of the drug because the identical doses of domperidone that failed to alter eating significantly inhibited gastric acid secretion. The results implicate central, but not peripheral, DA receptors in the control of the ingestion of palatable foods and also suggest that sham feeding is more sensitive to DA antagonism than real feeding.

Animals↗

PubMed1993

On the suppression of food intake in experimental models of colitis in the rat.

We measured daily food intake and body weight in rats before and after the induction of colitis by intrarectal administration of either 2,4,6-trinitrobenzenesulfonic acid in ethyl alcohol (TNBE) or 4% acetic acid (AA). Administration of TNBE or AA induced inflammation in the distal colon, which was reflected by a significant increase in myeloperoxidase (MPO) activity in the colon. On days 1, 2, and 3 after induction of colitis by TNBE, food intake fell by 80, 70, and 50%, respectively, compared with pretreatment values; food intake returned to normal by day 4. Body weight fell within 24 h after induction of colitis and remained 10% less than control for at least 5 days. Colitis induced by AA produced a similar pattern and degree of decreased food intake and weight loss. Treatment with the 5'-lipoxygenase inhibitor MK-886 significantly reduced concentrations of leukotriene B4 in the colon of TNBE-treated rats but did not affect food intake. In contrast, the cyclooxygenase inhibitor indomethacin decreased prostaglandin E2 concentrations in the colon but also attenuated the suppression of feeding by 52 and 64% on the first 2 days after induction of colitis by TNBE. These results identify a specific prostaglandin-mediated suppression of feeding in the rat with acute colitis induced by TNBE and illustrate the utility of this model for studying mechanisms underlying anorexia associated with inflammation of the gastrointestinal tract.

Acetates↗

PubMed1993

Characterization of suppression of food intake following acute colon inflammation in the rat.

Experimental colitis was induced in rats by intrarectal infusion of trinitrobenzenesulfonic acid and ethanol. Colitis was accompanied by a large suppression of food intake of 3 days duration. The reduction of food intake was effected through a reduction of meal size, with no change in meal frequency. Those same rats demonstrating approximately 70%-80% suppression of daily food intake showed no reduction of sham feeding. These data indicate that malaise alone is inadequate to explain the suppression of food intake associated with acute colitis. Rather, the data suggest that the suppression of eating results from an exaggerated postprandial satiety signal elaborated during the period of acute inflammation, an interpretation consistent with the demonstration of a slowed rate of gastric emptying in association with the colitis.

Analysis of Variance↗

PubMed1992

Hedonic response of sucrose likers and dislikers to other gustatory stimuli.

The majority of individuals can be classified as sweet likers or dislikers based on their hedonic (pleasure) response to sucrose solutions of varying concentrations. Our results indicate that the sweet liker/disliker distinction generalizes to sugars other than sucrose, i.e., glucose and fructose. As well, these individual hedonic response patterns are maintained even when a flavor and color are added to sucrose solutions. However, whether one is a sweet liker or disliker does not predict hedonic response to nonsweet tastes such as salt. These results indicate that the sweet liker/disliker distinction is a robust phenomenon which appears to generalize over, but is restricted to, sweet-tasting substances. The possibility that individual differences in hedonic response may predict preferences for, and intake of, complex tastes characteristic of foods encountered in the real world, is discussed.

Adult↗

PubMed1992

Facial expressions and genetic sensitivity to 6-n-propylthiouracil predict hedonic response to sweet.

Individuals differ in their hedonic response to sweet: sweet likers show increasing liking with increasing sucrose concentration, while sweet dislikers show increasing dislike with increasing concentration. Our results indicated that naive raters can correctly classify sweet likers and dislikers by observing subjects' facial responses to the taste of sucrose. Also, for both adults and children, the sweet liker/disliker distinction correlated strongly with the genetically determined ability to taste 6-n-propylthiouracil (PROP): PROP nontasters were almost always sweet likers, whereas sweet dislikers were almost always PROP tasters. Sweet dislikers also reported a purer sweet sensation than likers, who perceived nonsweet components in pure sucrose solutions. These results suggest that the sweet liker/disliker distinction is robust and valid, and that sensitivity to PROP may influence preference for sweet by altering the quality of sweet.

Adolescent↗

PubMed1992

Transection of the stria terminalis without damage to the medial amygdala does not alter behavioural sodium regulation in rats.

Damage to the medial region of the amygdala has been shown to impair mineralocorticoid-induced sodium appetite, while leaving intact sodium appetite induced through sodium depletion. This effect may result from the interruption of the flow of information through the stria terminalis (ST), a neural pathway linking the medial amygdala with the ventral forebrain. We determined the effect of transecting the ST of the rat, at a point remote from the medial amygdala, on sodium appetite induced with the administration of mineralocorticoids and with the natriuretic furosemide. Similar to control and amygdala lesioned rats, rats with ST knife-cuts displayed a normal sodium appetite following treatment with furosemide. However, unlike medial amygdala lesions, transection of the ST alone did not block mineralocorticoid-induced sodium appetite. Therefore, the inability of mineralocorticoids to induce a salt appetite in medial amygdala lesioned rats does not result from damage to the stria terminalis.

Amygdala↗

PubMed1991

Food cravings in a college population.

A questionnaire was administered to over 1000 male and female college undergraduates to collect self-reports regarding food cravings (defined as an intense desire to eat a specific food). Ninety-seven per cent of woman and 68 per cent of men reported experiencing food cravings. Chocolate was the most frequently reported food craved, especially among women. The majority of subjects reported that they indulged their food cravings at least half the time. Females tended to respond with more negative affect to indulging their cravings than men. Only 32 per cent of women perceived that their cravings were linked to menstrual cycles. There was no tendency for an increase in food cravings with dietary restraint. The data provided a detailed description of perceptions regarding food cravings among college-age adults, but also underscored some of the limitations of self-report measures of food craving. In spite of these limitations, however, the results challenge several assumptions regarding food craving and highlight some promising avenues for future investigation.

Adult↗

PubMed1991

Elevations of plasma glucose do not support taste-to-postingestive consequence learning.

We examined whether elevations in plasma glucose are a sufficient postingestive consequence to support taste-to-postingestive consequence learning. Because real, but not sham, feeding supports taste-to-postingestive consequence learning, we recorded changes in plasma glucose during sham and real feeding. For the 1st 15 min of the meal, both sham and real feeding produced similar elevations in plasma glucose. Thereafter, real feeding produced sustained elevations in plasma glucose, whereas sham feeding did not. However, mimicking the plasma glucose profile of real feeding in the sham feeding rat by infusing glucose intravenously did not produce taste-to-postingestive consequence learning. Using radiolabeled sucrose, we determined that the rise in plasma glucose during sham feeding results from absorption of nutrient. We conclude that elevations in plasma glucose in isolation are not a sufficient consequence to support taste-to-postingestive consequence learning.

Animals↗