Search PubMed⌕ Search

Biomedical subjects

A Sclafani

Publications and source records attributed to A Sclafani.

At least 55 records · Page 3Linked to original sources
PubMed1996

Capsaicin attenuates feeding suppression but not reinforcement by intestinal nutrients.

During and after a meal, the presence of nutrients in the intestine can be rapidly detected and signaled to the brain via visceral afferents. Intestinal infusions of carbohydrate and fat suppress food intake, and this satiety action is inhibited by capsaicin, a neurotoxin that produces a partial visceral deafferentation. This study determined if the postingestive reinforcing action of nutrients is also suppressed by capsaicin treatment. Food-restricted control and capsaicin-treated rats were trained to drink a flavored solution paired with intraduodenal infusions of carbohydrate (Polycose solution) on some days and, on other days, a differently flavored solution paired with intraduodenal water infusions. In a choice test, both groups displayed a strong preference for the Polycose-paired flavor. In a subsequent satiety test, however, intraduodenal Polycose suppressed sucrose sham feeding in the controls but not in capsaicin-treated rats. The same rats were next trained to associate new flavors with intraduodenal fat (corn oil emulsion) and intraduodenal water infusions. During training, oil infusions reduced oral intakes in the controls much more than in the capsaicin-treated rats. Both groups reliably preferred the oil-paired flavor in the subsequent choice test. These results indicate that, unlike the satiating effect of intestinal carbohydrate and fat, the reinforcing actions of these nutrients are not mediated by capsaicin-sensitive visceral afferents. The data also imply that the postingestive reinforcement produced by nutrients is not dependent on the nutrients' satiating quality.

Animal Nutritional Physiological Phenomena↗
PubMed1996

The importance of taste and palatability in carbohydrate-induced overeating in rats.

Rats offered a carbohydrate solution (sugar or polysaccharide) in addition to chow typically overeat and gain excessive weight. The present study sought to determine if the palatable taste of these solutions contributes to the overeating response. Adult female rats were fitted with chronic intragastric catheters and given ad libitum access to chow and a drinking fluid that was paired with intragastric infusions. For one group (P + S), the flavored solution was a highly preferred mixture of 2% Polycose and 0.2% saccharin paired with intragastric infusions of 30% Polycose. For a second group (SOA), the flavored solution (0.03% sucrose octaacetate) had unpreferred bitter taste and was paired with intragastric infusions of 32% Polycose. Thus both groups were effectively exposed to the postingestive effects of 32% Polycose but paired with a palatable (P + S) or unpalatable (SOA) flavor. A control group had water to drink paired with intragastric water infusions. During the 4-wk experimental period, the P + S group consumed 34% more total energy (chow + Polycose) and gained more weight than did the SOA and control groups. The P + S group also consumed substantially more flavored solution and more energy as Polycose compared with the SOA group. The SOA group did not gain reliably more weight than the control group, although their total energy intake was 13% higher than that of the controls. In a choice test conducted at the end of the experiment, the P + S group displayed a strong preference (98%) for the Polycose + saccharin solution over water. In contrast to the control group, which avoided the SOA solution relative to water, the SOA group preferred the SOA solution (71%) confirming prior reports of Polycose-conditioned SOA preferences. These results demonstrate that palatability has a major effect on the overeating and obesity produced by carbohydrate solutions. In the absence of a highly preferred taste, the postingestive actions of Polycose produce only a small hyperphagic effect and no excess weight gain.

Animals↗
PubMed1996

Effects of the lipase inhibitor orlistat on intake and preference for dietary fat in rats.

Orlistat (Ols), a potent inhibitor of pancreatic lipase, was added to the fat source (1 or 4 mg Ols/g fat) of a macronutrient self-selection diet fed to adult female rats. The rats responded to the drug-induced reduction in fat absorption by decreasing their dietary fat intake and increasing their protein and carbohydrate intake in a dose-related manner. Total caloric intake also increased, but body weight gain was inhibited compared with the nondrug control group. When Ols was removed from the diet, nutrient selection, caloric intake, and body weight returned to control levels. In additional short-term experiments (30 min/day), rats developed a preference for a plain fat diet over an Ols-fat diet (4 mg/g fat) and also for a cue flavor paired with plain fat over a flavor paired with Ols-fat. Yet, when not given the choice, the rats consumed nearly as much Ols-fat as plain fat diet. These results indicate that, by reducing fat absorption, Ols reduced the attractiveness of dietary fat, although it did not make the fat diet aversive. In clinical use, lipase inhibitors may be effective in reducing dietary fat intake by reducing both the consumption and absorption of fat.

Animals↗
PubMed1995

Carbohydrate, fat, and protein condition similar flavor preferences in rats using an oral-delay procedure.

Flavor preferences conditioned by carbohydrate (Polycose), protein (casein hydrolysate), and fat (corn oil) were compared using an oral-delay training method. In Experiment 1 separate groups of food deprived rats were trained to associate a CS+ flavor (e.g., grape-saccharin) with the delayed (10 min) presentation of isocaloric carbohydrate, protein, or fat sources. A CS- flavor (e.g., cherry-saccharin) was paired with the delayed presentation of an unflavored saccharin solution. In subsequent two-bottle tests the carbohydrate, protein, and fat trained groups displayed significant preferences for the CS+ over the CS-. In Experiment 2 each rat was trained to associate two new flavors with two of the three nutrients (e.g., orange with carbohydrate, and strawberry with protein). In subsequent two-bottle tests the rats equally preferred the two nutrient-paired flavors. Experiment 3 compared the preferences for the new CS+ flavors vs. the original CS-flavor. The rats displayed similar preferences for carbohydrate-, protein- and fat-paired CS+ over the CS-. The similar preferences obtained with the three different nutrients support the view that preference conditioning is mediated by the nutrients' caloric value. Other studies suggest, however, that nutrient-specific signals are also involved in the conditioning process.

Animals↗
PubMed1995

Carbohydrate-conditioned odor preferences in rats.

The effectiveness of odor cues to support nutrient-conditioned flavor preferences in rats was studied. When the rats drank fluid, the CS+ odor was paired with intragastric (IG) infusions of Polycose, and the CS- odor with IG water. In Experiment 1, rats trained with almond and anise odors presented with plain drinking water failed to acquire a CS+ odor preference. In contrast, rats in Experiment 2 formed a strong aversion to anise (or almond) paired with lithium chloride, which indicated that the odors were distinguishable to the rats. Experiment 3 showed that providing unique tastes (bitter or sour) in combination with the odors during training potentiated odor conditioning. The rats displayed a strong preference for the odor+taste CS+ and for the odor component alone. Experiment 4 showed that with another pair of odor (peppermint and vanilla), CS+ preferences could be conditioned in the absence of taste cues during training. These results demonstrate that rats can acquire strong nutrient-conditioned odor preferences.

Animals↗
PubMed1994

Flavor preferences conditioned by intragastric infusions of dilute polycose solutions.

Prior studies have obtained strong conditioned preferences (> 90%) for flavors paired with intragastric (IG) infusions of Polycose (hydrolyzed starch) over different flavors paired with IG water infusions. These experiments used concentrated Polycose solutions (16-32%; 0.6-1.2 kcal/ml) that contributed 50% or more of the animals' daily caloric intake. The present experiment sought to determine if calorically dilute solutions would also support preference conditioning. Adult female rats with gastric cannulas were trained with a cue solution (the CS+) paired with Polycose infusions. On alternate days a different cue solution (the CS-) was paired with IG water infusions. The CSs were unsweetened or saccharin-sweetened citric acid and sucrose octaacetate solutions that were available 22 h/day; chow was freely available. Separate groups were infused with Polycose at concentrations of 0.5%, 1%, 2%, and 4% (0.019-0.152 kcal/ml). The three higher concentrations conditioned flavor preferences of up to 89%. The infused Polycose represented only 1-14% of the animals' daily caloric intake and did not reliably reduce chow consumption. These findings demonstrate the sensitivity of the viscerosensory feedback system mediating flavor conditioning.

Animals↗
PubMed1994

Eating rates in normal and hypothalamic hyperphagic rats.

Two experiments were conducted to determine if hypothalamic hyperphagic rats eat at a faster than normal rate and if slowing the rate of eating would reduce their overeating. Experiment 1 used a 45 mg pellet eatometer to measure 24-h meal patterns and eating rates in control rats and rats made hyperphagic with medial hypothalamic (MH) knife cuts. The MH hyperphagic rats consumed larger and more frequent meals but ate at a slower rate than did control animals during both the dynamic and static phases of the syndrome. In Experiment 2, rats were given 30-min test meals with the same pellets presented in food cups (rather than one pellet at a time as with the eatometer). The MH rats consumed the pellets at the same rate as the controls, although their meals were twice as large. Experiment 1 also determined if slowing the rate of eating would reduce MH hyperphagia; eating rates were constrained by increasing the delay between successive pellet deliveries (normally < 1 s). An interpellet delay of 20 s reduced meal size and increased meal length and frequency but did not reliably reduce 24-h food intake in normal rats and dynamic or static phase MH rats. Interpellet delays of 40 or 60 s reduced daily food intake of static phase MH rats but only to control levels. These results indicate that MH hyperphagia is not associated with elevated feeding rates and is relatively unaffected by constraints on the rat's rate of eating.

Animals↗
PubMed1994

Learned preferences for real-fed and sham-fed polycose in rats: interaction of taste, postingestive reinforcement, and satiety.

Nutrient-conditioned flavor preferences have been obtained with a variety of procedures, but one study indicates that rats do not readily learn to prefer the flavor of real-fed food to the flavor of sham-fed food. This issue was reexamined in food-deprived rats trained to real feed (gastric fistula closed) and sham feed (gastric fistula open) different flavored Polycose solutions (cherry or grape). Sham-feeding intakes in the one-bottle training sessions (30 min) were limited to the amount consumed in real-feeding sessions; intakes were not limited during two-bottle preference tests (10 min). In Experiment 1, when tested with 32% Polycose solutions, the animals tended to prefer the sham-fed Polycose to the real-fed Polycose. When subsequently trained and tested with 8% Polycose solutions, the same animals displayed a strong preference (approximately 90%) for the real-fed Polycose. These findings were confirmed in Experiment 2 using separate groups. Rats trained with 8% Polycose readily learned to prefer the real-fed solution, and rats trained with 32% Polycose initially preferred the sham-fed Polycose solution. With additional training the 32% Polycose group developed a preference for the real-fed solution. In experiment 3, rats trained to real feed flavored 8% and 32% Polycose solutions developed strong preferences for the 32% solution. This finding suggests that the tendency to prefer sham-fed to real-fed 32% Polycose is not due to aversive postingestive effects of the real-fed solution. Taken together, the results indicate that Polycose has a postingestive positive reinforcing effect that can be revealed using the sham-feeding preparation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Glucose- and fructose-conditioned flavor preferences in rats: taste versus postingestive conditioning.

Flavor preferences conditioned by glucose and fructose were compared using two training methods. With the simultaneous method preferences can be reinforced by the flavor and/or the postingestive consequences of nutrients, whereas with the delayed method preferences are reinforced only by postingestive nutritive effects. In Experiment 1, food-deprived rats displayed similar preferences for flavors (CS+) added to an 8% glucose or 8% fructose solution over flavors (CS-) added to a noncaloric saccharin solution (simultaneous conditioning). Other rats learned to prefer a CS+ flavor paired with the delayed (10 min) presentation of 8% glucose over a CS- flavor paired with delayed saccharin. Fructose failed to condition a flavor preference with the delayed paradigm. Taken together, these data suggest that the preference for a flavor mixed in a fructose solution is reinforced by the sweet taste, not the postingestive effects of the sugar. Experiment 2 tested this idea by devaluing the taste of the sugar solutions by quinine adulteration. Rats initially avoided both glucose-quinine and fructose-quinine solutions in favor of a saccharin solution. Following one-bottle training, they came to prefer the glucose-quinine but not the fructose-quinine solution over the saccharin solution. The glucose-trained rats also showed stronger preferences for sucrose-quinine solutions than did the fructose-trained rats. These findings, along with other recent data, indicate that fructose-conditioned preferences are based primarily on the sugar's palatable taste. Glucose, in contrast, can condition strong preferences based on its taste as well as its postingestive actions.

Animals↗
PubMed1994

Nutrient-conditioned flavor preference and acceptance in rats: effects of deprivation state and nonreinforcement.

Rats acquire strong preferences for flavors paired with intragastric (IG) Polycose infusions. The present study investigated the ingestive responses to these flavors when they were no longer reinforced. All rats were first trained to associate a CS+ flavor with IG 32% Polycose and a CS- flavor with IG water during 23 h/day sessions. Experiment 1 examined the effects of deprivation on short-term (4 h/day) CS intakes under nonreinforcement conditions. Food deprivation selectively enhanced CS+ intake whereas water deprivation increased both CS+ and CS- intakes. The results also suggested that extinction training differentially affects CS+ preference and acceptance as measured by relative and absolute intakes. This was confirmed in a second experiment. The rats' absolute intake of the CS+ solution during 4 h/day sessions significantly decreased when it was no longer paired with IG Polycose infusions; yet the rats continued to show a strong preference for the CS+ over the CS- in both 4 h and 23 h/day tests. Experiment 3 examined the effects of extensive long-term extinction training on the CS+ preference. When the alternative was plain water, the CS+ preference extinguished over 12 days. Yet the same rats continued to prefer the CS+ to the CS- during 12 additional extinction days and during 16 extinction days that followed a 1-month rest period. The CS+ preference relative to the CS- was blocked only when the CS+ was paired with food deprivation and the CS- was paired with food repletion. These experiments confirm earlier reports of the resistance of Polycose-conditioned flavor preferences to extinction but also show that flavor acceptance is more susceptible to extinction. Flavor acceptance was not completely extinguished, however, and remained responsive to deprivation state.

Animals↗
PubMed1994

The VMH-dietary obese rat: a new model of non-insulin-dependent diabetes mellitus.

A model of non-insulin-dependent diabetes mellitus (NIDDM) has been developed in adult rats by combining bilateral electrolytic lesions of the ventromedial hypothalamus (VMH) and high fat-high sucrose diets. VMH-dietary obese rats showed fasting hyperinsulinemia (> or = 540 pM) and hypertriglyceridemia (> or = 180 mg/dl) generally within 3 wk on the protocol. Fasting hyperglycemia (> or = 10 mM) was observed in the majority of animals in seven consecutive experiments. Hyperglycemic animals showed impaired glucose tolerance despite high prevailing insulin levels. Pancreatic islets isolated from VMH-dietary obese rats showed a loss of insulin secretory response to glucose by week 5, before the onset of hyperglycemia. Islets from hyperglycemic rats no longer responded to an increase in glucose concentration and failed to suppress insulin release normally in response to 15 nM norepinephrine or to a decrease in glucose concentration. This model mimics the major characteristics of obesity-associated human NIDDM as well as several stages of its progression, rendering it useful for studying the etiology of the metabolic and secretory defects in the syndrome.

Animals↗
PubMed1993

Feeding response of rats to no-fat and high-fat cakes.

The nutritional effects of high-fat diets have been extensively studied in laboratory animals, but as yet few experiments have examined the feeding response of animals to newly developed fat substitutes. The present study used commercially available no-fat (0% fat, 92% carbohydrate) and high-fat (41% fat, 54% carbohydrate) cake to determine the effects of fat substitutes on food preference and caloric intake in rats. The first experiment showed that nondeprived rats found the high-fat and no-fat cakes equally palatable and highly preferred to lab chow. Food deprived rats, however, preferred the high-fat cake to the no-fat cake, which may be related to its higher caloric density. In the second experiment, rats fed high-fat cake, in addition to chow, for 30 days consumed more calories and gained more weight than did rats fed no-fat cake and chow. The no-fat cake group, however, overate and gained more weight than chow-only controls. The hyperphagic response to the no-fat cake can be attributed to its carbohydrate content, moisture, and high palatability. Thus, removing fat from the cake reduced, but did not eliminate, its obesity-promoting effect. Obviously, low-fat foods must be consumed in moderation if used for weight control.

Animal Feed↗
PubMed1993

The rat's preference for sucrose, polycose and their mixtures.

In one-bottle tests (30 min/day) food-deprived rats consumed significantly more 2% Polycose than 2% sucrose, and yet in two-bottle choice tests they did not consistently prefer Polycose to sucrose. A previously proposed explanation for this effect is that rats habituate, or develop oral satiety, to the flavor of sucrose more rapidly than to Polycose, and sucrose satiety generalizes to Polycose. This idea was not supported by the results of sequential 15-min one-bottle tests: the intake of 2% sucrose did not suppress subsequent Polycose intake. Instead, the failure of rats to consistently prefer Polycose to sucrose was attributed to the development of a drinking pattern that allowed the rats to mix the two solutions in their mouths. When the drinking spouts were nearby, the rats consumed similar amounts of sucrose and Polycose, but when the spouts were far apart, they consumed more Polycose than sucrose. That rats prefer the combined flavor of sucrose and Polycose to either flavor alone was confirmed in subsequent tests. Rats strongly preferred a 1% sucrose + 1% Polycose mixture to a plain 2% sucrose or 2% Polycose solution. They also preferred sucrose-Polycose mixtures to plain solutions at concentrations ranging up to 32%. The potency of the sucrose-Polycose mixture is presumably related to the activation of separate "sweet" and "polysaccharide" taste channels in the rat.

Animals↗
PubMed1993

Flavor preference produced by intragastric polycose infusions in rats using a concurrent conditioning procedure.

Prior studies demonstrate that nondeprived rats learn to prefer a flavor (the CS+) paired with intragastric (IG) nutrient infusions over another flavor (the CS-) paired with IG water infusions when the flavors are presented on alternate days. The present experiment determined if a nutrient-based preference could be established when both flavors were concurrently available. Adult female rats were fitted with two chronic gastric catheters and were given ad lib access to chow and two flavored solutions (a bitter sucrose octaacetate solution and a sour citric acid solution). Using an automated infusion system, consumption of the CS+ flavor was paired with IG infusions of 32% Polycose, and consumption of the CS- flavor was paired with IG infusions of water. Seven of the eight rats tested developed a strong flavor preference for the CS+ over the CS-; their CS+ preference increased from 53% on day 1 to 95% on day 8. (The remaining animal eventually displayed a 97% CS+ preference after it received one-bottle training with the CS flavors.) During the first several days of training, the rats tended to drink primarily one flavor per day, and consumed primarily one flavor per drinking bout. This provided them with relatively discrete flavor-consequence experiences that presumably facilitated flavor preference conditioning.

Animals↗
PubMed1993

Deprivation alters rats' flavor preferences for carbohydrates and fats.

The effects of food deprivation on rats' preferences for the flavors of different macronutrients were investigated. To minimize postingestive influences on flavor preferences, brief test sessions (30 min) and calorically dilute (0.08 kcal/g) solutions or suspensions were used. The findings revealed that whereas nondeprived rats preferred sucrose (2%) to hyrolyzed starch (2% Polycose), food-deprived rats strongly preferred Polycose to sucrose. Deprived rats also acquired a preference for a cue flavor paired with Polycose, while nondeprived rats preferred a sucrose-paired cue flavor. Food deprivation also caused rats to switch their preferences from sucrose to corn starch, and from sucrose to corn oil. Food deprivation did not, however, alter the rats' preference for Polycose over corn starch, and it blocked, but did not reverse, their preference for Polycose over corn oil. Taken together, the findings indicate that food deprivation enhances the preference for palatable nonsweet nutrients (Polycose, corn starch, corn oil) over a sweet nutrient (sucrose). This effect was specific to food deprivation; water deprivation did not reverse the rats' preference for sucrose to Polycose.

Animals↗
PubMed1993

Intragastric glucose but not fructose conditions robust flavor preferences in rats.

Prior work indicates that glucose and fructose differ in their postingestive reinforcing effects. The present study investigated this phenomenon by training rats to associate the intake of flavored water with intragastric (IG) infusions of 16% sugar solutions. In experiment 1, rats had one flavor [conditional stimulus (CS)] paired with IG sugar infusions (CS+; e.g., cherry) and another flavor paired with IG water (CS-; e.g., grape) 23 h/day; Chow was available ad libitum. In subsequent choice tests, rats infused with glucose displayed a strong preference (89%) for the CS+ flavor, whereas rats infused with fructose showed only a small and nonreliable CS+ flavor preference (62%). When next trained to associate one flavor (e.g., orange) with IG glucose and another flavor (e.g., strawberry) with IG fructose, rats in both groups developed a significant preference (81%) for the glucose-paired flavor. In experiment 2, food-deprived rats were trained 2 h/day to associate a CS+ flavor with IG sugar and a CS- flavor with IG water infusions. The glucose-reinforced rats displayed a near-total preference (95%) for the CS+ flavor, whereas fructose-reinforced rats showed a much smaller CS+ preference (67%). The preference findings indicate that the postingestive consequences of glucose are much more reinforcing than those of fructose. It appears that food conditioning is mediated by chemospecific actions of nutrients rather than their general satiating or energy repleting effects.

Animals↗
PubMed1991

Polysaccharides as taste stimuli: their effect in the nucleus tractus solitarius of the rat.

Rats show a pronounced preference for the tastes of starch-derived polysaccharides. Three of these compounds--Polycose, maltotriose and amylopectin--were used along with a standard array of chemicals in a study of their effectiveness as taste stimuli, as monitored by evoked single unit activity in the nucleus tractus solitarii (NTS). Maltotriose and amylopectin elicited very few spikes and no clear quality-related pattern of neural activity. Polycose, however, was an effective taste stimulus. It evoked an activity profile across neurons and over time that was poorly correlated with that of the prototypical sugar (sucrose) and only moderately related to those of the non-sugar prototypes (NaCl, HCl and quinine-HCl). The 14 cells (23%) that responded particularly well to Polycose were all members of neuronal subgroups that emphasized salt, acid and quinine sensitivity. Thus, despite the strong behavioral preference shown to Polycose, its neural profile is unlike those of other preferred stimuli. Polycose may represent a unique taste stimulus whose quality cannot be readily associated with those of the traditional 4 basic tastes.

Amylopectin↗