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Biomedical subjects

A Sclafani

Publications and source records attributed to A Sclafani.

At least 37 records · Page 2Linked to original sources
PubMed1999

Palatability and foraging cost interact to control caloric intake.

The combined effects of meal cost and food flavor on meal size were studied with a method that avoided the covariation of nutrient composition and caloric density with palatability. As rats (Rattus norvegicus) drank flavored fluids (unpalatable 0.05% sucrose octaacetate [SOA], neutral 0.05% saccharin, and palatable 2% Polycose + 0.2% saccharin [P + S]), liquid diet was infused intragastrically. Relative to saccharin, rats with free access ate 10% more calories in larger meals while consuming P + S and initially ate fewer calories in smaller but more frequent meals while drinking SOA. Other rats lever-pressed to begin meals, which halved meal number and doubled meal size relative to the free-access group. Although foraging rats also ate larger P + S meals and smaller SOA meals, the changes did not affect total intake. Without the usual differential postingestive effects of foods that differ in palatability, making food more costly blunts rats' response to its flavor.

Animals↗
PubMed1998

Increased flavor acceptance and preference conditioned by the postingestive actions of glucose.

In Experiment 1, rats were given daily 2-h access to chow and water and 20-h access to flavored solutions (cherry or grape). On alternate days, one flavor (CS+) was paired with intragastric infusions of 16% glucose and another flavor (CS-) with IG water. In subsequent choice tests, the rats strongly preferred (95%) the CS+ to the CS-. CS+ intake also greatly exceeded CS- intake during one-bottle training sessions (71 vs. 18 g/20 h). This increased acceptance was due to both increased bout size and number. When CS+ was paired with IG water (extinction test), CS+ bout size declined to CS- levels, while CS+ bout number and total intake remained elevated. In Experiment 2, rats trained with sucrose octa acetate and citric acid solutions also showed increased CS+ acceptance and preference in one- and two-bottle tests, respectively. The rats also consumed more CS+ than CS- during short-term (30 min/day) one-bottle tests and intraoral intake tests under both deprived and ad lib. feeding conditions. These results demonstrate that the postingestive actions of glucose can condition substantial increases in flavor acceptance as well as flavor preference.

Animals↗
PubMed1998

Flavor preferences conditioned by intragastric sugar infusions in rats: maltose is more reinforcing than sucrose.

Prior research indicates that glucose conditions much stronger flavor preferences in rats than does fructose. This could occur because intestinal absorption of fructose is much slower than that of glucose and because fructose malabsorption may have aversive consequences. Fructose absorption is facilitated when glucose is also present in the gut. The present study therefore compared the flavor conditioning effects of maltose (a glucose + glucose disaccharide) to those of sucrose (a glucose + fructose disaccharide). In Experiment 1, rats had different flavors paired with intragastric infusions of 32% maltose (CS+M), 32% sucrose (CS+S), and water (CS-) 23 h/day. In subsequent two-bottle tests, both CS+ solutions were strongly preferred to the CS-, but the CS+M was also preferred (78%) to the CS+S. Experiment 2A revealed that the rats also learned to prefer a CS+M to a CS+S when 16% sugar infusions were used. In Experiment 2B, the same rats preferred a flavor paired with 16% maltose to a flavor paired with 8% maltose. They did not reliably prefer a flavor paired with 16% sucrose to a flavor paired with 8% maltose. These results demonstrate that the postingestive actions of maltose are more reinforcing than those of sucrose. This indicates that fructose is less reinforcing than glucose even when malabsorption is not a factor. In contrast to their preference for the CS+M over the CS+S, the rats preferred sucrose to maltose when drinking the sugars by mouth. Therefore, sugar preferences mediated by oral taste receptors differ from those conditioned by postoral nutrient detectors.

Animals↗
PubMed1998

The rat's acceptance and preference for sucrose, maltodextrin, and saccharin solutions and mixtures.

Prior work indicates that rats prefer a mixture of sucrose and maltodextrin to either carbohydrate alone. The present experiment examined whether a sucrose + maltodextrin (S + M) mixture also increases total fluid intake as does saccharin + carbohydrate mixtures. In 23 h/day, one-bottle tests male rats consumed more of a 1% sucrose + 1% maltodextrin mixture than they did of either 2% sucrose or 2% maltodextrin. Adding 0.2% saccharin to the S + M mixture further stimulated consumption. The rats overconsumed the mixture solutions primarily by increasing bout size. In two-bottle choice tests the rats strongly preferred the S + M mixture to the 2% sucrose and 2% maltodextrin solutions and showed a nonreliable preference for the S + M + saccharin mixture to the S + M mixture. The palatability of the S + M mixture is thought to be related to the activation of separate "sweet" and "maltodextrin" tastes.

Animals↗
PubMed1998

Devazepide, a CCK(A) antagonist, attenuates the satiating but not the preference conditioning effects of intestinal carbohydrate infusions in rats.

Endogenous cholecystokinin (CCK) is thought to participate in the satiating action of foods, and some data suggest that it may also mediate their postingestive reinforcing effects. This was investigated by determining if the CCK(A) receptor antagonist, devazepide, attenuates flavor preference conditioning by intraduodenal (I.D.) carbohydrate infusions. In Experiment 1, food-restricted female rats were trained 30 min/day to associate a cue flavor (CS+) with I.D. infusions of 8% Polycose and a different flavor (CS ) with I.D. water infusions. Half of the rats (DEV group) were pretreated with devazepide (300 microg/kg body weight) and the other half (CON group) with vehicle, 30 min prior to CS training sessions and choice tests. Both groups displayed similar CS+ preferences (CON: 68%; DEV: 69%). In contrast, devazepide blocked the feeding inhibitory effects of I.D. Polycose infusion and cholecystokinin octapeptide injection in Experiment 2. A higher dose of devazepide (1200 microg/kg) also failed to inhibit preference conditioning by I.D. Polycose in Experiment 3. These results indicate that, although CCK(A) mechanisms play a role in the satiating effect of I.D. carbohydrates, they do not mediate their reinforcing effect. The present study, along with other recent reports, indicate that different mechanisms mediate the satiating and reinforcing actions of nutrients.

Animals↗
PubMed1998

High-fat diet preference and overeating mediated by postingestive factors in rats.

The role of postingestive factors in the preference for and overconsumption of high-fat (HF) foods, relative to high-carbohydrate (HC) foods, was investigated using a self-regulated intragastric feeding procedure. On one-bottle training days, rats drank one flavored saccharin solution [conditioned stimulus (CS) + HF] paired with intragastric infusions of an HF liquid diet, a second flavored solution (CS+HC) paired with an HC liquid diet, and a third flavored solution (CS-) paired with intragastric water. The diets had the same energy and protein content; the CS solutions and infusions along with chow were available ad libitum. The rats drank more CS and self-infused more diet on HF than HC training days. In two-bottle choice tests, the rats preferred the CS+HF to the CS+HC and both CS+HF and CS+HC to the CS-. The rats consumed more CS+HF than CS+HC by taking more bouts per day; bout sizes did not reliably differ. In a subsequent experiment, rats preferred the CS+HF even though diet intakes in training were matched. In a final experiment, the CS+HC and CS+HF intakes were equated in training by diluting the HC diet. Now the rats did not reliably prefer the CS+HF to the CS+HC, yet caloric intakes were much higher on CS+HF than CS+HC training days. Thus, relative to an isocaloric HC diet, the postingestive effects of HF diets stimulate overeating and condition a stronger flavor preference. Reduced satiety rather than increased reinforcement may be the direct promoter of overeating. However, postingestive reinforcement may enhance the selection of HF foods when a choice of HF and HC foods is available.

Animals↗
PubMed1997

Flavor preferences conditioned by intragastric polycose in rats: more concentrated polycose is not always more reinforcing.

Prior studies have obtained conditioned preferences for flavors paired with intragastric (IG) infusions of Polycose (hydrolyzed starch) at concentrations of 1-32% over a different flavor paired with IG water. The present study determined if rats would also learn to prefer a flavor paired with concentrated Polycose infusion over a flavor paired with a more dilute Polycose infusion. In Experiment 1, adult female rats were food-deprived and trained during alternating one-bottle sessions (30 min/day) to associate one flavored solution (the CS + 8) with IG infusions of 8% Polycose, a second flavored solution (the CS + 16) with IG infusions of 16% Polycose, and a third flavored solution (the CS-) with IG water infusions. In subsequent choice tests, the rats displayed similar preferences for the CS + 8 and CS + 16 over the CS-, but preferred the CS + 16 to CS + 8 in a direct choice test. A similar preference pattern was obtained in 22 h/day tests with the rats nondeprived. In Experiment 2, new rats were similarly trained and tested but with CS + 16 and CS + 32 solutions paired with 16% and 32% Polycose infusions, respectively. The rats preferred both CS+ solutions over the CS- solution in the short- and long-term tests. However, the CS + 16 was preferred over the CS + 32 by the food-deprived rats in the short-term tests. The two CS+ solutions were equally preferred in the long-term tests with food ad lib. These and other findings indicate that the postingestive reinforcing action of Polycose increases as concentration increases from 1% to 16% but does not increase further, and may actually decrease, at a 32% concentration. The rapid satiating effect of concentrated carbohydrate solutions may limit their reinforcing consequences.

Administration, Oral↗
PubMed1997

Diabetic rats prefer glucose-paired flavors over fructose-paired flavors.

Prior studies indicate that glucose has a more potent postingestive reinforcing effect than fructose. The role of insulin in this effect was examined by comparing sugar-conditioned flavor preferences in normal and streptozotocin-diabetic rats. In Experiment 1, diabetic rats, like normal rats, preferred a cue flavor that had been mixed into 8% glucose solution over a flavor mixed with 8% fructose. Both taste and postingestive properties of glucose may have contributed to this preference. Experiment 2 evaluated postingestive reinforcement by pairing cue flavors with intragastric infusions of glucose and fructose. Both diabetics and normals acquired a preference for the flavor paired with intragastric 16% glucose infusions over the flavor paired with 16% fructose infusions although the preference was somewhat smaller in the diabetic rats. Taken together, the results indicate that a normal insulin secretory response to glucose is not required for glucose-conditioned flavor preference. The diabetic rats' reduced flavor preference in Experiment 2 suggests that insulin may play some role in glucose conditioning although this may be secondary to alterations in gastrointestinal motility characteristic of diabetic animals.

Animals↗
PubMed1997

Learned controls of ingestive behaviour.

During the 25 year history of the Columbia Appetitive Seminar there have been many notable developments in ingestive behavior research. One area of rapid progress concerns learned controls of feeding behavior. During the 1960's and 1970's most research related to food learning focused on conditioned flavor aversions. While it was assumed that animals also learned to prefer foods based on their positive nutritive consequences, there were few experimental demonstrations of this effect. Examples often cited involved animals learning to prefer a flavor associated with recovery from illness or a vitamin deficiency. There were isolated reports in the 1960's of nutrient infusions increasing flavor preference and acceptance, but it wasn't until the 1970's that nutrient-based learning was firmly established, and not until the 1980's and 1990's investigated in detail. This brief review highlights some of the major findings of nutrient-based learning. Other important aspects of food learning (social, cultural, ecological, environmental) are not discussed here.

Eating↗
PubMed1997

Cypha [propionic acid, 2-(4-methoxyphenol) salt] inhibits sweet taste in humans, but not in rats.

Cypha, propionic acid, 2-(4-methoxyphenol) salt, is a commercially available sweet taste inhibitor used in food products. The present study examined whether or not Cypha blocked the sweet taste response of rats. This was accomplished by measuring the consummatory response of rats to sucrose solutions during short-term taste tests. Nondeprived female rats were given 2-bottle choice tests (10 min) with different sucrose solutions. When given the choice between 10% sucrose and 10% sucrose containing Cypha at concentrations of 0.0125% to 0.10%, the rats showed no reliable preference for one or the other solution. In other tests, they reliably preferred 10% sucrose to 8%, 6%, and 4% sucrose, demonstrating the sensitivity of the behavioral test. To confirm the activity of the Cypha sample, a second experiment was conducted with human subjects. Using a visual analogue scale, the subjects rated the sweetness of various sucrose solutions (0% to 10%) and 10% sucrose solutions containing Cypha at concentrations of 0.0125% or 0.025%. Cypha reliably reduced the sweetness ratings of the sucrose solution. The 10% sucrose + 0.0125% Cypha solution was judged isosweet to 2.3-2.9% sucrose, and the 10% sucrose + 0.025% Cypha solution was rated as isosweet to a 1.2% sucrose solution. Taken together, these data confirm prior reports on the sweetness-inhibitory effect of Cypha in humans and demonstrate its ineffectiveness in rats. These findings are consistent with other reported differences between rats and humans in their response to other sweetness inhibitors, as well as to artificial sweeteners.

Adolescent↗
PubMed1997

The role of gastric and postgastric sites in glucose-conditioned flavor preferences in rats.

Two experiments examined the role of gastric and postgastric contributions in the development of flavor preferences in rats. During training trials, food-deprived rats consumed, on alternate days, a cue flavor paired with glucose infusions and another flavor paired with water infusions. Preferences were assessed in choice tests between the two cue flavors without infusions. The first experiment compared preferences conditioned to a flavor paired with intraduodenal (ID) glucose infusions to those paired with intragastric (IG) infusions. ID glucose-conditioned preferences were as strong as that of IG glucose. The second experiment examined whether the actions of glucose in the stomach alone were sufficient to condition flavor preferences. Glucose infusions were restricted to the stomach with an inflated pyloric cuff and then removed at the end of 30-min training sessions before the cuff was deflated. Rats trained with this procedure did not develop a reliable flavor preference. Flavor preferences were obtained, however, when the cuff was inflated for 30 min after the end of the daily training sessions, or when the cuff was inflated during the training sessions but then deflated without removing the infused glucose. Both of these procedures allowed at least some of the infused glucose to empty into the intestine. Taken together, the results indicate that information from the stomach is neither necessary nor sufficient to produce glucose-conditioned flavor preferences. Such preferences are reinforced by the intestinal and/or postabsorptive actions of glucose.

Animals↗
PubMed1997

Preference conditioning alters taste responses in the nucleus of the solitary tract of the rat.

Aversive conditioning has an impact on the neural signal for the gustatory conditioned stimulus (CS). Here, we determined whether the code is also affected by preference conditioning. We paired the taste of MgCl2 (CS+) with intragastric nutrients in some rats (MG), and citric acid (CS+) with nutrients in others (CI). A control group (Control) experienced both tastants without nutrients. Preferences (>90%) developed for each CS+. We recorded responses to 16 taste stimuli in the nucleus of the solitary tract. Responsiveness of acid-oriented neurons to MgCl2 in MG rats was lower than in Controls, and its profile was more distinct from those of acidic and bitter stimuli. Total activity to citric acid was unchanged in CI rats. However, its temporal profile showed a decreased phasic component, making citric acid temporally distinct from nonsugars. Therefore, the responses to both CS+ were modified, each in its own manner, to be more distinct from those of aversive stimuli. The effects of preference conditioning, however, were weaker than those of aversive conditioning.

Animals↗
PubMed1996

Carbohydrate- and protein-conditioned flavor preferences: effects of nutrient preloads.

Food-deprived rats were trained to associate one flavor (CSProt) with intragastric (IG) infusions of protein (PROT; 10% calcium caseinate), a second flavor (CSCHO) with IG infusions of carbohydrate (CHO; 10% protein), and a third flavor (CS-) with IG water infusions during 30 min/day training sessions. (The CS flavors were cherry, grape, and orange saccharin solutions.) In subsequent two-bottle tests the rats reliably preferred both the CSProt 2nd CSCHO to the CS- and equally preferred the CSProt and CSCHO. The preference for the two nutrient-paired flavors was not altered by IG preloads of PROT or CHO delivered as three loads 120, 40, and 5 min prior to testing. However, single oral + gastric preloads of CSCHO + IG CHO and CSProt + IG PROT 45 min prior to test selectively increased the preference for the CSProt and CSCHO, respectively. In subsequent gastric-only and oral-only tests single IG preloads of PROT and CHO, but not CSProt and CSCHO preloads, selectively altered the rats' preference for CSCHO vs. CSProt. In a second experiment with new rats, oral + gastric preloads again selectively altered the preference for the CSCHO vs. CSProt, but gastric-only preloads failed to have this effect. These results demonstrate that rats can learn to associate different flavors with the postingestive effects of different nutrients, and modify their flavor preferences after nutrient preloads. Oral + gastric preloads were most effective in altering flavor preferences, whereas gastric-only preloads had inconsistent effects and oral-only preloads were ineffective.

Animals↗
PubMed1996

The composition of the maintenance diet alters flavor-preference conditioning by intragastric fat infusions in rats.

Prior studies indicate that intragastric (IG) fat infusions condition only weak flavor preferences in chow-fed rats using brief daily training sessions. The present study attempted to facilitate fat conditioning by feeding rats a high-fat maintenance diet or by adding an oily flavor to the conditioning stimuli. In Experiment 1, rats were fed restricted rations of either a chow-corn oil mixture (48% energy as fat, HF group) or regular chow (12% fat, LF group). During 1-bottle training sessions, drinking a flavored (CS+, e.g., cherry) saccharin solution was paired with IG fat (7.1% corn oil emulsion). On other days, an alternate flavor (CS-, e.g., grape) was paired with IG water. In subsequent 2-bottle tests between the CS+ and CS- flavors, the HF rats displayed a stronger CS+ preference than the LF rats (90% vs. 62%). Experiment 2 tested the effect of a semisynthetic HF maintenance diet (48% fat energy), using a conditioning procedure similar to that of Experiment 1. The rats displayed only a moderate (72%) CS+ preference. When switched to the chow-oil maintenance diet and retrained with new CS flavors, they developed a 90% CS+ preference. In Experiment 3, chow-fed rats were trained and tested with oily CSs (i.e., 2% corn oil was added to flavored saccharin solutions). They failed to show a preference for the CS+ paired with IG oil. Thus, increasing the level of fat in the maintenance diet can greatly enhance preference conditioning with IG fat, but the amplitude of the effect is influenced by the composition of the high-fat food. In contrast, adding a fatty flavor to the conditioning stimuli did not improve fat conditioning.

Animals↗
PubMed1996

Rats integrate meal cost and postoral changes in caloric density.

Rats can maintain energy intake in response to changes in the caloric density of food by compensatory shifts in the number and size of meals. This study challenged rats' regulation of intake in two ways: manipulating the caloric density covertly to remove orosensory cues and altering baseline meal patterns by increasing the cost of obtaining meals. Rats with gastric catheters were maintained on a complete liquid diet delivered by pumps to a drinking spout and to the stomach; within meals, a rat's licking at the spout controlled the timing and duration of the simultaneous isovolemic intragastric infusions. Prior to each meal, some of the rats were required to press a bar to activate the spout mechanism; when the meal cost was paid, a cue light signaled that licks would deliver food. The light remained on until the rat ceased licking for 10 consecutive min; to resume feeding, the rat had to pay the cost again. The standard diet pumped to the spout was prepared at 1 kcal/g; the intragastrically co-infused diet varied from 0 (water) to 2 kcal/g in 0.5-kcal/g increments. Each concentration was presented for at least 4 days. Separate groups of rats were studied at no cost, low cost (5 bar presses/meal), and high cost (80 bar presses/meal). As the infusate concentration increased, the rats ate fewer meals per day. Meal size by weight decreased as caloric density increased, with he largest meals taken when water was infused. Caloric meal size increased linearly with caloric density for all groups. Meal sizes in the low-cost group were similar to those of the no-cost group, but the latter took more meals per day and, therefore, consumed more total calories. High-cost meal patterns were parallel to those of the other groups, but with fewer, larger meals. All groups maintained a constant daily caloric intake across infusate concentrations. Meal patterns changed rapidly in response to these "covert" (untasted, isovolemic) changes in caloric density. Rats can, thus, integrate the cost of obtaining food and its postingestive benefits in the absence of mediating orosensory cues.

Animals↗
PubMed1996

Abdominal vagotomy does not block carbohydrate-conditioned flavor preferences in rats.

The effects of abdominal vagotomy on the flavor preferences conditioned by Polycose (a maltodextrin) were investigated in female rats. Using an oral-delay training method, a modest conditioned flavor preference (67%) was obtained in control rats but not in rats with subtotal abdominal vagotomy (hepatic branch intact). The rats were fed a chow diet, and gastric stasis in the vagotomized rats may have interfered with preference learning. To facilitate conditioning, the rats were switched to a liquid maintenance diet and trained with new flavors paired with intragastric (IG) infusions of Polycose and water. With this procedure, the vagotomized and control rats acquired strong preferences (83-88%) for the flavor paired with IG Polycose. In a second experiment, flavor preferences conditioned by IG Polycose were obtained in rats with total abdominal vagotomy although the preference was attenuated relative to control rats (79% vs. 97%). Gastric motor problems (dumping) may have been a factor because the vagotomized rats consumed much less flavored solution (and therefore received less IG Polycose) during training than did controls. These findings indicate that an intact vagus nerve is not necessary to obtain carbohydrate-conditioned preferences, although vagotomy may interfere with the conditioning in some experimental situations.

Animals↗
PubMed1996

Food deprivation increases the rat's preference for a fatty flavor over a sweet taste.

Previous research indicates that food deprivation increases the rat's preference for high-fat over low-fat foods. Since these foods differ in their flavors and post-ingestive effects, both factors may be implicated. The present study investigated preferences in food deprived and non-deprived rats using non-nutritive mineral oil emulsion (MO) and saccharin solution (SAC), which have a fatty flavor and sweet taste, respectively. The deprived rats consumed more MO than SAC in one- and two-bottle tests, while the non-deprived rats ingested as much SAC as MO in one-bottle tests and preferred SAC in two-bottle tests. Several aspects of the data suggest that the deprivation-related shift in preference between MO and SAC was determined by changes in long-term energy balance. A follow-up conditioning experiment discarded the possibility that the observed preference shift was related to differential reinforcing effects of the two substances. In conclusion, long-term food restriction increases the preference for an oily flavor over a sweet taste via a mechanism that does not involve nutritive feedback. It remains to be determined to what extent this alternation in flavor preference influences food selection when post-ingestive nutritive feedback can influence food choice.

Animals↗