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A Sclafani

Publications and source records attributed to A Sclafani.

At least 73 records · Page 4Linked to original sources
PubMed1991

Flavor preferences conditioned by sugars: rats learn to prefer glucose over fructose.

The reinforcing effects of glucose and fructose were compared using flavor preference conditioning paradigms. Female rats given access to flavored glucose and flavored fructose solutions developed preferences for the glucose- over the fructose-paired flavor, as well as for unflavored glucose over unflavored fructose. This effect was obtained with 8% and 32% solutions, and with nondeprived and deprived rats. In most cases, the glucose preference was not immediate but appeared only after the rats had one-bottle experience with the two sugars. Female rats also preferred a glucose-paired flavor over a flavor that was paired with a noncaloric saccharin solution. A similar but somewhat weaker preference was displayed for a fructose-paired flavor over a saccharin-paired flavor. Both male and female rats acquired preferences for flavored chow that was paired with the intake of a 32% glucose solution over flavored chow paired with 32% fructose intake. Together, these results indicate that glucose has more potent postingestive reinforcing effects than does fructose. This may explain why rats consume more glucose than fructose in one-bottle acceptance as well as two-bottle preference tests.

Animals↗
PubMed1991

Sucrose to polycose preference shifts in rats: the role of taste, osmolality and the fructose moiety.

Rats given continuous access to 32% sucrose and Polycose solutions initially preferred sucrose but over days reversed their preference and drank more Polycose than sucrose. The role of taste and postingestive factors in this preference shift were investigated in several experiments. A strong and persistent preference for saccharin-sweetened Polycose over unsweetened Polycose was eliminated by intervening experience with a sucrose vs. Polycose choice test, suggesting that the postingestive effects modify the attractiveness of sweet taste. Osmolality differences between sucrose and Polycose were ruled out as an important factor; increasing the osmolality of Polycose by addition of glucose did not prevent the sucrose to Polycose preference shift. Rather, the shift in preference appears to result from some postingestive consequence of the fructose moiety contained in sucrose. This is indicated by the findings that rats did not reliably prefer a fructose-Polycose mixture to a sucrose solution in long-term tests, but developed preferences for maltose over sucrose solutions, and for glucose + Polycose over fructose + Polycose mixtures. Also, a 32% glucose solution was strongly preferred to a 32% fructose solution. Other studies examined the parameters of the sucrose to Polycose preference shift. The Polycose preference was accomplished by increases in both Polycose meal size and frequency. It occurred only with relatively concentrated solutions (16 and 32%) and was incomplete when the carbohydrates were presented in powdered form. Preexposure to Polycose enhanced the preference shift, whereas preexposure to sucrose retarded the development of the preference, suggesting that the shift occurs because Polycose is more rewarding, rather than because sucrose is more aversive. Polycose preference was lost after several days without the solutions but redeveloped in subsequent sucrose vs. Polycose choice tests. Thus the preference shift appears to be due to taste-postingestive consequence conditioning but its expression is dependent upon the nutritional state of the animal.

Animals↗
PubMed1991

Cholecystokinin conditions flavor preferences in rats.

The present study investigated whether cholecystokinin (CCK), an intestinal hormone that is a putative satiety agent, can condition flavor preference in rats. In experiment 1 food-deprived rats were trained to consume two different-flavored saccharin solutions in separate one-bottle tests. One flavor (the CS+) was paired with intraperitoneal injections of CCK octapeptide (0.125-4 micrograms/kg); the other flavor was paired with intraperitoneal injections of saline. Flavor preferences were then assessed in subsequent two-bottle choice tests. The 0.125 and 0.25 micrograms/kg doses failed to suppress CS+ intake or produce flavor preferences. CCK at 0.5 micrograms/kg did not reliably suppress CS+ intake in the one-bottle tests but produced a reliable preference for the CS+ in the two-bottle tests; percent CS+ intakes ranged from 50 to 62% in the four preference tests. At 1 microgram/kg, CCK suppressed CS+ intake and produced a marginal preference for the CS+. The 2 micrograms/kg dose suppressed CS+ intake but failed to condition a CS+ preference. The 4 micrograms/kg dose of CCK produced a potent suppression of CS+ intake and a strong aversion to that flavor. The preference conditioning effect of CCK at 0.5 microgram/kg was replicated in a second experiment using flavored Polycose solutions. The finding that low doses of CCK condition flavor preferences in rats is compatible with the hypothesis that endogenous CCK can mediate satiety and further suggests a role for CCK in learned food preferences. The aversion conditioned by the highest dose of CCK does not detract from this interpretation, since food, if consumed in excess, can also have aversive consequences.

Animals↗
PubMed1990

Hyperphagia in rats produced by a mixture of fat and sugar.

The hyperphagic and weight-promoting effects of feeding rats a sugar-fat mixture were compared to those of presenting only one of the two nutrients. Experimental groups were fed sugar (sucrose), fat (corn oil), or a sugar-fat mixture as an option to chow; options were in the form of water solutions or emulsions. The control group was fed only chow. The sugar-fat group displayed a robust hyperphagia (greater than 36%), relative to the control group; the hyperphagic response was greater than that observed in the fat group but not in the sugar group. The sugar-fat group selected more calories from the option than the other two experimental groups. Body weight gains were also greater in the sugar-fat group than in the fat and sugar groups. Addition of saccharin to the fat emulsion increased fat and total intakes to levels close to those of the sugar-fat mixture. In a second experiment, the relative palatability of the plain and sweet fat emulsions was assessed with two-bottle preference tests. The sugar-fat mixture was preferred to the saccharin-fat mixture, which in turn was preferred to the plain-fat emulsion. These results suggest that the sweetness of the sugar-fat mixture contributed to the pronounced hyperphagia and obesity obtained with this diet option.

Animals↗
PubMed1990

Flavor preferences conditioned by intragastric polycose infusions: a detailed analysis using an electronic esophagus preparation.

The present series of experiments examined the rat's conditioned preference for flavors associated with intragastric (IG) Polycose infusions. Adult female rats were fitted with two chronic intragastric catheters and were trained to drink flavored water (CS+; e.g., cherry-water) paired with IG infusions of 32% Polycose. On alternate days a different flavor (CS-; grape-water) was paired with IG water infusions. The flavored water and chow were available 23 hr/day. In subsequent two-choice tests the rats displayed strong preferences for the CS+ flavor (up to 98%). The CS+ preference persisted for several weeks during extinction tests when both the CS+ and CS- were paired with IG water or with no infusions. The rats also preferred the CS+ to plain water which contrasts with the mild aversion naive rats display to the flavored water. The acquired preference for the CS+ flavor was not as strong, however, as the rats' innate preferences for the taste of saccharin or Polycose. Also, unlike their response to saccharin and Polycose, the rats' acceptance (absolute intake) of the CS+ flavor was not elevated. CS+ intake was increased, though, when saccharin was added to the flavored water. The rats reversed their flavor preference when the reinforcement contingencies were reversed. Also, in the absence of unique flavor cues, the rats learned to prefer, apparently based on somatosensory cues, the sipper tube that was paired with IG Polycose infusions. The effects of flavor and IG Polycose infusions on drinking patterns and caloric intake are also described.

Animals↗
PubMed1990

Developmental changes in sugar and starch taste preferences in young rats.

Recent studies indicate that neonatal and adult rats are attracted to the taste of sugar as well as to starch-derived polysaccharides (e.g., Polycose). The present study investigated whether the relative preference for sweet and starchy tastes changes during the postweaning to adulthood period in male and female rats. This was accomplished by giving growing rats 24-hr/day one-solution (sucrose or Polycose vs. water) and two-solution (sucrose vs. Polycose) preference tests over a 9-week period (from 28 to 98 days of age). Acceptance (absolute intake) of sucrose and Polycose was also evaluated by comparing solution intakes during one-solution tests with water baseline intakes. Dilute solutions were used to minimize postingestive caloric and/or colligative effects. When tested with 2% saccharide solutions, the rats strongly preferred sucrose to Polycose with the preference increasing in magnitude from weeks 1 to 9 of testing. Sucrose acceptance also increased, relative to that of Polycose, after the third test week. When tested with 0.06 molar solutions, the rats initially consumed more Polycose (week 1) but by the fifth test week their sucrose preference and acceptance exceeded that of Polycose. These results indicate that the preference for sweet taste, relative to that for starchy taste, increases with age. Contrary to previous findings, the sweet taste preference was somewhat stronger in the male rats than in the female rats.

Aging↗
PubMed1990

Fat appetite in rats: the response of infant and adult rats to nutritive and non-nutritive oil emulsions.

Fat appetite was studied in rats using corn oil and mineral oil emulsions. In Experiment 1 ingestive responses to intraoral infusions were measured in rat pups 6-15 days of age. By 12-15 days of age pups responded more to oil emulsions (10% and 30%) than they did to water or emulsifier solution. The corn and mineral oil emulsions were almost as effective as milk but less effective than sucrose (0.3M) in stimulating ingestion. Experiments 2 and 3 examined the acceptance and preference for oil emulsions in adult rats. The corn oil and mineral oil emulsions were equally acceptable to non-deprived rats, as measured by 3-min and 30-min one-bottle tests. Food deprivation increased the one-bottle intake of both emulsions. In two-bottle tests, rats displayed a slight corn oil preference when non-deprived, but developed a strong preference when food deprived. Taken together, the results suggest that rats have an unlearned attraction to the orosensory qualities of emulsified oils and they learn to prefer corn oil based on its postingestive nutritive effects.

Age Factors↗
PubMed1990

Fat appetite in rats: flavor preferences conditioned by nutritive and non-nutritive oil emulsions.

Two experiments examined the rat's preference for flavors associated with nutritive corn oil and non-nutritive mineral oil emulsions. In Experiment 1 food deprived rats developed a preference for a flavor mixed into a 7.1% corn oil emulsion over a flavor presented in water. A significant but weaker preference was obtained for a flavor mixed into a 7.1% mineral oil emulsion. In Experiment 2 the rats acquired a preference for a flavor that preceded the ingestion of the corn oil emulsion by 10 min. The mineral oil emulsion, however, failed to condition a flavor preference using this delay paradigm. The results suggest that both the orosensory properties (flavor) and postingestive nutritive effects of oil can reinforce flavor preferences. The appetite for dietary fats is, therefore, a combined response to the flavor and nutritive qualities of this class of nutrients.

Animals↗
PubMed1990

The conditioning of aversions to familiar and preferred flavours: a new aversion therapy model.

The present study examined the ability of rats to develop aversions to familiar flavours and to flavours that they had previously acquired a preference for. Rats were first conditioned to prefer a CS+ flavour over a CS- flavour by pairing CS+ intake with the consumption of a starch solution (16% Polycose). A second group was exposed to the same training but preference conditioning was prevented by inhibiting starch digestion with the drug acarbose. The rats were next given aversion training; the CS+ flavour was now paired with toxicosis (LiCl injection) while the CS- flavour paired with a control treatment (NaCl injection). The results of two-choice tests revealed that aversion training produced significant avoidance of the CS+ flavours in both the group that had acquired a preference for this flavour as well as in the no-preference group. The value of using conditioned flavour preferences as targets for aversions to model the aversion therapy approach to alcoholism is discussed.

Journal Article↗
PubMed1989

Flavor preferences conditioned by intragastric fat infusions in rats.

The present series of experiments determined if rats would learn to prefer cue flavors that were paired with intragastric (IG) infusions of fat. Adult female rats were fitted with gastric catheters and were trained to drink a flavored (CS+) solution, e.g., cherry-water, associated with IG infusions of a corn oil emulsion. On other days, an alternately flavored (CS-) solution, e.g., grape-water, was paired with IG infusions of water. The preference between the CS solutions was then assessed with 2-bottle choice tests. In Experiment 1, food-restricted rats were given saccharin-sweetened CS solutions for 10 min/day followed by IG infusions of a 7.1% oil emulsion or water. In subsequent choice tests they displayed a small (60%) but significant preference for the CS+ solution. In Experiments 2-5, rats had access to the CS solutions for 20 or 23 hr/day; drinking the CS solutions automatically triggered IG infusions of oil or water (electronic esophagus preparation). Infusions of 7.1% oil failed to produce a significant preference for the CS+ solution in rats given ad lib access to chow, and offered unsweetened CS flavors. Increasing the oil concentration (14.5% and 29%) did not facilitate the formation of a preference, nor did infusing the rats with a preingested oil emulsion. However, rats restricted to 2 hr/day access to chow, and 20 hr/day access to the CS solutions acquired a significant (85%) preference for the CS+ flavor; subsequent training and testing with saccharin-sweetened CS solutions increased the preference for the CS+ flavor to 95%. Ad lib fed rats trained with saccharin-sweetened CS solutions also developed a reliable preference (76%) for the CS+ flavor paired with IG oil; this preference persisted during four extinction tests when both CS+ and CS- flavors were paired with IG water. These results demonstrate that, as with other macronutrients (carbohydrate, protein), the postingestive effects of fats can condition flavor preferences, and suggest that the postingestive actions of nutrients play an important role in food selection and reward.

Animals↗
PubMed1989

Dietary fat-induced hyperphagia in rats as a function of fat type and physical form.

The influence of dietary fat on food intake and weight gain was assessed by feeding adult female rats diets that differed in the type and form of fat, as well as in the availability of other macro- and micronutrients. Compared to chow-fed controls, the various fat diets increased total food intake by 4% to 27%. Specifically, rats fed chow and a separate source of fat (fat option diet) consumed more fat and total calories, and gained more weight when the fat source was emulsified corn oil rather than pure corn oil or was vegetable shortening rather than corn oil. However, corn oil and shortening had similar effects on caloric intake and weight gain when presented as emulsified gels. Also, pure and emulsified-gel forms of shortening did not differ in their effects on caloric intake and weight gain. Supplementing the vegetable shortening with micronutrients, however, enhanced its hyperphagia-promoting effect. The results of two-choice tests revealed that the rats' preferences for the orosensory properties of the various fat sources did not account for the differential hyperphagias obtained. Rather, it appears that long-term fat selection and caloric intake are influenced primarily by postingestive factors. Fat selection and total intake were determined not only by the fat source itself, but also by the other diet options. That is, rats selected more fat and consumed more calories when chow was the alternative food than when separate sources of carbohydrate and protein were available.

Animals↗
PubMed1988

Ontogeny of polycose and sucrose appetite in neonatal rats.

Rat pups 3 to 15 days of age were infused with sucrose or Polycose solutions (.03 or .3 M) through oral cannulas and their solution intake, mouthing behavior, and general locomotor activity were recorded. Overall, the pups displayed similar ingestive responses to Polycose and sucrose. They discriminated between .3 M sucrose and water as early as 6-days of age, and between .3 M Polycose and water as early as 9-days of age. However, at the .03 M concentration the pups responded to Polycose before they responded to sucrose. The results confirm previous reports that rat pups have an unlearned preference for sucrose and demonstrate that a similar preference exists for starch-derived polysaccharides. The Polycose appetite displayed by the neonatal rats is consistent with results obtained with adult animals which suggest that rats have taste receptors for starch-derived polysaccharides as well as for sugars.

Aging↗
PubMed1988

Sucrose-induced hyperphagia and obesity in rats fed a macronutrient self-selection diet.

Adult female rats were allowed to self-select their diet from separate sources of fat, protein, and carbohydrate (starch). Other rats were fed a composite diet that matched the nutrient composition chosen by the self-selecting rats (50% fat, 28% protein, 22% carbohydrate) or a low-fat, high-carbohydrate chow diet. Half of the rats in each diet condition were given access to a 32% sucrose solution for 30 days. Sucrose availability increased total caloric intake (approximately 20%) and body weight gain in all three groups compared to control groups not fed the sucrose solution. The selection animals compensated for their sucrose intake by reducing their fat intake, and to a lesser degree, their starch intake; protein intake was the least affected by sucrose availability. The selection rats consumed less sucrose than the chow-fed rats and displayed a smaller increase in weight, relative to controls, than the chow-fed rats. These differences were attributed to the high-fat intake of the selection animals since similar results were obtained with the rats fed the composite diet. In particular, both the selection and composite diets produced mild obesity in the absence of sucrose. The results demonstrate that sucrose-induced overeating and overweight is not an artifact of restraining the diet choices of rats to a pure sugar and a nutritionally complete diet.

Animal Nutritional Physiological Phenomena↗
PubMed1988

PVN-hindbrain pathway involved in the hypothalamic hyperphagia-obesity syndrome.

This study examined the involvement of caudal brainstem projections of the hypothalamic paraventricular nucleus (PVN) in the medial hypothalamic (MH) hyperphagia-obesity syndrome. Experiment 1 demonstrated that a unilateral parasagittal knife cut in the MH combined with a contralateral coronal knife cut in either the ventrolateral pons (vP) or ventrolateral medulla (vM) significantly increased food intake and body weight in adult female rats. Overeating and overweight were also produced by a unilateral MH knife cut combined with a contralateral oblique cut under the nucleus of the solitary tract and dorsal motor nucleus of the vagus complex (NST/DX). In contrast, an MH cut x dorsolateral medullary cut combination did not increase food intake or body weight compared to a MH cut alone or sham surgery. Experiment 2 demonstrated that the hyperphagia/obesity effect of MH x vP knife cuts was comparable to that obtained with bilateral PVN lesions, but less than that produced by bilateral MH knife cuts. Bilateral vP cuts also increased body weight but the effect was less than that obtained with the other experimental treatments. Feeding the rats a high-fat diet rather than chow potentiated the hyperphagia and obesity syndromes produced by the various lesion conditions. Taken together, these findings suggest that the medial hypothalamic hyperphagia and obesity syndrome is due, in part, to damage to PVN projections to the caudal brainstem, the NST/DX complex in particular. The functional significance of this PVN-hindbrain "feeding" pathway and the identity of extra-PVN components of the hyperphagia-obesity syndrome remain to be established.

Animals↗
PubMed1988

Histochemical identification of a PVN-hindbrain feeding pathway.

Unilateral coronal knife cuts through the ventrolateral pontine reticular formation produce overeating and overweight when combined with contralateral parasagittal knife cuts in the medial hypothalamus (MH). The knife cuts were in a position to sever fiber projections from the paraventricular nucleus to the hindbrain. The present study used histochemical techniques to confirm that hyperphagia-producing knife cuts transect PVN-hindbrain fiber connections. In Experiment 1, adult female rats received a unilateral coronal knife cut in the ventrolateral pontine reticular formation. Horseradish peroxidase (HRP) was applied to the knife cut region and two to three days later brains were processed for the localization of neurons labeled with HRP. HRP-labeled neurons were found in the PVN, particularly in the caudal parvocellular region. Additional HRP-labeled neurons were observed in other medial hypothalamic areas but none were found in the ventromedial nucleus. HRP-filled cells were also found in the lateral hypothalamus, central nucleus of the amygdala, and in the nucleus of the solitary tract (NST). Many of the PVN projections to the hindbrain contain oxytocin and Experiment 2 determined if hyperphagia-inducing knife cuts sever PVN oxytocinergic fibers. Adult female rats received unilateral MH cuts, unilateral pontine cuts, or a contralateral combination of both cuts. One to eight days later the brains were processed for immunocytochemistry. The MH cuts and pontine cuts were found to interrupt descending oxytocinergic fibers. Taken together, these results support the hypothesis that interruption of a direct PVN-hindbrain oxytocinergic projection is responsible for the hypothalamic hyperphagia-obesity syndrome. However, the results do not rule out the involvement of a multisynaptic pathway or additional neurochemical systems.

Animals↗
PubMed1988

Starch-induced overeating and overweight in rats: influence of starch type and form.

In Experiment 1, adult female rats were fed, in addition to chow and water, a carbohydrate source that consisted of pure amylopectin corn starch or hydrolyzed corn starch (Polycose) in either a dry powder form or a hydrated gel form. Over the 30-day test periods, carbohydrate intake, total food intake, and body weight gain were greater with the Polycose than with the amylopectin, and greater with the gel form than with the powder form of the carbohydrates. The amylopectin gel produced overeating and overweight relative to a chow-fed control group, although the effects were less than that obtained with the Polycose gel. In a second experiment, test meals of the carbohydrate gels produced larger postmeal increases in plasma glucose than did the carbohydrate powders. There was no effect of carbohydrate type (amylopectin vs. Polycose) on the plasma glucose response. In Experiment 3, the addition of amylopectin to a Polycose gel reduced carbohydrate and total caloric intake. Both orosensory and postingestive factors may contribute to the differential food intake and body weight gains produced by the different types (Polycose vs. amylopectin) and forms (gel vs. powder) of carbohydrates.

Amylopectin↗