Taste as a dipsogenic stimulus.

Studied solution drinking in 50 male, nondeprived, Sprague-Dawley albino rats to determine how much animals will drink for reasons of taste alone. 4 different taste stimuli (sucrose, glucose, sodium saccharin, and sodium chloride) were used, each covering a wide range of concentrations. The same Ss were then retested after 16 hr. of water deprivation, and intakes under deprived and nondeprived conditions were compared. Results show that Ss ingested large volumes of sweet solutions in the absence of any need, and that water deprivation added only a small increment to the already high intakes of sweet solutions. Sodium chloride solutions, on the other hand, were ingested in relatively small quantities by nondeprived Ss, but water deprivation produced a large increase in intake. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hunger enhances the expression of calorie- but not taste-mediated conditioned flavor preferences.

Compared ethanol-mediated flavor preferences to preferences mediated by saccharin, which is sweet but noncaloric, and sucrose, which is both sweet and caloric in 4 experiments, using 74 Long-Evans rats. Ss learned to associate grape or orange flavor conditioned stimulus/stimuli (CS) with (1) ethanol or saccharin solution or (2) either the other unconditioned stimulus/stimuli (UCS) or plain tap water. They were then given 2-bottle choice tests between the flavor CSs apart from the UCSs. Flavors associated with 5% ethanol were preferred over saccharin-paired and water-paired flavors by sated Ss, and food deprivation during the choice test enhanced this preference. Flavors associated with 8% sucrose were preferred over water-paired flavors, and this preference was also enhanced by food deprivation. Flavors associated with 0.028% or 0.25% saccharin were preferred over flavors paired with water. In all cases, calorie-mediated preferences, at their highest levels, were stronger than taste-mediated preferences. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Flavor preferences in cats (Felis catus and Panthera sp.).

Conducted 4 experiments with 28 domestic and 12 wild cats to examine flavor preference in cats. In the 1st experiment domestic Ss exhibited no preference (both in 24-hr and 1-hr 2-choice preference tests) for any of a variety of carbohydrate or artificial sweeteners regardless of whether a water or saline diluent was employed. A preference for sucrose or lactose dissolved in dilute milk compared with dilute milk alone was observed. This preference may have been based on textural rather than flavor characteristics of the milk-sugar solution. In the 2nd experiment a similar lack of preference for carbohydrate sweeteners was found when using 5-min 2-choice preference tests with wild Ss (genus Panthera). In light of this lack of sweet preference among cats, Exps III and IV examined responses to solutions of hydrolyzed protein and individual amino acids and to emulsified fat mixtures. Solutions of hydrolyzed soy, lactalbumin, and casein; l-alanine and l-proline solutions; and butterfat mixtures were all preferred to the diluent. It is suggested that a pattern of responses characterized by an avidity for protein and fat products and no avidity for carbohydrate sweeteners may be typical of strict carnivores like cats. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Increased motivation in rats with ventromedial hypothalamic lesions.

25 female albino rats were implanted with chronic electrodes aimed for the ventromedial hypothalamic area (VMH), deprived to 82% of normal weight, and trained on a 2-min VI schedule for food reinforcement. After rates of response became stable, bilateral DC lesions were made, and weight was held constant. Over 10 days after lesioning, Ss with extensive VMH damage showed increases in rates of response for food. Unilateral lateral hypothalamic lesions resulted in decreases in response rates followed by recovery, regardless of VMH damage. Under more severe deprivation (48 hrs and 72 hrs), Ss with extensive VMH damage showed further increases in response rate. Results indicate that VMH lesions increased food motivation. Some factors which can produce opposite results are discussed. (38 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neonatal ablations of the gustatory neocortex in the rat: Taste aversion learning and taste reactivity.

Sprague-Dawley rats sustaining ablations of gustatory neocortex (GN) at 2, 10, 20, or 60 days of age were compared with control-lesion and anesthetized controls (N?=?151) in the acquisition and extinction of a learned taste aversion. Ss were also tested for taste preference across 5 concentrations of NaCl solution (.04, .08, .15, .3, and .6 M). Results indicate that GN ablation disrupted aversion acquisition and extinction regardless of age at surgery. Taste-response functions for solutions shown by all GN Ss mirrored those of controls: preference (relative to water baseline) for middle concentrations and rejection of the strongest concentration. It is suggested that the 20- and 60-day-old GN Ss were hyperresponsive to the suprathreshold concentrations of NaCl (excepting the .6-M concentration). The increased response to NaCl in 20- and 60-day-old GN Ss may have been related to the significant decreases in water consumption relative to that of controls. Water consumption of controls and GN Ss in 2- and 10-day-olds was essentially equal. It is concluded that infant ablation of the GN does not spare normal taste aversion learning and that rats with GN ablations, regardless of age at surgery, respond in a normal manner to the hedonic aspects of NaCl solutions. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ingestive responses to homeostatic challenges in rats with ablations of the anterolateral neocortex.

Because rats with either anterolateral neocortical (AN) or lateral hypothalamic (LH) damage initially display similar feeding and drinking deficits and recovery patterns, the present study examined the possibility that anterolateral neocortical ablations would also produce similar chronic ingestive impairments to glucoprivic and hydrational challenges. 73 male Sprague-Dawley rats received AN or dorsoposterior neocortical lesions or served as unoperated controls. Ss with AN ablations exhibited normal feeding responses to food deprivation and glucoprivation induced by insulin (4–26 U/kg, sc) or 2-deoxydextroglucose (2-DG [125 or 250 mg/kg, ip]), but their response to 500 mg/kg or 2-DG was impaired. These Ss also drank normally in response to hypertonic saline injections and following water deprivation but only if food was available during the test session. Results indicate that, although the anterolateral neocortex and LH are anatomically related, these brain regions appear to be functionally dissimilar in terms of the regulation of ingestion. (39 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Chronic voluntary nicotine drinking enhances nicotine palatability in rats.

Examined the response of rats to nicotine (NI) solutions with the brief-exposure, taste reactivity (TR) test, and a 2-bottle, 24-hr preference test. Naive nondeprived Ss were administered intraoral infusions of distilled water and 1 μg/ml, 5 μg/ml, 10 μg/ml, 25 μg/ml, 50 μg/ml, and 100 μg/ml NI. NI solutions up to a concentration of 50 μg/ml elicited a number of ingestive TR responses similar to that by water. Ingestive responses significantly decreased and aversive TR responses significantly increased in response to 100 μg/ml nicotine. On the basis of these results, 2-bottle preferences for water vs 1 μg/ml, 5 μg/ml, and 0 μg/ml (water control group) NI were measured in 3 groups of naive Ss. Ss initially showed an equal preference for 0 μg/ml and 1 μg/ml NI. After 16 days of exposure, however, Ss developed a significant preference for 1 μg/ml NI. The preference ratio for 5 μg/ml NI significantly increased during the experiment, but the preference ratio remained significantly less than that for 1 μg/ml and 0 μg/ml NI solutions. Last, TR responses elicited by intraoral infusions of 1 μg/ml and 5 μg/ml NI were then measured in these Ss having had the 2-bottle experience. Ss showing a 2-bottle preference for the 1 μg/ml NI solution displayed significantly more ingestive TR responses to 1 μg/ml and 5 μg/ml NI than did the control Ss. Data indicate that prolonged voluntary access to NI results in an increased preference for NI and modifies the immediate oral/gustatory reactivity of the Ss to NI. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Behavioral and neurochemical effects of neonatal administration of monosodium {l}-glutamate in mice.

Studied the feeding behavior, activity level, and thermoregulatory ability of 117 CL-1 mice made obese by neonatal administration of monosodium {l}-glutamate (MSG). The degree of obesity and other characteristics of the syndrome depended on age, diet, and housing condition. Carcass fat determinations demonstrated the presence of obesity in all MSG Ss; however, body weight was elevated over control levels only in adult mice caged in groups. Group-housed MSG Ss also failed to increase food intake in response to food deprivation and were both hypoactive and hypothermic. Individually caged MSG Ss showed normal activity levels and body temperature, an attenuated response to food deprivation, and an enhanced response to a high-fat diet. Since MSG obesity may be the consequence of damage to the dopamine-rich arcuate nucleus of the hypothalamus, a 2nd goal was to measure central catecholamines and examine any changes in the MSG S's behavioral responses to catecholaminergic drugs. Ss treated with MSG sustained some loss of hypothalamic dopamine, but no systematic relation between central catecholamines and behavioral aspects of the syndrome could be discerned. (46 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attention and habituation: Odor preferences, long-term memory, and multiple sensory cues of novel stimuli.

Investigation of and habituation to novel stimuli are part of exploratory behavior of rodents. They are necessary for assessing the environment in seeking food and sexual partners and in avoiding predators. Six experiments tested male and female Mongolian gerbils (Meriones unguiculatus) in a stimulus-elicited investigation paradigm. Findings indicate that (1) Ss initially showed preference for odors of strange male bedding and for odors of home cage bedding and then habituated. There was no preference between these 2 odors, although they could be discriminated. The complex odor stimulus elicited more response than any of the components tested. (2) Memory of an object or odor was demonstrated up to 4 wks later. (3) Sensory deprivation by blinding, anosmizing, or removing somatosensation of the upper snout made only small differences in investigation. The removal of any 2 of these sensory inputs produced more interference with the response, but all Ss investigated the stimulus. It is concluded that attention to novelty and habituation after repeated exposure are very robust behaviors and are mediated through multiple sensory channels. (41 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of lesions of the gustatory neocortex on taste aversion learning in the rat.

In 5 experiments, 110 normal male Long-Evans hooded rats and 125 Ss with lesions of the gustatory neocortex (GN) were compared for their ability to learn aversions to taste cues paired with toxicosis. When the taste presentation was followed immediately by toxicosis, normal Ss and 8 Ss with lesions of the posterior (visual) neocortex learned aversions to sucrose, sodium chloride, quinine hydrochloride, and hydrochloric acid solutions. Ss with GN lesions learned aversions to all solutions except sucrose. In preference tests, all solutions were shown to be discriminable from water by both normal and GN-lesioned Ss. Under conditions in which a 6-hr delay separated taste presentation and toxicosis, normals again learned specific aversions to all 4 solutions, but Ss with GN lesions failed to learn specific aversions to sucrose, sodium chloride, and hydrochloric acid solutions. It was shown that the ability of Ss with GN lesions to learn aversions to sucrose and quinine depended on stimulus concentration. It is proposed that the data can be accounted for by postulating a change in the threshold for taste illness associations following GN lesions. (30 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Social deprivation and stimulus satiation in the albino rat.

Conducted 2 experiments, with a total of 288 male Sprague-Dawley albino rats, to explore the mechanisms whereby social deprivation leads to increased sociability in rats. Exp I housed Ss alone or in pairs with additional nonsocial stimulation, with additional response opportunities, or with no added social surrogates for 3 wks prior to testing for sociability. Social deprivation led to a strong increase in sociability, and this was not ameliorated by stimulus or response enrichment. Exp II exposed alone or pair-housed Ss to handling, human contact, or no stimulation and found that human exposure did serve a social surrogate function. This result suggests that sociability in rats represents to some degree a search for complex and unpredictable stimulation. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Some hedonic consequences of the confirmation and disconfirmation of expectances.

In a test of the hypothesis that events which disconfirm expectancies will be perceived as unpleasant, Ss tasted a random sequence of sweet and bitter solutions. On the basis of certain signals given by the E, they developed expectancies or hypotheses about whether the next solution would be bitter or sweet. On trials when the Ss' expectancies were disconfirmed due to incorrect signals, the solutions were judged to taste more unpleasant. Thus, a bitter solution was rated more bitter; a sweet solution was rated less sweet. The results were interpreted in terms of Festinger's theory of cognitive dissonance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sucrose preferences of hungry and thirsty rats as a function of duration of stimulus presentation.

Studied sucrose preference in 3 experiments with 6, 12, and 12 male Holtzman albino rats. With progressively shorter intervals of repeated stimulus presentation (continuous down to 10 sec/min) in 2-choice brief exposure tests, thirsty Ss dropped from 90-50% preference for 6 or 12% sucrose over water, and showed little preference for 12 over 6%. Hungry Ss maintained a 90% preference for sucrose over water at all intervals but showed a decrement for 12 over 6% sucrose. For thirsty Ss (a) sucrose preference was a joint function of amount of exposure time and time between exposures, and (b) presentation order of different exposure durations was important. Results are discussed in terms of approach "arousal" and "decay" as a function of concentration and type of deprivation. (20 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of dietary NaCl deprivation during early development on behavioral and neurophysiological taste responses.

Investigated whether the gustatory system can be modified by restricting dietary NaCl during early development by recording neurophysiological taste responses in Sprague-Dawley rats at various times after deprivation (Exp I), and by measuring behavioral taste preferences in 3 groups of 7 NaCl deprived adult rats (Exp II). Overall findings indicate that Ss deprived of dietary NaCl from the 3rd day of gestation to 12 days postnatally and then placed on a NaCl-replete diet had chorda tympani nerve responses similar to those of nondeprived Ss when recordings were made at 28 days of age and older; however, preferences for NaCl solutions over water were significantly less than those of controls when tested at adulthood. NaCl deprivation in Ss from the 3rd day of gestation to approximately 35 days postnatally resulted in altered chorda tympani nerve responses to NaCl but not to other stimuli such as NH?Cl and KCl. Thus, it is concluded that restriction of dietary NaCl at a period in the rat's development when peripheral and central taste responses are changing results in short-term alterations in peripheral neural responses and in long-term changes in preference behaviors. (36 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Commitment to social deprivation and verbal conditioning.

Control Ss who experienced high prior deprivation of a reinforcing stimulus (approval) responded more with a reinforced response in a verbal conditioning situation than Ss less deprived. Other Ss committed themselves to undergoing postexperimental deprivation of social reinforcement after the same high prior social deprivation. A model suggested by dissonance theory predicted that such Ss who committed themselves for lower rewards would experience greater dissonance; the greater the dissonance, the more could Ss justify their decisions and reduce dissonance by reducing their motive for social reinforcement, consequently behaving in the conditioning situation as Ss who had low motivation for social reinforcement. As expected, experimental Ss in the High Dissonance condition who committed themselves for low reward ($1.00) responded less to social reinforcement, i.e., they showed a smaller increase in response strength of emission of verbal behavior than Control Ss or Low Dissonance Ss who committed themselves for high reward ($5.00). (19 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of degree of obesity, food deprivation, and palatability on eating behavior of humans.

Monitored the eating behavior of 20 obese and 20 normal weight Ss in the context of tasting tests. Intake was measured following a solid food preload and following a period of food deprivation. All Ss participated in both conditions. Under all experimental conditions obese Ss ate more than normal weight Ss. The effect of a preload was similar in both groups. Obese Ss, however, were more responsive to their preference functions than were normal weight Ss. The fruitfulness of using brief exposure tests for determining differential modes of eating behavior is discussed. (24 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Oral somatosensory factors in dietary self-selection after food deprivation and supplementation.

In 2 experiments with 72 male albino Sprague-Dawley rats, trigeminally deafferented Ss were subjected to nutritional stresses while being allowed to balance protein and carbohydrate intake from 3 separate dietary fractions. Partially trigeminally deafferented Ss that had recovered a normal protein ratio (protein/total intake) underwent total food deprivation (Exp I) or intragastric (IG) supplementation of protein or carbohydrate suspensions (Exp II). In response to deprivation, control Ss increased protein intake above ad-lib levels, but not carbohydrate intake. In response to IG supplementation, they decreased protein intake disproportionately more than carbohydrate intake when the fluid consisted of protein and vice versa when the fluid consisted of carbohydrate. The recovered deafferented Ss showed no selective increase in protein intake after deprivation and no differential compensation to nutrient supplementation. This suggested that recovery of the protein ratio after partial trigeminal deafferentation could not fully replace the function of trigeminal somatosensory input. The possible roles of other orosensory and of postingestional factors for recovery are discussed. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential effects of septal, preoptic, and habenula ablations on thirst-motivated behaviors in rats.

Two experiments used a total of 59 male Sprague-Dawley rats. Bilateral septal lesions dramatically enhanced barpressing rates generated under progressive ratio schedules of reinforcement. This increased barpressing was dependent on deprivation level but independent of the type of deprivation (i.e., food or water). Equivalent effects on barpressing were observed in Ss with bilateral medial forebrain bundle lesions at the level of the lateral preoptic area. Septal lesions, medial forebrain bundle lesions, and habenula lesions did not result in a hyperreactivity to bitter quinine solutions. Hyperreactivity to quinine was observed only in Ss with medial preoptic lesions. This medial preoptic lesion also impaired operant responding for water on a progressive ratio schedule of reinforcement. It is suggested that the medial preoptic lesion produced a deficit in thirst-motivated behavior. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Do taste factors contribute to the mediation of ethanol intake? Ethanol and saccharin-quinine intake in three rat strains

Several recent studies have suggested that ethanol-preferring rodents may also have an affinity for sweet solutions (saccharin, sucrose) and, conversely, that saccharin preference may predict ethanol preference. The purpose of the present investigation was to determine whether intake of ethanol and saccharin-quinine (SQ) solutions would be related in three nonselected strains of rats who differ in their ethanol preference: Lewis, Wistar Kyoto, and Wistar. In the first phase of the experiment, all animals were presented with an ascending series of ethanol solutions (2 to 10%) in free choice with water, followed by a 10-day maintenance period of 10% ethanol with water. In the second phase, the same animals were presented with an ascending series of SQ solutions (saccharin: 0.4%, quinine: 0.001 to 0.04%) in free choice with water, followed by a 10-day maintenance period of 0.4% saccharin with 0.04% quinine and water. The results revealed an absence of a direct relationship between ethanol and SQ consumption. The ethanol-nonpreferring Lewis rats showed a greater preference for the SQ solutions than Wistar Kyoto rats, whereas the ethanol-preferring Wistar Kyoto strain consistently consumed significantly less SQ. Wistar rats showed relatively stable consumption levels for both solutions that fell between those of the other two strains. These results suggested that the relationship between ethanol and SQ preference in rats was not a direct one and did not support the findings in the literature of a simple overall positive relationship between sweet and ethanol preference. These data do, however, provide further evidence for taste factors in the mediation of self-selection of ethanol in rats.     

Specificity of acquired aversions to taste qualities in hamsters and rats.

372 golden hamsters and 120 Sprague-Dawley rats tasted 1 of 27 solutions before receiving an ip injection of apomorphine, then were tested for aversions to 4 solutions prototypic of human taste qualities: sucrose, NaCl, HCl, and quinine HCl. With most of the solutions described as sweet employed as CSs, Ss acquired an aversion to sucrose. With CSs described as either salty or sour by humans, Ss acquired an NaCl aversion in the former case or an HCl aversion in the latter case; an aversion to quinine HCl was acquired with 2 of the 3 CSs described as sour. With most of the CSs described as bitter or as having a bitter component, Ss acquired a quinine HCl aversion. Patterns of S activity evoked across 4 classes of peripheral gustatory neurons when the CSs were applied to the tongue were similar to the patterns of aversions across the 4 test stimuli for the CSs. This suggests that 4 neural channels mediate the sensations evoked by the 4 test solutions in rats and hamsters, perhaps even in human beings. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)