Relation of consummatory responses and preabsorptive insulin release to palatability and learned taste aversions.

In 6 experiments with 68 male Sprague-Dawley rats, the oral stimulation arising from food in the mouth produced a stereotyped sequence of ingestive consummatory responses and a rapid release of insulin prior to the absorption of nutrients into the blood. Conversely, when noxious taste stimuli were infused into the mouth, a different, aversive set of consummatory responses was evoked, and no insulin was released. These experiments demonstrate that pairing a sapid taste solution with LiCl reversed the consummatory response sequence to subsequent presentations of that taste from ingestion to aversion and abolished the preabsorptive release of insulin to that taste; this indicated an experience-produced shift in the palatability of the taste. It was further shown that a palatable but categorically noncaloric taste elicited behavioral ingestion but no insulin release. It is concluded that separate but related control systems operate to produce consummatory behavior and ingestive neuroendocrine responses. (64 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sodium depletion enhances salt palatability in rats.

Stereotyped fixed action patterns (FAPs) elicited in rats by oral infusions of taste solutions can be classified as either ingestive or aversive. They reflect the palatability of the taste and can be modified by learning and by the physiological state of the animal. The present 2 experiments, with 5 male Sprague-Dawley rats, demonstrated that when the physiological state of the S was altered by sodium depletion, the pattern of FAPs elicited by oral infusions of 0.5 M NaCl shifted from a mixture of ingestive and aversive components (while sodium replete) to exclusively ingestive ones (while sodium deplete). This shift in taste reactivity occurred the 1st time the Ss were made sodium deplete. A similar shift did not accompany infusions of 0.01 M HCl, a taste solution that also elicited mixed ingestive and aversive FAPs. This result suggests that the shift in response to NaCl was not due to a general change in ingestive bias or to a general taste deficit. On the basis of the change in FAPs, it is concluded that the palatability of highly concentrated salt solutions increases in sodium-deplete rats. Such a shift in salt palatability may be instrumental in directing the appetitive behavior of the animal. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A quantitative comparison of taste reactivity behaviors to sucrose before and after lithium chloride pairings: A unidimensional account of palatability.

Alterations in the motivation to ingest sucrose can be quantified by measuring the number and type of oral motor and somatic responses (i.e., taste reactivity [TR]) that are elicited by sucrose. In 2 experiments, rats had intraorally infused sucrose paired with LiCl injections for several trials, or they were injected with LiCl and had sucrose infused every 5 min during the 30-min postinjection period (data from A. C. Spector et al, 1988). In both experiments, ingestive TR responses decreased, whereas aversive TR responses increased over trials. Individual response components that comprise the ingestive and aversive categories followed the same trends of increase or decrease but changed at different rates as a function of number of trials or exposures. Overall, the array of response components could be projected onto a single unidimensional scale of palatability to capture the motivational states that ranged from acceptance to rejection. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Distinguished Scientific Award for an Early Career Contribution to Psychology: Kent C. Berridge.

Cites Kent C. Berridge for the American Psychological Association Distinguished Scientific Award for an Early Career Contribution to Psychology. Berridge is recognized for his role in developing the arsenal of behavioral methods available for a neurological analysis of behavior. His application of the oral-motor taste reactivity test to understanding the hedonic processes underlying palatability evaluations has given rise to a hypothesis of independent controls of aversive and ingestive response production. Beyond focusing attention on the behavioral categories within taste reactivity and grooming, he examined the rules governing how identifiable behavioral elements are strung together over time. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Control of fluid palatability by exteroceptive Pavlovian signals.

Two experiments, with 15 male albino rats, investigated whether discrete auditory conditioned stimulus/stimuli (CS) that signal the availability or onset of taste unconditioned stimulus/stimuli (UCS) (sucrose, quinine) can control orofacial responses in the absence of those UCSs. In Exp I, one auditory stimulus (CS+) was paired with the delivery of a sucrose solution to the magazine floor, and another auditory stimulus (CS–) was never followed by sucrose. Following conditioning, oral infusions of water that were preceded by the CS+ were found to elicit more ingestive (sucrose-typical) orofacial responses than did water alone or water preceded by the CS–. In Exp II, the conditioned ingestive reactions to a signal for sucrose observed in Exp I again occurred, and conditioned aversive (quinine-typical) orofacial responses occurred in response to water infusions preceded by a former signal for quinine. Data suggest that perceived palatability may be influenced by Pavlovian associations involving exteroceptive CSs and illustrate the importance of supporting stimuli in modulating the effects of Pavlovian associations on behavior. (41 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ethanol Palatability and Consumption by High Ethanol-Drinking Rats: Manipulation of the Opioid System With Naltrexone.

Three experiments examined the effect of acute naltrexone treatment on both taste reactivity and consumption of ethanol in high ethanol-preferring rat lines: Alko Alcohol-Accepting (AA) rats (Experiments 1 and 2) and Alcohol-Preferring (P) rats (Experiment 3). A 3.0 mg/kg naltrexone dose was ineffective at altering ethanol palatability for either line, whereas 7.5 mg/kg was effective at reducing palatability of 10% ethanol for AA, but not P, rats, as reflected by both a decrease in ingestive responding and an increase in aversive responding. The effects of naltrexone on ethanol consumption were quite consistent: At both dosages, acute naltrexone treatment significantly decreased consumption of 10% ethanol. Termination of naltrexone resulted in an immediate increase in ethanol consumption to control levels. Results show that ethanol palatability and consumption can be dissociated in the rat and that the organization of opioidergic mechanisms that mediate ethanol responses may vary between rat lines. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Area postrema mediates the formation of rapid, conditioned palatability shifts in lithium-treated rats.

The rapid acquisition and subsequent retention of lithium-induced conditioned changes in taste reactivity responses to sucrose were examined in rats with the area postrema (AP) either ablated or intact. On 2 conditioning days, a series of brief intraoral sucrose infusions was paired with the effects of LiCl or NaCl injections. Repeated associations of the sucrose taste with the effects of lithium significantly reduced ingestive responses and increased aversive responses only in the AP-intact group. AP-ablated rats treated with LiCl and rats injected with NaCl displayed an ingestive pattern of responses. Only the AP-intact rats, previously injected with LiCl, subsequently displayed evidence of a conditioned taste aversion. We conclude that toxin activation of the AP is required to produce the conditioned shift in taste reactivity responses and subsequent expression of a taste aversion in rats treated with lithium. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Toxin-induced conditioned changes in taste reactivity and the role of the chemosensitive area postrema

Conditioned taste avoidances (CTAs) are an important component of behavioral regulation of ingestion. In the laboratory CTAs can be produced by pairing a novel taste stimulus with the physiological feedback produced by a toxin, such as lithium. Such toxins putatively activate a chemosensitive brainstem structure, the area postrema, which ultimately results in the production of a CTA. The present review describes a series of studies which examined conditioned changes in taste reactivity responses (TRRs) when a novel intraoral sucrose taste was paired with the effects of an intraperitoneal (IP) injection of LiCl, and the role of the area postrema in the formation of conditioned palatability shifts. It was first of all necessary to examine the effects of area postrema ablations on TRRs to a range of intraoral sucrose and quinine stimulus intensities. In the first study area postrema lesioned rats exhibited concentration dependent changes in TRRs to these taste stimuli that were very similar to those exhibited by sham lesioned rats. The second study demonstrated that 30 s intraoral infusions of sucrose (0.3 M), presented at 5 or 10 min intervals following an IP injection of LiCl (3.0 meq), resulted in conditioned changes in TRRs. These were characterized by orderly, gradual reductions in ingestive responses and increases in aversive responses. Finally, when area postrema lesioned rats (Study 3) were subjected to this conditioning procedure (brief sucrose presentations paired with the effects of LiCl) no evidence for conditioned or unconditioned changes in TRRs to sucrose were obtained. Lesioned rats injected with LiCl behaved similarly to sham lesioned rats injected with NaCl. These series of studies provide evidence indicating that the chemosensitive area postrema mediates the formation of conditioned palatability shifts induced by treatment with a toxin such as lithium.     

Taste reactivity as a dependent measure of the rapid formation of conditioned taste aversion: A tool for the neural analysis of taste-visceral associations.

Investigated the ability of animals to form taste aversions following neural manipulations. In Exp 1, 10 rats received intraoral infusions of sucrose every 5 min starting immediately after the injection of LiCl. 12 controls were injected with NaCl. Oromotor and somatic taste reactivity behaviors were videotaped and analyzed. Lithium-injected Ss decreased their ingestive taste reactivity over time; aversive behavior increased. Controls maintained high levels of ingestive responding and demonstrated virtually no aversive behavior following sodium injection. Ss were tested several days later for a conditioned taste aversion (CTA). Rats previously injected with lithium demonstrated significantly more aversive behavior than controls. Exp 3 revealed that when similarly treated rats were tested for a CTA while in a lithium-induced state, difference in the ingestive behavior was observed. In Exp 2, naive rats were injected with NaCl or LiCl but did not receive their 1st sucrose infusion for 20 min. Ss also received infusions at 25 and 30 min postinjection. There were no differences in the task reactivity behavior displayed. Rats dramatically changed their oromotor responses to sucrose during the period following LiCl administration, provided the infusions started immediately after injection, a change attributable to associative processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Taste reactivity to alcohol and basic tastes in outbred mice

The taste reactivity test was used to determine the response of outbred mice to orally infused taste solutions. For the initial measures, mice (n = 10) were tested with 3%, 6%, 9%, and 12% (v/v) alcohol and four taste solutions: sucrose, sodium chloride, hydrochloric acid, and quinine hydrochloride (a single concentration of each). A second group of naive mice (n = 16) was tested with 5%, 10%, 20%, 30%, and 40% alcohol. The final set of measures with naive mice (n = 26) was taken with a range of sucrose concentrations: 0.01 M, 0.05 M, 0.1 M, 0.5 M, and 1.0 M. In general, mice made similar reactivity responses to all solutions tested. A predominant component of the mouse response to all infused fluids was forelimb flailing; gaping was also a common response to all solutions. Despite the large number of aversive-type responses, mice rejected very little fluid via passive drip or fluid expulsion. The single, significant difference in responding to the four taste stimuli was that mice made fewer aversive responses to sucrose. Differential responding to the 5 to 40% alcohol concentrations and sucrose concentrations was observed. Mice increased ingestive responding as the concentration of alcohol and sucrose increased. Aversive responding decreased reliably only with increases in the sucrose concentration. Data provide the first reported taste reactivity responses of mice to orally infused taste solutions. These results can be compared with the extant data available in rats and can also be used as a basis for exploring taste factors in genetically defined mouse populations.     

Taste reactivity to alcohol in rats.

Rats were infused intraorally with 4 concentrations of ethanol (3%, 6%, 9%, and 12%), and their subsequent oral, facial, and bodily responses were videotaped and analyzed. Naive rats did not display significant changes in ingestive-type responding over the concentrations tested. A significant increase in aversive responses was noted, with the largest number of aversive responses found with the 12% solution. Initial reactivity failed to predict subsequent consumption when rats were given free access to the same alcohol concentrations during 2-bottle tests. Reactivity testing after the period of alcohol access indicated that only the aversive responding changed significantly from the initial reactivity, with rats showing fewer aversive responses. The results indicated how the taste of alcohol is perceived by naive rats and how this perception is changed after consummatory experience with alcohol. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Trigeminal deafferentation and ingestive behavior in rats.

For studying the role of orosensory input in the control of ingestive behavior, 46 male albino Wistar rats were subjected to varying degrees of trigeminal deafferentation in 2 experiments. Somatosensory branches that convey touch, temperature, and pain from the oral cavity were sectioned selectively, and muscles of mastication and taste afferents were left intact. Severe intake deficits were produced, including aphagia, adipsia, and prolonged hypophagia, accompanied by a corresponding decrease in body weight. The deficits were proportional to the extent of deafferentation and were most severe when upper and lower portions of the mouth were affected. Although somatosensory impairment affected the organization of the consummatory response, all Ss could bite, chew, and lick. Analysis of feeding patterns showed that minimally (mandibular) deafferented Ss compensated for the consummatory inefficiency by increasing meal duration but failed to initiate meals at the normal rate, thus keeping food intake below normal levels. Results suggest that oral somatosensory input is critical for the mechanisms that regulate ingestive behavior. (45 ref)) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Amount of training and cue-evoked taste-reactivity responding in reinforcer devaluation.

In two experiments, rats received minimal (16) pairings of one auditory conditioned stimulus (CS) cue with a sucrose reinforcer, and extensive (112) pairings of another auditory CS with that reinforcer. After sucrose was devalued by pairing it with lithium chloride in some rats (Devalue groups) but not others (Maintain groups), taste reactivity (TR) and other responses to unflavored water were assessed in the presence of the auditory CSs alone. The minimally trained CS controlled substantially more evaluative TR responses than the extensively trained CS. Those TR responses were hedonic (positive) in the Maintain groups, but aversive (negative) in the Devalue groups. By contrast, food cup entry and other responses thought not to reflect evaluative taste processing were controlled more by the extensively trained cue. These responses were reduced by sucrose devaluation comparably, regardless of the amount of training. The results suggest rapid changes in the content of learning as conditioning proceeds. Early in training, CSs may be capable of activating preevaluative processing of an absent food reinforcer that includes information about its palatability, but that capability is lost as training proceeds. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

ACTH and ACTH4–20 modification of neophobia and taste aversion responses in the rat.

A series of 6 experiments assessed the effects of ACTH and the ACTH analog ACTH4–20 on drinking in conditioned taste aversion and neophobic situations using a total of 168 male Sprague-Dawley rats as Ss. Both substances delayed the extinction of a conditioned taste aversion established by a single pairing of lithium chloride with milk (Exp I). However, in this situation, the ACTH parent peptide was more potent behaviorally. ACTH supressed milk consumption in Ss with no toxicosis experience (Exp II). This effect was apparently not due to the conditioning of a taste aversion (Exp III) with ACTH serving as a weak aversive UCS. Exogenous ACTH (Exp IV) or ACTH4–20 (Exp V) did not enhance neophobia; however, repeated injections of ACTH suppressed drinking. This ACTH suppression was related to the familiarity/novelty of the substance being consumed. The neophobic response to milk was not accompanied by pituitary-adrenal activation (Exp VI). Both neophobic and conditioned taste aversion situations appear to be useful for assessing peptide effects on consummatory behavior. (36 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Taste avoidance, but not aversion, learning in rats lacking gustatory cortex.

Control rats rapidly learned to avoid drinking either a sucrose solution (Exp 1) or an NaCl solution (Exp 2) when the taste was paired with illness. These rats also produced aversive reactivity to each of these solutions in a taste reactivity test. Rats that lacked gustatory cortex (GC) learned to avoid drinking sucrose and NaCl, albeit at a slower rate than control rats. GC rats failed to display aversive reactivity to these tastes. The GC rats did show normal aversive reactivity to a strong quinine HCl solution during additional tests. It is suggested that the avoidance developed by GC rats did not entail a palatability shift of the conditional stimulus as it did in control rats. This altered learning strategy may account for the consistent learning deficits found in GC rats trained to avoid tastes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rats learn to like the taste of morphine.

When rats are forced to drink a morphine solution as their only source of fluid, they eventually reverse their initial preference and drink more morphine than water in a 2-bottle preference test. Two experiments with 13 male Holtzman rats examined the cause of this shift in preference using the taste reactivity test, which involves the analysis of fixed action patterns elicited by taste solutions infused into Ss' mouths. Three morphine concentrations (0.03, 0.6, and 1.5 mg/ml) and 2 levels of motivation (drug-replete and drug-withdrawal states) were studied. A greater percentage of ingestive taste reactivity responses occurred to the oral morphine infusion in morphine-raised than in water-raised Ss. Data are inconsistent with the idea that enhanced morphine ingestion is caused by anticipation of positive consequences. Instead, they support the idea that rats come to "like" the flavor of the morphine solution; in other words, the palatability evaluation of the morphine changes, possibly through an association between the flavor and the hedonically positive effects of the morphine. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Posttrial corticosterone administration enhances the effects of incentive downshift: Exploring the boundaries of this effect.

Posttrial administration of corticosterone was previously shown to enhance consummatory successive negative contrast (cSNC) in rats. The present series of experiments provides additional information that helps determine the boundaries of this effect. Posttrial corticosterone administration (1) enhances cSNC when rats experience a large downshift (32% to 4% sucrose), but not after a small downshift (8% to 4% sucrose; Experiment 1); (2) has no effect in an anticipatory negative contrast situation in which 4% sucrose precedes 32% sucrose in daily trials (Experiment 2); (3) does not support the development of a conditioned taste aversion to 4% sucrose, in the absence of an incentive downshift (Experiment 3); and (4) facilitates the extinction of consummatory behavior (Experiment 4). These results suggest that corticosterone facilitates the encoding of an egocentric aversive memory of the incentive downshift experience. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Brainstem mediates diazepam enhancement of palatability and feeding: microinjections into fourth ventricle versus lateral ventricle

The hypothesis that benzodiazepine-induced hyperphagia is due to a specific enhancement of the palatability of foods has been supported by previous 'taste reactivity' studies of affective (hedonic and aversive) reactions to taste palatability. Diazepam and chlordiazepoxide enhance hedonic reactions of rats (rhythmic tongue protrusions, etc.) to sweet tastes in a receptor-specific fashion. A role for brainstem circuits has been indicated by a previous demonstration of the persistence of the taste reactivity enhancement by diazepam after midbrain decerebration. The present study examined whether benzodiazepine brainstem receptors are the chief substrates for palatability enhancement even in intact brains. We compared the effectiveness of benzodiazepine microinjections to elicit feeding and enhance hedonic reactions when delivered into either the lateral ventricle (forebrain) or the fourth ventricle (brainstem) of rats. The results show diazepam is reliably more effective at eliciting feeding and enhancing positive hedonic reactions to oral sucrose when microinjections are made in the fourth ventricle than in the lateral ventricle. We conclude that brainstem neural systems containing benzodiazepine-GABA receptors are likely to be the chief substrates for benzodiazepine-induced palatability enhancement.     

Morphine enhancement of sucrose palatability: analysis by the taste reactivity test

The ability of morphine to modify sucrose palatability was assessed by the taste reactivity test. In Experiment 1, rats were injected with morphine (0.0, 0.5, 2.0, and 10.0 mg/kg, subcutaneously), 30 min before receiving a 10-min intraoral infusion of 2% or 20% sucrose solution. A dose of 2.0 mg/kg morphine enhanced ingestive reactions elicited by both concentrations of sucrose solution. In Experiment 2, the interval between morphine pretreatment and the taste reactivity test was manipulated. Rats given 2.0 mg/kg morphine 30 or 120 min before testing displayed enhanced ingestive reactions elicited by 20% sucrose solution during the first 5 min of a 10-min test. The results support the hypothesis that morphine enhances the hedonic assessment of sucrose solution.     

Morphine- and naltrexone-induced modification of palatability: Analysis by the taste reactivity test.

Used the taste reactivity (TR) test, a direct measure of the hedonic properties of a tastant, to assess in Sprague-Dawley rats the ability of morphine (an opiate agonist) and naltrexone (an opiate antagonist) to modify the palatability of a bitter quinine solution and a sweet sucrose solution. Morphine reduced the aversive hedonic properties of both novel and familiar quinine solution (0.05% and 0.1%) but did not modify the palatability of 20% sucrose solution. Naltrexone reduced the positive hedonic properties of sucrose solution (2% and 20%) but did not modify the palatability of 0.05% quinine solution. The pattern of results suggests that the modification of feeding produced by opiate agonists and antagonists may be mediated by a hedonic shift in the palatability of the tastant. (PsycINFO Database Record (c) 2010 APA, all rights reserved)