Consumption Of Saccharin Solution Research Articles

Optogenetic stimulation in the medial prefrontal cortex modulates stimulus valence from rewarding and aversive to neutral states.

Understanding the modulations of the medial prefrontal cortex (mPFC) in the valence of the stimulus from rewarding and aversive status to neutral status is crucial for the development of novel treatments for drug addiction. This study addressed this issue and examined whether optogenetic ChR2 photostimulation in the cingulate, prelimbic, and infralimbic cortices of the mPFC regulated the valence of saccharin solution consumption from the rewarding property, the aversive property induced by morphine's conditioning, and the neutral states via saccharin extinction processes after morphine's conditioning. All rats received virus infection, buried optical fiber, optical stimulation, water deprivation, and saccharin solution consumption phases. In Experiment 1, rats were given ChR2 virus infection into the cingulate cortex (Cg1), prelimbic cortex (PrL), and infralimbic cortex (IL) to influence the rewarding saccharin solution consumption under photostimulation. In Experiment 2, rats were given ChR2 or EYFP virus infection into the Cg1, PrL, and IL to alter the saccharin solution consumption in the morphine-induced aversively conditioned taste aversion (CTA) and the saccharin solution consumption in the neutral state following the extinction process under photostimulation. Later, the immunohistochemical staining with c-Fos protein was performed for the Cg1, IL, PrL, nucleus accumbens core, nucleus accumbens shell, central amygdala, basolateral amygdala, ventral tegmental area, and dentate gyrus. The results showed that optogenetic PrL stimulation decreased the rewarding valence of saccharin solution consumption and increased the morphine-induced, aversive valence of saccharin solution consumption. PrL stimulation decreased the neutral valence of saccharin solution consumption via the extinction process. Cg1 optogenetic stimulation increased the rewarding valence of saccharin solution consumption and the aversive valence of saccharin solution consumption induced by morphine in conditioning. Optogenetic IL stimulation increased the aversive valence of saccharin solution consumption induced by morphine via conditioning. Altogether, optogenetic stimulation in the subareas of the mPFC modulated the reward, aversion, and neutral valences of the stimulus and altered neuronal activity in the mPFC, amygdala, nucleus accumbens, and hippocampus. Notably, the change of valence was temporary alternation during light-on related to the light-off periods. However, the findings may provide insights in the development of novel treatments for addictive symptoms.

Examination of nicotine and saccharin reward in the Goto-Kakizaki diabetic rat model

Morbidity and mortality attributed to type 2 diabetes have exponentially increased in the US. At exceptionally high risk is a subpopulation of persons with type 2 diabetes who smoke, which are shown to have decreased success rates of smoking cessation than euglycemic smokers. Preclinical research in our laboratory has shown that the rewarding effects of nicotine are enhanced in the streptozotocin and high-fat diet rodent model of diabetes. It is presently unclear whether this enhancement of nicotine reward can be demonstrated in other insulin resistant rat models. This study aimed to determine if a similar increase in nicotine reward is found in Goto-Kakizaki (GK) rats, a model of the spontaneous formation of insulin resistance in an inbred sub-strain of Wistar rat. Nicotine conditioned place preference (CPP) was examined in Sprague-Dawley (SD), Wistar, and GK rats. A robust nicotine CPP was found in SD and Wistar rats, but nicotine CPP was not detected in GK rats. Locomotor activity was also evaluated in all three strains, and GK rats demonstrated significantly less activity as compared to SD and Wistar rats. To further assess reward behavior in GK rats, consumption of saccharin solution was measured over a 48 -h period. GK rats showed a significant increase in saccharin intake compared to SD rats. These findings suggest that GK rats experience an enhanced hedonic processing as compared to SD rats. The lack of nicotine CPP in GK rats may be due to deficits in learning and memory, thus hindering their ability to acquire or express a place preference.

Evaluating the various phases of cisplatin-induced emesis in rats

Use of cisplatin as a chemotherapeutic agent causes acute and delayed emesis. Kaolin, saccharin solution and normal feed consumption have been evaluated as an index of cisplatin-induced emesis in rats; however, the most preferable of these methods for evaluating the various phases of emesis remains unclear. In the current study, kaolin, saccharin solution and normal feed consumption following cisplatin administration (6 mg/kg intraperitoneally) were simultaneously investigated in rats. Kaolin consumption increased significantly following cisplatin administration and was attenuated by granisetron administration 0–24 h following the injection. Saccharin solution consumption, however, decreased significantly 0–48 h following cisplatin administration, however, was attenuated by administration of granisetron within 0–24 h only. A reduced intake of normal feed was observed in the control group and was reversed by granisetron within the 0–72 h period. The present study indicates that kaolin consumption may be evaluated as an index of cisplatin-induced acute emesis and saccharin solution consumption may be evaluated as an index of delayed emesis, while normal feed consumption as an indicator of anorexia nervosa may be suitable to evaluate all phases of emesis and serve as an indicator of quality of life.

Delta-opioid receptor blockade in the ventral pallidum increases perceived palatability and consumption of saccharin solution in rats

The ventral pallidum (VP) is involved in ingestive behaviour. It receives dense GABAergic projections from the nucleus accumbens. GABAergic terminals in the VP co-express enkephalin, an endogenous ligand of delta-opioid receptors. The role of the delta-opioid receptors in the VP in the context of ingestive behaviour remains unclear, in contrast to the well-understood involvement of the mu-opioid receptors. We used the single-bottle test to examine the effects of VP microinjections of the delta-opioid receptor antagonist naltrindole on consumption of a saccharin solution. Naltrindole injections significantly increased the intake of saccharin, but not water, during a 2-h test session. We also investigated perceived palatability of saccharin using a taste reactivity test. The drug treatments increased ingestive responses to intraorally infused saccharin. Further experimentation explored the role of VP delta-opioid receptors in behavioural responses to saccharin that were previously paired with malaise upon the retrieval of conditioned taste aversion (CTA). Naltrindole-injected rats exhibited longer latency for the first occurrence of aversive responses than vehicle-injected control rats. However, there was no between-group difference in total aversive responses. These results suggest that naltrindole injections into the VP induce an enhancement of perceived palatability of a normally preferred saccharin solution, and thereby facilitate consumption of the solution. On the other hand, delayed aversive responses to the conditioned aversive saccharin suggest that the delta-opioid receptors in the VP mediate the initiation of aversive taste reactivity responses to the conditioned stimulus upon CTA retrieval.

Effects of Food Availability and Administration of Orexigenic and Anorectic Agents on Elevated Ethanol Drinking Associated With Drinking in the Dark Procedures

Drinking in the dark (DID) procedures have recently been developed to induce high levels of ethanol drinking in C57BL/6J mice, which result in blood ethanol concentrations reaching levels that have measurable affects on physiology and/or behavior. The present study determined if increased ethanol drinking associated with DID procedures may be motivated by caloric need rather than by the postingestive pharmacological effects of ethanol. To this end, food availability was manipulated or mice were given peripheral administration of orexigenic or anorectic agents during DID procedures. C57BL/6J had 2-hours of access to the 20% (v/v) ethanol solution beginning 3-hours into the dark cycle on days 1 to 3, and 4-hours of access to the ethanol bottle on day 4 of DID procedures. In Experiment 1, the effects of food deprivation on ethanol consumption during DID procedures was assessed. In Experiments 2 and 3, mice were given intraperitoneal (i.p.) injection of the orexigenic peptide ghrelin (0, 10 or 30 mg/kg) or the anorectic protein leptin (0 or 20 microg/g), respectively, before access to ethanol on day 4 of DID procedures. In Experiment 4, hourly consumption of food and a 0.05% saccharin solution were assessed over a period of hours that included those used with DID procedures. Consistent with previous research, mice achieved blood ethanol concentrations (BECs) that ranged between 100 and 150 mg% on day 4 of DID experiments. Neither food deprivation nor administration of orexigenic or anorectic compounds significantly altered ethanol drinking with DID procedures. Interestingly, mice exhibited their highest level of food and saccharin solution consumption during hours that overlapped with DID procedures. The present observations are inconsistent with the hypothesis that C57BL/6J mice consume large amounts of ethanol during DID procedures in order to satisfy a caloric need.

Depression after status epilepticus: behavioural and biochemical deficits and effects of fluoxetine

Depression represents one of the most common comorbidities in patients with epilepsy. However, the mechanisms of depression in epilepsy patients are poorly understood. Establishment of animal models of this comorbidity is critical for both understanding the mechanisms of the condition, and for preclinical development of effective therapies. The current study examined whether a commonly used animal model of temporal lobe epilepsy (TLE) is characterized by behavioural and biochemical alterations involved in depression. Male Wistar rats were subjected to LiCl and pilocarpine status epilepticus (SE). The development of chronic epileptic state was confirmed by the presence of spontaneous seizures and by enhanced brain excitability. Post-SE animals exhibited increase in immobility time under conditions of forced swim test (FST) which was indicative of despair-like state, and loss of taste preference in saccharin solution consumption test which pointed to the symptomatic equivalence of anhedonia. Biochemical studies revealed compromised serotonergic transmission in the raphe-hippocampal serotonergic pathway: decrease of serotonin (5-HT) concentration and turnover in the hippocampus, measured by high performance liquid chromatography, and decrease of 5-HT release from the hippocampus in response to raphe stimulation, measured by fast cyclic voltammetry. Administration of fluoxetine (FLX, 20 mg/kg/day for 10 days) to naive animals significantly shortened immobility time under conditions of FST, and inhibited 5-HT turnover in the hippocampus. In post-SE rats FLX treatment led to a further decrease of hippocampal 5-HT turnover; however, performance in FST was not improved. At the same time, FLX reversed SE-induced increase in brain excitability. In summary, our studies provide initial evidence that post-SE model of TLE might serve as a model of the comorbidity of epilepsy and depression. The finding that behavioural equivalents of depression were resistant to an antidepressant medication suggested that depression in epilepsy might have distinct underlying mechanisms beyond alterations in serotonergic pathways.

Further evidence that the discriminative stimulus properties of indorenate are mediated by 5-HT 1A/1B/2C receptors

Indorenate (5-methoxytryptamine β-methylcarboxylate, INDO) is a serotonin (5-hydroxytryptamine, 5-HT) agonist that has affinity for 5-HT 1A/1B/2C receptors. Unlike other anxiolytics such as 5-HT receptor agonists, INDO may not share tolerance or dependency with the benzodiazepine anxiolytics. It has been reported that the discriminative stimulus properties of 5-HT 1A/1B/2C agonists, but not those of 5-HT 3/4 agonists, generalize to INDO. Therefore, the aim of the present study was to obtain further evidence on the differential involvement of 5-HT 1A/1B/2C receptors in the discriminative stimulus properties of INDO by evaluating its interactions with antagonists of the 5-HT 1A, 5-HT 1B, 5-HT 2C, and 5-HT 3/4 receptor subtypes. Rats were trained to discriminate INDO from saline in a conditioned taste aversion paradigm. For Group D +S −, administration of INDO signalled that saccharin flavour was followed by LiCl, while injection of vehicle signalled safe consumption of saccharin solution. Group D −S + had the contingencies reversed. After this training, rats had generalization tests where INDO administration was preceded by different doses of the following antagonists: WAY100635 (5-HT 1A), NAN190 (5-HT 1A), methiothepin (5-HT 1A/1B/2C), GR127935 (5-HT 1B/1D), ketanserin (5-HT 2A/2C), ritanserin (5-HT 2C/2A), mesulergine (5-HT 2C/2A), metergoline (5-HT 2C/2A), SB206553 (5-HT 2B/2C), and tropisetron (5-HT 3/4). In Group D +S −, the order of potency to block the discriminative stimulus properties of INDO was WAY100635>ketanserin>ritanserin>GR127935>mesulergine≅SB206553>metergoline>methiothepin>NAN190, while in Group D −S +, the order was WAY100635>GR127935>ketanserin>ritanserin>mesulergine≅SB206553>metergoline>methiothepin>NAN190. Tropisetron did not produce any alteration of the discriminative control by INDO. These results suggest that the discriminative signal of INDO is mediated by 5-HT 1A/2C/1B receptors and that blockade of any of its components produces a degradation of its discriminative effects.

Reduction in preference for saccharin by repeated unpredictable stress in mice and its prevention by imipramine.

The present study set out to establish the chronic mild stress (CMS) animal model of depression in male CD-1 mice, a commonly used mouse strain. Mice were exposed to a series of mild stressors (e.g. soiled bedding, paired housing, cage tilt, white noise) presented in a continuous unpredictable fashion. Intermittently, CMS was discontinued and the mice were presented with both water and a palatable saccharin solution (0.1% w/v) in a two-bottle choice test overnight (15 h). Repeated exposure of these mice to the stressors led to a reduction in preference for the saccharin solution. This change in preference was attributed to an increase in the consumption of water rather than a decrease in the consumption of saccharin solution. Over time and with extensive testing, CMS no longer affected performance in the two-bottle saccharin preference test. Treatment with the tricyclic antidepressant imipramine (20 mg/kg i.p., once daily) had a varied effect on the CMS-induced change in preference for saccharin, dependent on the timing of initiation of imipramine treatment. In the first instance, following 5 weeks of CMS where a reduction in saccharin preference was established, treatment with imipramine for a further 5 weeks maintained the stress-induced deficit in saccharin preference. However, using a different approach, pre-treatment with imipramine once daily for 2 weeks, prior to onset of CMS, and co-treatment thereafter, attenuated CMS-induced changes in saccharin preference. Finally, when imipramine treatment was scheduled to begin with the CMS procedure, imipramine failed to prevent the CMS-induced reductions in saccharin preference. Changes in behaviour observed after exposure to CMS may be linked to a stress-induced deterioration of the sensitivity of the mice to a rewarding stimulus. Treatment with imipramine can reduce these behavioural changes but is only effective when given repeatedly prior to onset of CMS.

Protection against radiation-induced conditioned taste aversion by Centella asiatica

Radiations are known to cause behavioural perturbations like conditioned taste aversion (CTA), performance decrement, learning, etc., even at very low doses. The manifestation of radiation-induced behavioural degradation has not been understood well and requires further studies. Therefore, the effects of low-dose whole-body 60Co γ-irradiation in male rats were studied in terms of body weight and CTA learning. For CTA, the consumption of saccharin solution was considered as a parameter. To protect against the adverse effects of radiation, Centella asiatica (aqueous extract) was tested and compared with ondansetron, a standard antiemetic drug. A dose of 2 Gy incurred significant body weight loss [ t(9)=9.00, P<.05] and induced CTA in rats [ t(26)=9.344, P<.01]. Administration of C. asiatica (100 mg/kg bw ip, 2 Gy, −1 h) rendered significant radioprotection against radiation-induced body weight loss and CTA that became evident on the second postirradiation day [ t(7)=0.917, P≫.05; t(7)=4.016, P>.05]. Ondansetron (1 mg/kg bw) elicited higher degree of protection against CTA [ t(7)=3.641, P>.05] than C. asiatica [ t(7)=7.196, P>.05] on the first postirradiation day, but on the second postirradiation day, both were equally effective [ t(7)=3.38, P>.05; t(7)=4.01, P>.05]. In case of C. asiatica-treated animals, however, there was a consistently declining CTA from the second to the fifth postirradiation day whereas in ondansetron-treated animals it was inconsistent. Present investigation suggests that C. asiatica could be useful in preventing radiation-induced behavioural changes during clinical radiotherapy.

Sex Dimorphism in Saccharin Consumption in Rat Ontogenesis. Effect of Age of Weaning

Formation of the taste reaction of preference-rejection of a sweet solution was studied in males and females of Wistar rats weaned at the age of 17 (group 1), 21 (group 2), 26 (group 3), and 30 days (group 4). During 35 days the animals maintained in individual cages were allowed to choose between the 0.2% saccharin solution and water. It has been shown that at the beginning of the testing period the most pronounced neophobia was characteristic of females in the groups 1 and 2 and of males in the group 2. Analysis of data for the whole testing period indicates that in females of the groups 1 and 4 the saccharin consumption level is higher than in males. On the contrary, in the groups 2 and 3 the males exceeded the females by this parameter. The same regularity was also revealed in comparing data on a relative level of the saccharin solution consumption when determined as a percentage of the total volume of fluid consumed for 24 h. Thus, the age of weaning has an essential effect on sex dimorphism in formation of the preference–rejection taste reaction in rats.

Effects of genistein exposure on sexually dimorphic behaviors in rats.

The phytoestrogen genistein, the principal isoflavone in soybeans, has adverse effects on animal reproduction. As adult physiology and behavior are sensitive to perturbation by developmental estrogens, exposure to genistein during development may produce behavioral alterations as well. Pregnant rats were fed soy-free diets containing 0, 25, 250, or 1250 ppm genistein (approximately 0, 2, 20, or 100 mg/kg/day) beginning on gestational day 7, and offspring continued on these diets through postnatal day (PND) 77. Male and female offspring were assessed for levels of sexually dimorphic behaviors: open field activity, play behavior, running wheel activity, and consumption of saccharin- and sodium chloride-flavored solutions. Consumption of the salt solution was affected by genistein, with animals in the 1250-ppm group drinking significantly more than controls; consumption of plain water was unaffected. Genistein treatment also significantly affected play behavior; although no treated group was significantly different from controls, and the effect was not sexually dimorphic. Running wheel activity and saccharin solution consumption showed significant sex differences, but no effects of genistein treatment. Gestational duration, total and live pups per litter, and total and live litter sex ratios were not significantly affected by genistein. However, average weight per live pup at birth and offspring body weights from PND 42-77 were significantly decreased in the 1250-ppm group. Body weight and food intake for the dams were also significantly decreased in the 1250-ppm group. These results indicate that developmental genistein treatment, at levels that decrease maternal and offspring body weight, causes subtle alterations in some sexually dimorphic behaviors.

Selective breeding for high and low alcohol preference in mice.

High and low alcohol preference (HAP and LAP, respectively) mice were created by 10 generations of bidirectional selection for differences in two-bottle choice alcohol consumption. The progenitors used for selection were HS/lbg mice, which are a genetically defined, outbred stock. During selection, mice had 24-h, daily access to 10% alcohol (v/v) and water ad libitum for 30 days and were selected based on the alcohol (g/kg) consumed per day over the entire period. Food was available ad libitum. At S10, line means for alcohol consumption differed greatly, with consumption of over 12 g/kg per day in the HAP mice and less than 2 g/kg per day in the LAP mice. Realized heritability for bidirectional selection was approximately 0.2. Female mice consumed more alcohol than male mice. There were no differences between lines in alcohol elimination rate, nor were there line differences in intake of salt or quinine solutions. However, consumption of saccharin solutions was greater in HAP mice than LAP mice, consistent with previous findings of a genetic correlation between sweet preference and alcohol drinking. Because the mouse genome is relatively well characterized, these selected lines should prove a useful tool for assessment of the genetic basis of, and phenotypes that correlate with, alcohol drinking.

The Influence of Postweaning Housing Conditions on Drug-Induced Conditioned Taste Aversion

Postweaning social isolation can influence the sensitivity of rats to several effects of drugs of abuse. The present study investigated the influence of postweaning housing conditions on the sensitivity of rats to the aversive effects of a number of psychoactive agents using a conditioned taste aversion (CTA) test procedure. Development of a CTA was assessed by pairing administration of the drug with the consumption of a 0.05% (weight/volume) saccharin solution in water-deprived (18 h) rats in a 20 min drinking period. Saccharin consumption was then measured in 20 min test sessions over the next 4 consecutive days. Consumption of saccharin solution was significantly reduced in both isolated and enriched rats following administration of d-amphetamine (2 mg/kg), cocaine (30 mg/kg), morphine (10 mg/kg), nicotine (1.0 mg/kg), caffeine (20 mg/kg), alcohol (1.5 g/kg), and LiCl (0.15 M, 4 ml/kg). There was no significant effect of housing conditions on the CTA induced by cocaine, nicotine, alcohol, or LiCl; however, isolation-reared rats were found to be less sensitive to the aversive effects of d-amphetamine, morphine, and caffeine in this paradigm. These results suggest that rearing rats in social isolation induces an attenuation in sensitivity to the aversive effects of some psychoactive agents.

Active Posture Control during Experimental Motion Sickness in Guinea-Pigs

This study evaluated active posture control in guinea-pigs under motion sickness stimulation. Twelve guinea-pigs, which received training to stay on a moving perch, were divided into two groups: a motion sickness stimulation group and a control group. The motion sickness group was given a combined stimulation of turntable rotation and optokinetic drum rotation, and the control group was given turntable stimulation alone. Motion sickness was evaluated by conditioned taste aversion to saccharin solution. Active posture control was evaluated by the angle of nose tip displacement and the staying duration (length of time that guinea-pigs stayed on the turntable). The consumption of saccharin solution increased in the control group but did not increase in the motion sickness group. The motion sickness group showed a significant increase in the mean angle of nose tip displacement and a significant decrease in the staying duration on the turntable. These results indicate that active posture control was disturbed by motion sickness stimulation.

Endotoxin produces a depressive-like episode in rats

Activation of the immune system produces psychological and physiological effects, which resemble the characteristics of depression. The present study was designed to investigate further, in rats, the similarity between the behavioral effects of immune activation and a model of depression in animals. Reduction in the preference for and consumption of saccharin solutions and suppression of sexual behavior were used as models of one essential feature of depression, the inability to experience pleasure (anhedonia). Other measures testing this model were the reduction in food consumption, body weight, locomotor activity, and social interaction. It was found that systemic injection of lipopolysaccharide (endotoxin), which is a potent activator of the immune system, significantly decreased saccharin preference in fluid-deprived rats. Lipopolysaccharide (LPS) also decreased free consumption of saccharin, but not water, in non-deprived rats. Several indices of male sexual behavior were significantly suppressed following LPS administration. Chronic, but not acute, treatment with the tricyclic antidepressant imipramine abolished the suppressive effect of LPS on saccharin preference. Moreover, chronic, but not acute, treatment with imipramine also reduced and facilitated the recovery from the suppressive effects of LPS on food consumption, body weight, social interaction and activity in the open-field test. The results suggest that activation of the immune system in rats produces anhedonia and other depressive-like symptoms, which can be attenuated or completely blocked by chronic treatment with an antidepressant drug.

Both conditioned taste preference and aversion induced by corticotropin-releasing factor.

Postprandial administration in the rat of a wide variety of drugs, peptides and toxins suppresses future consumption of a meal of previously unfamiliar but otherwise attractive saccharin-flavored solution. Since the intensity of this conditioned flavor aversion in the rat is sensitive to plasma stress hormone levels, the present study examined the effects on flavor conditioning of corticotropin-releasing factor, a peptide known to be involved in behavioral and hormonal responses to stress. In two-bottle water vs. saccharin choice tests, CRF (0.5 microgram ICV) increased significantly the consumption of saccharin solution following a single saccharin/CRF pairing, while a tenfold larger dose of CRF (5 micrograms ICV) abolished saccharin intake following two saccharin/CRF pairings. Hence, exogenous CRF is capable of inducing both flavor preference and aversion in a dose- and situation-dependent manner. Further, direct neurotropic actions of CRF probably subserve its aversive effect since dexamethasone pretreatment weakened but did not prevent CRF-induced conditioned taste avoidance. These results suggest that at low doses CRF can produce arousal actions that result in taste preference and at higher doses produces aversive effects that are reflected in taste avoidance.

Chlordiazepoxide nonspecifically enhances consumption of saccharin solution

Following the establishment of a saccharin-amphetamine, saccharin-lithium or saccharin-saline association, rats were given a two-bottle test of preference for saccharin and water. Thirty min prior to the test, half of the rats were pretreated with chlordiazepoxide (9 mg/kg) and half of the rats were pretreated with saline. The results revealed that pretreatment with chlordiazepoxide (CDP) nonselectively enhanced saccharin consumption regardless of wheter the flavored solutionshad been paired with amphetamine, lithium or saline. These redults provide evidence that CDP enhances the palatability of flavored solutions.

CGS 8216, a novel anorectic agent, selectively reduces saccharin solution consumption in the rat

The pyrazoloquinoline CGS 8216, a high-affinity ligand for benzodiazepine, recognition sites, significantly reduced the consumption of a preferred 0.05% sodium saccharin solution in a 30 min two-bottle test. A highly significant effect was detected at 5.0 mg/kg, IP and at higher doses. The consumption of water and 0.6% saline, in two-bottle tests, or of quinine solution and water, in a forced-choice test, was not reliably affected by CGS 8216. The results point to a sensitive and selective intrinsic effect of CGS 8216 on ingestional responses in the rat.

Successive, simultaneous, and anticipatory contrast in the consumption of saccharin solutions.

Contrast effects were obtained in rats in the consumption of saccharin solutions in three different paradigms. Degree of negative contrast varied as a function of concentration disparity, but not equally in the three procedures. Successive negative contrast occurred following shifts from 0.15% to either 0.075% or 0.05% saccharin but did not occur following shifts to 0.10% or 0.125% saccharin. Some degree of simultaneous contrast was obtained with all four concentration disparities. Anticipatory contrast, where the intake of the first substance is suppressed by a more preferred second substance, occurred only in the case of the 0.05%-0.15% difference in concentrations. It was suggested that the several contrast paradigms engage somewhat different psychological processes differentially involving emotional, sensory, and associative mechanisms, but all lead to behavior based on relative value. A modification of Toates's (1981) incentive model of ingestive behavior was suggested to incorporate relativity effects based on both associative and nonassociative factors in the consumption of both nutritive and nonnutritive substances.

Successive, simultaneous, and anticipatory contrast in the consumption of saccharin solutions.

Successive, simultaneous, and anticipatory contrast in the consumption of saccharin solutions.