Orosensory Properties Research Articles

Impact of vanilla flavor on nicotine taste, choice, intake, and seeking behaviors.

Flavors can alter the orosensory properties of tobacco products. Specifically, flavors can serve as an oral cue for smokeless tobacco products. We aimed to investigate the impact of oral vanillin, the principal chemical of vanilla flavor in tobacco products, on nicotine's taste, and nicotine choice, intake, and seeking behaviors. Experiments were performed in young adult Sprague Dawley rats. We employed a two-bottle free-choice test (2BC) to measure the preference for different concentrations of vanillin and its effect on nicotine preference. To explore the long-term effects of early exposure to sweetened vanillin, we utilized a combined 2BC and intraoral self-administration (IOSA) model. We assessed the nicotine taking and seeking behaviors in the presence or absence of vanillin. We performed a taste reactivity test (TRT) to quantify liking (ingestive) and disliking (aversive) taste responses to oral nicotine with or without vanillin. In 2BC, female rats preferred vanillin containing solutions more than their male counterparts. In IOSA, vanillin alone and in combination with nicotine led to greater IOSA compared to water. Female rats self-administered vanillin plus nicotine more than male rats. Vanillin increased motivation to nicotine taking, but only in females. In TRT, vanillin increased nicotine's ingestive responses but blocked aversive responses in both sexes. These results indicate that vanilla flavor can increase oral nicotine intake. It can also increase liking and decrease disliking of nicotine's taste. Furthermore, the impact of vanilla flavor on nicotine taste and nicotine choice, intake, and seeking behaviors is concentration and sex dependent.

Perspective: Plant-Based Meat Alternatives Can Help Facilitate and Maintain a Lower Animal to Plant Protein Intake Ratio.

The health and environmental advantages of plant-predominant diets will likely lead to increasing numbers of consumers reducing their reliance on animal products. Consequently, health organizations and professionals will need to provide guidance on how best to make this change. In many developed countries, nearly twice as much protein is derived from animal versus plant sources. Potential benefits could result from consuming a higher share of plant protein. Advice to consume equal amounts from each source is more likely to be embraced than advice to eschew all or most animal products. However, much of the plant protein currently consumed comes from refined grains, which is unlikely to provide the benefits associated with plant-predominant diets. In contrast, legumes provide ample amounts of protein as well other components such as fiber, resistant starch, and polyphenolics, which are collectively thought to exert health benefits. But despite their many accolades and endorsement by the nutrition community, legumes make a negligible contribution to global protein intake, especially in developed countries. Furthermore, evidence suggests the consumption of cooked legumes will not substantially increase over the next several decades. We argue here that plant-based meat alternatives (PBMAs) made from legumes are a viable alternative, or a complement, to consuming legumes in the traditional manner. These products may be accepted by meat eaters because they can emulate the orosensory properties and functionality of the foods they are intended to replace. PBMAs can be both transition foods and maintenance foods in that they can facilitate the transition to a plant-predominant diet and make it easier to maintain. PBMAs also have a distinct advantage of being able to be fortified with shortfall nutrients in plant-predominant diets. Whether existing PBMAs provide similar health benefits as whole legumes, or can be formulated to do so, remains to be established.

Dietary experience with glucose and fructose fosters heightened avidity for glucose-containing sugars independent of TRPM5 taste transduction in mice

ABSTRACT Objective Experience with metabolically distinct sugars, glucose and fructose, enhances attraction to the orosensory properties of glucose over fructose. To gain insight into which sensory signals are affected, we investigated how this nutritive learning reshapes behavioral responding to various sugars in brief access taste tests in C57BL6/J (B6) mice and assessed whether sugar-exposed mice lacking the TRPM5 channel involved in G-protein coupled taste transduction could acquire these types of preferences for glucose-containing sugars. Methods B6, TRPM5 knockout (KO), and TRPM5 heterozygous (Het) mice were given extensive access to water (sugar naïve) or 0.316, 0.56, and 1.1 M glucose and fructose (sugar-exposed) and then tested, whilst food deprived, for their relative avidities for glucose, fructose, sucrose, maltose, and/or a non-metabolizable glucose analog in a series of taste tests. Results Sugar-exposed B6 mice licked relatively more for glucose than fructose, driven by an increased avidity for glucose, not an avoidance of fructose, and licked more for maltose, compared to their sugar-naïve counterparts. Sugar-exposed B6 mice did not lick with such avidity for a non-metabolizable glucose analog. TRPM5 KO mice took longer to acquire the sugar discrimination than the Het controls, but both groups ultimately licked significantly more for glucose than fructose. Het mice displayed clear preferential licking for sucrose over fructose, while licking comparably high for glucose, sucrose, and maltose. KO mice licked significantly more for maltose than sucrose. Conclusions Collectively, the findings suggest that ingestive experience with glucose and fructose primarily reprograms behavioral responding to a TRPM5-independent orosensory signal generated by glucose-containing sugars.

The effect of cocoa alkalization on the non-volatile and volatile mood-enhancing compounds

Alkalization is a process to improve color, dispersibility and flavor of cocoa powder but is likely to have a negative effect on the phytochemicals. Hereto, the impact of alkalization degree (none, medium and high) on the potential mood-enhancing compounds corresponding to the four levels of the mood pyramid model (flavanols, methylxanthines, biogenic amines and orosensory properties) was investigated. The phytochemical content, analyzed via UPLC-HRMS, showed reduction of specific potential mood-enhancing compounds upon alkalization, implying a decrease in bitterness and astringency. Moreover, volatile compounds analysis via HS-SPME-GC–MS indicated that alkalization reduced the levels of volatile compounds, responsible for acidity, fruity, floral and cocoa aromas. With respect to the orosensory properties, the cocoa powder palatability was suggested to be increased due to reduced acidity, bitterness, and astringency, while the desired volatile compounds were reduced. However, sensorial analysis is required to link the volatile results with the overall effect on the flavor perception.

Profiling Individual Differences in Alcoholic Beverage Preference and Consumption: New Insights from a Large-Scale Study.

Alcoholic beverage consumption plays an important role in European culture, and in many contexts drinking alcohol is socially acceptable and considered part of the diet. Understanding the determinants of alcohol preference and consumption is important not only for disease prevention, intervention, and policy management, but also for market segmentation, product development, and optimization. The aim of the study was to investigate the effect of individual responsiveness to various oral sensations on self-reported liking and intake of 14 alcoholic and non-alcoholic beverages (including beers, wines, spirits, and cocktails) considering gender, age, and oral responsiveness (measured through response to 6-n-propyl-2-thiouracil -PROP, basic tastes, astringency, and pungency) in a large sample of Italian consumers. Data were collected from 2388 respondents (age range 18–60 years; mean age = 37.6, SD = 13.1; 58.2% women). These results indicate that notwithstanding the strong gender difference, with women generally liking and consuming fewer alcoholic beverages than men, liking patterns in the two genders were similar. Three liking patterns for different alcoholic beverages largely driven by orosensory properties were identified in both genders. “Spirit-lovers” constituted the smallest group (12%), consumed alcoholic beverages of any kind (not only spirits) more than the other segments, and were mainly men aged 30–45. “Beer/wine lovers” (44%) were the oldest group with no difference by gender. “Mild-drink lovers” (44%) liked alcoholic drinks with intense sweet taste and/or mixers that moderate ethanol perception. They were mainly women, aged 18–29, had a lower consumption of alcohol, and a higher orosensory responsiveness than the other two groups. The results also suggest the opportunity to develop personalized recommendations towards specific consumer segments based not only on socio-demographics but considering also perceptive variables. Finally, our data suggest that increased burning and bitterness from alcohol may act as a sensory hindrance to alcoholic beverage overconsumption.

The Role of Post-Ingestive Feedback in the Development of an Enhanced Appetite for the Orosensory Properties of Glucose over Fructose in Rats.

The simple sugars glucose and fructose share a common “sweet” taste quality mediated by the T1R2+T1R3 taste receptor. However, when given the opportunity to consume each sugar, rats learn to affectively discriminate between glucose and fructose on the basis of cephalic chemosensory cues. It has been proposed that glucose has a unique sensory property that becomes more hedonically positive through learning about the relatively more rewarding post-ingestive effects that are associated with glucose as compared to fructose. We tested this theory using intragastric (IG) infusions to manipulate the post-ingestive consequences of glucose and fructose consumption. Food-deprived rats with IG catheters repeatedly consumed multiple concentrations of glucose and fructose in separate sessions. For rats in the “Matched” group, each sugar was accompanied by IG infusion of the same sugar. For the “Mismatched” group, glucose consumption was accompanied by IG fructose, and vice versa. This condition gave rats orosensory experience with each sugar but precluded the differential post-ingestive consequences. Following training, avidity for each sugar was assessed in brief access and licking microstructure tests. The Matched group displayed more positive evaluation of glucose relative to fructose than the Mismatched group. A second experiment used a different concentration range and compared responses of the Matched and Mismatched groups to a control group kept naïve to the orosensory properties of sugar. Consistent with results from the first experiment, the Matched group, but not the Mismatched or Control group, displayed elevated licking responses to glucose. These experiments yield additional evidence that glucose and fructose have discriminable sensory properties and directly demonstrate that their different post-ingestive effects are responsible for the experience-dependent changes in the motivation for glucose versus fructose.

Food portion size influences accompanying beverage selection in adults

When trying to reduce food portion size, it is important that meal satisfaction is, as far as possible, preserved. Otherwise, individuals may select accompaniments to the meal (e.g., snacks, beverages) to achieve satisfaction and, in doing so, negate any benefit of the original portion size reduction. This study investigated whether varying portion sizes of food would influence choice of accompanying beverages. That is, when presented with a food portion size that is smaller or larger than their ideal, an individual may compensate by choosing a beverage based on its satiating and/or orosensory properties to balance the expected satiation and satisfaction of a meal. Data from an online interactive study (n = 93) was analysed using multilevel ordinal logistic regression models. Food portion size (100, 300, 500, 700, or 900 kcal) predicted beverage choice (water, low-energy sweetened beverage, high-energy sweetened beverage). For example, the sweetened beverages were more likely to be selected with small food portion sizes (p < .001). Participant ideal food portion size did not interact with this relationship. Participants appear to have recognised that sweetened beverages provide flavour and/or energy, and used them to compensate for a smaller meal. While switching to a low-energy beverage with an increased food portion size is advantageous for energy balance, choosing a high-energy beverage with a decreased food portion size is likely to be detrimental for those attempting to reduce energy intake and body weight.

Mood Components in Cocoa and Chocolate: The Mood Pyramid.

Cocoa and chocolate, prepared from cocoa beans that originate from the fruits of the cocoa tree Theobroma cacao, have a long-standing reputation as healthy food, including mood-enhancing effects. In spite of many clinical trials with chocolate, cocoa, or its constituents, the mechanisms of action on mood and cognition remain unclear. More in particular, it is still controversial which constituents may contribute to the psychopharmacological activities, ranging from the major cacao flavanols and methylxanthines to the minor amines, amides, and alkaloids. In this review a critical appraisal is made of recent studies on mood and cognition, with a special emphasis on analytical characterization of the test samples. It is concluded that the mood and cognition-enhancing effects of cocoa and chocolate can be ranked from more general activities associated with flavanols and methylxanthines, to more specific activities related to minor constituents such as salsolinol, with on top the orosensory properties of chocolate. Therefore, the "mood pyramid" of cocoa and chocolate is proposed as a new concept. To understand the role and interactions of the different major and minor constituents of cocoa, it is recommended that all test samples used in future in vitro, in vivo, or human studies should be phytochemically characterized in much more detail than is common practice today.

Brief Exposures to the Taste of Ethanol (EtOH) and Quinine Promote Subsequent Acceptance of EtOH in a Paradigm that Minimizes Postingestive Consequences.

Aversion to the orosensory properties of concentrated ethanol (EtOH) solutions is often cited as a primary barrier to initiation of drinking and may contribute to abstention. These aversive properties include gustatory processes which encompass both bitter-like taste qualities and trigeminal-mediated irritation. Chronic intermittent EtOH access (CIA) results in substantial and persistent increases in EtOH consumption, but the degree to which this facilitation involves sensory responding to EtOH and other bitter stimuli is currently undetermined. Long-Evans rats were given brief-access licking tests designed to examine the immediate, taste-guided assessment of the palatability of EtOH and quinine solutions. Rats were assessed once in a naïve state and again following previous brief-access exposure, or following 4weeks of CIA. The relationship between the sensitivity to the aversive orosensory properties of EtOH and quinine following EtOH access and the impact of antecedent quinine exposure on the acceptance of EtOH were determined in 2 parallel studies. Both brief access to EtOH and 4-week CIA resulted in substantial rightward shifts in the concentration-response function of brief-access EtOH licking, indicating that EtOH exposure increased acceptance of the taste of EtOH. The initial sensitivity to the aversive orosensory properties of EtOH and quinine was positively correlated in naïve rats, such that rats that were initially more accepting of quinine were also more accepting of EtOH. Rats that sampled quinine immediately prior to tasting EtOH exhibited successive positive contrast in that they were more accepting of highly concentrated EtOH, relative to a water-control group. Increased EtOH acceptance following exposure is, at least in part, facilitated by a decrease in its aversive sensory properties. Both long- and short-term access increase the palatability of the taste of EtOH in brief-access licking tests. Moreover, the sensitivity to the bitterness of quinine was predictive of acceptance of EtOH indicating some commonality in the sensory mechanisms that mediate the initial acceptance of the 2 stimuli. Accordingly, immediate prior exposure to quinine results in increased acceptance of EtOH, suggesting that successive positive contrast between oral stimuli may contribute to increased alcohol consumption.

Polyphenol-rich curry made with mixed spices and vegetables increases postprandial plasma GLP-1 concentration in a dose-dependent manner.

Glucagon-like peptide-1 (GLP-1) plays an important role in glucose homeostasis. Evidence is emerging that dietary bioactive phytochemicals such as polyphenols can increase GLP-1 concentration in vivo. Spices are rich in polyphenols and have oro-sensory properties, both of which can increase GLP-1 secretion. We therefore investigated the effects of mixed spices intake on postprandial GLP-1 concentration. Using a randomised, controlled, dose-response crossover trial in 20 young, healthy, Chinese men, volunteers were served white rice with 3 doses of curry made with mixed spices and vegetables. These test meals were isocaloric and macronutrient matched. Plasma total GLP-1 concentrations were measured before (baseline) and for up to 3 h after the consumption of test meals. We found a significant dose dependent increase in total AUC of plasma GLP-1 concentrations, adjusted for baseline, with increasing mixed spice doses [adjusted mean (±SEM) of 10568.3 ± 1267.9, 12391.8 ± 1333.94, and 13905.1 ± 1267.6 pg ml-1.min for Dose 0 Control, Dose 1 Curry and Dose 2 Curry respectively (p = 0.019)]. Consumption of polyphenol rich mixed spices and vegetables can therefore increase in vivo GLP-1 concentration.

Does eating good-tasting food influence body weight?

Does eating good-tasting food influence body weight? To investigate, we first established some concentrations of sucralose and mineral oil in chow that mice strongly preferred. Then, in Experiment 1, we compared groups of 16 mice fed plain chow (i.e., chow with no additives) to groups fed chow with added (a) sucralose, (b) mineral oil, (c) sucralose and mineral oil, or (d) sucralose on odd days and mineral oil on even days. During a 6-week test, the body weights and body compositions of the five groups never differed. In Experiment 2, we compared groups of 18 mice fed plain chow or plain high-fat diet to groups fed these diets with added sucralose. During a 9-week test, the high-fat diet caused weight gain, but the body weights of mice fed the sucralose-sweetened diets did not differ from those fed the corresponding plain versions. Two-cup choice tests conducted at the end of each experiment showed persisting strong preferences for the diets with added sucralose and/or mineral oil. In concert with earlier work, our results challenge the hypothesis that the orosensory properties of a food influence body weight gain. A good taste can stimulate food intake acutely, and guide selection toward nutrient-dense foods that cause weight gain, but it does not determine how much is eaten chronically.

Effects of ethanol exposure in a familiar or isolated context during infancy on ethanol intake during adolescence.

Early exposure to ethanol affects ethanol intake later in life. This early experience encompasses exposure to social stimuli and the pharmacological and orosensory properties of ethanol. The specific contribution of each type of stimulus to subsequent ethanol intake remains unknown. We assessed the intake of various concentrations of ethanol in a familiar or isolated context during infancy and the lingering effects of this experience on ethanol intake during adolescence. On postnatal day 3 (PD3), PD7, and PD11, rats were given 5% ethanol or water in a nursing or isolated context (Experiments 1 and 2). Intake tests (ethanol vs. water) were conducted during adolescence. Experiment 2 matched the amount of fluid ingested during infancy in both contexts and subsequently tested ethanol consumption during adolescence. The results revealed a facilitative effect of the nursing context on fluid intake during the tests in infancy. Pups stimulated with ethanol but not water in the isolated context exhibited an increase in ethanol consumption during adolescence. This effect disappeared when the isolated infants were matched to receive the same amount of ethanol ingested by their nursed counterparts. In Experiment 3, isolated infant rats were exposed to different ethanol concentrations (.0%, 2.5%, 5.0%, and 10.0%), and drug consumption was tested during adolescence. This exposure increased adolescent ethanol intake, regardless of the alcohol concentration (Experiment 3). The common denominators that resulted in enhanced ethanol intake during adolescence were preexposure to ethanol via active consumption of the drug that induced a low-to-moderate level of intoxication in an isolated context.

In search of flavour-nutrient learning. A study of the Samburu pastoralists of North-Central Kenya

Much of our dietary behaviour is learned. In particular, one suggestion is that ‘flavour-nutrient learning’ (F-NL) influences both choice and intake of food. F-NL occurs when an association forms between the orosensory properties of a food and its postingestive effects. Unfortunately, this process has been difficult to evaluate because F-NL is rarely observed in controlled studies of adult humans. One possibility is that we are disposed to F-NL. However, learning is compromised by exposure to a complex Western diet that includes a wide range of energy-dense foods. To test this idea we explored evidence for F-NL in a sample of semi-nomadic pastoralists who eat a very limited diet, and who are lean and food stressed. Our Samburu participants (N = 68) consumed a sensory-matched portion (400 g) of either a novel low (0.72 kcal/g) or higher (1.57 kcal/g) energy-dense semi-solid food on two training days, and an intermediate version on day 3. Before and after each meal we measured appetite and assessed expected satiation and liking for the test food. We found no evidence of F-NL. Nevertheless, self-reported measures were very consistent and, as anticipated, expected satiation increased as the test food became familiar (expected-satiation drift). Surprisingly, we observed insensitivity to the effects of test-meal energy density on measures of post-meal appetite. To explore this further we repeated a single training day using participants (N = 52) from the UK. Unlike in the Samburu, the higher energy-dense meal caused greater suppression of appetite. These observations expose interesting cross-cultural differences in sensitivity to the energy content of food. More generally, our work illustrates how measures can be translated to assess different populations, highlighting the potential for further comparisons of this kind.

Nontargeted metabolite profiles and sensory properties of strawberry cultivars grown both organically and conventionally.

Strawberry (Fragaria × ananassa Duch.) contains many secondary metabolites potentially beneficial for human health, and several of these compounds contribute to strawberry sensory properties, as well. In this study, three strawberry cultivars grown both conventionally and organically were subjected to nontargeted metabolite profiling analysis with LC-qTOF-ESI-MS and to descriptive sensory evaluation by a trained panel. Combined metabolome and sensory data (PLS model) revealed that 79% variation in the metabolome explained 88% variation in the sensory profiles. Flavonoids and condensed and hydrolyzable tannins determined the orosensory properties, and fatty acids contributed to the odor attributes of strawberry. Overall, the results indicated that the chemical composition and sensory quality of strawberries grown in different cultivation systems vary mostly according to cultivar. Organic farming practices may enhance the accumulation of some plant metabolites in specific strawberry genotypes. Careful cultivar selection is a key factor for the improvement of nutritional quality and marketing value of organic strawberries.

Optimizing the Orosensory Properties of Model Functional Beverages: The Influence of Novel Sweeteners, Odorants, Bitter Blockers, and Their Mixtures on (+)‐Catechin

The use of flavor-modifying strategies are important to improving the sensory profile of some excessively bitter and astringent functional ingredients, such as (+)-catechin (CAT). Two bitter blockers (ß-cyclodextrin [CYCLO], homoeriodictyol sodium salt [HED]), two sweeteners (sucrose [SUC], rebaudioside A [REB]), and two odorants (vanillin [VAN], black tea aroma [TEA]) were assessed for their efficacy at modifying the bitterness and astringency of CAT in model aqueous solutions. The intensity of oral sensations elicited by CAT was determined in duplicate in binary, ternary, and quaternary mixtures of these stimuli by a trained panel (n = 15) using a 15 cm visual analogue scale. Overall, bitterness and astringency were most effectively reduced by ternary solutions containing CYCLO + REB or CYCLO + SUC (68%, 60%, and 45%, 43% for bitterness and astringency, respectively). Odorants were not effective at modifying the bitterness or astringency of CAT. We conclude that the use of select bitter blockers and sweeteners may be of value in optimizing the flavor and acceptance of functional food and beverages fortified with phenolic compounds. (+)-Catechin is a bitter-tasting plant-derived health-promoting phenolic compound of interest to functional food and beverage manufacturers. We investigated the efficacy of bitter blockers, plant-based sweeteners, and odorants in decreasing the bitterness and astringency elicited by (+)-catechin. Some of these additives, both alone and in combination, reduced bitterness and astringency, and may therefore assist in optimizing the flavor and consumer acceptance of some phenolic-based functional foods and beverages.

Endocannabinoids: An appetite for fat

It has been known for decades that marijuana causes the “munchies,” i.e., a hunger for palatable food, and for more than 10 y that endocannabinoids (eCBs), in some ways marijuana's counterpart in the organism, are orexigenic mediators (1). When injected in the hypothalamus (HT) or nucleus accumbens (NAc), two key brain areas for the homeostatic and hedonic control of food intake, these compounds stimulate food consumption by acting at the cannabinoid CB1 receptor, one of the two G protein-coupled receptors for marijuana's psychotropic and appetite-inducing component, Δ9-tetrahydrocannabinol (2, 3). Conversely, systemic pharmacological blockade of CB1 receptors causes anorectic effects in rodents exposed to palatable food, or food-deprived for a few hours, and in obese animals (3–6). The two most studied eCBs, anandamide and 2-arachidonoylglycerol (2-AG), are considered local mediators produced by cells only following stimulation, and in this they differ from other signals controlling food intake, which are released into the bloodstream and/or prestored in vesicles (1). What makes the eCBs similar to most orexigenic signals is the fact that their concentrations in the HT and NAc, but also in the proximal intestine, which transmits to the brain the state of “emptiness” or “fullness” of the gut, increase during food deprivation and decrease immediately after food consumption (3, 7, 8). This mechanism is presumably caused by the opposing effects on eCB levels of hormones such as leptin, on the one hand, and ghrelin and corticosterone, on the other hand, the levels of which also vary during food deprivation and refeeding (1, 6). These food intake- and hormone-sensitive changes in eCB signaling are thought to play a key role in the regulation of (i) the release of central neurotransmitters and neuropeptides controlling food intake and (ii) the activity of vagal fibers from the duodenum to the brainstem, which signal gastric distension (1). In this scenario, the results of the elegant study by DiPatrizio and coworkers published in PNAS (9), although in full agreement with the general orexigenic function of eCBs and CB1 receptors, might seem somewhat surprising. In fact, the authors report that a fatty meal elevates eCBs selectively in the rat proximal small intestine, and propose that this effect: (i) is induced by the orosensory properties of the meal; (ii) is mediated by vagal afferent and efferent terminals, and (iii) reinforces fat intake via CB1 receptor activation (9).

Orosensory contributing compounds in crowberry ( Empetrum nigrum) press-byproducts

Berries of crowberry ( Empetrum nigrum) were fractionated by juice pressing, ethanol extraction, solvent evaporation and supercritical fluid extraction. Phenolic compounds, sugars and acids in the fractions were analysed by high-performance liquid chromatography and gas chromatography. The sensory characteristics of the fractions were studied by using generic descriptive analysis. Most of the sugars were located in the juice and this was perceived as the sweetest of the fractions. The majority of the phenolic compounds were anthocyanins, located in the press residue. Ethanol extracted nearly all the phenolic compounds from the press residue. The extracts were the most bitter and astringent of the fractions. Eight flavonol glycosides and two flavonol aglycones were discovered to contribute particularly to bitterness and astringency. After ethanol extraction, only fibres and seeds were left, and the supercritical fluid extraction removed only a small amount of compounds from this fraction, which did not have any impact on sensory properties. This study shows that crowberries are rich in different nutrients and some of them are contributing to orosensory properties. The sequential fractionation by ethanol ended up in products with substantial differences in their orosensory characteristics and nutrient composition. Stepwise fractionation empowers versatile and beneficial ways to exploit the berries in food industry.

Endogenous nociceptin modulates diet preference independent of motivation and reward

Previous studies show that the opioid peptide nociceptin stimulates food intake. Here, we studied nociceptin receptor knockout (NOP KO) mice in various behavioral paradigms designed to differentiate psychological and physiological loci at which endogenous nociceptin might control feeding. When presented a choice under food restriction, NOP KO mice displayed reduced preference for high sucrose diet, but lower intake of high fat diet under no-choice conditions. These responses were absent under ad libitum feeding conditions. Conditioned place preference to high fat diet under food-deprived conditions was unaltered in NOP KO mice, suggesting no difference in reward responses. Furthermore, operant food self-administration under a variety of conditions showed no genotype-dependent differences, suggesting no differences in the motivational properties of food. Taste reactivity to sucrose was unchanged in NOP KO mice, though NOP KO mice had altered aversive reactions to quinine solutions under ad libitum feeding, suggesting minor differences in the affective impact of palatable and unpalatable tastants. Although NOP KO mice re-fed following food-deprivation showed normal increases in plasma glucose and insulin, multidimensional scaling analysis showed that the relationship between these measures, body weight and plasma leptin was substantially disrupted in NOP KO, particularly in fasted mice. Additionally, the typical positive relationship between body weight and plasma leptin was considerably weaker in NOP KO mice. Together, these findings suggest that endogenous nociceptin differentially modulates diet preference depending on macronutrient content and homeostatic state, independently of the motivating, rewarding or orosensory properties of food, but may involve metabolic or postingestive processes.

Ethanol, Saccharin, and Quinine: Early Ontogeny of Taste Responsiveness and Intake

Rat pups demonstrate high levels of immediate acceptance of ethanol during the first 2 weeks of postnatal life. Given that the taste of ethanol is most likely perceived by infant rats as a combination of sweet and bitter, high intake of ethanol early in ontogeny may be associated with age-related enhanced responsiveness to the sweet component of ethanol taste, as well as with ontogenetic decreases in sensitivity to its bitter component. Therefore, the present study compared responsiveness to ethanol and solutions with bitter (quinine) and sweet (saccharin) taste in terms of intake and palatability across the first 2 weeks of postnatal life. Characteristic patterns of responsiveness to 10% (v/v) ethanol, 0.1% saccharin, 0.2% quinine, and water in terms of taste reactivity and fluid intake were assessed in rat pups tested on postnatal day (P) 4, 9, or 12 using a new technique of on-line monitoring of fluid flow through a two-channel intraoral cannula. Taste reactivity included analysis of ingestive and aversive responses following six intraoral infusions of the test fluids. This taste reactivity probe was followed by the intake test, in which animals were allowed to voluntarily ingest fluids from an intraoral cannula. Pups of all ages showed more appetitive responses to saccharin and ethanol than to water or quinine. No age-related differences were apparent in taste responsiveness to saccharin and ethanol. However, the age-related pattern of ethanol intake drastically differed from that of saccharin. Intake of saccharin increased from P4 to P9 and decreased substantially by P12, whereas intake of ethanol gradually increased from P4 to P12. Intake of ethanol was significantly lower than intake of saccharin on P9, whereas P12 pups took in more ethanol than saccharin. The findings of the present study indicate ontogenetic dissociations between taste reactivity to ethanol and saccharin and intake of these solutions, and suggest that high acceptance of ethanol early in ontogeny may not be associated with its orosensory properties but rather with the pharmacological effects of ethanol.

Infant rats exhibit aversive learning mediated by ethanol's orosensory effects but are positively reinforced by ethanol's post-ingestive effects

Previous work suggest aversive and appetitive hedonic effects of intraorally delivered EtOH in pre-weanling rats. Pups are reluctant to perform an operant response when reinforced with intraoral EtOH infusions, a result suggesting aversive orosensory properties of EtOH. Yet, post-absorptive effects of ethanol seem capable of supporting appetitive conditioning. Two experiments were conducted to test this phenomenon. Both included a pre-exposure phase (postnatal day 13, PD13) comprising intraoral stimulation with water or EtOH. In Experiment 1, pups were given pairings between a tactile conditioned stimulus (CS) and intraoral infusions of EtOH or water. A subsequent tactile preference test revealed that pups spent significantly less on the EtOH-related CS relative to time spent on the alternative CS. In Experiment 2 pups were exposed to a texture CS (sandpaper) while intraorally infused with EtOH or during a later EtOH post-infusion interval. A tactile locational test conducted on PD16 indicated that EtOH-pre-exposed animals that experienced sandpaper paired with EtOH's post-absorptive effects exhibited a significant preference for the CS, even relative to a control group that experienced non-reinforced exposure to the tactile CS during conditioning. These results confirm that intraoral ethanol acts as an aversive tastant. A brief pre-exposure to EtOH allows later expression of appetitive learning mediated by the drug's post-ingestive effects.