Conditioned Food Aversion Research Articles

Histone H3 Acetylation is Asymmetrically Induced Upon Learning in Identified Neurons of the Food Aversion Network in the Mollusk Helix Lucorum.

Regulation of gene expression is an essential step during long-term memory formation. Recently, the involvement of DNA-binding transcription factors and chromatin remodeling in synaptic plasticity have been intensively studied. The process of learning was shown to be associated with chromatin remodeling through histone modifications such as acetylation and phosphorylation. We have previously shown that the MAPK/ERK (mitogen-activated protein kinase/extracellular signal-regulated kinase) regulatory cascade plays a key role in the food aversion conditioning in the mollusk Helix. Specifically, command neurons of withdrawal behavior exhibit a learning-dependent asymmetry (left–right) in MAPK/ERK activation. Here, we expanded our molecular studies by focusing on a potential MAPK/ERK target – histone H3. We studied whether there is a learning-induced MAPK/ERK-dependent acetylation of histone H3 in command neurons RPa(2/3) and LPa(2/3) of the right and left parietal ganglia and whether it is asymmetrical. We found a significant learning-dependent increase in histone H3 acetylation in RPa(2/3) neurons but not in LPa(2/3) neurons. Such an increase in right command neurons depended on MAPK/ERK activation and correlated with a lateralized avoidance movement to the right visible 48 h after training. The molecular changes found in a selective set of neurons could thus represent a lateralized memory process, which may lead to consistent turning in one direction when avoiding a food that has been paired with an aversive stimulus.

Hunger increases memory for conditioned food aversion: role of central Orexin

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A tasty morsel: the role of the dorsal vagal complex in the regulation of food intake and swallowing. Focus on “BDNF/TrkB signaling interacts with GABAergic system to inhibit rhythmic swallowing in the rat,” by Bariohay et al.

energy balance depends on the regulation of two central circuits that control feeding behavior. On one hand, the central nervous system (CNS) must coordinate and integrate appetite, food-seeking behavior, and thermoregulation. On the other hand, signals relating to satiety (e.g., from the gut) and

Social models fail to induce diet and feeding site avoidance in naïve yearling steers

Social learning can be of critical importance to cattle grazing rangeland environments with high variability of food resources across space and time. Experienced individuals can greatly facilitate foraging decisions (what to eat and where to eat) of naïve peers in such settings. We conducted an experiment with cattle to investigate strength and persistence of socially induced food and feeding site avoidance behaviours. Sixteen naïve yearling steers were paired with 16 social models that had either not been trained (control) or been trained with an emetic (LiCl), electrical shock or both to avoid: (a) an unsafe high-quality food (LiCl); (b) an unsafe high-quality feeding site (shock); or (c) both the unsafe high-quality food and the unsafe high-quality feeding site (LiCl + shock). Ten-minute trials were conducted in an experimental arena containing three artificial feeding sites each consisting of groups of bowls with either high- (HQ) or moderate-quality (MQ) foods (HQ = barley and oat grain; MQ = Bermuda grass hay). Unsafe high-quality (UHQ, surrounded by traffic cones) and safe moderate-quality (SMQ) feeding sites consisted of nine rubber bowls containing either HQ or MQ foods. The safe high-quality (SHQ) feeding site consisted of two groups of eight bowls containing HQ food, which surrounded the UHQ and SMQ feeding sites. Social models did not induce diet and feeding site avoidance behaviours in naïve steers; they exerted small and transient changes in the feeding behaviour of their naïve counterparts. Consequences to the individual outweighed social influences; when naïve animals experienced the same punishment contingencies as their social models, their behavioural patterns closely resembled those of their social model. Conditioned food and location aversions via LiCl were apparently influenced by prior exposure to target foods and the experimental arena. Conversely, conditioned feeding site avoidance via shock was apparently not influenced by prior exposure to target foods or the experimental arena.

Various mechanisms of contextual memory involvement in recalling the processes of food aversive conditioning in snails

Mechanisms of involvement of contextual memory in the retrieval of food aversion conditioning were studied in the snail Helix lucorum. The reaction for food aversion conditioning was found to be observed only in the conditioning context and never in the neutral context. The reminding procedure (presentation of conditioning food stimuli) performed after the injection of cycloheximide, an inhibitor of protein synthesis, and the placement of snails in the conditioning context, produced long-term amnesia. The injection of cycloheximide in the conditioning context without the subsequent reminding procedure did not result in the long-term amnesia. Food aversion conditioning also produced contextual conditioning, which was characterized by an increase in the latency of “differential” food consumption. The results indicate differences between the mechanisms of contextual memory involved in the storage and retrieval of food aversion conditioning in snails.

The effect of dextromethorphan in preventing cholecalciferol‐induced poison shyness and sickness‐induced anorexia in the laboratory Norway rat

Overcoming bait and poison shyness is critical to the success of pest control operations against rats and other rodents. The authors hypothesized that the N-methyl-D-aspartate receptor blocker, dextromethorphan, could prevent the acquired memory of sickness and sickness-induced anorexia resulting from rodents eating poisoned bait. Cholecalciferol (1/4 LD(50)) was mixed with dextromethorphan and fed to rats on two 2 day sessions, with an 18 day break in between. Dextromethorphan did not prevent poison shyness; during the second poisoning period, both the cholecalciferol only and the cholecalciferol plus dextromethorphan groups had lower intakes of the bait compared with the control and dextromethorphan only groups. In addition to the previously recorded symptoms of cholecalciferol poisoning, the rats in this trial were observed to have nose bleeds, weepy eyes, laboured breathing and, in the case of the cholecalciferol only treated group, a period of decreased water intake followed by a period of increased water intake. There was also a period of increased water intake in the cholecalciferol plus dextromethorphan group. Dextromethorphan failed to prevent poison shyness and the anorectic effect of cholecalciferol. However, it did reduce anorexia from 17 days in the cholecaliferol group to 8 days in the cholecalciferol plus dextromethorphan group.

Yeast Proteins Enhance Satiety in Rats

This study was designed to characterize the suppressant effect of yeast protein and purified peptides on energy intake. For this purpose, 5 experiments were carried out using adult male Wistar rats. Rats that consumed ad libitum a standard yeast protein diet ate significantly less and were leaner over 21 d than rats that consumed ad libitum a standard milk protein diet (Expt. 1). Moreover, rats fed a high yeast protein load reduced their next meal and daily energy intake more than rats fed any other well-balanced, amino acid, high protein load (soy, total milk protein, or wheat gluten) and more than those fed a wheat starch diet (Expt. 2). Purified peptides from the yeast protein extract produced similar effects on subsequent energy intake (Expt. 3). Study of the behavioral satiety sequence showed that rats consuming P14-y or P55-y diets ad libitum did not acquire a conditioned food aversion (Expt. 4). Finally, a preliminary study of gastric emptying in rats fed yeast protein loads showed that yeast protein was emptied more rapidly through the pylorus than total milk protein during a meal, which may induce satiety (Expt. 5). Taken together, these experiments show that yeast proteins enhance satiety in rats more than other proteins.

Efficacy of male scent glands and urine in masking poison bait odour in female house rats, Rattus rattus

Experiments were carried out to possibly reduce bait shyness of female house rats by masking the poison (rodenticide-Zn3P2) with male pheromonal gland secretions, i.e. preputial/cheek glands and urine. The poison bait mixed with the extract of preputial and cheek glands, and urine was found to be effective in masking poison bait shyness. Preputial and cheek gland extracts cumulatively mixed with poison bait increased the poison bait consumption and consequently the mortality of female rats. The results reveal that among three pheromone sources, preputial gland extract was the most effective followed by urine and cheek gland extract. The results further reveal that the urine and glandular secretion from male origin may have the ability to increase the poison bait acceptance in female rats probably by altering the taste memory by pheromone odours.

The Neuroscience of Pleasure. Focus on “Ventral Pallidum Firing Codes Hedonic Reward: When a Bad Taste Turns Good”

For more than 2,000 years, philosophers have struggled to define, let alone explain, pleasure or hedonics. With contemporary animal models and techniques, scientists now have the ability to provide a comprehensive description of this affective state by examining its neural underpinnings. In this issue of the Journal of Neurophysiology (p. 2399 –2409), Tindell and colleagues use an elegant, reductionist approach to take a profound step in defining these neural foundations (Tindell 2006). The authors control for various elements of reward that historically have confounded researchers ambitious enough to attempt to study such an intangible topic. Specifically, Tindell and colleagues establish a role for ventral pallidum (VP) neurons in encoding hedonics. The authors infused an unpalatable concentration of saline into the oral cavities of rats while recording the extracellular electrophysiological activity of single VP neurons. Aversive orofacial reactions to the unpalatable taste were simultaneously measured. Three days later, rats were made sodium deplete and retested. In a sodium-depleted state, these rats now exhibited a behavioral switch from aversive taste reactivity to appetitive taste reactivity coincident with increased VP activity to the infusion of saline (similar to responses for a palatable sucrose solution). The clever implicit controls indicate that the altered electrophysiological activity encodes a hedonic shift rather than alterations in motivated behavior or sensory coding.

Generalization of conditioned food aversions in grazing sheep and its implications for food categorization

When grazing on heterogeneous pastures, herbivores may rely on food item generalization and categorization processes for reducing information processing while selecting their diet. The objective of this study was to assess the generalization of an aversion by grazing sheep for items differing by one or two criteria from an item against which they were negatively conditioned. Four items cultivated in pots were offered to the animals, resulting from the combination of an intrinsic criterion, i.e. grass species (ryegrass and fescue) and a transitory criterion, i.e. sward height (tall and short). We assessed the generalization process by comparing binary choices between the initially preferred tall ryegrass and the three other items, before and after animals had been partially conditioned against tall ryegrass. This method proved useful in assessing the generalization of an aversion. Sheep did not generalize their aversion on the basis of sward height but rather on species: they increased their preference for tall fescue and decreased their instantaneous preference for short ryegrass after having been conditioned against tall ryegrass. The generalization of an aversion through different states of a same species could indicate the possibility of a species-based categorization by grazing herbivores.

Cost-Effective Strategies for the Sustained Control of Bait-Shy Vertebrate Pests in New Zealand

The brushtail possum is a significant conservation pest and major vector of bovine tuberculosis in New Zealand. Previous control simulation studies have suggested that aerial control with bait containing sodium monofluoroacetate (1080) is the most cost-effective large-scale possum control strategy. However, there is a growing awareness that the survivors of 1080 control can develop ‘bait shyness’, and this can markedly alter the efficacy of ongoing 1080 control operations. Several alternative toxicants are registered for possum control but all are ground based, differ in their mode of action, and are more expensive than aerial 1080 control. A new possum control simulation model was developed to assist in identifying the most cost-effective control strategy that would achieve a sustained 80% population reduction, given bait-shy behaviour and immigration from adjacent non-controlled areas. The simulation results indicated that it is possible to achieve a sustained 80% population reduction (over a 10-year period) using a 1080-based control strategy, provided at least 90% of all ‘susceptible’ possums are killed in each control operation. In the event of an unsuccessful 1080 control operation (i.e., only a 60% kill), cyanide bait plus trapping, or brodifacoum bait provided the most cost-effective strategy of ‘mopping up’ 1080 bait-shy survivors. However, sufficient numbers of traps must accompany the cyanide bait to ensure that the majority of 1080 bait-shy possums are targeted. Sensitivity analysis indicated that the most important variable influencing the overall success of any control strategies was the rate of re-colonization following control. With the high rates of immigration that are sometimes observed in small forest reserves (i.e., <100 ha), it was not possible to sustain an 80% population reduction using any combination of toxicants. However, higher rates of immigration are probably exceptional and the rate used in these simulations is considered more typical, particularly for moderate-to-large forest stands where most possum control is conducted.

Effect of β-amyloid peptide on behavior and synaptic plasticity in terrestrial snail

A large body of evidence implicates β-amyloid peptide (βAP) and other derivatives of the evolutionarily highly conserved amyloid precursor protein (APP) in the pathogenesis of Alzheimer's disease. However, the functional relationship of APP and its proteolytic derivatives to synaptic plasticity is not well known. We demonstrate that 30 min exposure to the 25–35 fragment of βAP do not markedly change the dynamics of synaptic responses in identified neurons of terrestrial snail while a significant decrease of long-term sensitization was observed after 180 min βAP bath application. In the behavioral experiments, a significant reduction of sensitization, and decreased ability to develop food-aversion conditioning was observed after βAP injection. Our results clearly demonstrate that the neurotoxic 25–35 fragment of βAP may play a significant role in behavioral plasticity by chronically eliminating certain underlying forms of synaptic plasticity. The study also proposes a novel invertebrate model to Alzheimer's disease.

Summation of latent inhibition and overshadowing in a generalized bait shyness paradigm of rats

This paper reports a single experiment using four groups of rats. A group of thirsty rats showed aversion to sodium chloride (NaCl) solution in testing after drinking lithium chloride (LiCl) solution, demonstrating generalized bait shyness due to the common "salty" taste. The other two groups of rats were treated identically except that the rats were either exposed to NaCl solution prior to drinking the LiCl solution or allowed to drink LiCl-sucrose solution instead of the LiCl solution. The weaker salt aversion observed in these groups indicates latent inhibition and overshadowing, respectively. The rats in the fourth group were preexposed to NaCl and allowed to drink the LiCl-sucrose solution. The weakest salt aversion in this group suggests summation of latent inhibition and overshadowing effects.

Conditioned food aversion to eggs in captive-reared ferrets, Mustela furo: a test of seven potential compounds

Much of New Zealand's native fauna is threatened by introduced mammalian predators. We tested whether conditioned food aversion (i.e. avoidance of particular prey items subsequent to exposure to the same foods that contain an illness-inducing compound) could reduce consumption of birds’ eggs by introduced ferrets ( Mustela furo). We used captive-reared ferrets, and tested single doses of seven illness-inducing compounds (ethinyl oestradiol, paracetamol, potassium antimony tartrate, sodium monofluoroacetate, thiabendazole, lithium chloride, levamisole hydrochloride). None of the compounds tested induced a consistent aversion to eggs in ferrets. The proportion of ferrets ( n = 4–10) that refused to eat untreated eggs 7 days after eating treated eggs ranged from 0 to 20%. We suspect these proportions are an optimistic reflection of what might occur in the field because aversion to food attenuates with time (unless additional treatments can be readily applied), and aversion is less likely to occur in animals that are more accustomed to eating the target foods (as might be the case for wild animals). Furthermore, protection of New Zealand's native birds often requires that predation be reduced to very low levels. Our results did not encourage us to further investigate the utility of conditioned food aversion for protecting birds’ eggs from ferrets in New Zealand.

Conditioned food aversion elicited by the temperature of drinking water as a conditioned stimulus in rats

It is known that taste can act as a conditioned stimulus (CS) for conditioned food aversion. In the present study, in order to examine whether or not the temperature of drinking water can be a CS, we conducted behavioral experiments in Wistar rats. The following results were obtained: (1) The rats subjected to aversive conditioning to 5 or 40 °C distilled water could learn to avoid these CSs, but they did not avoid any taste stimuli. (2) The rats subjected to aversive conditioning to 5 or 40 °C 0.1 M sucrose developed a generalized avoidance to sucrose at any temperature. (3) When rats familiarized to 25 °C 5 mM saccharin-Na (Sacc) were subjected to aversive conditioning to 5 or 40 °C Sacc, they avoided the respective CS, but they did not generalize it to any other stimuli even if having the same temperature as the CS. (4) The rats which had undergone transection of the taste nerves (chorda tympani and glossopharyngeal nerves) could acquire the conditioned response to the temperature of the CS. These results suggest that rats can be conditioned to temperature aversion and that the taste nerves are not needed in the formation of this conditioning.

The relationship between susceptibility to nausea and vomiting and the possession of conditioned food aversions

Because nausea and vomiting play an important role in the formation of conditioned food aversions, individual differences in susceptibility to nausea and vomiting may contribute to interindividual variation in conditioned food aversion acquisition. Two surveys reveal that, among female participants, self-reported motion sickness susceptibility is positively correlated with the number of conditioned food aversions possessed, but no such correlation appears among male participants.

Conditioned food aversion elicited by the temperature of drinking water as a conditioned stimulus in rats

It is known that taste can act as a conditioned stimulus (CS) for conditioned food aversion. In the present study, in order to examine whether or not the temperature of drinking water can be a CS, we conducted behavioral experiments in Wistar rats. The following results were obtained: (1) The rats subjected to aversive conditioning to 5 or 40 °C distilled water could learn to avoid these CSs, but they did not avoid any taste stimuli. (2) The rats subjected to aversive conditioning to 5 or 40 °C 0.1 M sucrose developed a generalized avoidance to sucrose at any temperature. (3) When rats familiarized to 25 °C 5 mM saccharin-Na (Sacc) were subjected to aversive conditioning to 5 or 40 °C Sacc, they avoided the respective CS, but they did not generalize it to any other stimuli even if having the same temperature as the CS. (4) The rats which had undergone transection of the taste nerves (chorda tympani and glossopharyngeal nerves) could acquire the conditioned response to the temperature of the CS. These results suggest that rats can be conditioned to temperature aversion and that the taste nerves are not needed in the formation of this conditioning.

Conditioned food aversion elicited by multi-stimuli of taste and hardness as conditioned stimuli

Conditioned food aversion elicited by multi-stimuli of taste and hardness as conditioned stimuli

Wheel running produces conditioned food aversion

Previous investigations of conditioned taste aversion (CTA) induced by wheel running have used flavored liquids such as conditioned stimuli (CSs). Assuming that classical conditioning mediates activity anorexia, it is expected that CTA induced by physical activity should extend to food stimuli. The main purpose of the present experiment was to investigate this possibility. Rats were given a 60-min access to a running wheel [unconditioned stimulus (US)] either before or after being exposed to a novel distinctive flavored food (CS). An additional group had access to running wheels 4 h after receiving the CS food. Results from the present experiment indicate that regimented and contingent periods of wheel running decrease consumption of a food available before wheel running in nondeprived rats.

Meat Is Good to Taboo: Dietary Proscriptions as a Product of the Interaction of Psychological Mechanisms and Social Processes

Abstract Comparing food taboos across 78 cultures, this paper demonstrates that meat, though a prized food, is also the principal target of proscriptions. Reviewing existing explanations of taboos, we find that both functionalist and symbolic approaches fail to account for meat's cross-cultural centrality and do not reflect experience-near aspects of food taboos, principal among which is disgust. Adopting an evolutionary approach to the mind, this paper presents an alternative to existing explanations of food taboos. Consistent with the attendant risk of pathogen transmission, meat has special salience as a stimulus for humans, as animal products are stronger elicitors of disgust and aversion than plant products. We identify three psychosocial processes, socially-mediated ingestive conditioning, egocentric empathy, and normative moralization, each of which likely plays a role in transforming individual disgust responses and conditioned food aversions into institutionalized food taboos.