Olfaction and taste senses in sturgeon behaviour

Olfaction is one of the fundamental senses for spawning and feeding behaviour in sturgeons. The olfactory spectra of free amino acids affecting behaviour in sturgeon species of the family Acipenseridae are narrow and similar. The threshold concentrations for effective amino acids (glycine and L-alanine) are 1 μM The taste spectra are highly species specific, especially for the oral taste modality. There is a good correlation between the responses of extra-oral and oral taste systems within the same species. The extra-oral taste system is more sensitive and has a wider effective spectrum than the oral system. The extra-oral taste system develops more rapidly than oral taste system during sturgeon ontogenesis.     

Conditioned aversion to sweet and salt in genetically obese and lean Zucker rats1

Conditioned taste aversion to threshold and suprathreshold concentrationsof sodium chloride, sucrose, and other sweeteners was measuredin obese and lean female Zucker rats. In the first experiment0.1M sodium chloride, 0.1M sucrose, or water was paired witha constant dosage of apomorphine hydrochloride (6.72 mg IP foreach rat). The magnitude of conditioned aversion to sucrose(0.1M and 0.316M) and sodium chloride (0.1M and 0.316M) followingthe initial conditioning trial was similar for obese and leanrats. However, repeated cycles of conditioning and extinctiontrials resulted in decreased sucrose intakes for obese ratsand increased sucrose intakes for lean rats. No changes in intakeoccurred with sodium chloride. In the second experiment 0.1M sucrose or water was paired withdoses of apomorphine hydrochloride based on each rat's bodyweight (30 mg/kg IP). The magnitude of aversion to sucrose (0.01M,0.0316M, 0.1M, 0.316M) and other sweetners (0.75M glucose, 0.1Msucrose, 0.001M sodium saccharin, and 0.025M sodium cyclamate)were similar for obese and lean rats. These data suggest thatrepeated testing with sucrose, rather than differences in sensorytaste factors, contributes to the previous reports of decreasedintake and sweet preference of obese rats.     

Preference and aversion for brain stimulations estimated by the conditioned place preference

Rats implanted with chronic electrode into the medial forebrain bundle at the level of the hypothalamus (which elicited self-stimulation behaviour) display conditioned place preference after repeated stimulations of this area; conversely rats implanted into the mesencephalic dorso-medial tegmentum (which elicited switch-off behaviour) present conditioned place aversion after such repeated stimulations. Furthermore rats implanted in these two area without exhibiting self-stimulation or switch-off behaviours also display preference or aversion for the location paired with the brain stimulations. It was thus hypothesized that the conditioned place preference procedure seemed to present a higher sensitivity than the bar pressing procedures to detect preference or aversion for brain stimulation. Moreover the activation of the medial forebrain bundle which was associated with positive affect is more effective for a long term retention of the preferred location than midbrain periventricular reticular activation which induces a negative affect.     

Dietary salt levels affect salt preference and learning in larval Drosophila

Drosophila larvae change from exhibiting attraction to aversion as the concentration of salt in a substrate is increased. However, some aversive concentrations appear to act as positive reinforcers, increasing attraction to an odour with which they have been paired. We test whether this surprising dissociation between the unconditioned and conditioned response depends on the larvae's experience of salt concentration in their food. We find that although the point at which a NaCl concentration becomes aversive shifts with different rearing experience, the dissociation remains evident. Testing larvae using a substrate 0.025 M above the NaCl concentration on which the larvae were reared consistently results in aversive choice behaviour but appetitive reinforcement effects.     

Role of IL-4 in aversion induced by food allergy in mice

To ascertain the role of IL-4 in aversion to antigen induced by food allergy, wild type and IL-4 deficient BALB/c mice were sensitized with ovalbumin and challenged orally with egg white. Sensitized wild type mice had increased production of IL-4 by spleen and mesenteric lymph node cells in vitro, higher levels of serum anti-ovalbumin IgE and IgG1, aversion to ingestion of the antigen and loss of body weight after continuous oral challenge. Intestinal changes in wild type sensitized mice included eosinophil infiltration and increased mucus production. The IL-4 deficiency impaired the development of food allergy and the aversion to antigen, suggesting the involvement of the antigen specific antibodies. When IL-4 deficient mice received serum from sensitized wild type donors, the aversion was restored. These results indicate that production of IL-4 and specific IgE/IgG1 antibodies correlate with aversion to antigen induced by food allergy in mice.     

The significance of apical K+ channels in mudpuppy feeding behavior

Behavioral experiments were conducted to determine the effectsof known potassium channel blockes, minnow extract (a naturalfood substance), and otber taste stimuli on feeding behaviorin the mudpuppy (Necturus maculosus). Groups of 10–15mudpuppies were presented with one or more of the followingchemicals dissolved in gelatin cubes: H₂O (control), NaCl (1.0M; 0.2 M), crude minnow extract (0.1 g/ml), CaCl₂ (1.0 M), citricacid (0.1 M; pH2, 0.01 M; pH 3), quinine HCl (0.1 M), tetraemylammoninmchloride (TEA; 0.1 M), KCl (1.0 M) and an amino acid mixturecontaining L-phenylalanine, L-arginine, L-histidine, L-valine,L-glutamic acid and L-lysinc at concentrations of 0.02 M and0.04 M each. Crude minnow extract was centrifuged and separatedinto components consisting of the following fractions: >500D, >1000 D and >14 000 D, each of which was presentedto mudpuppies in cubes. Results were expressed as the percentageof animals rejecting the cube within 5 min of taking the cubeinto the oral cavity. Statistical analysis using the Fisherexact test indicated that cubes containing chemicals known toblock (CaCl₂, TEA, citric acid and quinine) or permeate (KCl)apical K⁺ channels in mudpuppy taste cells were more aversivethan control cubes, and aversion was concentration-dependentIn contrast, cubes containing minnow extract and componentsof minnow extract < 14 000 D were significantly preferredover control cubes. Cubes containing a mixture of minnow extractand an aversive chemical were significantly less aversive thancubes containing only an aversive chemical. These findings suggestthat activation of the apical K⁺ conductance in mudpuppy tastecells triggers an aversive response, but the aversion can beameliorated by low molecular weight compounds present in minnowextract.     

Taste aversion learning in preweanling rats exposed to alcohol prenatally

The effects of prenatal alcohol exposure on the development of a conditioned taste aversion were examined in preweanling rat pups. Mothers of these pups were fed isocaloric liquid diets containing either 35 or 0% ethanol-derived calories (EDC) from gestation days 6 through 20. A pair-feeding procedure was employed, and an ad lib lab chow control group was also included. At 5, 10, or 15 days of age, pups were infused with a saccharin solution through a cannula implanted in the oral cavity. Half of the pups in each group were then injected with lithium chloride (LiCl), which served as the poisoning agent, and the other half with sodium chloride (NaCl) as a control. Animals were subsequently tested for a conditioned aversion to the saccharin solution. At 15 days of age, all of the pups in the LiCl-poisoned group demonstrated a conditioned taste aversion to the saccharin solution, but the degree of this aversion was less in alcohol-exposed offspring. At 10 days of age, a taste aversion was learned, although it was not as strong as that shown by 15-day-old pups, and it appeared to be learned equally well by all of the prenatal treatment groups. At 5 days of age, there was marginal support for taste aversion learning. Again, it did not interact with prenatal treatment. The ontogenic differences in taste aversion learning exhibited by alcohol-exposed offspring relative to controls are discussed in terms of altered hippocampal development.     

An animal model to assess aversion to intra-oral capsaicin: increased threshold in mice lacking substance p.

Despite the widespread consumption of products containing chemicals that irritate the oral mucosa, little is known about the underlying neural mechanisms nor is there a corresponding animal model of oral irritation. We have developed a rodent model to assess aversion to capsaicin in drinking water, using a paired preference paradigm. This method was used to test the hypothesis that the neuromodulator substance P (SP) plays a role in the detection of intra-oral capsaicin. 'Knockout' (KO) mice completely lacking SP and neurokinin A due to a disruption of the preprotachykinin A gene and a matched population of wild-type (WT) mice had free access to two drinking bottles, one containing water and the other capsaicin at various concentrations. Both KO and WT mice showed a concentration-dependent aversion to capsaicin. KO mice consumed significantly more capsaicin than WT at a single near threshold (1.65 microM) concentration, indicating that SP plays a limited role in the detection and rejection of oral irritants.     

The taste characteristics of sodium-saccharin in the rat: a re-examination of the dual taste hypothesis

A conditioned flavor aversion (CFA) was used to measure thetaste characteristics of 0.005 and 0.025 M Na-saccharin in therat. At neither concentration did the rats show generalizationto NaCl, quinine HCl or SO₄, sucrose octa-acetate or HCl, whereasgeneralization to sucrose was found at both concentrations.When the CFA was formed to 0.0001 M quinine HCl, no direct evidencewas found for generalization of the aversion to either saccharinconcentration. Thus at the two concentrations used Na-saccharinwould appear to be primarily sucrose-like in the rat taste systemwhen behavioral criteria are used.     

Behaviorally conditioned suppression of the immune response by antilymphocyte serum

Previous studies have shown that cyclophosphamide, a drug with a broad spectrum of cytotoxic activity and one that produces noxious gastrointestinal side effects, can elicit taste aversion conditioning when paired with a non-immunosuppressive oral stimulus (saccharin) resulting in immunosuppression after subsequent exposure to the paired stimulus (1). The study reported here indicates that rabbit anti-rat lymphocyte serum (ALS) which is selectively cytotoxic for lymphocytes and does not produce sensory side effects can similarly induce taste aversion conditioning of the immune response. Rats were exposed to oral saccharin paired with ALS injection. Upon subsequent reexposure to saccharin alone the immunosuppressive effects of ALS were reenlisted and the primary mixed lymphocyte culture response of conditioned rats to allogeneic lymphocytes was suppressed by 35% compared to controls. The demonstrated influence of psychologic factors on the immune response has far reaching implications, especially to human medicine, and their role in the course of disease and recovery in man demands further investigation.     

Long-term retention of a poorly learned saccharin aversion : Evidence for an incubation effect

The retention of a weak conditioned saccharin aversion was tested using independent groups over a 14-day period. The delay between CS (saccharin 0.1 %) and US (LiCl 0.15 M) was 6 hours. Significant variations in the retention function were observed, in particular an improvement of memory - i.e. an incubation effect - over the 14-day period. This result suggests that retention of conditioned taste aversion may share common features with the retention of more classical aversive conditioning.     

Investigating the effect of emetic compounds on chemotaxis in Dictyostelium identifies a non-sentient model for bitter and hot tastant research

Novel chemical entities (NCEs) may be investigated for emetic liability in a range of unpleasant experiments involving retching, vomiting or conditioned taste aversion/food avoidance in sentient animals. We have used a range of compounds with known emetic /aversive properties to examine the possibility of using the social amoeba, Dictyostelium discoideum, for research into identifying and understanding emetic liability, and hence reduce adverse animal experimentation in this area. Twenty eight emetic or taste aversive compounds were employed to investigate the acute (10 min) effect of compounds on Dictyostelium cell behaviour (shape, speed and direction of movement) in a shallow chemotaxic gradient (Dunn chamber). Compound concentrations were chosen based on those previously reported to be emetic or aversive in in vivo studies and results were recorded and quantified by automated image analysis. Dictyostelium cell motility was rapidly and strongly inhibited by four structurally distinct tastants (three bitter tasting compounds--denatonium benzoate, quinine hydrochloride, phenylthiourea, and the pungent constituent of chilli peppers--capsaicin). In addition, stomach irritants (copper chloride and copper sulphate), and a phosphodiesterase IV inhibitor also rapidly blocked movement. A concentration-dependant relationship was established for five of these compounds, showing potency of inhibition as capsaicin (IC(50) = 11.9 ± 4.0 μM) > quinine hydrochloride (IC(50) = 44.3 ± 6.8 μM) > denatonium benzoate (IC(50) = 129 ± 4 μM) > phenylthiourea (IC(50) = 366 ± 5 μM) > copper sulphate (IC(50) = 1433 ± 3 μM). In contrast, 21 compounds within the cytotoxic and receptor agonist/antagonist classes did not affect cell behaviour. Further analysis of bitter and pungent compounds showed that the effect on cell behaviour was reversible and not cytotoxic, suggesting an uncharacterised molecular mechanism of action for these compounds. These results therefore demonstrate that Dictyostelium has potential as a non-sentient model in the analysis of the molecular effects of tastants, although it has limited utility in identification of emetic agents in general.     

Risk aversion and religious behaviour: Analysis using a sample of Danish twins

Economics offers an analytical framework to consider human behaviour including religious behaviour. Within the realm of Expected Utility Theory, religious belief and activity could be interpreted as an insurance both for current life events and for afterlife rewards. Based on that framework, we would expect that risk averse individuals would demand a more generous protection plan which they may do by devoting more effort and resources into religious activities such as church attendance and prayer, which seems to be in accordance with previous empirical results. However, a general concern regards the problems of spurious correlations due to underlying omitted or unobservable characteristics shaping both religious activities and risk attitudes. This paper examines empirically the demand for religion by analysing the association between risk attitudes on the one hand, and church attandance and prayer frequency on the other controlling for unobservable variables using survey data of Danish same-sex twin pairs. We verify the correlation between risk preferences and religion found previously by carrying out cross-sectional analyses. We also show that the association between risk attitudes and religious behaviour is driven by the subgroup of individuals who believe in an afterlife. In addition, when re-analysing our results using panel data analyses which cancel out shared factors among twin pairs, we find that the correlation found between risk aversion and religious behaviour is no longer significant indicating that other factors might explain differences in religious behaviour. Caution is needed in the interpretation of our results as the insignificant association between risk aversion and religious behaviour in the panel data analyses potentially might be due to measurement error causing attenuation bias or lack of variation within twin pairs rather than the actual absence of an association.     

QUININE HYDROCHLORIDE ACCEPTABILITY AFTER WATER DEPRIVATION IN GALLUS DOMESTICUS

The latency to peck and show the oral aversion response wasmeasured when 6 Brown Leghorn hens were presented with eitherwater or 0.005 M quinine hydrochloride (QHCl) after either 2,4 or 6 h water deprivation. The absence of any differences inthe latencies to peck at water with the 3 deprivation schedulesindicated no significant increase in the level of motivation,whereas, it was found that the latencies to peck at the quininesolution were significantly reduced with increasing deprivation.After 2 h deprivation the birds showed significantly longerlatencies than with water but after 6 h deprivation there wasno significant difference. By comparing the ratio values ofthe number of pecks followed by the oral aversion response dividedby the total number of pecks given to the QHCl solution it wasfound that there was a significant decrease in this ratio from2 to 6 h deprivation. It was suggested that the increase inacceptance of the quinine hydrochloride following deprivationmay be due to changes in ‘taste’ sensitivity.     

Not such silly sausages: Evidence suggests northern quolls exhibit aversion to toads after training with toad sausages

The invasion of toxic cane toads (Rhinella marina) is a major threat to northern quolls (Dasyurus hallucatus) which are poisoned when they attack this novel prey item. Quolls are now endangered as a consequence of the toad invasion. Conditioned taste aversion can be used to train individual quolls to avoid toads, but we currently lack a training technique that can be used at a landscape scale to buffer entire populations from toad impact. Broad‐scale deployment requires a bait that can be used for training, but there is no guarantee that such a bait will ultimately elicit aversion to toads. Here, we test a manufactured bait – a ‘toad sausage’ – in a small captive trial, for its ability to elicit aversion to toads in northern quolls. To do this, we exposed one group of quolls to a toad sausage and another to a control sausage and compared the quolls' predatory responses when presented with a dead adult toad. Captive quolls that consumed a single toad sausage showed a reduced interest in cane toads, interacting with them for less than half the time of their untrained counterparts and showing reduced Attack behaviour. We also quantified bait uptake in the field, by both quolls and non‐target species. These field trials showed that wild quolls were the most frequent species attracted to the baits, and that approx. 61% of quolls consumed toad‐aversion baits when first encountered. Between 40% and 68% of these animals developed aversion to further bait consumption. Our results suggest that toad‐aversion sausages may be used to train wild quolls to avoid cane toads. This opens the possibility for broad‐scale quoll training with toad aversion sausages: a technique that may allow wildlife managers to prevent quoll extinctions at a landscape scale.     

Avoidance behaviour and anxiety in rats irradiated with a sublethal dose of gamma-rays

The aim of this study was to assess, whether a sublethal dose of gamma-rays will influence the avoidance behaviour and anxiety in rats and whether the response to radiation depends on time of day of its application. Adult male Wistar rats were tested in elevated plus-maze, in hot plate test and in the light/dark box in 4 regular intervals during a day. After two weeks the animals were irradiated with a whole-body dose 6 Gy of gamma-rays. One day after irradiation the animals were repeatedly tested in the same way, as before irradiation. In the plus-maze test an increased level of anxiety was established. The irradiation significantly decreased the locomotor activity of rats, but the extent of exploratory and comfortable behaviour were not altered. After irradiation, an elevated aversion to the thermal stimulus was observed in the hot plate test. The effects of radiation were more pronounced in the light period of the day, than in the dark one. No significant differences in aversion to light were detected after irradiation. The obtained results indicate, that sublethal doses of ionizing radiation can markedly influence the reactivity of animals to adverse stimuli, their motoric activity and emotional status, as well.     

Assaying the Effect of Levodopa on the Evaluation of Risk in Healthy Humans

In humans, dopamine is implicated in reward and risk-based decision-making. However, the specific effects of dopamine augmentation on risk evaluation are unclear. Here we sought to measure the effect of 100 mg oral levodopa, which enhances synaptic release of dopamine, on choice behaviour in healthy humans. We use a paradigm without feedback or learning, which solely isolates effects on risk evaluation. We present two studies (n = 20; n = 20) employing a randomised, placebo-controlled, within-subjects design. We manipulated different dimensions of risk in a controlled economic paradigm. We test effects on risk-reward tradeoffs, assaying both aversion to variance (the spread of possible outcomes) and preference for relative losses and gains (asymmetry of outcomes - skewness), dissociating this from potential non-specific effects on choice randomness using behavioural modelling. There were no systematic effects of levodopa on risk attitudes, either for variance or skewness. However, there was a drift towards more risk-averse behaviour over time, indicating that this paradigm was sensitive to detect changes in risk-preferences. These findings suggest that levodopa administration does not change the evaluation of risk. One possible reason is that dopaminergic influences on decision making may be due to changing the response to reward feedback.     

Parabrachial unit activities after the acquisition of conditioned taste aversion to a non-preferred HCl solution in rats

Abstract In a behavioral experiment, rats reliably acquired a taste aversion to non-preferred 0.01 M HCl that had been previously paired with intraperitoneal injection of 0.15 M LiCl. These rats showed aversions to other acidic solutions such as malic acid and tartaric acid. In a neurophysiological experiment, the neuronal activities of the parabrachial nucleus (PBN) were recorded after the acquisition of conditioned taste aversion (CTA) to 0.01 M HCl in urethane-anesthetized rats. Neuronal responses to the conditioned stimulus (CS) did not change on the whole but decreased in the dorsal region to the brachium conjunctivum. The proportion of HCl-best to NaCl-best units was lower in the CTA group than in controls. The spontaneous firing rate was lower in the CTA group than in controls. Correlation coefficients between the HCl CS and normally preferred tastes (sucrose and NaCl) were more negative and those between HCl and quinine were more positive in the CTA group than in the controls. These results may be explained by the notion that gustatory responses of PBN neurons are concerned with alterations in taste hedonics after the acquisition of conditioned taste aversions.     

Learned food aversion with and without an odour cue for protecting untreated baits from wild mammal foraging

Lethal methods of controlling wildlife foraging damage may present difficulties regarding conservation, ethics, welfare, and efficacy, providing an imperative to develop non-lethal alternatives. Learned food aversions offer a benign, targeted alternative to culling. However, food aversions are more readily associated with taste than with non-taste cues, and successful management applications have been limited primarily to reducing (bird) damage to treated items. To determine whether untreated foods might be protected without becoming damaged through sampling (tasting), we tested the role of an odour cue in learned food aversions with wild mammals using three conditioning treatments: (a) a combination of ziram (aversive agent) and clove oil (novel odour); (b) ziram; (c) clove oil. We tested two predictions: (1) ziram will produce learned aversion towards untreated foods; (2) training with the ziram–clove combination will produce enhanced aversion towards untreated foods in the presence of a clove odour cue. We collected detailed behavioural data from free-ranging animals using video surveillance. With European badgers Meles meles, both ziram treatments invoked innate aversion to baits. Ziram did not produce learned aversion to untreated foods, but conditioning badgers with the ziram–clove combination produced learned aversion towards untreated foods in the presence of the odour cue. The clove control did not affect badger behaviour. Our results support the second, but not the first, prediction with badgers. Red foxes Vulpes vulpes attended the ziram and the clove treatments only. Foxes displayed innate aversion to ziram, and subsequently developed learned aversions to untreated baits. Our results with foxes therefore support the first prediction, but we were unable to test the second. Learned food aversions using odour cues could potentially provide non-lethal protection for untreated foodstuffs, such as eggs, crops, and fruit, from mammalian pest species.     

Human punishment is motivated by inequity aversion, not a desire for reciprocity

Humans involved in cooperative interactions willingly pay a cost to punish cheats. However, the proximate motives underpinning punitive behaviour are currently debated. Individuals who interact with cheats experience losses, but they also experience lower payoffs than the cheating partner. Thus, the negative emotions that trigger punishment may stem from a desire to reciprocate losses or from inequity aversion. Previous studies have not disentangled these possibilities. Here, we use an experimental approach to ask whether punishment is motivated by inequity aversion or by a desire for reciprocity. We show that humans punish cheats only when cheating produces disadvantageous inequity, while there is no evidence for reciprocity. This finding challenges the notion that punishment is motivated by a simple desire to reciprocally harm cheats and shows that victims compare their own payoffs with those of partners when making punishment decisions.