Polygenic determination of quinine aversion among mice

There are substantial differences among inbred mouse strainsin avoidance of quinine solutions in two-bottle preference tests.x A Mendelian cross-breeding experiment was conducted to testthe hypothesis that a single locus Qui has a major influenceon quinine aversion. Inbred strains C57B1/6J (B6, avoider) andC3HeB/FeJ (C3, indifferent) were progenitors of two segregatinggenerations. Phenotypic ratios for 100 µM and 30 µMquinine sulfate (QSO4) in these generations were not consistentwith ratios expected for a single gene. Frequency distributionsfor individual preference ratios were more characteristic ofa polygenic trait. An outbred strain (CFW/Crl) which displayssegregation for the Soa locus was tested for both QSO4 and sucroseocta-acetate (SOA) avoidance. Correlated avoidance patternsfor the two bitter compounds were found in these mice. A Soaeffect might not have been seen in the C3.B6 cross because bothstrains are relatively poor SOA avoiders. A second Mendeliancross was made between strains C3 and SWR/J (SW, SOA and QSO4avoider). One segregating generation was tested with both compounds.In these mice, as in the CFW population, QSO4 aversion was correlatedwith SOA aversion. These results suggest that quinine aversionis polygenic, that there is a relationship between SOA sensitivityand quinine sensitivity, and that this association may be theresult of variation at the Soa locus.     

Gurmarin suppression of licking responses to sweetener-quinine mixtures in C57BL mice

Gurmarin (Gur) is a peptide that selectively suppresses responses of the chorda tympani nerve to sweet substances in rats and mice. In the present study, we examined the effect of Gur on behavioral responses to sweet substances in C57BL mice. To accomplish this, we developed a new short-term lick test and measured numbers of licks for 10 s for sweet substances mixed with quinine hydrochloride (QHCl) in water-deprived mice. Numbers of licks for sucrose mixed with 1 or 3 mM QHCl increased with increasing concentration of sucrose from 0.01 to 1.0 M. Oral infusion with 30 micro g/ml Gur produced significant decreases in responses to concentration series for sucrose mixed with 3 mM QHCl, whereas no such effect by Gur was observed in responses to QHCl alone or QHCl-mixed HCl, NaCl or monosodium glutamate. The Gur suppression of QHCl-mixed sucrose responses, which otherwise lasted for 2-3 h, rapidly returned to approximately 80% of control levels after oral infusion with beta-cyclodextrin. These results are comparable to neural data previously found in chorda tympani responses, and thereby provide further evidence for Gur as a sweet response inhibitor in C57BL mice. In the other aspect, our newly developed short-term test can also provide a tool for measurements of taste-guided behavioral responses to sweeteners.     

On the sense of taste in two Malagasy Primates (Microcebus murinus and Eulemur mongoz)

The relationship between phylogeny and taste is of growing interest.In this study we present recordings from the chorda tympaniproper (CT) nerve of two lemuriforme primates, the lesser mouselemur (Microcebus murinus) and the mongoose lemur (Eulemur mongoz),to an array of taste stimuli which included the sweeteners acesulfame-K,alitame, aspartame, D-glucose, dulcin, monellin, neohesperidindihydrochalcone (NHDHC), saccharin, sodium superaspartame, stevioside,sucralose (TGS), sucrose, suosan, thaumatin and xylitol, aswell as the non–sweet stimuli NaC1, citric acid, tanninand quinine hydrochloride. In M.murinus the effects of the tastemodifiers gymnemic acid and miraculin on the CT response wererecorded. Conditioned taste aversion (CTA) experiments in M.murinusand two-bottle preference (TBP) tests in E.mongoz were alsoconducted. We found that all of the above tastants except thaumatinelicited a CT response in both species. The CTA technique showedthat M.murinus generalized from sucrose to monellin but notto thaumatin. The intake of aspartame, ranging in concentrationfrom 0.1 to 30 mM was measured in E.mongoz with TBP tests. Atno concentration did we see a preference, but there was a significantrejection of 10 and 30 mM aspartame (P     

Effect of Oxidized Arachidonic Acid and Hexanal on the Mouse Taste Perception of Bitterness and Umami

The oxidization of fatty acids generates many volatile compounds forming an aroma, but little is known whether mammals use gustatory sense to detect the oxidized products as a taste or only use olfactory sense to detect as an aroma. We examined in this study the effect of aqueous extracts of the compounds from autoxidized arachidonic acid (AA) ethyl ester or hexanal which is the predominant component generated from oxidized AA by the anosmic mouse licking performance to a tastant. The addition of the water extract from oxidized AA or hexanal to a quinine hydrochloride (QHCl) solution decreased the anosmic mice licking frequency at several concentrations of QHCl. Hexanal also reduced the licking frequency of anosmic mice conditioned to avoid MSG at several concentrations of monosodium glutamate (MSG). These results suggest that hexanal would affect mouse taste perception to QHCl and MSG via the gustatory sensation.     

Response properties of the glossopharyngeal taste system of the mud puppy (Necturus maculosus)

Summary The responses of individual glossopharyngeal neurons of the mud puppy,Necturus maculosus, were examined over an extended concentration series of NaCl, HCl, quinine hydrochloride (QHCl) and sucrose solutions. Neuron isolation was evaluated by a computer program that sorted neural impulses according to amplitude (Fig. 1). When sufficient isolation existed, a second program counted the impulses in each test period as well as in pre- and post-stimulus periods. Response latencies were calculated independently.The response to taste stimulation took one of three forms: 1) increased activity, 2) decreased activity, or 3) increased activity to the water rinse. For each concentration series the magnitude (SR) and latency functions of the responses were determined. These varied among stimuli and among nerve fibers (Fig. 4). However, the SR and latency functions were found in specific combinations, the most unique being one in which both functions remained constant over an entire concentration series (Fig. 4E, F).Most neurons responded to more than one of the stimuli. Many, however, responded to at least one of the stimuli with a particular form of response and combination of SR and latency functions (Fig. 6). In this sense they may be considered chemospecific as well as multiply sensitive. Despite the many types of response, the sum of the individual SR functions closely resembled the SR functions of the whole nerve (Fig. 7) and the summed latencies produced a temporal pattern with a phasic component similar to that of the whole nerve response (Fig. 8).Abbreviations SR stimulus concentration vs response magnitude - L latency of response - +,0, -,I (SR orL) magnitude or latency functions with positive, zero, negative or indeterminate slope - QHCl quinine hydrochloride Supported in part by NIH Grant NS09168The authors wish to thank Mr. Marc Schneider for the computer programs and his expert assistance and Mrs. G. Chapman of Florida State University for photography. We also thank Dr. David V. Smith for his critical comments. This work was submitted in partial fulfillment of the requirements for the Ph. D. degree to Michigan State University by the senior author.     

Extra-lingual chemoreceptors in the chicken (Gallus domesticus)

The oral aversion behaviour of the chicken (head shaking, beakwiping and tongue/beak movements) was measured following oralstimulation with 0.1 M quinine hydrochloride, 40% sucrose, 3M sodium chloride, 5 M acetic acid and pure methyl anthranilate.Section of the lingual and laryngolingual nerves did not affectthe oral aversion behaviour and therefore demonstrates the presenceof functional extra-lingual chemoreceptors. The results arediscussed in relation to previous anatomical findings.     

Gustatory neural response latencies in the frog

The major rate limiting steps in bullfrog peripheral nerve gustatoryresponse latencies were studied by measuring glossopharyngealnerve multi-unit activity, detecting response onset times, andcalculating rates of stimulus diffusion to receptor cells andsignal propagation along first order neurons. The stimulus deliverytechnique minimized physicochemical and mechanical artifacts,as well as neural responses to mechanical stimulation of thetongue. Neural activity was processed in 10 ms bins. Responseonsets were determined by a criterion that compared the statisticalprobability of the neural events during stimulus liquid presentationswith those during both Ringer's solution presentations afteradaptation to Ringer's and no-stimulus control conditions. Thiscriterion yielded response latencies of 70–110 ms for10 mM CaCl₂, 2 mM quinine hydrochloride, and 10^–5 M and10^–6 M cantharidin or Ringer's, and H₂O. No responsesoccurred during presentations of 10^–7 M cantharidin orRinger's after adaptation to Ringer's, or during the no-stimuluscontrol condition. From the measured latencies and calculatedrates of stimulus diffusion to receptor cells, and signal propagationalong first order neurons, we conclude that taste receptor cellevents and not perireceptor or signal propagatiog events arethe major rate limiting steps in gustatory response latencies.     

Effects of melanin-concentrating hormone on licking microstructure and brief-access taste responses

The effects of intracerebroventricular application of melanin-concentrating hormone (MCH) on licking for sucrose, quinine hydrochloride (QHCl), and water solutions were evaluated in two experiments. In experiment 1, rats received 90-min access to sucrose and water solutions after MCH or vehicle microinjection to the third ventricle (3V). MCH increased intake largely through increases in the rate of licking early in the meal and in the mean duration of lick bursts, suggesting an effect on gustatory evaluation. Therefore, in experiment 2, brief access tests were used with a series of sucrose and QHCl concentrations to behaviorally isolate the effects of intracerebroventricular MCH on gustatory evaluation. MCH uniformly increased licking for all sucrose solutions, water, and weak concentrations of QHCl; however, it had no effect on licking for the strongest concentrations of QHCl, which were generally avoided under control conditions. Thus MCH did not produce nonspecific increases in oromotor activity, nor did it change the perceived intensity of the tastants. We conclude that MCH enhanced the gain of responses to normally accepted stimuli at a phase of processing after initial gustatory detection and after the decision to accept or reject the taste stimulus. A comparison of 3V NPY and MCH effects on licking microstructure indicated that these two peptides increased intake via dichotomous behavioral processes; although NPY suppressed measures associated with inhibitory feedback from the gut, MCH appeared instead to enhance measures associated with hedonic taste evaluation.     

Learned aversions and taste qualities in hamsters

Interralations among taste perceptions in gloden hamsters (Mesocricetusauratus) were examined using generalizaions of learned tasteaversions. If stimulus A is avoided given a taste aversion hasbeen established to stimulus B, and vice versa, A and B ‘cross-generalize’.Stimuli within five groups cross-generalized. The groups ofcompounds were (i) sweeteners (fructose, saccharin, sucrose);(ii) sodium salts (NaCl, NaNO₃, Na₂SO₄): (iii) non-sodium salts(KCl, MgSO₄ NH₄Cl) plus quinine HCl; (iv) acids (acetic, hydrochloric,citric); and (v) urea. Only two pairs of stimuli from differentgroups cross-generalized (HCl—NH₄Cl. quinine HCl—urea).Neural patterns of response recorded form chorda tympam nervefibers in hamsters suggest that taste receptors on the anteriortongue distinguish among three groups of taste stimuli: sweeteners,sodium salts, and a group including non-sodium salts, acids,quinine HCl and urea. Neurons innervating other taste fieldsare likely to provide the information that hamsters use to discriminateamong the tastes of non-sodium-salt and non-sweetener stimuli.     

Taste reactivity and Fos expression in GAD1-EGFP transgenic mice

The central distribution of QHCl-elicited Fos-like immunoreactivity (FLI) suggests the location of a brain stem circuit that controls the oral rejection response. Although many species display an oral rejection response to bitter stimuli, the distribution of FLI associated with this response has been investigated only in rats. Fos data are minimal for the mouse, a species of increasing importance, due to its use in molecular and transgenic studies and taste-evoked oromotor responses are also only incompletely described in these rodents. We investigated these questions in FVB/NJ mice and a related transgenic strain (FVB-Tg(GadGFP)4507) that expresses green fluorescent protein in a subset of GAD1-containing neurons. QHCl, sucrose, or water delivered through intraoral cannulae yielded behavioral profiles that clearly differentiated QHCl from sucrose. Similar to rat, the number of neurons expressing FLI in the medial third of the solitary nucleus was elevated following QHCl compared with the other stimuli. In mice expressing green fluorescent protein, there was a pronounced distribution of GABAergic neurons in the ventral half of the solitary nucleus. Approximately 15% of solitary neurons expressing Fos were GABAergic, but this proportion did not differ according to stimulus.     

Gustatory sensitivities of the hamster's soft palate

The response properties of taste receptors distributed on thesoft palate of the hamster were studied by recording integratedresponses from the greater superficial petrosal (GSP) nerveStimuli were concentration series of sucrose, NaCl, HCl andquinine hydrochloride (QHCl), and several other 0.1 M saltsand 0.5 M sugars. For comparison, integrated responses wererecorded from the chorda tympani (CT) nerve in many of the sameanimals from which recordings were made from the GSP. Responsesin each preparation were scaled relative to the phasic responseto 0.1 M NaCl and were then expressed for each nerve as a proportionof the total response magnitude (TRM)—the sum of all theresponses to the four concentration series. In this way, therelative response of each nerve to all of the stimuli couldbe evaluated. There were significant differences between theGSP and CT nerves in the responses to NaCl, QHCl and sucrose.Both the phasic and tonic responses to sucrose were larger inthe GSP than in the CT, whereas the tonic responses to NaCland QHCl were smaller. The slopes of the concentration-responsefunctions for NaCl, HCl and sucrose were significantly differentbetween the two nerves. The responses to 0.1 M sodium and lithiumsalts were significantly greater in the CT than in the GSP;whereas the 0.5 M sugars elicited responses in the GSP thatwere 2–3 times greater than in the CT nerve. A comparisonof the relative responsiveness to 0.3M sucrose, 0 3 M NaCl,0.01 M QHCl, 0.01 M HCl and distilled water among the GSP, CT,glossopharyngeal (IXth) nerve and superior laryngeal nerve (SLN)indicated that the vast majority of information about sucroseand NaCl is transmitted to the brainstem by the VIIth nerve. ¹Present address: Department of Oral Physiology, Kagoshima UniversityDental School, Kagoshima 890, Japan     

Rats (Rattus norvegicus) and pigeons (Columbia livia) are sensitive to the distance to food,but only rats request more food when distance increases

Three experiments investigated foraging by rats and pigeons. In Experiment 1, each response on a manipulandum delivered food to a cup, with the distance between the manipulandum and the cup varying across conditions. The number of responses made before traveling to collect and eat the food increased with distance for rats, but not for pigeons. In Experiment 2, two manipulanda were placed at different distances from a fixed food source; both pigeons and rats preferentially used the manipulandum closest to the food source. Experiment 3 was a systematic replication of Experiment 1 with pigeons. In different conditions, each peck on the left key increased the upcoming hopper duration by 0.5, 1.5 or 2.5 s. Completing a ratio requirement on the right key of 1, 4, 8, 16 or 32 pecks, depending on the condition, then produced the food hopper for a duration that depended on the number of prior left pecks. As the ratio requirement increased on the right key, pigeons responded more on the left key and earned more food. Overall, the results replicate previous research, underlining similarities and differences between these species. The results are discussed in terms of optimal foraging, reinforcer sensitivity and delay discounting.     

Categorical counting

Pigeons pecked on three keys, responses to one of which could be reinforced after a few pecks, to a second key after a somewhat larger number of pecks, and to a third key after the maximum pecking requirement. The values of the pecking requirements and the proportion of trials ending with reinforcement were varied. Transits among the keys were an orderly function of peck number, and showed approximately proportional changes with changes in the pecking requirements, consistent with Weber's law. Standard deviations of the switch points between successive keys increased more slowly within a condition than across conditions. Changes in reinforcement probability produced changes in the location of the psychometric functions that were consistent with models of timing. Analyses of the number of pecks emitted and the duration of the pecking sequences demonstrated that peck number was the primary determinant of choice, but that passage of time also played some role. We capture the basic results with a standard model of counting, which we qualify to account for the secondary experiments.     

The sweet-bitter taste of alcohol: aversion generalization to various sweet-quinine mixtures in the rat

Rats were trained to avoid a 5% alcohol solution and then testedwith either sweet + quinine hydrochloride solutions (Experiment1) or sweet + hydrochloric acid solutions (Experiment 2). Thesweet stimuli used were sucrose, glucose, fructose and saccharin.Significant aversion generalization was found only in Experiment1 where trained rats generalized to all four test stimuli, thussuggesting that alcohol has a sweet taste (in combination withbitter) not specific to one sweetener. No significant aversiongeneralization was noted in Experiment 2 when sweet + hydrochloricacid solutions were tested. In Experiment 3, rats were trainedto avoid 6% alcohol and tested with sucrose + quinine hydrochloridemixtures with varying concentrations of each component. In general,rats showed generalization of the alcohol aversions across thevarious concentrations of sucrose and quinine hydrochloridetested.     

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.     

Relationship between feather pecking and ground pecking in laying hens and the effect of group size

The aim of this experiment was to study the relationship between feather pecking and ground pecking in laying hens and the effect of group size on feather pecking behaviour. Hisex White hens were kept in floor pens in group sizes of 15, 30, 60 and 120 birds, each with four replicates. Behavioural observations were performed at four different ages and focused on the number of feather pecks and aggressive pecks, both given and received. The part of the body pecked and the location of the bird was recorded as well as the number of pecks made to the floor, feeder and drinker.The results showed that most feather pecking activity occurred in the largest group size (120 birds) and there was some evidence of an increasing frequency of aggressive pecks with increasing group size. The parts of the body which were targets for feather pecking varied depending on the location of the bird giving the peck and the bird receiving it. When looking at the behaviour of individuals, birds doing a lot of feather pecking also showed more ground pecking.     

Behavioral research in pigeons with ARENA: An Automated Remote Environmental Navigation Apparatus

Three experiments established the effectiveness of an Automated Remote Environmental Navigation Apparatus (ARENA) developed in our lab to study behavioral processes in pigeons. The technology utilizes one or more wireless modules, each capable of presenting colored lights as visual stimuli to signal reward and of detecting subject peck responses. In Experiment 1, subjects were instrumentally shaped to peck at a single ARENA module following an unsuccessful autoshaping procedure. In Experiment 2, pigeons were trained with a simultaneous discrimination procedure during which two modules were illuminated different colors; pecks to one color (S+) were reinforced while pecks to the other color (S−) were not. Pigeons learned to preferentially peck the module displaying the S+. In Experiment 3, two modules were lit the same color concurrently from a set of six colors in a conditional discrimination task. For three of the colors pecks to the module in one location (e.g., upper quadrant) were reinforced while for the remaining colors pecks at the other module (e.g., lower quadrant) were reinforced. After learning this discrimination, the color-reinforced location assignments were reversed. Pigeons successfully acquired the reversal. ARENA is an automated system for open-field studies and a more ecologically valid alternative to the touchscreen.     

The taste of alcohol for rats as revealed by aversion generalization tests

In six experiments, naive rats were trained to avoid alcoholby pairing its presentation with lithium chloride-induced illness.Rats were then tested for aversion generalization by presentingvarious test solutions. Rats trained to avoid either 3, 6 or9% (v/v) alcohol generalized the aversion to a sucrose + quininehydrochloride solution. The five remaining binary combinationsof sucrose, sodium chloride, hydrochloric acid and quinine hydrochloridefailed to produce significant generalization in trained rats(Experiment 1). In further experiments, rats trained to avoid6% alcohol showed significant aversion generalization to a varietyof sucrose + other ‘bitter’ solutions (Experiment2) and sucrose + acid solutions (Experiment 3). Varying theconcentration of hydrochloric acid in a sucrose + acid mixtureproduced small but uniform degrees of aversion generalization(Experiment 4). Rats trained to avoid 6% alcohol did not generalizethe aversion to sucrose alone, regardless of concentration (Experiment5). Finally, in Experiment 6, rats trained to avoid 6% alcoholsuppressed consumption over a range of alcohol concentrations.These results confirm that, for rats, the taste of alcohol hasa complex set of characteristics; sweet taste in combinationwith other tastes appears to be the most similar as it is tothese solutions that rats with alcohol aversions show the mostgeneralized avoidance.     

Preference for sucralose predicts behavioral responses to sweet and bittersweet tastants

Rats can be classified as either sucralose avoiders (SA) or sucralose preferrers (SP) based on their behavioral responses in 2-bottle preference, 1-bottle intake, and brief-access licking tests. The present study demonstrates that this robust phenotypic variation in the preference for sucralose predicts acceptance of saccharin, an artificial sweetener with a purported concentration-dependent "bitter" side taste and a 0.25 M sucrose solution adulterated with increasing concentrations of quinine hydrochloride (QHCl). Specifically, SA displayed decreased preference for and intakes of saccharin (≥41.5 mM) and sucrose-QHCl (>0.5 mM QHCl) solutions, relative to SP. In a second experiment involving brief-access (30-s) tests, SP and SA did not differ in their unconditioned licking responses across a range of sodium chloride or QHCl solutions (0.03-1 mM). However, the acceptability threshold for sucrose was lower in SA, relative to SP (0.06 and 0.13 M, respectively). Our findings suggest that phenotypic differences in sucralose preference are indicative of a more general difference in the hedonic processing of stimuli containing "bittersweet" or "sweet" taste qualities.     

Quinine and citric acid elicit distinctive Fos-like immunoreactivity in the rat nucleus of the solitary tract

The present experiment investigated Fos-like immunoreactivity (FLI) in the nucleus of the solitary tract (NST) after intraoral infusions of 0.1 M citric acid, 0.3 M NaCl, and 0.3-30 mM quinine monohydrochloride (QHCl) in awake, behaving rats. Increases in QHCl concentration produced increases in the numbers of FLI-labeled neurons in the rostral part of the intermediate (i(r)) and rostral (r) NST, but the topographic distribution of FLI was consistent across QHCl concentrations and distinctive compared with effects of citric acid. Quinine elicited FLI concentrated in the medial third of the nucleus; acid elicited more broadly distributed FLI concentrated farther laterally. Surprisingly, in contrast to QHCl and citric acid, NaCl produced FLI that was indistinguishable from that produced by water. Although the functional significance of these patterns is unknown, citric acid and QHCl are nonpreferred stimuli but produced different oromotor behaviors. QHCl (30 mM) elicited approximately 3.2 times as many gapes as citric acid (0.1 M), and acid elicited more ingestive responses. Parallel differences in FLI expression suggest that different NST regions may have distinctive roles in triggering oromotor behaviors.