Relationship between vomiting and taste aversion learning in the ferret: studies with ionizing radiation, lithium chloride, and amphetamine.

The relationship between emesis and taste aversion learning was studied in ferrets (Mustela putorius furo) following exposure to ionizing radiation (50-200 cGy) or injection of lithium chloride (1.5-3.0 mEq/kg, ip). When 10% sucrose or 0.1% saccharin was used as the conditioned stimulus, neither unconditioned stimulus produced a taste aversion, even when vomiting was produced by the stimulus (Experiments 1 and 2). When a canned cat food was used as the conditioned stimulus, lithium chloride, but not ionizing radiation, produced a taste aversion (Experiment 3). Lithium chloride was effective in producing a conditioned taste aversion when administration of the toxin was delayed by up to 90 min following the ingestion of the canned cat food, indicating that the ferrets are capable of showing long-delay learning (Experiment 4). Experiment 5 examined the capacity of amphetamine, which is a qualitatively different stimulus than lithium chloride or ionizing radiation, to produce taste aversion learning in rats and cats as well as in ferrets. Injection of amphetamine (3 mg/kg, ip) produced a taste aversion in rats and cats but not in ferrets which required a higher dose (> 5 mg/kg). The results of these experiments are interpreted as indicating that, at least for the ferret, there is no necessary relationship between toxin-induced illness and the acquisition of a CTA and that gastrointestinal distress is not a sufficient condition for CTA learning.     

The interval between the CS and the UCS as a determiner of generalization performance

Rats were trained in a conditioned taste aversion paradigm in order to determine whether a trace interval between the conditioned stimulus (CS) and the unconditioned stimulus (UCS) would result in the forgetting of stimulus attributes. Accordingly, subjects were conditioned with milk (CS), given either an immediate or a delayed injection of lithium chloride (UCS), and tested 48 h later with either milk or chocolate milk, a generalized flavor. The rats conditioned immediately following the presentation of the CS avoided milk more than chocolate milk, indicating discrimination between the two flavors. Those conditioned after a trace interval avoided both flavors equally, suggesting a loss of stimulus attributes of the original CS. Delay rats, however, still exhibited substantial learning when compared with controls not experiencing the UCS. These results allege a role for the forgetting of stimulus attributes during a trace interval in addition to following a complete learning episode.     

Flavor preexposures in a conditioned taste aversion situation: a dissociation of behavioral and endocrine effects in rats

A series of experiments examined the effects of flavor preexposures on pituitary-adrenal/behavior relations in a conditioned taste aversion paradigm. It was found that reexposure to a novel milk solution paired earlier with lithium chloride (LiCl) elicited conditioned activation of the pituitary-adrenal system (Experiment 1). The unconditioned response to LiCl (measured by changes in plasma levels of corticosterone) did not vary as a function of prior (2 and 5 vs. 10) exposures to the milk solution (Experiment 2). Increased familiarity with the substance (resulting from 10 prior exposures) rendered the conditioning of a taste aversion to this substance less effective. Further, reexposure to this familiar substance after its pairing with LiCl was not accompanied by the characteristic conditioned pituitary-adrenal activation (Experiment 3). By titrating the number of conditioned stimulus (CS) preexposures (Experiment 4) it was found that within the range of preexposures manipulated (5-10), subjects exhibited (a) a coupling of behavioral and pituitary-adrenocortical responses when the conditioned taste aversion to the milk solution was paralleled by elevated plasma corticosterone (5-6 preexposures), (b) a coupling of these two response systems when flavor consumption was accompanied by suppressed plasma titers of corticoids (9-10 preexposures), or (c) a dissociation of the two system when the conditioned taste aversion was not accompanied by conditioned adrenocortical activity (7-8 preexposures). These data are discussed in terms of a dissociation in the effects of CS preexposures on conditioned adrenocortical and behavioral response systems.     

味觉厌恶性条件反射与条件反射性免疫抑制的研究

以环磷酰胺的注射为非条件刺激（ＵＣＳ）,糖精水的摄入为条件刺激（ＣＳ）,并以血白细胞和淋巴细胞数量及脾淋巴细胞的转化反应为免疫指标,糖精水的饮用量为行为指标,通过改变条件刺激与非条件刺激结合的次数来观察条件反射性厌恶行为与条件反射性免疫抑制的反应。结果表明不管是一次性的还是两次性的ＣＳ－ＵＣＳ结合训练都能使动物明显地建立起味觉厌恶性条件反射,然而条件反射性免疫抑制只在两次性ＣＳ－ＵＣＳ结合训练后才     

Acquisition of a conditioned taste aversion becomes context dependent when it is learned after extinction

A conditioned taste aversion experiment tested context-switch effects on retrieval of conditioned stimulus (CS)-unconditioned stimulus (US) acquisition performance in rats. A context switch impaired performance when the target flavour was trained in a context where a different flavour underwent extinction. Conditioned taste aversion in the absence of previous extinction of the alternate flavour was not context dependent. It is suggested that the ambiguity in the meaning of the extinguished cue leads animals to pay attention to the context, so that the information learned in that context becomes context dependent.     

Acquisition of a conditioned taste aversion becomes context dependent when it is learned after extinction

A conditioned taste aversion experiment tested context-switch effects on retrieval of conditioned stimulus (CS)–unconditioned stimulus (US) acquisition performance in rats. A context switch impaired performance when the target flavour was trained in a context where a different flavour underwent extinction. Conditioned taste aversion in the absence of previous extinction of the alternate flavour was not context dependent. It is suggested that the ambiguity in the meaning of the extinguished cue leads animals to pay attention to the context, so that the information learned in that context becomes context dependent.     

Conditioning Method Dramatically Alters the Role of Amygdala in Taste Aversion Learning

Although an important role for the amygdala in taste aversion learning has been suggested by work in a number of laboratories, results have been inconsistent and interpretations varied. The present series of studies reevaluated the role of the amygdala in taste aversion learning by examining the extent to which conditioning methods, testing methods and lesioning methods, influence whether amygdala lesions dramatically affect conditioned taste aversion (CTA) learning. Results indicated that when animals are conditioned with an intraoral (I/O) taste presentation, lesions of amygdala eliminate evidence of conditioning whether animals are tested intraorally or with a two-bottle solution presentation. Dramatic effects of amygdala lesions on CTA learning were seen whether lesions were made electrolytically or using an excitotoxin. In contrast, when animals were conditioned using bottle presentation of the taste, electrolytic lesions attenuated CTAs but did not eliminate them, and excitotoxic lesions had no effect. These results are consistent with the hypothesis that neural structures critical for CTA learning may differ depending on the extent to which the method of conditioned stimulus delivery incorporates a response component.     

Rho-associated kinase in the gustatory cortex is involved in conditioned taste aversion memory formation but not in memory retrieval or relearning

Rho-associated kinase (ROCK) is intimately involved in cortical neuronal morphogenesis. The present study explores the roles of ROCK in conditioned taste aversion (CTA) memory formation in gustatory cortex (GC) in adult rat. Microinjection of the ROCK inhibitor Y-27632 into the GC 30 min before CTA training or 10 min after the conditioned stimulus (CS) impaired long-term CTA memory (LTM) formation. ROCK inhibitor had no effect on taste aversion when injected before the first LTM test day and did not alter taste aversion on subsequent test days. Microinjection of ROCK inhibitor into GC 30 min before preexposure to the taste CS had no effect on latent inhibition of CTA learning suggesting that ROCK is involved in CS-US association rather than taste learning per se. Cumulatively, these results show that ROCK is needed for normal CTA memory formation but not retrieval, relearning or incidental taste learning.     

Does taste or odor activate the same brain networks after retrieval of taste potentiated odor aversion?

When simultaneous presentation of odor and taste cues precedes illness, rats acquire robust aversion to both conditioned stimuli. Such a phenomenon referred to as taste-potentiated odor aversion (TPOA) requires information processing from two sensory modalities. Whether similar or different brain networks are activated when TPOA memory is retrieved by either the odor or the taste presentation remains an unsolved question. By means of Fos mapping, we investigated the neuronal substrate underlying TPOA retrieval elicited by either the odor or the taste conditioned stimulus. Whatever the sensory modality used to reactivate TPOA memory, a significant change in Fos expression was observed in the hippocampus, the basolateral nucleus of amygdala and the medial and the orbito-frontal cortices. Moreover, only the odor presentation elicited a significantly higher Fos immunoreactivity in the piriform cortex, the entorhinal cortex and the insular cortex. Lastly, according to the stimulus tested to induce TPOA retrieval, the BLA was differentially activated and a higher Fos expression was induced by the odor than by the taste in this nucleus. The present study indicates that even if they share some brain regions, the cerebral patterns induced by either the odor or the taste are different. Data are discussed in view of the relevance of each conditioned stimulus to reactivate TPOA memory and of the involvement of the different labeled brain areas in information processing and TPOA retrieval.     

Conditioned taste aversion induced by motion is prevented by selective vagotomy in the rat

The role of the vagus nerve in motion-induced conditioned taste aversion (CTA) was studied in hooded rats. Animals with complete, selective gastric vagotomy failed to form conditioned taste aversion after multiple conditioning sessions in which the conditioned stimulus (a cider vinegar solution) was drunk immediately before a 30-min exposure to vertical axis rotation at 150 degrees/s. Results are discussed with reference to the use of CTA as a measure of motion-induced "sickness" or gastrointestinal disturbance, and, because motion-induced CTA requires that both the vagus nerve and the vestibular apparatus be intact, in light of the possible convergence of vagal and vestibular functions.     

Context-dependent latent inhibition in taste aversion learning

The effects of taste stimulus preexposure, either in the presence or in the absence of a specific contextual cue consisting of a specific noise-producing bottle, upon the conditioning and testing of conditioned taste aversions to the taste (saccharin) plus context (noisy-bottle) compound stimulus were investigated. Four groups of rats were given preexposure trials (latent inhibition) to either: (1) novel saccharin in novel noisy bottles, (2) novel saccharin in familiar silent bottles, (3) familiar water in novel noisy bottles, (4) familiar water in familiar silent bottles, in six trials. During conditioning, saccharin was presented in the noisy bottles followed by lithium chloride for all the groups. At testing, saccharin was presented in the noisy bottles for both one-bottle and two-bottle tests of aversion. It was indicated that the conditioning decrement produced after both saccharin and noisy bottle preexposure was overwhelmingly greater than any produced after preexposure to the elements. These results, discussed in relation to current theories of latent inhibition and perceptual learning, further underline the overwhelming significance of exteroceptive contextual elements in conditioned taste aversions.     

Weanling and senescent rats process simultaneously presented odor and taste differently than young adults

Weanling, young-adult, and senescent Wistar albino rats had a novel odor/taste stimulus or a single taste stimulus either paired or explicitly unpaired with the unconditioned stimulus, lithium chloride. Animals were then given a saccharin vs water preference test. Standard preference scores indicated that the odor competed with taste for association with the US in young-adult rats but potentiated the conditioned aversion to taste in weanling and senescent rats. Results were interpreted in terms of age-related attentional differences which were hypothesized to account for infantile amnesia and for the memory dysfunction typically observed in senescent animals.     

The effect of manipulating CS hedonic value on the magnitude of a conditioned taste aversion

This study was designed to assess how the hedonic value of a conditioned stimulus (CS) might mediate the strength of a conditioned taste aversion (CTA). Results indicated that as the hedonic value of the CS increased, the severity of the aversion associated with the CS attenuated.     

The effect of manipulating CS hedonic value on the magnitude of a conditioned taste aversion

This study was designed to assess how the hedonic value of a conditioned stimulus (CS) might mediate the strength of a conditioned taste aversion (CTA). Results indicated that as the hedonic value of the CS increased, the severity of the aversion associated with the CS attenuated.     

ACTH and ACTH4-10 modification of neophobia and taste aversion responses in the rat.

A series of experiments assessed the effects of ACTH and the ACTH analogue ACTH4-10 on drinking in conditioned taste aversion and neophobic situations. Both substances delayed the extinction of a conditioned taste aversion established by a single pairing of lithium chloride with milk (Experiment 1). However, in this situation, the ACTH parent peptide was more potent behaviorally. Administration of ACTH suppressed milk consumption in animals with no toxicosis experience (Experiment 2). This effect was apparently not due to the conditioning of a taste aversion (Experiment 3) with ACTH serving as a weak aversive unconditioned stimulus. Administration of exogenous ACTH (Experiment 4) or ACTH4-10 (Experiment 5) did not enhance neophobia; however, repeated injections of ACTH suppressed drinking. This ACTH suppression was related to the familiarity/novelty of the subtance being consumed. The neophobic response to milk eas no accompanied by pituitary-adrenal activation (Experiment 6). Both neophobic and conditioned taste aversion situation appear to be useful for assessing peptide effects on consummatory behavior.     

Taste potentiation of auditory aversions in rats (Rattus norvegicus): a case for spatial contiguity

An aversion for an auditory stimulus was established in laboratory rats when a tone was spatially and temporally contiguous with a novel taste in a food conditioned stimulus compound followed by toxicosis. The procedure involved varying the location of the tone relative to a novel tasting food. During toxicosis conditioning, one group ate sweet food with a speaker located in the food, two groups ate sweet food with the speaker displaced (near or far) from the food, and a fourth group was presented with a tone without food available. It was found that the potentiation of auditory aversions required both the presence of a novel taste and spatial contiguity between the taste and the tone.     

Conditioned taste aversion is enhanced when the unconditioned stimulus is presented in a different context

Using a conditioned taste aversion procedure with rats as the subjects, two experiments examined the effect of presenting a conditioned stimulus (CS saccharin solution) in one context followed by an unconditioned stimulus (US LiCl) in a different context. Experiment 1 showed that animals which received the above-mentioned procedure (Group D) showed a more marked conditioned aversion to the CS than animals which were given both the CS and the US in the same context (Group S). Experiment 2 found that in both Group D and Group S, aversion to the CS increased when the subjects were exposed to the conditioned context after the conditioning. These findings supported the argument that the strength of the CS-US association acquired during conditioning is compared with that of the context-US to determine the magnitude of aversion revealed to the CS.     

Taste Aversion Learning Based on Swimming and Lithium Chloride Injection in Rats: Implications From Cross-familiarization Tests and Stimulus Selectivity1

In rats, swimming causes avoidance of the taste solution consumed immediately before the swimming. Several lines of research have shown that this taste avoidance reflects Pavlovian conditioned aversion based on correlations between the taste and swimming-induced nausea. The present research compared swimming-based taste aversion learning (TAL) with conventional TAL based on nausea-inducing lithium chloride (LiCl). By exploiting cross-familiarization techniques, Experiments 1A and 1B suggested that different physiological states are induced by swimming and LiCl. This claim was supported by Experiment 2, which reports stimulus selectivity in saccharin and sucrose aversions based on swimming and LiCl.     

Potentiation of latent inhibition

Rats were given exposure either to an odor (almond) or a compound of odor plus taste (almond plus saline), prior to training in which the odor served as the conditioned stimulus. It was found, for both appetitive and aversive procedures, that conditioning was retarded by preexposure (a latent inhibition effect), and the extent of the retardation was greater in rats preexposed to the compound (i.e., latent inhibition to the odor was potentiated by the presence of the taste). In contrast, the presence of the taste during conditioning itself overshadowed learning about the odor. We argue that the presence of the salient taste in compound with the odor enhances the rate of associative learning, producing a rapid loss in the associability of the odor. This loss of associability will generate both overshadowing and the potentiation of latent inhibition that is observed after preexposure to the compound.     

对体液免疫反应的条件反射性调节

以饮糖精水作为条件刺激(conditioned stimulus,CS),腹腔注射免疫抑制剂环磷酰胺作为非条件刺激(unconditioned stimulus,UCS)训练Wistar大鼠,3天后腹腔注射卵清蛋白(ovalbunfin,OVA)抗原,观察再次单独条件刺激对原发性体液免疫反应的作用。结果发现．一次CU-UCS结合训练导致CS组大鼠对再现糖精水产生厌恶反应,外周血中抗OVA-IgG抗体水平显著低于UCS组。两次CS-UCS结合训练并多次给予条件刺激后,CS组大鼠抗OVA-IgG的条件性免疫抑制效应与一次CS-UCS结合训练及再次给予一次条件刺激的反应类同。这些结果证明条件刺激增强了环磷酰胺对动物原发性体液免疫反应的抑制作用．这种条件性体液免疫抑制作用是相对稳定和有限度的,不易受条件反射建立参数的影响。