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Results for “Avoidance Learning”

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PubMed1982

Odor aversion learning by the rat fetus.

Rat fetuses were exposed to an odor stimulus on day 20 of gestation via amniotic injection and then injected with LiCl. In a CER paradigm, 10 day old pups were trained to approach an anesthetized dam in a runway for suckling reinforcement. When running speeds had stabilized the odor stimulus experienced in-utero was introduced into the test chamber. This odor took on aversive properties as a function of its pairing with LiCl, as evidenced by a decrease in running speed on CER trials and increases in the number of trials that were terminated because pups failed to traverse the runway. These data indicate that the fetal rat is capable of odor aversion learning.

Animals↗

PubMed1984

The effect of amygdala-kindled seizures on the acquisition of taste and odor aversions.

Two experiments were conducted to investigate the effect of amygdala-kindled seizures on the acquisition of fluid aversions using taste, odor, and compound taste-odor cues. In Experiment 1 all subjects were poisoned with lithium chloride 30 minutes after ingesting a novel taste. Experimental subjects were either kindled 15 minutes following ingestion or 15 minutes following LiCl injection. The strength of the taste aversion in the kindled animals was significantly attenuated compared to nonkindled controls. There was a tendency for kindling within the CS-US interval to be more disruptive than kindling that occurred after LiCl injection. The second study explored the effect of kindling after the CS on the development of aversions to an odor cue or a compound taste-odor cue. This study found that kindling after drinking effectively blocked the acquisition of both odor and taste aversions and compounding did not affect the strength of the odor aversion.

Amygdala↗

PubMed1985

Some behavioral factors related to the effects of cold-restraint stress in rats: a factor analytic-multiple regression approach.

Recently, some individual differences in rats have been shown to be related to stress-induced physiological responses. As yet there has been no attempt to incorporate measurement techniques from the psychometric field to this line of research. The present study was conducted to examine the utility of applying such methods to animal research. Physiological responses to cold-restraint stress in 26 male rats were investigated using a factor analytic-multiple regression procedure. Nineteen behavioral and physiological measures obtained during open-field testing, motor activity monitoring, and passive avoidance learning were subjected to a principle components factor analysis. Five factors were extracted which reflected exploratory behavior, general activity level, metabolic rate, behavioral reactivity, and autonomic reactivity. The obtained factor scores were used to predict physiological responses to four hours of supine cold-restraint using a step-wise multiple regression procedure. General activity level was the best predictor of adrenal weight and temperature loss. Autonomic reactivity was the best predictor of ulcer incidence and severity. Applications of these statistical procedures are discussed.

Animals↗

PubMed1986

Disturbance of motoric function as behavioral measure of impaired cerebral circulation in mice.

Aim of the present experiments was to elaborate an experimental model exhibiting the functional consequences of a moderate impairment of cerebral circulation sensitive enough for testing the long-term cerebroprotective effect of different drugs. In preliminary experiments mice survived unilateral occlusion of the carotid artery. This intervention, however, severely impaired the motor skill of the animals as measured by their activity on the rotating treadmill. Motimeter activity was also diminished following unilateral carotid occlusion. Somewhat unexpectedly, a more complex pattern of learned behavior in a one-trial learning passive avoidance paradigm was only modestly affected by unilateral carotid occlusion. Papaverine (2.0 mg/kg) normalized the motor incoordination measured on the rotating treadmill. The data suggest that impaired motoric function, as a result of unilateral carotid occlusion, might be a useful experimental tool to analyse functional consequences of impaired cerebral circulation and a sensitive test for screening of drugs with presumed cerebroprotective action.

Animals↗

PubMed1987

Caffeine enhancement of saccharin but not cyclamate flavor avoidance.

The present experiments were designed to assess whether caffeine, a substance that potentiates human perception of some artificial sweeteners, might also enhance perception of such substances by rats. In Experiment 1, rats were given varied concentrations of saccharin, cyclamate, and caffeine in 2-choice tests. 'Indifference thresholds' for these substances were 3.9 X 10(-4) M, 1 X 10(-3) M, and 1.6 X 10(-7) M, respectively. In Experiment 2, concentrations of saccharin and cyclamate just above and below indifference were used as stimuli in a flavor avoidance learning (FAL) paradigm. 'Suprathreshold' concentrations of saccharin and cyclamate produced reliable FAL while 'subthreshold' concentrations did not. In Experiment 3, rats were exposed to a low concentration of caffeine followed by presentations of subthreshold concentrations of saccharin or cyclamate as stimuli in a FAL paradigm. Saccharin FAL was observed but cyclamate FAL was not, suggesting that caffeine preexposure selectively potentiated detection of saccharin. In Experiment 4, animals were given saccharin or cyclamate with or without prior exposure to caffeine in a FAL paradigm. During subsequent tests, animals were presented with saccharin or cyclamate following exposure to caffeine saccharin or cyclamate mixed with caffeine saccharin or cyclamate alone. Saccharin FAL was observed following caffeine preexposure, but mixing with caffeine had no effect. These findings of selective potentiation are consistent with previous studies of human sensitivity after caffeine preexposure. Moreover, the present results support the notion that inhibitory A1 adenosine receptors are involved in modulating the perceived intensity of some flavors.

Animals↗

PubMed1989

Prenatal ethanol and stress in mice: 2. Development and behavior of fostered offspring.

On days 12 to 17 of gestation, B6D2F2 mice were pair-fed liquid diets containing either 25% ethanol-derived calories or an isocaloric amount of maltose-dextrin. During this time, half the mice in each dietary condition also underwent two daily one-hour periods of restraint stress. All pups were fostered at birth to untreated mothers whose pups, in turn, were fostered to the treated mothers. Two additional groups of untreated dams were included, the pups in one group being fostered to other untreated dams while the rest remained with their biological mothers. Prenatal ethanol retarded neurobehavioral development on day 32 postconception and also decreased pup body weight at birth and at weaning, and brain weight on day 32 and at weaning. Prenatal stress decreased body weight at birth in the pair-fed controls only, increased open field activity at weaning and affected retention of a learned passive avoidance task. Undernutrition due to the pair feeding procedure decreased pup birth weight. There were a few effects on untreated pups fostered to treated dams, but these were marginal. These results do not support a role of stress-induced physiological changes in ethanol teratogenicity.

Animals↗

PubMed1990

Effects of medullary afferent vagal axotomy and area postrema lesions on short-term and long-term NaCl-induced taste aversion learning.

This series of experiments demonstrates a functional dissociation between the area postrema (AP) and the vagus nerve in short-term taste aversion learning (TAL). Although medullary axotomy of the afferent component of the vagus disrupted the learning observed with NaCl-induced short-term (nondelayed) TAL, lesioning the AP failed to interfere with the discriminative process employed by the animals under the same conditions. However, involvement of neither the vagus nerve nor the AP seemed to be indispensable for learning in NaCl-induced long-term (delayed) TAL. The possibility that the vagus nerve and the AP are involved in temporally distinct visceral processing is discussed.

Afferent Pathways↗

PubMed1991

Conditioned taste aversion but not adrenal activity develops to ICV administration of interleukin-1 in rats.

In a previous investigation with mice, the paired presentation of either odor or taste cues with the peripheral (IP) administration of the immunoactive peptide interleukin-1 (IL-1) led to the conditioned enhancement of glucocorticoid production. The present study found that an initial central infusion of IL-1 in the presence of saccharin cues produced a robust taste aversion but not a conditioned elevation of either ACTH or corticosterone production. These results indicate that the glucocorticoid response induced by centrally administered IL-1 in rats is independent of the behaviorally aversive properties of this cytokine which are conditionable. The differential effects of IP versus ICV administration of IL-1 on glucocorticoid conditioning requires a clearer specification of the respective signaling mechanisms and pathways activated by these two routes of administration.

Adrenocorticotropic Hormone↗

PubMed1991

Modulation of body temperature through taste aversion conditioning.

Injection of rats with bacterial lipopolysaccharide (LPS) results in an initial fall in body temperature followed by a fever. Lithium chloride (LiCl) injection induces a fall in body temperature without subsequent fever production. When these substances were incorporated as unconditioned stimuli in a taste aversion conditioning paradigm, using saccharin flavour as the conditioning stimulus, these differential effects on body temperature were reenlisted on reexposure to saccharin alone 7 days after conditioning. The changes in body temperature on reexposure were similar in direction and kinetics as on the conditioning day although reduced in magnitude. The finding of a true conditioned effect in these studies is in contrast to the paradoxical or compensatory conditioned body temperature responses described elsewhere using different conditioning models. This apparent conflict may be explained on the basis of different unconditioned stimuli acting on efferent versus afferent arms of a negative feedback system. Since body temperature changes often occur in association with immune responses, these findings may have implications to behavioural conditioning of immunity, the outcome of which may reflect the indirect effects on immunity of inadvertent conditioning of thermoregulatory changes.

Animals↗

PubMed1991

Estradiol-induced conditioned taste aversion and place aversion in rats: sex- and dose-dependent effects.

Effects of various doses (0-250 micrograms/kg, SC) of estradiol-17 beta (E2) in a two-bottle choice conditioned taste aversion and a two-compartment conditioned place preference procedure were studied in male and female rats. Dose-dependent taste aversion and place aversion effects of E2 were established, and the conditioned taste aversion procedure was found to be more sensitive in detecting aversive properties of E2 than the conditioned place preference procedure. Although aversive properties of E2 were found in both sexes, the effects were clearly more prominent in males as compared to females. From this study, it was concluded that E2 acts as an unconditioned aversive stimulus in both male and female rats capable of gaining control over different types of behavior by associative learning.

Animals↗

PubMed1991

Conditioned activation of fetal behavior.

Previous demonstrations of prenatal learning have relied upon experimental protocols involving training at one gestational age and testing at a later age, potentially confounding effects of experience and retention with developmental changes in the fetus's behavioral repertoire. In this study, a single-session paradigm, which involved the pairing of a neutral chemosensory stimulus (sucrose CS) with a second stimulus that activates behavior (lemon US), was used to assess the learning capacity of the rat fetus. Four CS-US pairings were effective in promoting behavioral activity in 20-day-old rat fetuses when they were reexposed to the sucrose CS alone. The functional expression of conditioned behavioral activation on day 20 of gestation occurs at a time when CNS structures, many of which are involved in sensory processing and learning in older animals, are still undergoing rapid differentiation in the rat fetus.

Animals↗

PubMed1992

Learned preference for the limiting amino acid in rats fed a threonine-deficient diet.

Preference for an odor associated with protein is only seen in protein-deprived rats. We hypothesized that rats depleted of the amino acid threonine (THR) would prefer a flavored solution paired with a THR replete diet. Rats were given a flavored drink paired with THR-deficient (DEV) diet followed by a second flavor paired with a corrected (COR) diet. In choice testing, the animals clearly selected the COR-paired flavor, while control rats preferred the other flavor. This did not, however, differentiate between aversion to the DEV-paired flavor and learned preference for the COR-paired flavor. In subsequent tests, an unpaired flavor was given rather than the DEV-paired flavor. The COR-paired flavor was included in the test as before. In the second and third trials, using either DEV or a less profoundly deficient diet, animals depleted of THR selected the COR-paired flavor to a greater extent than control rats. We conclude that animals deficient in the essential amino acid, THR, show a learned preference for the flavor paired with repletion.

Amino Acids, Essential↗

PubMed1992

Defensive burying following injections of cholecystokinin, bombesin, and LiCl in rats.

Past research indicates that feeding is reduced for animals injected with cholecystokinin and bombesin. One explanation for this effect suggests that these peptides act as natural satiety signals; an opposing view asserts that bombesin and cholecystokinin reduce feeding through malaise. The present experiment tested the basic assumptions associated with these positions using the defensive burying procedure. Groups of rats were given sweetened condensed milk followed by IP injections of bombesin (6, 16, and 32 micrograms/kg), cholecystokinin (0.7, 1.4, and 2.9 micrograms/kg), LiCl (6.4 mg/ml), or saline. The results showed that animals injected with cholecystokinin, bombesin, and LiCl developed learned aversions to the milk and actively buried the milk spout with their bedding. The findings provide further support for the view that bombesin and cholecystokinin induce malaise rather than satiety.

Animals↗

PubMed1992

Plasma testosterone concentration in adult male rats following acquisition of copulation-illness associations.

Prior research has identified stimuli and procedures that elicit increments in plasma testosterone in copulating male rats. In the present experiment, we demonstrate that associative inhibition of copulatory behaviors in male rats is not correlated with and cannot be attributed to a conditioned suppression of testosterone. Each male rat was paired with an inaccessible estrous female for 7 min and was then given an opportunity to copulate. Two groups received an injection of either lithium chloride (LiCl; 0.3 M, 20 ml/kg, IP) or saline (0.3 M, 20 ml/kg, IP) immediately after each of 11 pairings spaced at 3- to 4-day intervals. A third group received a noncontingent injection of LiCl 24 h after each pairing. After an initial screening for copulatory behaviors, a fourth group received only handling comparable to that received by the other three groups. Rats that received contingent LiCl gradually ceased to copulate; rats that received either noncontingent LiCl or saline remained vigorous copulators. Male rats were returned to their home cages on Trial 12 after 7-min exposure to an inaccessible female. Blood was collected by decapitation 38 min later. Testosterone levels, measured by radioimmunoassay, were significantly higher for saline than for handled control rats. Testosterone levels for handled control rats, however, were comparable to those of copulating and noncopulating rats that had received either noncontingent or contingent LiCl, respectively.

Animals↗

PubMed1992

Conditioned facilitatory modulation of the response to an aversive stimulus in the crab Chasmagnathus.

A mild electrical shock delivered to the walking legs of the crab Chasmagnathus granulatus through a fine layer of sea water, induces a running response that declines after repeated stimulation. Herein, a first series of experiments was aimed at conditioning the response to a light or a dark pulse, but no detectable CR was disclosed during training nor in a later test with the CS alone, even though several stimulus parameters were assayed. In a second series, crabs were repeatedly exposed during training to a light pulse (CS) immediately followed by shock (UCS), and after a 6-h rest interval, tested with either CS-UCS or UCS. The CS-UCS presentation at testing elicited a higher recovery (potentiated recovery, circa 70%) than that evoked by the UCS alone (unconditioned recovery, circa 35%) (Experiment 3). An experiment including the explicitly unpaired control procedure (Experiment 4), confirmed that the enhanced response (CR) to the shock (UCS) (measured as potentiated recovery) is conditioned to an illumination signal (CS). An alternative explanation of the potentiated recovery in terms of retardation of habituation proved hardly tenable (Experiment 5). In Experiment 6, crabs were exposed to a variety of light pulse shock and dark pulse shock temporal relationships, and results were found consistent with a delay of reinforcement gradient when light termination was considered as CS. Thus a decrease in luminance is able to become associated with shock and to condition an enhanced response regardless of light termination being the offset of a light pulse or the onset of a dark pulse.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Testosterone as appetitive and discriminative stimulus in rats: sex- and dose-dependent effects.

Stimulus properties of subcutaneously injected testosterone were studied in male and female rats. In a conditioned place preference procedure, dose-dependent effects (doses: 0, 0.5, and 1 mg/kg) were observed in males. In females, no place preference could be established (doses: 0, 1, and 3 mg/kg). In addition, 1 mg/kg testosterone acquired discriminative stimulus control in male rats in a taste aversion procedure. Animals injected with this hormone prior to saccharin-LiCl pairings and with its vehicle prior to saccharin-NaCl pairings suppressed fluid intake following the administration of testosterone and not following the administration of the vehicle. Subsequent generalization tests revealed dose-dependent stimulus control of this hormone (range of substitution doses: 0.125-2 mg/kg). It is concluded from the results that at least pharmacological (supraphysiological) doses of testosterone may act as appetitive stimuli in male rats, but not in female rats. Furthermore, in male rats (pharmacological doses of) testosterone also possess discriminative stimulus properties.

Animals↗

PubMed1993

Taste-potentiated odor aversion learning based on amphetamine.

This study sought to determine whether a taste can potentiate a conditioned odor aversion based on amphetamine as well as those based on lithium. A taste-potentiated odor aversion (TPOA) based on lithium was obtained in Experiment 1 only with a low concentration of an almond odor. This concentration was used in Experiment 2 where the taste, 0.1% saccharin, potentiated an odor aversion based on 1 mg/kg d-amphetamine. This was replicated in Experiment 3 where potentiation was found with doses of both 1 and 3 mg/kg amphetamine, and no effect of dose was detected. It was concluded that TPOA learning is not restricted to drugs such as lithium that produce conditioned unpalatability as well as conditioned aversions to a taste, because amphetamine does not produce conditioned unpalatability at the doses used here. Furthermore, because in Experiment 3 postconditioning extinction of the saccharin aversion removed the potentiation effect, it appears that this form of TPOA may depend on an association between the odor and taste, as proposed by within-compound theory.

Amphetamine↗

PubMed1993

Evidence for a direct central anorectic effect of tumor-necrosis-factor-alpha in the rat.

This study was designed to investigate the effect of tumor necrosis factor-alpha (TNF) on the control of food intake in rat. The specific aims were: a) to evaluate the effects of central (ICV) or peripheral (IP) microdoses of TNF on food intake; b) to show that the TNF-induced anorexia results from a direct action of the mediator on the central nervous system; c) to demonstrate that the anorexic activity of TNF is not due to nonspecific malaise. In the first experiment, ICV administration (0.5-4.0 micrograms) of recombinant-murine tumor necrosis factor-alpha (rmTNF) significantly reduced food intake in a dose-dependent manner. The maximal effect (-66%) was observed 5 h after a 4.0 micrograms dose. In contrast, rm TNF did not affect feeding behavior when injected IP, indicating that the anorexic activity was centrally mediated. The estimated DE50 was 2.0 micrograms/rat by the ICV route. In the second experiment, the place conditioning paradigm was used to show that TNF administered ICV at 2.0 micrograms/rat did not induce aversive or deleterious effects as compared to naltrexone given IP at the equi-anorectic dose 5.0 mg/kg. It was concluded that TNF reduces food intake in rats by a direct action on the central nervous system.

Animals↗