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PubMed1993

Learned preference and aversion for complete and isoleucine-devoid diets in rats.

Choice tests using flavored solutions were conducted to demonstrate a learned preference or aversion in rats fed replete (complete) or isoleucine (ILE)-devoid diets. In the first learning trial, rats demonstrated a preference for the flavored solutions paired with the replete diet at 6 and 24 h (p < 0.001), and an aversion for the solutions paired with the ILE-devoid diet at 6 h (p < 0.05). In the second trial, using a different concentration of tastant, rats ingested significantly more of the flavored solution paired with the replete diet at 24 h (11.4 +/- 3.0 g vs. 5.4 +/- 1.0 g, respectively; p < 0.05), and significantly more of a novel flavored solution than of the solution paired with the ILE-devoid diet at 24 h (12.4 +/- 2.4 g vs. 1.7 +/- 0.6 g, respectively; p < 0.001). These results suggest that learning contributes to the rat's ability to self-select diets that promote growth, and that a learning paradigm pairing flavored solutions with complete and indispensible amino acid-devoid diets may be used to demonstrate learned preferences and aversions for such diets in rats.

Animals↗

PubMed1993

Impairment of the gustatory engram by generalised seizure activity without associated loss of conditioned taste aversion.

Three experiments are reported concerning the disruption of conditioned taste aversion (CTA) by generalised seizure activity (GSA) induced by electroconvulsive shock (ECS). Rats were taught CTAs by pairing either strong or weak taste cues (10% or 2.5% sucrose solutions) with either strong (0.15 M) or weak (0.05 M) doses of LiCl. In Experiment 1 it is shown that a 2.5% sucrose cue combined with a weak dose of LiCl will reproduce the disruptive effect of GSA when the CTA is established using a 10% sucrose cue. Likewise, a CTA acquired using a 2.5% sucrose cue paired with a strong dose of LiCl will simulate the failure of GSA to disrupt a CTA which has been established with a 10% sucrose cue. These findings support the theory that GSA acts to disrupt CTA by weakening the gustatory engram and an apparent inability to disrupt CTA by GSA does not necessarily signify that the gustatory engram itself remains intact. In Experiment 2, a CTA was established to a 2.5% sucrose cue using the more toxic dose of LiCl. It is shown that GSA will cause a substantial learning loss irrespective of whether it is interpolated within the taste-illness interval, or after the aversion has been acquired. It is concluded that the gustatory engram continues to reside in an active labile state even after the CTA has been established. In Experiment 3 it was estimated that the memory of the 2.5% sucrose cue must have been reduced to just over half of its original strength in order to create the learning loss reported in Experiment 2.

Animals↗

PubMed1993

Behaviors of rats with insidious, multifocal brain damage induced by seizures following single peripheral injections of lithium and pilocarpine.

Several domains of behavior were measured in rats (n = 465) 10 days to 100 days after induction of limbic seizures by a single subcutaneous injection of lithium and pilocarpine. These rats displayed enhanced intragroup aggression but normal muricide; gustatory neophobia and conditioned taste aversion were virtually eliminated. Severe working and reference memory deficits were evident within the radial arm maze. Both state-dependent memory and possible situation-dependent precipitation of spontaneous seizures were suggested. The behavioral changes were considered commensurate with the multifocal pattern of thalamic, hippocampal/amygdaloid, and limbic cortical damage.

Acetylcholine↗

PubMed1993

Does a learned taste aversion contribute to the anorectic effect of bacterial lipopolysaccharide?

The present study addressed the possible role of a conditioned taste aversion in the anorectic effect of bacterial lipopolysaccharide (LPS) in the rat. Pairing an intraperitoneal (IP) injection of LPS (100 micrograms/kg b.wt.) with the subsequent presentation of a familiar diet (FD) or of a novel-tasting saccharin diet (SD) for several hours did not affect FD or SD intake when the same diet was offered several days later after 12 h of food deprivation. However, food intake during the second presentation of SD was reduced when food was not withheld prior to the test. In a similarly designed experiment, the antipyretic and antiinflammatory drug indomethacin (5 mg/kg b.wt., IP) attenuated the anorectic effect of LPS during the initial pairing, but did not affect the inhibition of SD intake in LPS-pretreated rats during the second feeding test. The antiemetic trimethobenzamide (5 mg/kg b.wt., IP) failed to influence the anorectic effect of LPS. Lesion of the area postrema (AP) and the adjacent nucleus of the solitary tract (NST) was found to enhance the anorectic effect of LPS, but the development of tolerance to this effect remained unchanged in AP/NST-lesioned animals. In spite of the ability of LPS to induce a taste aversion that inhibits feeding under certain conditions (novel-tasting diet, no food deprivation prior to the feeding test), the findings indicate that a learned taste aversion is not the only contributor to the anorectic effect of LPS.

Animals↗

PubMed1995

State-dependent retention produced with estrus in rats.

State-dependent retention (SDR) has frequently been demonstrated with drug-induced physiological changes which apparently serve as contextual cues for memory. These support the assumption that commonly occurring endogenous dispositions play a role in memory, yet there are few reports showing SDR with states that are likely to be part of an organism's natural experiences. To determine if behavioral estrus could produce SDR, ovariectomized female rats were rendered estrus via hormone injections or remained anestrus via placebo injections, trained with quinine-laced apple juice, and later tested while in the same or different state for reactions towards pure juice. SDR was not evident in the amount of juice consumed; however, those tested in the same state as the initial experience were slower to initiate drinking than those tested in a different state revealing a state-dependent influence on memory related to phases of the ovarian cycle.

Animals↗

PubMed1994

Food aversion conditioned in anesthetized sheep.

We discovered that a food aversion could be conditioned in anesthetized sheep. Sheep were allowed to eat a familiar food (alfalfa-grain pellets) for 30 min, and 90 min later they were given either an intraruminal (IR) injection of water (C), an IR injection of LiCl (L), anesthesia followed by an IR injection of water (A), or anesthesia followed by an IR injection of LiCl (A+L). Induction of anesthesia was by an intravenous injection of pentobarbitone sodium, and maintenance of deep anesthesia was by halothane. Sheep were maintained in deep anesthesia for 2 h to ensure that the effects of LiCl on the acquisition of a food aversion, which occur within about 1 h, were completed before they awakened. When tested 5 days later, sheep that received LiCl (treatments L and A+L) consumed less alfalfa-grain pellets than sheep that did not receive LiCl (treatments C and A) (241 g vs. 306 g; p = 0.057). Intake of sheep that were anesthetized (treatments A and A+L) did not differ from that of sheep that were not anesthetized (treatments C and L) (295 g vs. 252 g; p = 0.183). Nor was there an interaction between LiCl and anesthesia (p = 0.423). Thus, we conclude that changes in preferences for foods caused by postingestive feedback occur automatically every time food is ingested (i.e., they are noncognitive), and the kind and amount of feedback is a function of the match between the food's chemical characteristics and its ability to meet the animal's current demands for nutrients.

Anesthesia, General↗

PubMed1994

Representation of hedonics and quality of taste stimuli in the parabrachial nucleus of the rat.

The distribution of evoked expression of the proto-oncogene c-fos was immunohistochemically examined in the parabrachial nucleus (PBN) of water-deprived rats after free ingestion of palatable liquids, after intra-oral infusion of aversive taste solutions including various bitter substances, and after an intraperitoneal injection of LiCl. C-fos immunoreactive neurons (c-fos neurons) were densely packed in the external lateral subnucleus (els), external medial subnucleus (ems), dorsal lateral subnucleus (dls), central lateral subnucleus (cls), and the central medial subnucleus (cms) depending on the kind of stimulation. The rostral part of the els may be related to general visceral inputs; the caudal part of the els, negative hedonics or aversive behavior; the dls, positive hedonics or ingestive behaviour. Both the ems and the els may be related to taste information for bitter tasting compounds and HCl; the cls, for sucrose and saccharin; and the cms, for NaCl.

Animals↗

PubMed1995

Retention of rotationally induced taste aversions.

Retention interval effects are seen in single-element taste-aversion learning when taste aversions are significantly weaker if testing occurs 1 day after conditioning compared to tests conducted 3 or more days after conditioning. Since all previous demonstrations of this phenomenon have occurred following conditioning with the drug lithium chloride (LiCl), it was necessary to determine if the increased drinking at the 1-day interval was due to the aftereffects of LiCl. The present experiment explored the presence of retention interval differences following the use of a nonpharmacological unconditioned stimulus (US), rotational stimulation. Following a saccharin-rotation pairing, a saccharin aversion was seen at a 5-day testing interval, and this aversion was significantly stronger than the aversion observed at a 1-day test. Thus, these results are clear in showing that the retention interval effect occurs following conditioning with a nonpharmacological US, and this outcome allows for the refutation of an aftereffects of LiCl hypothesis.

Animals↗

PubMed1996

Retention of conditioned taste aversion to NaCl after chorda tympani transection in Fischer 344 and Wistar rats.

Fischer 344 (F344) rats fail to prefer sodium chloride (NaCl) solution to water, and this behavior is dramatically altered by bilateral transection of the chorda tympani nerve (CTX). Tests of retention and generalization of a conditioned taste aversion (CTA) to 0.15 M NaCl were used to assess alterations in salt taste perception after CTX. A CTA was established to 0.15 M NaCl in groups of F344 and Wistar rats after two pairings with LiCl (IP, 2% body weight; 0.15 M). After conditioning, animals received bilateral CTX or sham operations. Approximately 2 weeks after surgery animals were tested for retention of the CTA. Aversion to 0.15 M NaCl was evident in CTX and SHAM rats that had been conditioned prior to surgery, with no apparent difference in magnitude as a function of surgical condition. Thus, although CTX profoundly alters F344 rats' hedonic response to NaCl, it does not alter perceptual characteristics so markedly that NaCl is no longer recognized as the stimulus presented during aversion conditioning. Rather these studies suggest that in both the F344 and Wistar strains the chorda tympani nerve is not necessary for retention of a presurgical CTA to NaCl. These studies, therefore, do not provide evidence of changes in NaCl perceptual "quality" as a consequence of CTX either in F344 rats, where such changes were indicated by the preference data, or in the Wistar rat, where they were not.

Afferent Pathways↗

PubMed1996

EEG arousal, sympathetic activity, and brown adipose tissue thermogenesis after conditioned taste aversion.

Conditioned taste aversion was induced in rats by pairing saccharin with intraperitoneal LiCl injection. Animals injected with NaCl served as controls. After evaluating the preference levels for saccharin in rats of both groups, the animals were anesthetized with urethane and the duration of EEG desynchronization, firing rate of sympathetic nerves innervating interscapular brown adipose tissue (BAT), and temperature of the same tissues were recorded, before and after oral stimulation with saccharin or water. The EEG desynchronization was longer in conditioned rats after stimulation with saccharin. Firing rate of sympathetic nerves was higher in conditioned rats after presentation of saccharin. BAT temperature, decreased in conditioned rats after saccharin stimulus, was unchanged in the three other conditions. In a second experiment temperature and firing rate of sympathetic nerves of BAT were recorded after oral presentation of water or saccharin in rats treated as in the first experiment and injected with the alpha 1-adrenergic blocker prazosin. As in the first experiment, saccharin presentation in conditioned animals enhanced the neural sympathetic activity, whereas differently from the first experiment it increased BAT temperature. No changes were found in the same measurements in the three other conditions. The drop in interscapular BAT temperature found in the first experiment, an unexpected finding, probably depends on the use of lithium as unconditioned stimulus, because LiCl interacting with adrenergic receptors changes the two-phase response, normally seen in interscapular BAT after increased sympathetic activity, in a single-phase response.

Adipose Tissue, Brown↗

PubMed1976

Facilitation of retention performance in mice by posttraining diethyldithiocarbamate.

These experiments examined the effects in mice of posttraining injections of diethyldithiocarbamate (DDC) upon retention (7 days after training) of active avoidance learning and upon whole brain catecholamine levels. When administered immediately following training, DDC enhanced retention performance. The degree of enhancement varied directly with dose. DDC did not significantly affect retention performance if the injections were delayed 1 or 4 hours after training. Also, DDC administered 30 min prior to training did not affect retention performance. DDC (900 mg/kg) produced a large but transient increase in whole brain dopamine (DA) levels while norepinephrine (NE) levels were lowered.

Animals↗

PubMed1980

Effects of 6-hydroxydopamine and amphetamine on rat mothering behavior and offspring development.

Selective CNS dopamine depletion was produced in neonatal female rats by administration of 6-hydroxydopamine and desmethylimipramine. These rats were subsequently tested as adults for maternal behavior toward their own offspring and received d-amphetamine prior to half of these sessions. The effects of early, selective CNS dopamine depletion and its related developmental disruptions on later care of offspring and response to amphetamine were thereby assessed. Pup retrieval, nest building, crouching, and locomotor behaviors were studied in 6-OHDA + DMI treated mothers while offspring were examined with respect to weight, density of fur, age of eye opening, and shuttlebox avoidance learning. Depletion of brain dopamine to 30% of control concentrations was associated with increased crouching time but with no other differences in caregiving, offspring development, or response to amphetamine. Although profound neonatal depletion of dopamine leads to a variety of disturbances in early life, later maternal behavior is adequate and apparently enhanced. The possible role of compensatory brain mechanisms is discussed.

Amphetamine↗

PubMed1988

Antiamnesic effects of D-pipecolic acid and analogues of Pro-Leu-Gly-NH2 in rats.

The antiamnesic effects of prolyl-leucyl-glycinamide (PLG) and analogues of this tripeptide were investigated in rats. Retrograde amnesia was induced by electroconvulsive shock treatment and the degree of amnesia was characterized by the attenuation of one-trial learning passive avoidance response. PLG resulted in dose-dependent attenuation of retrograde amnesia. Structural modifications included N-terminal protection, substitution of the C-terminal NH2 group, replacement of the N-terminal amino acid, and replacement of the second amino acid of the tripeptide. Some tripeptides, all of them containing D-pipecolic acid instead of the N-terminal proline, were more effective than PLG. Therefore, D-pipecolic acid, D-pipecolamide and their N-terminally protected analogues were also investigated, and were found to have powerful antiamnesic effects.

Amnesia↗

PubMed1995

Effects of RGH-2202 on behavioral deficits after focal cerebral ischemia in rats.

We investigated the effects of RGH-2202 (posatirelin, (-)-(2S)-N-[(1S)-1-[[(2S)-2-carbamoyl-1-pyrrolidinyl[carbonyl]-3- methylbutyl]-6-oxopipecolamide), a thyrotropin-releasing hormone (TRH) analog, on behavioral changes during a chronic phase of focal ischemia in rats in comparison with the parent peptide. The left middle cerebral artery (MCA) was occluded under halothane anesthesia, and the subsequent behavioral changes were observed for 35 days. RGH-2202 (1, 3, and 10 mg/kg) and TRH (10 mg/kg) were given IP just after the operation and afterward once a day for 14 days. MCA-occluded rats exhibited neurologic symptoms including hemiplegia and abnormal posture and disturbance of passive avoidance learning during the entire 35-day observation period. The repeated treatment with either peptides improved the neurologic and cognitive deficits. In addition, a recovery from deficits was still advanced after discontinuation of the drug treatment. In these effects, RGH-2202 was about three times more potent than TRH. Neural tissue damage in drug-treated groups, measured by omega 3 binding site densities 35 days after MCA occlusion, was included to be less than that in the vehicle-treated group. These results suggest that appropriate treatment with RGH-2202 may be useful in the treatment of functional disturbances after focal cerebral ischemia.

Animals↗

PubMed1994

Genetic dissection of consolidated memory in Drosophila.

Behavioral and pharmacological experiments in many animal species have suggested that memory is consolidated from an initial, disruptable form into a long-lasting, stable form within a few hours after training. We combined these traditional approaches with genetic analyses in Drosophila to show that consolidated memory of conditioned (learned) odor avoidance 1 day after extended training consisted of two genetically distinct, functionally independent memory components: anesthesia-resistant memory (ARM) and long-term memory (LTM). ARM decayed away within 4 days, was resistant to hypothermic disruption, was insensitive to the protein synthesis inhibitor cycloheximide (CXM), and was disrupted by the radish single-gene mutation. LTM showed no appreciable decay over 7 days, was sensitive to CXM, and was not disrupted by the radish mutation.

Animals↗

PubMed1996

Behavioral, structural and neurochemical asymmetries in the avian brain: a model system for studying visual development and processing.

The emphasis of this review is on the visual systems and lateralized visually guided behavior in several avian species. Lateral asymmetry is known to be present in the tectofugal visual projections to the forebrain of the pigeon and in the thalamofugal visual projections to the forebrain of the chicken. These structural asymmetries are discussed in the context of the behavioral and neurochemical asymmetries. While recognizing the need to investigate the organization of both of the visual pathways within one avian species; this review reasons inductively that the lateralized organization of the two visual pathways leads to binocular input to the right hemisphere via the thalamofugal visual system and to the left hemisphere via the tectofugal visual system. For each system, input to the other hemisphere is primarily monocular. This specialization of the hemispheres for visual processing has predictable effects on behavior. The role of asymmetrical light stimulation of the eyes of the embryo in determining the lateralizations in the visual pathways and some behaviors is discussed, as are other lateralizations generated or altered by imprinting and passive avoidance learning.

Animals↗

PubMed1990

Ontogenetic differences in the association of gustatory and tactile cues with lithium chloride and footshock.

Using a double dissociation design with 15% sucrose solution and exposure to a heat lamp (34 degrees C) as CSs and 0.3 M LiCl and 1-mA footshock as USs, the present study found 15-day-old rats to show selective associations similar to those found in adults. Five-day-old pups, however, expressed similar sucrose aversions when this solution was paired with either LiCl or footshock, whereas they expressed heat aversions after heat-LiCl but not heat-shock pairings. Results are discussed with respect to previous data on selective associations in pups, current theories on selective associations, and ontogenetic differences in stimulus selection.

Age Factors↗

PubMed1990

Ethanol-mediated taste aversions and state-dependency in preweanling (16-day-old) rats.

Requirements for conditioning of an ethanol-mediated taste aversion in 16-day-old rat pups were examined. Experiment 1 demonstrated that preweanling rats are capable of acquiring, in two trials, an aversion to a 15% sucrose solution when followed by intragastric intubation of a 1.2 g/kg dose of 17% v/v ethanol, but not when followed by a 0.4 g/kg dose. Comparison was with control animals given sucrose followed by an equivalent volume isocaloric Half and Half. When the 0.4 g/kg dose of ethanol preceded sucrose presentation by 30 min (Experiment 2), the aversion was learned, suggesting that the effective delay between the sucrose and the critical consequences of the ethanol had been too long with the former procedure. Expression of the sucrose aversion required, however, the reinstatement of the context of intoxication--state-dependent retention. Finally, the results of Experiment 3B indicated that, in addition to the association between the sucrose and the aversive consequences of alcohol intoxication, the orosensory cues resulting from alcohol's direct elimination, via such processes as respiration and salivation, became associated with the appetitive properties of the sucrose. This was evidenced by a conditioned increase in preference for ethanol odor. Possible age-related differences in the ability to associate stimuli with alcohol's unconditioned consequences, and in state dependency are discussed.

Animals↗