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At least 613 records · Page 34Linked to original sources
PubMed2000

Novelty enhances retrieval of one-trial avoidance learning in rats 1 or 31 days after training unless the hippocampus is inactivated by different receptor antagonists and enzyme inhibitors.

Rats were implanted bilaterally with cannulae in the CA1 region of the dorsal hippocampus. The animals were trained in one-trial step-down inhibitory avoidance and tested either 1 or 31 days later. Some of the animals were exposed, 1 h prior to retention testing, to a novel environment. This was a 50-cm high, 50-cm wide and 39-cm high wooden box covered on the inside with black plastic. Through the cannulae, 10 min prior to the retention test, the rats received 0.5-microl infusions of saline, of a vehicle (2% dimethylsulfoxide in saline), or of the following drugs: the glutamate NMDA receptor blocker, aminophosphonopentanoic acid (AP5, 5.0 microg), the AMPA receptor blocker, 6,7-cyanonitroquinoxaline-2,3-dione (CNQX, 1.25 microg), the generic glutamate metabotropic receptor antagonist, alpha-methyl-(4-carboxyphenyl)glycine (MCPG), the inhibitor of cAMP-dependent protein kinase (PKA), Rp-cAMPs (0.1 or 0.5 microg), or the inhibitor of the mitogen-activated protein kinase (MAPK), PD098059 (10 or 50 microM). CNQX and PD098059 were dissolved in the vehicle; AP5 and Rp-cAMPs were dissolved in saline. All these drugs except AP5 had been previously found to alter retrieval of this task. Novelty markedly enhanced retention test performance of the avoidance task. The drugs, in accordance with previous results, and with the exception of AP5 at any of the two training-test intervals and of CNQX at the 31-day interval, hindered retention test performance. The results indicate that the effect of novelty on retrieval can not be observed if the major biochemical mechanisms of retrieval (AMPA receptors, PKA, MAPK) are blocked, i.e. if the hippocampus was temporarily inactivated by drugs that inhibit those mechanisms.

Animals↗
PubMed1989

Effects of phenylethylamine on rat locomotor behavior and avoidance learning.

1. The effects of beta-phenylethylamine (PEA) alone and in association with caroxazone, a potent inhibitor of monoamine oxidase B (MAO B), on the activity and long-term memory in the wheel-shaped activity monitor and on fixed-interval two-way avoidance acquisition were studied in rats. In a separate study, we determined the effects of PEA and of d-amphetamine on the variable-interval two-way avoidance acquisition. 2. The action of PEA was markedly different from that of amphetamine in several aspects. The stimulating effects of PEA in the wheel-shaped activity monitor were of a more subtle nature than those of amphetamine and in the variable-interval two-way avoidance acquisition PEA had no effect, while amphetamine improved performance. 3. PEA did not induce an increase in path-choice stereotypy, but caroxazone did. The absence of any caroxazone-session interaction effects on the path iteration frequency suggested that there were no long-term memory effects. 4. In the fixed-interval two-way avoidance acquisition experiments, PEA increased the avoidance responses of rats while caroxazone had no effect. The association of the two drugs did not potentiate either.

Animals↗
PubMed1989

Plasma corticosterone and renin activity during two-way active avoidance learning in spontaneously hypertensive and Wistar-Kyoto rats.

The spontaneously hypertensive rat (SHR) exhibits increased sympathetic and behavioral responses to several types of environmental stress compared to its normotensive progenitor, the Wistar-Kyoto rat (WKY). The aim of the present study was to investigate response-dampening mechanisms in the SHR. This study examines whether learning to control a stressful environment reduces behavioral and neuroendocrine activation in the SHR. Twelve SHR and 12 WKY were subjected to daily sessions (S) of 20 trials of signaled two-way active avoidance. Another 12 SHR served as maturation controls. Blood samples were collected immediately after S 1, S 5, and S 14 and plasma level of corticosterone (p-CS) and plasma renin activity (PRA) were measured. There was an insignificant tendency for the SHR to exhibit larger increases in p-CS in response to stress than the WKY did. By S 5 both groups had attained the avoidance task. However, the level of p-CS was the same as after S 1, showing that activation is independent of the number of shock pulses received and performance. Postsession p-CS decreased between S 5 and 14, slightly more so in the SHR than in the WKY. The SHR exhibited lower PRA than the WKY, but there were no significant effects of exposure to the avoidance schedule. Behaviorally, the SHR exhibited shorter latency to escape in the first trial than the WKY did. The SHRs were hyperactive compared to the WKY, showing more ambulation and rearing behavior. The maturation control SHR reached the same mean arterial pressure as the SHRs which were tested. After S 14, signal duration was shortened from 10 to 3 s for six additional sessions. Both p-CS and PRA increased, while at the same time ambulation and rearing behavior decreased. These data show that the relationship between behavioral control and adrenocortical activation is normal in the SHR in spite of differences in behavior. The present results also confirm previous data on hyperreactivity to footshocks in two-way active avoidance tasks in the SHR.

Animals↗
PubMed1993

Effects of oxiracetam, physostigmine, and their combination on active and passive avoidance learning in mice.

The nootropic drug oxiracetam (50 and 100 mg/kg) had no effect on one-trial passive avoidance acquisition in CD-1 mice, while the acetylcholinesterase inhibitor physostigmine improved passive avoidance performance at doses of 0.025 and 0.05 mg/kg given either pre- or posttraining. In a multitrial avoidance task (shuttle-box), a consistent tendency to better performance was displayed by mice receiving oxiracetam (50 and 100 mg/kg) or physostigmine (0.01 and 0.025 mg/kg, but not 0.05 mg/kg). Combinations of the two drugs never improved active or passive avoidance performance more than drugs given separately. This indicates no advantage in combining nootropics and anticholinesterase inhibitors to improve learning and memory.

Animals↗
PubMed1999

Changes in phosphorylation of Ca2+/calmodulin-dependent protein kinase II (CaMKII) in processing of short-term and long-term memories after passive avoidance learning.

Characteristic autophosphorylation of calcium/ calmodulin-dependent protein kinase II (CaMKII) and its consequences have made this kinase an interesting target in studying the molecular pathway for important neuronal functions including learning and memory formation. In this article, we use immunoprecipitation and immunoblotting methods to detect changes in phosphorylation of CaMKII during memory formation in 1-day-old chicks trained in a single trial passive avoidance task. A 60-kDa protein has been immunoprecipitated from the chick brain with an anti-rabbit CaMKII antibody. This protein shows strong and specific immunoactivities with antibodies against the calmodulin binding site of CaMKII, and the N and C terminals of beta-CaMKII. Commercially available anti-phosphoserine and anti-phosphothreonine antibodies are shown to sensitively detect phosphorylation of purified CaMKII. The basal phosphorylation of CaMKII from the intermediate medial hyperstriatum ventrale (IMHV) and lobus parolfactorius (LPO) regions of the chick brain is shown to be largely right hemisphere-lateralized. When chicks are subjected to a passive avoidance training experience, a specific increase in CaMKII phosphorylation is induced in the IMHV and LPO of the left hemisphere from those chicks whose memory for the training experience is successfully retrieved. While this specific increase in CaMKII phosphorylation is seen in both the left IMHV and left LPO in short-term memory, it is detectable only in the left LPO associated with long-term memory retrieval. The present results provide evidence that in vivo changes in phosphorylation of CaMKII are associated specifically with processing of distinct memory stages, which take place in specific brain regions.

3T3 Cells↗
PubMed1985

Unlike beta-endorphin, dynorphin 1-13 does not cause retrograde amnesia for shuttle avoidance or inhibitory avoidance learning in rats.

Posttraining administration of the opioid peptides, beta-endorphin or the enkephalins, is known to cause retrograde amnesia for a variety of tasks in rats. The present paper studies the effect of the posttraining administration of dynorphin 1-13 on retention of a step-down inhibitory avoidance task and of a shuttle avoidance task. For the purpose of comparison, the effect of human beta-endorphin was also studied. In confirmation of previous results, beta-endorphin (1.0 or 10.0 micrograms/kg, IP) caused retrograde amnesia for the two tasks. Dynorphin 1-13 had no effect at doses between 0.008-125.0 micrograms/kg IP or 1.25-125.0 ng/rat ICV in the inhibitory avoidance task, or at doses of 5.0, 25.0, or 125.0 micrograms/kg in the shuttle avoidance paradigm. These findings suggest that, in contrast to beta-endorphin, dynorphin 1-13 may not be involved in memory regulation at the posttraining period in rats.

Amnesia↗
PubMed1997

The decrease of serotonin release induced by a tryptophan-free amino acid diet does not affect spatial and passive avoidance learning.

We assessed whether consumption of a diet lacking in tryptophan (TRP) resulted in alteration in learning and memory performance and hippocampal 5-HT release in rats. Two hours after the acute administration of TRP-free (T) and balanced (B) diet rats were trained in a one-trial passive avoidance task. The two groups of rats showed no significant difference in retention latencies. Two other groups of rats, fed with the above diets during the acquisition of a radial-arm maze task, showed no difference in baseline performance. The acute ingestion of the T diet produced a significant and long lasting decrease of hippocampal and cortical 5-HT release in rats when compared to the B diet, while the 12th day of the T diet, 5-HT was not detectable in the dialysate. These data indicate that the diminished brain release of 5-HT induced by a T diet is not sufficient to impair cognitive processes.

Animals↗
PubMed1988

Memory deficit in passive-avoidance learning in bulbectomized Long-Evans hooded rats.

Male and female Long-Evans hooded rats were subjected to either olfactory bulb damage or control surgery. Olfactory bulb removal resulted in increased mouse killing, increased irritability to handling, and increased open-field activity. In acquisition trials on a modified passive-avoidance apparatus, control animals habituated rapidly to the apparatus, while OB rats showed little evidence for habituation. All controls showed 24-hour retention of shock on the last acquisition trial, while OB rats showed the typical retention deficit, despite being given a behavioral alternative to withholding a response. The P-A deficit in OB rats appears to be a learning/memory deficit, not the result of heightened activity.

Aggression↗
PubMed1994

Corticosterone enhances long-term retention in one-day-old chicks trained in a weak passive avoidance learning paradigm.

Glucocorticoids are released during learning situations and can trigger neural actions through binding to receptors in different brain areas. The possible role of a glucocorticoid action in long-term memory formation was studied, in day-old chicks, by using a passive avoidance task which chicks otherwise only retain for a few hours (< 10) after training. Thus, we examined the effects of intracerebral corticosterone administration on retention 24 h posttraining. The results showed that chicks injected with corticosterone (1 microgram) at either 15 min pretraining or at 5, 30, 60 min (but not 120, 180, or 360 min) posttraining retained the passive avoidance response when tested 24 h posttraining. Studies with specific mineralocorticoid or glucocorticoid receptor antagonists (RU 28318 or RU 38486, respectively) indicated that this increase in retention by corticosterone might be mediated through glucocorticoid receptors. In order to assess whether the facilitatory effect of corticosterone was mediated through an effect on protein synthesis mechanisms, the protein synthesis inhibitor anisomycin was administered prior to corticosterone. However, this treatment only partially attenuated the effect of the steroid, suggesting that corticosterone may influence other cellular processes involved in the formation of long-term memory for the avoidance behaviour.

Animals↗
PubMed1994

Suppression of long-term potentiation induction during alert wakefulness but not during 'enhanced' REM sleep after avoidance learning.

Major learning events are typically followed by a period during which the number and/or duration of rapid-eye movement sleep episodes is increased. Processes critical to memory formation are thought to take place during this interval of 'enhanced' rapid-eye movement sleep. We therefore compared the capacity for long-term potentiation during rapid-eye movement sleep and alert wakefulness after learning. Rats were chronically implanted with electrodes for stimulation of the perforant path and recording of evoked potentials and EEG in the dentate gyrus. After obtaining baseline recordings, rats were trained on a 40-trial two-way active avoidance task. Conditioned rats exhibited a two-fold increase in the mean duration of rapid-eye movement sleep episodes, as reflected by a prolongation of the hippocampal theta rhythm. There was no change in the sleep pattern of pseudoconditioned controls, which received explicitly unpaired tones and foot shocks in a yoked design. High-frequency stimulation was applied during the second, third, and fourth major rapid-eye movement sleep episodes after active avoidance training. Another group was tetanized at matching time points during alert wakefulness. After pseudoconditioning, tetanus applied during wakefulness or rapid-eye movement sleep readily induced long-term potentiation, and there was no difference between groups in the magnitude of increase for the population excitatory postsynaptic potential slope or the population spike height as measured 1 h, 24 h, and 5 days post-tetanus.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2006

The Self-Report Psychopathy Scale and passive avoidance learning: a validation study of race and gender effects.

The reliability and validity of the Self-Report Psychopathy Scale (SRPS) was examined in a noninstitutionalized offender sample of mixed gender and race. Adequate alpha coefficients were obtained for the total sample and across gender and race. The SRPS was compared to measures of trait anxiety and passive avoidance errors. SRPS total, primary, and secondary scores were positively and significantly correlated with trait anxiety and passive avoidance (commission) errors, but not omission errors. Employing hierarchical regression models, no anxiety, gender, or ethnic effects were found. Intelligence confounded the relationship between psychopathic traits and passive avoidance errors. Findings provide tentative support of the SRPS as a valid measure of psychopathy.

Adolescent↗
PubMed1988

Intra-amygdala injections of corticotropin releasing factor facilitate inhibitory avoidance learning and reduce exploratory behavior in rats.

The effects of intra-amygdala injections of corticotropin-releasing factor (CRF) on memory and exploratory behavior in rats were examined in the present study. Rats with chronically implanted cannulae received intra-amygdala injections of vehicle or CRF at a dose of 0.01, 0.1 or 1.0 micrograms, either immediately after the inhibitory avoidance training or prior to the open field activity test. Results indicated that while CRF at low (0.01 microgram) and high (1.0 micrograms) doses produced no significant effect on retention or exploration, immediate post-training intra-amygdala injections of CRF at the medium dose (0.1 microgram) significantly improved retention of the inhibitory avoidance response. The same dose of CRF, given shortly prior to the open field activity test, decreased locomotor activity, rearing and hole-poke responses in rats. These results suggest that the amygdala is one of the anatomical loci involved in CRF modulation of memory processing and exploration in rats. The implication of CRF in mediating the influences of stress on behavior is discussed.

Amygdala↗
PubMed1998

Flavor avoidance learning and its implications in reducing strychnine baiting hazards to nontarget animals.

In reforested areas, underground strychnine baiting to control pocket gophers (Thomomys mazama) poses a hazard to golden mantled ground squirrels (Spermophilus lateralis) and yellow pine chipmunks (Eutamias amoenus). We designed this study to assess whether: 1) chemical insensitivity to bitter tastes might explain the ingestion of strychnine; 2) pocket gophers would avoid four bitter-tasting compounds: quebracho (QUEB), sucrose octaacetate (SOA), quinine hydrochloride (QHCl), and denatonium benzoate (DB); and 3) nontarget species could be trained to avoid strychnine paired with the most aversive compound. Our results showed that while all species readily consumed strychnine, the nontarget species could be conditioned to avoid it. Moreover, while high (0.1%) concentrations of DB, quinine hydrochloride, and quebracho reduced consumption by pocket gophers, 0.05% DB was inoffensive. Nontarget animals readily avoided 0.05% DB, and avoidance was stronger after conditioning. Together, our results suggest that all of the rodents tested are insensitive to strychnine, high concentrations of some bitter tastes may be effective pocket gopher repellents, and lower concentrations of DB may selectively repel nontarget animals from strychnine baits.

Animals↗
PubMed1981

Avoidance learning under delayed shock termination in prenatally x-irradiated rats.

Groups of MPI male albino rats were exposed to x-irradiation of 200 rad on Day 17 of gestation. Irradiated and control rats were trained in a shuttle box with either immediate or .5-sec delayed termination of both the electric shock (US) and the conditioned stimulus (CS) on escape trials. An avoidance response always produced prompt CS termination. Irradiated rats showed a higher degree of avoidance behaviour than controls and, under the delay condition, tended to run rapidly in the CS-US interval.

Animals↗
PubMed1990

Pre- and post-training lesions of the intermediate medial hyperstriatum ventrale and passive avoidance learning in the chick.

Three distinct nuclei of the chick forebrain--the intermediate medial hyperstriatum ventrale (IMHV), lobus parolfactorius (LPO), and paleostriatum augmentatum (PA)--show metabolic, morphological, and neurophysiological changes following training on a passive avoidance task, suggesting that these and other areas of the chick forebrain participate in memory formation for this task. Considerable evidence exists for lateralization of memory processes in the chick. Several experiments examined the effects of lesions in the IMHV on the ability of chicks to learn and retain the avoidance task. Pre-training bilateral lesions in the IMHV produced an impairment in avoidance responding tested three hours after training. Pre-training unilateral lesions in the left but not the right IMHV resulted in a similar impairment. However, bilateral IMHV ablations, given either 1 or 6 h post-training, did not impair retention. IMHV lesions did not impair retention of a simple escape learning task. These results are consistent with other studies that have examined the effects of bilateral IMHV lesions on acquisition of passive avoidance and extend these findings by demonstrating lateralization of acquisition involving the left IMHV. The results also suggest that, as early as one hour post-training, the IMHV is not necessary to retain the memory and indicate that other forebrain structures, possibly the LPO or PA, may maintain the memory trace following training. Hypotheses to account for these results and indications of future research are discussed.

Animals↗