Intertrial interval manipulations and passive avoidance retention in young Long-Evans hooded rats

Results of several studies indicate that young rats generally require more training than do adults to reach comparable criterion levels of passive avoidance behavior. In addition, younger rats generally show poorer retention performance than adults. In the present study, preweanling and weanling Long-Evans rats were given passive avoidance training at intertrial intervals (ITI) of 2 min, 1 hr, or 24 hr until a 600-s criterion was obtained. A 2-week retention test also was given to each subject. Results indicate that ITI had little effect on rate of acquisition or retention. Acquisition and retention performance did improve with age, as is typically reported with other strains of rats. The present results support previous acquisition and retention studies indicating that the ability to acquire and retain a passive avoidance task for weanling and preweanling rats increases with age.     

The impairment of one-trial passive avoidance learning in chicks caused by prenatal aluminum exposure

Prenatal aluminum exposure may affect the development of the embryo and alter the capacity for learning and memory in adults. The chick embryo is a good experimental model to study the effect of prenatal toxin exposure on cognitive defects in offspring, because it eliminates maternal confounding variables. In the present study, we applied a one‐trial passive avoidance‐learning task in day‐old chicks to examine the effects of prenatal aluminum chloride injections (2, 20, and 200 mM in 200 µl per egg, daily over a period of 4 successive days) on memory consolidation. The data suggest that chicks injected with aluminum chloride (20 mM) daily from E12 to E15 had significantly impaired short‐term memory, intermediate‐term memory, and long‐term memory (LTM) after training (p < .05) but chicks injected with aluminum chloride (2 mM) had impaired LTM only. © 2011 Wiley Periodicals, Inc. Dev Psychobiol 54:133‐138, 2012.     

Behavior-genetic analysis of the paradise fish,Macropodus opercularis. II. Passive avoidance learning in inbred strains

Passive dark avoidance conditioning was studied in four inbred strains of paradise fish in the presence and absence of a fish-like dummy during the training process. Strain differences were found in exploratory activity during habituation trials and also in the sensitivity to the mild electric shock punishment. The impact of the fish-like dummy also depended on the genotype.This work was supported by Grant 328/82 from the Hungarian Academy of Sciences.     

Factors influencing one-trial passive avoidance behavior: implications for studies of retrograde amnesia (RA)

Rats were run in a step-through one-trial passive avoidance task. The effects of preexposure (or familiarization) to the apparatus, prehandling outside of the apparatus, and postshock delay in the apparatus were studied. Preexposure to the apparatus significantly increased one-trial passive avoidance; with no preexposure little passive avoidance learning was obtained. Prehandling did not significantly increase the strength of passive avoidance behavior. Postshock delay did not increase passive avoidance behavior. The results are discussed in terms of their implications for studies of retrograde amnesia (RA) which use one-trial passive avoidance learning.     

Failure of vasopressin to enhance memory in a passive avoidance task in rats

Several authors have suggested that the neurohypophysial hormone arginine-8-vasopressin (AVP) facilitates both the consolidation and the retrieval of memory. This conclusion has relied mainly on the finding that AVP increases the latency of re-entry into a box where shock has previously been encountered, that is, in a passive avoidance task. Our results do not support this interpretation. On the contrary, we found that post-trial, intraventricular (i.t.) administration of AVP (1 ng in 1 μl) produced relatively short as well as long latencies (a bimodal effect), suggesting that the peptide acts on motivational processes, for example by increasing arousal.     

Open-field behavior, habituation and passive avoidance learning: Effect of ACTH and hydrocortisone on Normal and adrenalectomized rats

Exploratory behavior (GMA) and habituation rate (IH) were studied in an open-field situation in normal and adrenalectomized rats. Following this procedure the rats were subjected to passive avoidance learning (PA). Wide-spreading individual differences were observed in the exploratory behavior and the tendency of habituation of normal rats. As compared to the normal values, either the adrenalectomy which was performed 24 hr, 7 days and 28 days prior to the experiments or the ACTH and hydrocortisone treatment failed to modify the GMA and the IH significantly. An improvement of PA was found in the normal rats following ACTH and hydrocortisone treatment. In the adrenalectomized animals the hydrocortisone proved to be effective, whereas ACTH did not influence PA. No correlation was found between GMA, IH versus PA values and the influence of ACTH and hydrocortisone administration on these parameters. It is concluded that the direction of PA is unpredictable on the basis of the open-field test performed on R-Amsterdam strain of rats, and the effect of ACTH on passive avoidance learning is mediated through the adrenal glands.     

NMDA receptors are involved in Ginkgo extract-induced facilitation on memory retention of passive avoidance learning in rats

Herbal therapies are commonly used to enhance memory and learning. Ginkgo biloba has shown to be one of the most popular herbs that is used to treat amnesia and retard age related memory deficits. Although, there have been several reports on the memory enhancing effects of Ginkgo, involvement of glutamatergic system that plays pivotal role in learning and memory has not been precisely assessed so far. The current study intended to investigate the effect of Ginkgo intake on amnesia while NMDA (N-methyl D-aspartic acid) receptors blocked by the administration of MK-801. The study used passive avoidance (PA) task to investigate the effect of chronic administration of Ginkgo extract (40 and 90 mg/kg; oral) on the memory span in male Wistar rats, suffering from MK-801-induced forgetfulness (0.06 and 0.1 mg/kg; i.p.). The results indicate that Ginkgo was able to remove MK-801-induced forgetfulness, indicating that Ginkgo can affect memory retention but not effect on passive avoidance acquisition, using pathways other than glutamatergic system as well. The results might indicate that Ginkgo extract can be effective in removing forgetfulness caused by inhibiting NMDA receptors from performing their activities.     

Cytochemical characteristics of the brain in rats differing in active avoidance learning ability

Brain structures were examined in two mouse strains differing in active avoidance learning in a shuttle box. Protein content and concentration, area of the cytoplasm and nuclei of neuron in layers III and V of the sensorimotor cortex were higher in rats with high learning ability. The detected morphochemical differences between the same brain structures of rats with high and low learning capacity can be attributed to this capacity. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 130, No. 9, pp. 263–264, September, 2000     

Cytochemical characteristics of the brain in rats differing in active avoidance learning ability

Brain structures were examined in two mouse strains differing in active avoidance learning in a shuttle box. Protein content and concentration, area of the cytoplasm and nuclei of neuron in layers III and V of the sensorimotor cortex were higher in rats with high learning ability. The detected morphochemical differences between the same brain structures of rats with high and low learning capacity can be attributed to this capacity. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 130, No. 9, pp. 263–264, September, 2000     

Intraventricular infusions of anti-NCAM PSA impair the process of consolidation of both avoidance conditioning and spatial learning paradigms in Wistar rats

Processing of information for long-term storage requires specific patterns of activity that lead to modification of synapse structure and eventual change in neural connectivity pattern. Morphological change associated with memory consolidation is reliant on neural cell adhesion molecule (NCAM) function and that of its polysialylated variant (NCAM PSA). Across species and paradigms, a transient frequency increase of polysialylated neurons in the hippocampal dentate has been found necessary for memory consolidation, however, recent studies suggest that NCAM PSA may serve to suppress memory formation in certain paradigms. As intraventricular infusions of NCAM blocking antibodies have been used successfully to demonstrate its time-dependent role at the 6 h post-training period of memory consolidation, we employed the same procedure to demonstrate a functional requirement for NCAM PSA in the consolidation of two commonly used behavioral paradigms: avoidance conditioning and spatial learning in Wistar rats. Anti-PSA was found to significantly induce amnesia of the passive avoidance response when infused at the 10 h post-training time, a period coincident with the learning-associated increase in dentate polysialylated cell frequency. Moreover, the amnesia became apparent at the 48 h recall time and was not apparent at the 24 h post-training time, suggesting a possible role in memory reconsolidation. A similar anti-PSA action was observed following water maze training in aged animals but was not apparent in young animals, an effect suggested to be due to inadequate antibody saturation of the polysialylated cell population. These studies confirm the requirement for NCAM PSA in memory consolidation and separate it from that of NCAM.     

Effects of additional cues on passive avoidance learning and extinction in rats with hippocampal lesions

Following the acquisition of a water-rewarded approach response in a straight runway, the effects of introducing shock in the goal box (passive avoidance - PA) or withdrawing reinforcement (extinction) were compared in hippocampal, cortical, and operated control groups of rats. Under standard test conditions, hippocampal groups were impaired in PA learning and showed strong resistance to extinction, relative to the control groups. When additional cues were provided such that external stimuli associated with goal box events could be easily detected early in the runway, performance differences between the hippocampal and control groups were eliminated in the PA test and significantly reduced in extinction. The results emphasize the inefficient processing by hippocampally-damaged animals of stimulus cues following a shift in experimental contingencies.     

Peculiarities of active avoidance conditioning in rats with various forms of inherited arterial hypertension

Peculiarities of active avoidance conditioning were studied in NISAG rats (hereditary stress-induced arterial hypertension) and spontaneously hypertensive SHR rats. Conditioning was successful in 90% normotensive Wistar rats and in only 9.1% NISAG rats. Hypertensive SHR rats were intermediate between Wistar and NISAG rats by their learning capacity (66.7%). Our results suggest that differences in learning capacity of hypertensive rats are determined by genetic characteristics of animal behavior and emotional state, rather than blood pressure elevation. __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 142, No. 10, pp. 386–388, October, 2006     

Serotoninergic mechanisms of the effects of neurotensin on passive avoidance behavior in rats

The aim of the present work was to identify the features of the actions of neurotensin on administration into the substantia nigra or dorsal cervical nucleus on the reproduction of passive avoidance reactions in rats. The results showed that the action of neurotensin administered into the substantia nigra was accompanied by sharp reductions in passive avoidance reactions, while administration into the dorsal cervical nucleus, conversely, led to increases in these reactions and slowing of their extinction. The effects of microinjections of the serotonin 5-HT(1A) receptor agonist 8-hydroxydipropylaminotetraline (8-OH-DPAT) into these brain structures were analogous to the effects of neurotensin. The different behavioral effects of administration of neurotensin corresponded to identifiable changes in the levels of serotonin and its metabolite 5-hydroxyindoleacetic acid in the caudate nuclei of the brain. These data led to the conclusion that the effects of neurotensin on passive avoidance behavior are associated with the regulation of the emotional state of the animals via actions on the functions of brain serotoninergic structures.     

Passive avoidance in prenatally X-irradiated rats

Twenty-nine albino rats which had received 200 R of X irradiation on the 16th day of gestation were given together with 38 nonirradiated control animals, 4 trials in a passive avoidance conditioning situation. Irradiated animals showed significantly more passive avoidance behavior than did the controls. In a second experiment, animals from both groups were subsequently tested in a shuttle-box, active avoidance situation. Here, also, the irradiated animals showed more avoidance behavior than the controls. It was hypothesized that the findings are related to increased fearfulness in prenatally irradiated rats.     

Discriminated lever press avoidance conditioning in male and female rats

Discriminated lever press avoidance and step through passive avoidance conditioning were studied in male and female rats. In lever press avoidance female rats showed superior avoidance performance, less intertrial responding and shorter durations of leverholding than male rats. Castration of males tended to improve their avoidance performance, whereas ovariectomy had no effect. In passive avoidance more males than females showed an avoidance response. From these results it is concluded that aversive stimulation seems to elicit different behavior tendencies in male and female rats rendering males less prepared for active avoidance, but at the same time more prepared for passive avoidance conditioning. The data do not support the hypothesis that sex differences in activity underly the dimorphism in active and passive avoidance conditioning.     

The effect of iron deficiency during development on passive avoidance learning in the adult rat

Offspring of iron-deprived and normal female Long Evans rats were placed on either iron deficient or a normal diet from weaning to 115 days. At 100 days of age, they were trained on a single trial passive avoidance shuttlebox task. At 115 days of age they were sacrificed for measures of liver and brain non-haem iron, and haemoglobin concentrations. Brain iron levels were shown to be affected more by maternal iron diet than postweaning iron diet. The reverse was true for liver iron and haemoglobin, while bodyweight was dependent only on maternal diet. At the behavioural level, no effects were observed on number of trials to extinction. However, maternally deprived offspring showed significantly shorter escape latency on the learning trial and fewer false entries on extinction trials, with postweaning diet exerting no effect on these behaviours. The behavioural results may be interpreted in terms of increased sensitivity to noxious stimuli in maternally deprived rats. No simple explanation for the iron status results is apparent.     

Effects of retention interval and gonadectomy on sex differences in passive avoidance behavior

Female rats show more response suppression in aversively motivated learning when the effect of presentation of an aversive stimulus upon subsequent responding is measured immediately, whereas males show more suppression in procedures in which the effect of an aversive stimulus is measured after longer intervals. To test whether this divergence can indeed be attributed to temporal parameters, step through passive avoidance was studied using various intervals between shock and retention trial. In contrast to the hypothesis, males showed more response suppression than females when tested directly after shock presentation. This sex difference was also observed at longer intervals. The highest levels of passive avoidance was observed at a 15 minute interval in all groups. Ovariectomy had no effect on the performance of females, but castration of males significantly decreased their performance. These findings demonstrate that the presence of testosterone in adulthood is critical for the masculine pattern of this behavior.