Effects of early experiences on shock-and illness-induced passive avoidance behaviors

Rats were either handled, shocked, or unmanipulated during the preweaning period or during the 21 days immediately following weaning. At maturity animals were tested in 2 passive avoidance situations. Half the animals were first tested in an illness-induced taste aversion situation using sour water as the CS and different doses of cyclophosphamide as the US. The remaining animals were first tested in a 1-trial passive avoidance situation using a “step-through” apparatus and a single electric shock. Early experience had no effect on the development of a taste aversion at any dosage of cyclophosphamide. Prior conditioning of a taste aversion did influence performance in the step-through avoidance situation. Fewer of these previously conditioned animals attained the training criterion and, within this previously conditioned population, the handled groups displayed less “emotional” behavior than the controls. Response latencies in the shock-induced passive avoidance test did not differentiate between handled and shocked animals. Animals manipulated prior to weaning had consistently shorter latencies than the unmanipulated controls.     

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.     

The Effects of the Duration of Adaptation to Laboratory Conditions on the Formation of a Passive Avoidance Reflex in Rats

The level of adaptation of rats to their new living conditions was studied during formation of a passive avoidance habit using a single combination. A short acclimation period (3 days) had positive influences on the ability of rats to retain a memory trace. There was a negative correlation between step-through latency and measures of anxiety behavior in the elevated cross maze. A change in the adaptation period to nine days decreased the state of anxiety and the level of performance of the conditioned response. There were no correlations between these measures. The modulating role of the level of adaptation to living conditions, associated with different levels of anxiety, in a passive one-session avoidance learning model was assessed.     

Age effects on passive avoidance behavior of vasopressin-deficient Brattleboros

Experiments in which vasopressin-deficient Brattleboros were tested in a passive avoidance procedure have yielded contradictory results. Some investigators observed the passive avoidance behavior of these subjects to be inferior to that of normal controls, while others failed to observe such differences. Inspection of the literature suggested that age differences between subjects which participated in these experiments might be responsible for the discrepancy. In the present experiment, HO-DI and HE Brattleboro rats of different ages were tested in the standard passive avoidance task. Passive avoidance performance of HO-DIs was, indeed, influenced by the age of the subject at the time of testing; HO-DIs reentered the shock compartment sooner than HE at 35 days, but later than HE at 120 days. There was no difference between the two groups of subjects at 60 days. The percentage of HO-DIs which reentered the shock compartment on the post-shock trial decreased with increasing age.     

The effects of somatostatin and somatostatin antiserum on the retention of passive avoidance behavior after neofrontal decortication in rats

Rats were tested for passive avoidance behavior in a one-trial step-through learning paradigm. After the learning trial, the animals underwent neofrontal decortication or sham operation. On the 8th day after operation, the lesioned or sham-operated rats received intracerebroventricular (ICV) injections of somatostatin (SST; 4 micrograms/2 microliters) or somatostatin antiserum (SST-AB; 2 microliters) 1 hr before the retention test. Decortication alone decreased the latency in comparison to that in the sham-operated group, and ICV treatment did not influence this impairment. After treatment with SST-AB the latency decreased, indicating that endogenous SST may play a role in the maintenance of normal memory processes.     

Passive avoidance behavior and response thresholds in adult male rats after early postnatal undernutrition.

Rats were undernourished from birth to 25 days of age. Although severely growth retarded, they had probably received more attention from their mothers than had well fed pups. When the previously undernourished rats were tested as adults in a passive avoidance situation they showed stronger passive avoidance behavior than controls rats. When the rats were retested at a later age in a situation where they were given different intensities of inescapable electric shock, the previously undernourished rats showed more jump responses, and more frequent vocalizations than control rats. Analysis of jump responses revealed that the previously undernourished rats had a lower jump threshold than control rats.     

Septal vasopressin modulates motility and passive avoidance in pinealectomized rats.

Experiments were performed to investigate the role of central arginine vasopressin (AVP) in an interrelationship with the pineal gland on motility and passive avoidance response in rats. The involvement of the pineal gland in behavioral paradigms was examined using pinealectomized (PE) and pineal-intact (sham-operated and nonoperated) animals. Central administration of 200 pg AVP or 40 ng of the AVP receptor antagonist, d(CH2)sThyr(Et)VAVP (AAVP) was performed into the mediolateral septum by means of microdialysis probes. The blockade of vasopressinergic neurotransmission or neuromodulation into the septal area by AAVP decreased the motility in both pineal-intact groups, whereas AVP was without effect. In PE rats during AVP administration an increased motility was found, but AAVP was without effect. In pineal-intact rats the avoidance latency of passive avoidance retrieval was not influenced after application of both AVP and AAVP. However, an increase in avoidance latency was found both immediately and 24 h after AVP or AAVP administration into the septum of PE rats. The results support the hypothesis that septal AVP modulate motility and passive avoidance behavior and this modulation is influenced by the pineal gland.     

糖尿病合并脑缺血再灌注导致学习记忆障碍大鼠模型的建立

目的建立糖尿病合并脑缺血再灌注导致学习记忆障碍大鼠模型。方法Wistar大鼠70只,分为正常对照组,糖尿病 假手术组,脑缺血组,糖尿病 脑缺血组。腹腔注射链脲佐菌素建立糖尿病模型,3d后双侧颈总动脉夹阻再灌注2次。术后1个月用跳台和Morris水迷宫判断其学习记忆能力,取海马组织,HE染色观察CA1区的细胞分布。结果电击后5min模型组的被动回避反应下台潜伏期明显缩短(P<0.01),24h后仍小于其他各组(P<0.05)。模型组学会主动回避反应的训练次数显著多于其他3组(P<0.001)。模型组在目标象限停留的时间最短(P<0.01),游泳的距离也最短(P<0.05)。结论糖尿病合并脑缺血再灌注可在短期内造成学习记忆障碍,糖尿病可加重脑缺血造成的脑损伤。     

Behavioral and endocrine responses of rats with hereditary hypothalamic diabetes insipidus (Brattleboro strain)

Behavioral and endocrine profiles were established of homozygous (HO-DI) and heterozygous (HE-DI) rats with hereditary hypothalamic diabetes insipidus in comparison to Wistar strain rats. HO-DI rats were inferior in acquiring and maintaining active and passive avoidance behavior. Behavioral deficits were most obvious in a step-through one-trial learning passive avoidance test and least in multiple trial one way active avoidance test. Plasma corticosterone levels determined after the retention test appeared to be closely related to the passive avoidance behavior of the HO-DI rats. Passive avoidance immediately after the single learning trial was associated with elevated plasma corticosterone level; absence of avoidance and absence in plasma corticosterone elevation was observed 24 hr after learning. These observations are compatible with the hypothesis that vasopressin is involved in the consolidation and/or retrieval of learned responses. Differences between HO-DI and Wistar rats in open field behavior, in response threshold to electric footshock, and in a number of somatic endocrine parameters are reported and discussed.     

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 relationship between the antidiuretic activity of rat eye plexus blood and passive avoidance behaviour

Antidiuretic activity (AD-activity) of eye plexus blood in rats increases during a 24 hr postshock retention trial of a passive step-through avoidance response. The rate of increase in AD-activity was related to the intensity of the shock to which the animals had been exposed previously. If avoidance latency was increased by the administration of ACTH_4–10 or desglycinamide lysine vasopressin (DG-LVP) 1 hr prior to the 24 hr postshock retention trial, AD-activity rose concomitantly. The influence of ACTH_4–10 on avoidance latency which generally has disappeared 24 hr after a single injection in contrast to a single injection of DG-LVP which affects avoidance latency for several days, was reflected in a time dependent rise in AD-activity of eye plexus blood.     

Cholecystokinin octapeptide increases passive avoidance latencies in rats

Intraperitoneal injections of either 0.9% NaCl or cholecystokinin octapeptide (CCK-8) were paired with electrical footshock using a standard passive avoidance conditioning procedure for rats. Passive avoidance behavior was measured either 24 or 48 hr following the conditioning. No CCK-8 effect upon passive avoidance behavior was observed at the 24 hr test, but CCK-8 (100 micrograms/kg and 200 micrograms/kg) produced longer passive avoidance latencies at the 48 hr test. Control rats showed a decrease in passive avoidance latencies from 24 hr to 48 hr, while the CCK-8 rats did not show such a trend.     

Sex hormones and behavioral reactions

The paper provides a comparative analysis of the effects of imbalance of gonadal hormones on behavioral processes in rats of both sex. Learning was assesses in active and passive avoidance paradigms, behavior was evaluated in the "open field" test. Hemigonadectomy in male rats or hemiovariectomy in female rats was found to fail to modify the dynamics of acquisition and reproduction of active avoidance and passive reactions as compared to the controls, but to affect the pattern of animal behavior in the "open field" test. Castration of rats of both sex impaired the acquisition and retention of active avoidance performance. Excess of testosterone in male rats significantly inhibited the ability of the animals to form an active avoidance response. Excessive estradiol levels in female rats accelerated the acquisition of active avoidance performance and greatly attenuated extinction of this performance. Gonadal hormonal treatment did not alter the reproducibility of passive avoidance performance. The lack of estrogens resulted in amnesia of passive avoidance performance while that of androgens failed to destroy passive avoidance performance. Excessive estradiol in female rats or its lack in male rats significantly modified the pattern of animal behavior in the "open field" test. The absence of estrogens or their excess did not affect the behavior of rats with exception of individual components.     

Differential effects of ACTH4-10, DG-AVP, and DG-OXT on heart rate and passive avoidance behavior in rats.

A computerized telemetry system was used to monitor heart rate (HR), core temperature (CT), and gross locomotor activity in rats treated with saline or neuropeptides during a passive avoidance behavior task. Rats were exposed to a single mild footshock (0.15 mA, for 3 s). Retention tests were conducted at 24 and 48 h after the learning trial. One h prior to the 24-h retention test, each rat received one of the following treatments (SC): saline (SAL), desglycinamide [Arg8]-vasopressin (DG-AVP), ACTH4-10, or desglycinamide-oxytocin (DG-OXT), at a dose of 3 micrograms/rat for DG-AVP and DG-OXT, and 50 micrograms/rat for ACTH4-10. Rats treated with SAL showed a modest increase in avoidance latency accompanied by bradycardia at both retention tests. Rats receiving DG-AVP retained the highest avoidance latency among the experimental groups at both the 24- and 48-h retention test. These rats showed a decrease in HR of the same magnitude as the SAL-treated animals at both retention tests. Rats treated with ACTH4-10 showed an increase in avoidance latency during the 24-h but not during the 48-h retention test. In addition, following ACTH4-10 treatment, a tachycardiac response was found during the 24-h retention test. DG-OXT induced both behavioral and cardiac responses opposite to those found in rats given DG-AVP. CT gradually increased while the rats remained on the platform, irrespective of the treatment. Changes in HR and CT were not influenced by somatomotor activity, as no difference in gross locomotor activity was found among the groups.(ABSTRACT TRUNCATED AT 250 WORDS)     

Disrupting circadian rhythms in rats induces retrograde amnesia

Disrupting circadian organization in rats by phase-shifting the illumination cycle or by exposure to a reversed day/night cycle or to continuous light, resulted in retrograde amnesia for passive avoidance behavior. This retrograde amnesia induced by phase-shifting lasted at least 2 days, and gradually diminished the longer the rats were exposed to the new illumination cycle. Retention performance was not impaired when rats were exposed to phase-shifting for 3-5 days before the learning trial. The retrograde amnesia due to changing the illumination cycle is probably due to retrieval disturbances. Extinction of active avoidance behavior was facilitated in rats exposed to a phase-shifted illumination cycle, but social and explorative behavior of rats tested in dyadic encounters were not affected by changing the normal illumination cycle. It is concluded that phase-shifting may result in amnesia for newly learned behavioral responses, but not for more innate behavioral patterns.     

Passive avoidance behavior in lean and obese rats with ventromedial hypothalamic lesions

Lean and obese rats with ventromedial hypothalamic lesions performed reliably worse than control animals in the acquisition of a step-down passive avoidance task. However, obese rats performed significantly better than lean VMH animals, which consistently leaped off the platform on the second and succeeding trials. While there were no significant differences between groups in the acquisition of a step-through passive avoidance task, lean and obese rats with VMH lesions took reliably longer than control animals to reach criterion when an identical step-through response had previously been reinforced (punishment-extinction of a one-way conditioned avoidance response). Both lean and obese VMH-damaged rats made more punished approach responses to water than control animals following water-deprivation to 88% of body weight, but only lean VMH rats made a significantly greater number of punished approach responses to liquid food than unoperated animals following food-deprivation to 88% of body weight. The number of punished consummatory responses appeared to be influenced by baseline intake. Among the animals tested in more than one paradigm, there was a significant positive correlation between the number of punished consummatory responses and the number of shocks received during punishment-extinction of the one-way CAR, but no relationship was observed between the performances in either of these and the step-down avoidance paradigm. The impaired passive avoidance behavior by rats with VMH lesions is attributed to both an inability to inhibit a previously reinforced response and a change in response tendencies to aversive stimuli.     

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.     

Does paradoxical sleep deprivation disturb memory trace consolidation?

The effect of water tank PSD on memory in the passive avoidance test as well as on open field behavior was studied in rats. The effect of combining water tank PSD with a period of normal sleep-wakefulness cycle or with PSD by non-emotional awakening was investigated in a special series of experiments. It is concluded that PSD, even by the water tank procedure, does not disturb trace consolidation and formation of long-term memory in the passive avoidance test. However, a change in the correlation of motor-exploratory activity and fear reaction, due to the stressful situation intrinsic in the water tank PSD procedure, does not allow the animals to reach comparatively long temporal criteria in the passive avoidance test.     

Behavioral response of rats with cortical lesions to cholinomimetics.

This study examined the performance of cortically lesioned rats and their response to cholinomimetic agents in passive avoidance and water maze tasks. Lesions encompassing mainly the frontal and parietal cortices produce a deficit in a 5-day passive avoidance retention test. This deficit was attenuated by the intraperitoneal (IP) administration of muscarinic agonists or an anticholinesterase. In the Morris water maze task, lesioned vehicle-treated animals showed greater escape latency times when compared to their sham counterparts. Cholinomimetics, injected daily during acquisition, improved mean escape latency time on days 3 and 4 of testing. The performance of the various groups in a cued version of the water task did not differ. This work demonstrates that performance deficits arising from neocortical loss can be attenuated by cholinergic drugs.     

Ontogeny of passive avoidance: Role of task demands and development of species-typical behaviors

Preweanling rats 10 to 15 days of age were given passive avoidance training in a circular chamber in which the floor comprised one shock electrode and the wall the other. All ages showed acquisition of the response, but both rate of learning and asymptotic performance increased with age. Yoked-shock controls, adaption controls, and naive controls did not demonstrate passive avoidance on subsequent test trials, ruling out alternative interpretations based on sensitization to shock, fatigue, familiarity with the apparatus, and handling. From 10 to 15 days of age, improved performance was due in part to the transition from stereotyped shock-elicited behavior in the younger pups to discrete withdrawal from shock in the older pups. A paradoxical deterioration of performance was observed from 20 to 25 days of age, attributable to the development of species-typical defense reactions which were incompatible with the avoidance response. Retention of the avoidance response was found to increase from about 6 hr in the 10-day-old to at least 5 days in the 15-day-old. The data suggest that maturation of storage and/or retrieval mechanisms, rather than perceptual or experiential changes induced by development, is responsible for improved retention during ontogeny.