Effect of Dehydroepiandrosterone on Avoidance Behavior of Adult Male Rats

We studied the effect of repeated intraperitoneal treatment with dehydroepiandrosterone in doses of 0.1 and 0.7 mg/kg on conditioned-response activity and behavior of adult male rats. The effect of dehydroepiandrosterone on learning was estimated in conditioned active and passive avoidance response paradigms. Chronic administration of dehydroepiandrosterone in low and high doses had no effect on retention of conditioned passive avoidance response in adult male rats 24 h after learning. However, chronic administration of dehydroepiandrosterone in low dose impaired acquisition of the conditioned active avoidance response. It should be emphasized that chronic administration of dehydroepiandrosterone in high dose did not modulate acquisition and retention of this reaction.     

Peripheral vasopressin accelerates extinction of conditioned taste avoidance

Both peripheral and central administration of vasopressin improves retention and delays extinction when given before or after acquisition of shock avoidance learning. For conditioned taste avoidance, however, vasopressin prolongs extinction when injected peripherally before acquisition tests and accelerates extinction when infused intracerebroventricularly after acquisition. The following experiments were designed to determine whether this inconsistency is based on the route of administration or timing of vasopressin treatment. Because acquisition of conditioned taste avoidance is strengthened when an agent that is capable of inducing avoidance is administered after LiCl injection, it was determined in experiment 1 that a 6 microg/kg dose of vasopressin did not induce conditioned taste avoidance when administered 50 min after consumption of a sucrose solution. In experiment 2, it was determined that this dose of vasopressin accelerated extinction of a LiCl-induced conditioned taste avoidance when given 50 min after LiCl injection. These results suggest that the inconsistency is not based on route of administration. In experiment 3, it was determined that there was a tendency for animals to show prolonged extinction when vasopressin was administered 20 min before access to a sucrose solution. All of the results taken together suggest that the differential effects of vasopressin on extinction are due to the timing of administration. It was suggested that vasopressin accelerates extinction when given after acquisition by reducing the effectiveness of LiCl and it prolongs extinction when given before acquisition by altering neural responsiveness in areas mediating conditioned taste avoidance.     

Effects of infrasounds on the conditioned avoidance response

Animals were exposed to infrasounds during the acquisition of a conditioned avoidance response. When compared to controls they showed performance decrements both in acquisition and retention, 24 hours later. Possible modes of action are discussed.     

Effect of dehydroepiandrosterone on avoidance behavior of adult male rats

We studied the effect of repeated intraperitoneal treatment with dehydroepiandrosterone in doses of 0.1 and 0.7 mg/kg on conditioned-response activity and behavior of adult male rats. The effect of dehydroepiandrosterone on learning was estimated in conditioned active and passive avoidance response paradigms. Chronic administration of dehydroepiandrosterone in low and high doses had no effect on retention of conditioned passive avoidance response in adult male rats 24 h after learning. However, chronic administration of dehydroepiandrosterone in low dose impaired acquisition of the conditioned active avoidance response. It should be emphasized that chronic administration of dehydroepiandrosterone in high dose did not modulate acquisition and retention of this reaction. Translated fromByulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 138, No. 7, pp. 63–67, July, 2004 This work was supported by the Regional Social Foundation for Russian Medicine.     

Differential effects of electrical stimulation of amygdala, caudate-putamen or substantia nigra pars compacta on taste aversion and passive avoidance in rats

The effect of unilateral, low-intensity subseizure electrical stimulation of the basolateral nucleus of the amygdala (ABL), caudate-putamen (CD) or substantia nigra pars compacta (SNC) on the acquisition and retention of a conditioned taste aversion and a step-down passive avoidance response were compared in two separate experiments. In Experiment 1 electrical stimulation of the ABL while rats were drinking saccharin prior to poisoning with LiCl disrupted conditioned taste aversion. Stimulation of the CD or SNC had no disruptive effect on taste aversion. In contrast, stimulation at all 3 brain loci disrupted the retention of a passive avoidance response in Experiment 2. The implications of these data for the hypothesis of dual neural control systems for shock avoidance behavior and taste aversion, are discussed.     

Effects of nucleus basolateralis amygdalae neurotoxic lesions on aversive conditioning in the rat

After bilateral stereotaxic administration of ibotenic acid on the n. basolateralis amygdalae, male adult rats were tested in the light-dark box apparatus to measure the time-course of the acquisition and retention of passive and active avoidance responses. The results show that after the lesions both passive avoidance and active avoidance acquisition were impaired. Passive avoidance responses were retained quite well, while active avoidance responses disappeared quickly. Conditioned freezing was almost completely absent. Thus it appears that the n. basolateralis plays a facilitatory role in all the conditioned responses which were investigated.     

Prolonged ethanol consumption influences shuttle box and passive avoidance performance in rats

Rats were chronically maintained on an ethanol liquid diet for 16 days. Three weeks after cessation of ethanol intake, animals were tested for the acquisition of shuttle box avoidance and the retention of passive avoidance behaviour. Alcohol consuming rats showed a significant impairment of acquisition in the shuttle box task, and a slight impairment in the retention of the passive avoidance response. It is concluded that ethanol or its metabolites can induce long-term effects on learning and memory processes, even after cessation of drug consumption.     

Conditioned taste aversion in vasopressin-deficient rats (Brattleboro strain)

Brattleboro rats are homozygous for diabetes insipidus (DI), lacking the ability to synthesize vasopressin. Previous studies reported learning deficits in DI rats on passive avoidance tasks using footshock. Other studies, however, could not replicate these results. In two experiments, we studied the learning of DI and control Long Evans (LE) rats in a different avoidance paradigm: conditioned taste aversion (CTA). In the first experiment a mild CTA to saccharin was established gradually using low levels of an illness-inducing agent (lithium chloride). In the second experiment a strong CTA was established in one acquisition trial and the extinction of the conditioned aversion was followed for 12 trials. The two experiments found no differences between the DI and LE rats in either the magnitude or the rate of acquisition and extinction of the CTA. These results suggest that vasopressin is not involved in the acquisition and retention of CTA, and support previous studies indicating that vasopressin may not be involved in avoidance learning.     

Age effects in the acquisition and retention of active and passive avoidance learning by rats

Three groups of 8 male albino rats within each of the age ranges 24, 50, and 100 days were trained on an active avoidance task to a criterion of 10 successive avoidances. The number of trials to criterion was found to be a monotonic function of age. One group at each age was tested immediately thereafter for passive avoidance of the conditioning chamber, another group was tested for passive avoidance after 25 days, and the third was tested for retention of active avoidance after 25 days. Groups at 50, 75, and 125 days were used as controls for the active avoidance retention groups. All animals took significantly fewer trials to relearn the active avoidance after 25 days than did controls on the acquisition of the original learning task. On passive avoidance 24-day olds performed less efficiently than the older groups and failed to show any retention after 25 days.     

Blind mice are not impaired in T-maze footshock avoidance acquisition and retention

The processing of visual information during learning and memory is considered to be a vital function of the hippocampus. Some researchers believe that the sole purpose of the hippocampus is to process visuo-spatial information, whereas other investigators believe that the hippocampus integrates cues from multiple sources. In the current studies, we tested the effects of vision loss on a hippocampal task, acquisition and retention with T-maze footshock avoidance conditioning. Acquisition and retention, in adult-blinded mice, were not significantly impaired in T-maze footshock avoidance. Blindness did not affect activity, footshock startle or motivation to avoid shock. The same doses of memory enhancing drugs that improve memory in sighted mice improved memory in blind mice. Electrolytic lesions in blind mice, which destroyed 31+/-4% of the hippocampus, significantly impaired acquisition and retention for T-maze footshock avoidance and so demonstrated that the hippocampus retained its integrative role in blind mice. The current findings show that blind mice are as capable of learning T-maze footshock avoidance as sighted mice and that the hippocampus retains its important role in blind mice in learning and memory processing. It is concluded that the T-maze footshock avoidance conditioning task is a spatially but not visually dependent task that is hippocampally dependent.     

脑创伤对大鼠学习记忆功能的影响

目的：观察ＴＢＩ后大鼠主动性条件回避反应（ＡＣＡＲ———穿梭箱实验，ｓｈｕｔｌｅｂｏｘｔｅｓｔ）及被动性条件回避反应（ＰＣＡＲ———步入与步下实验，ｓｔｅｐｔｈｒｏｕｇｈａｎｄｓｔｅｐｄｏｗｎｔｅｓｔ）的变化。方法：用２０ｇ重物从不同高度垂直坠落至大鼠一侧暴露的硬脑膜复制脑创伤（ＴＢＩ）模型。结果：重度ＴＢＩ后大鼠ＡＣＡＲ的习得率和保持率均出现下降，ＰＣＡＲ的步入和步下潜伏期缩短；轻度ＴＢＩ后仅表现出ＡＣＡＲ的习得率降低。结论：ＴＢＩ易导致脑高级功能障碍，其受损程度与原发伤情有关。     

The effects of excitotoxic lesions of the substantia innominata, ventral and dorsal globus pallidus on the acquisition and retention of a conditional visual discrimination: implications for cholinergic hypotheses of learning and memory

The effects of ibotenic acid-induced lesions of the ventral pallidum/substantia innominata region, the dorsal pallidum or both on the acquisition and retention of a conditional visual discrimination have been studied in the rat. Lesions of the ventral pallidum and large lesions of the dorsal and ventral pallidum severely impaired both the acquisition and retention of the conditional discrimination. Dorsal pallidal lesions had similar, but less marked effects. The same lesions also impaired the retention of a passive avoidance task, but had no effect on a conditioned taste aversion. Neurobiological investigations revealed that the lesions destroyed cholinergic neurons in the magnocellular nucleus basalis and caused reductions in cortical choline acetyltransferase activity of about 30-40%. Tract-tracing experiments indicated that the lesions destroyed, in particular, cholinergic neurons projecting to the frontal dorsolateral cortex and also those projecting to more posterior cortex, but not the occipital lobes. Contingency analysis of the behavioural, neurochemical and neuroanatomical data indicated that those animals with the largest decreases in choline acetyltransferase activity, or the largest areas of neuronal loss in the ventral and dorsal globus pallidus, were most impaired in the retention of the conditional discrimination. The results do not, therefore, indicate a simple relationship between cholinergic neuronal loss and the retention of response rules essential for performance of the task ("reference memory"). The relevance of the results to cholinergic hypotheses of learning and memory is discussed.     

Unilateral hippocampal lesions prevent recall of a passive avoidance task in day-old chicks.

The role of the hippocampal system in learning and memory processes in the chick was investigated. A series of experiments examined the effects of lesions in the hippocampal system on the acquisition and retention of a passive avoidance task. Chicks given pretraining bilateral hippocampal lesions showed a decrease of retention of the avoidance response evaluated 3 h posttraining. When given unilaterally, left, but not right lesions, resulted in reduced avoidance. However, bilateral posttraining lesions, made 1 h after training, did not interfere with retention of the task. These results suggest an involvement of the hippocampal system in learning processes in the chick.     

Effect of seleptine on retrieval of active avoidance task in rats

We have examined seleptine, a new derivative of the atypical neuroleptic clozapinum, on the retrieval of the active avoidance task in rats placed in a shuttlebox. Retention of the conditioned response was assessed in the test of repeated training for the same task to the score achieved in the first session. After oral seleptine (100 mg/kg), the retention of the active avoidance task was deteriorated to a greater extent than the ability for a new learning. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 126, No. 7, pp. 28–30, July, 1998     

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.     

Kainate and electrolytic lesions of the lateral habenula: effect on avoidance responses

Male Sprague Dawley rats (n = 24), which received either bilateral electrolytic lesions, kainic acid lesions or sham treatments in the lateral habenula, were tested for acquisition of a one-way, conditioned avoidance response. Animals with electrolytic lesions failed to learn the avoidance task within 15 trials. In contrast, rats with kainic acid lesions performed as well as the control group. The results indicate that the disruption of the septal-medial habenula-interpenduncular nucleus pathway may be responsible for the observed avoidance deficit in electrolytically lesioned animals.     

Acquisition and retention of an avoidance response by rats of different ages.

Rats, 21, 120, and 480 days of age, were given acquisition training in a 1-way avoidance task and tested for retention of the response 1 and 30 days later. Whereas the 480-day-old rats showed poorer performance during acquisition, the 21-day-old rats showed the greatest impairment of long term retention. The results suggest that age differences in performance are due to intrinsic maturational processes.     

Anterior thalamic lesions and neuronal activity in the cingulate and retrosplenial cortices during discriminative avoidance behavior in rabbits

Bilateral electrolytic lesions of the anteroventral (AV) nucleus of the thalamus given after training impaired retention performance (extinction and reacquisition) of rabbits in a differential avoidance conditioning task. In addition, the lesions abolished the excitatory, discriminative multiple-unit discharges that had developed in the cingulate and retrosplenial cortices to the auditory conditional stimuli (CSs) during the course of behavioral acquisition, prior to the induction of the lesions. The excitatory discharges were supplanted in the subjects with lesions by CS-elicited reduction of neuronal firing to levels below the prestimulus baseline. Lesions given before training did not disrupt behavioral acquisition, but they did eliminate the excitatory tone-elicited neuronal discharges that normally occur in the cortex before and during training. The CS-elicited reduction of neuronal firing did not occur at the beginning of training in the subjects given lesions before training, but it developed during the course of training. The lesions did not eliminate the excitatory and discriminative neuronal activity of the prefrontal cortex. These results demonstrate that excitatory and discriminative neuronal discharges in the cingulate and retrosplenial cortices are critically dependent on the connections of these areas with the anterior thalamic nuclei. Also the lesion-induced disruption of performance during extinction and reacquisition but not during original learning confirms a prediction from past electrophysiological studies, that the AV thalamic nucleus is involved in the mediation of the maintenance and retention of the conditioned avoidance behavior, but not in its original acquisition.     

LHRH and rat avoidance behavior: influence of castration and testosterone

Pretraining subcutaneous administration of a high dose of LHRH (100 micrograms/kg) to intact rats impaired acquisition of a conditioned avoidance response (CAR) in a two way shuttle box. Acquisition of a CAR was also decreased when LHRH was administered to castrated rats. LHRH antagonized the dose related impairment in acquisition and retention performance induced by testosterone in castrated animals. The results are discussed based on the interrelationships between castration, testosterone, LHRH and brain monoamines.     

High doses of vasopressin delay the onset of extinction and strengthen acquisition of LiCl-induced conditioned taste avoidance

When low doses of vasopressin are given 50 min after pairing sucrose consumption with a high dose of LiCl, extinction of the LiCl-induced conditioned taste avoidance is accelerated. These low doses of vasopressin do not themselves induce conditioned taste avoidance when paired with sucrose consumption. Predicated on previous studies administering two avoidance-inducing agents after sucrose consumption, studies were designed to determine whether high doses of vasopressin capable of inducing conditioned taste avoidance would (1) delay rather than accelerate extinction of a conditioned taste avoidance induced by a high dose of LiCl and (2) strengthen acquisition of a conditioned taste avoidance induced by a low dose of LiCl. The results of three studies showed that doses of 9 and 18 microg/kg of vasopressin induced a conditioned taste avoidance when injected 50 min after sucrose consumption, delayed the onset of extinction when injected 50 min after pairing sucrose consumption with a high dose of LiCl, and strengthened acquisition of a conditioned taste avoidance when injected 50 min after pairing sucrose consumption with a low dose of LiCl. Taken together, these data suggest that the delay in onset of extinction is due to a strengthening of acquisition. It has been suggested that vasopressin is a mnemonic neuropeptide that delays extinction of learned tasks. However, for conditioned taste avoidance, the evidence for the effects of low doses of vasopressin on extinction do not support this hypothesis and the evidence for high doses of vasopressin can be accounted for by the avoidance-inducing properties of vasopressin.