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PubMed1975

Evoked potential correlates of early conditioning in the rat ontogeny.

In rats aged 2-8 weeks cortical EP to CS (20 flash - tone combinations, 0,9/sec, reinforced since the 10th application by electric shocks to the hind leg) were studied within different kinds of behavioral responses during avoidance learning and extinguishing. In contrast to our results in freely moving rats no developmental trend was found in this kind of avoidance (lifting of the hind leg). Average EP within reinforced trials (with escape or no reactions) differed in isolated application of CS from those when both CS and US were acting together. In younger animals the EP to CS combined with US were characterized by an evident late negative wave which shifted later (5-6 weeks toward the early negative complex. The EP changes in the auditory cortex were more pronounced, whereas visual EP with CS-US combination were rather decreased. In the youngest animals (2 weeks) the auditory EP within trials with avoidance were characterized by a distinct short latency deflection of the first positive wave, whereas in EP to extinguished CS the second deflection of the first positive wave prevailed. Also in these phenomena, the typical changes were clearly revealed in the auditory cortex. At later developmental stages (starting the 3rd, more prominently the 4th and 5th week) the wave following primary positive - negative complex was shifted toward the negativity if the animal responded by an avoidance; on the contrary an ample positive, often a double-peak wave arose if the response was extinguished. The stimulus and reaction dependence in the cortical EP showed the role of not yet fully mature cerebral cortex in avoidance learning. Both, fast as well as with some delay running processes participated in the observed phenomena during the ontogenetical development.

Animals↗

PubMed1983

Prior training and intermittent retraining attenuate pimozide-induced avoidance deficits.

Although the effects of neuroleptics on avoidance behavior have been studied extensively, no studies have systematically investigated the possible relationship between these effects and prior training. This paper reports the effects of prior training and intermittent retraining on pimozide-induced avoidance deficits. Experiment 1 investigated the effects of pimozide (0.5 or 1.0 mg/kg IP) on one-way avoidance responding in groups of rats (n = 15 or 16) that had received 0, 2, 3, or 10 prior sessions of training (10 trials per session). All trained groups were more resistant to the disruptive effects of the drug than the groups receiving no prior training but the 2, 3, and 10 session pretrained groups did not differ significantly from one another. However, the avoidance responding of the pretrained groups eventually was impaired across the 15 sessions of testing under the drug condition; this effect was shown not to be attributable to an accumulation of the drug with repeated dosing. Experiment 2 showed that periodic retraining in the absence of pimozide reversed the cumulative session-to-session disruptive effects of the low and high dose of pimozide on avoidance responding, a finding not previously reported. The results suggest that dopaminergic systems play a role in the acquisition and maintenance of operant response learning. Avoidance learning fails to occur if training is conducted in untrained, pimozide-treated animals. Pretrained animals, when injected with pimozide, can maintain avoidance responding for several sessions but lose this ability in the continued absence of normal dopamine function; however, intermittent retraining can prevent this eventual loss of avoidance responding.

Animals↗

PubMed1977

Active and passive avoidance in rats as a function of age.

Rats of four age groups: young (30 days of age), adolescent (180 days of age), adult (365 days of age), and old (547 days of age) were trained on active and passive avoidance tasks. There was impaired acquisition and 30-day rentention of passive-avoidance learning in both young and old rats, compared to the intermediate age groups, and marked impairment of acquisition and retention of active-avoidance learning in the old rats. Learning impairment is thus associated with immaturity as well as senescence.

Aging↗

PubMed1979

Differential effects on learning by ventromedial vs lateral hypothalamic posttrial injection of substance P.

The effects of post-trial injection of substance P (SP) into the lateral hypothalamus (LH) and the ventromedial hypothalamus (VMH) on passive avoidance learning was studied in rats. In the VMH, 50 ng and 500 ng SP influenced neither learning of a step-down avoidance nor of an alcove avoidance response. In contrast to these findings, 500 ng SP injected into the LH significantly enhanced retention of the alcove avoidance task. Similarly, in the step-down avoidance experiment, learning was strongly facilitated by posttrial injection of 50 ng as well as 500 ng SP into the LH. These results, together with our previous data showing amnesia with posttrial injection of SP into amygdala and substantia nigra, suggest that exogenously applied SP influences the activity of those brain regions shown to contain high densities of SP-positive nerve terminals. Interestingly, the effects of posttrial SP injection parallel the effects of post-trial electrical brain stimulation on passive avoidance learning. Hence, posttrial SP retroactively facilitates or impairs learning depending on where in the brain it is injected.

Animals↗

PubMed1990

Effects of changes in peripheral and cerebral glucose metabolism on locomotor activity, learning and memory in adult male rats.

Interactions of glucose and cognitive function have been reported both in the presence of elevated arterial blood glucose levels and with decreased cerebral glucose metabolism. In order to test the peripheral vs. central effects of this phenomenon, we induced irreversible hyperglycemia and depression of cerebral glucose metabolism in separate designs by means of either intraperitoneal (i.p.) or intracerebroventricular (i.c.v.) administration of streptozotocin (STZ), which is known to damage insulin-producing cells. Behavioral functions, such as locomotor activity, learning, and memory, were investigated under these different conditions. IP treatment with STZ decreased locomotor activity and increased initial step-through latencies on the passive avoidance test. No effects of elevated arterial blood glucose levels on retention of passive avoidance learning checked at 24 h and 144 h after training were observed. I.c.v. treatment of STZ increased the rate of locomotor activity and impaired retention in the passive avoidance test at 24 h, without further forgetfulness at 144 h. This finding may indicate disturbed acquisition and/or consolidation of memory, which may remain impaired but at a constant level, without further deterioration. Enhanced motor activity and impaired acquisition of passive avoidance learning without further impairment have also been reported as a characteristical behavioral pattern after disruption of the cholinergic system. It is therefore postulated that the observed behavioral abnormalities consequent on an impairment of cerebral glucose metabolism may be suggestive of cholinergic dysfunction.

Animals↗

PubMed1992

Kindling and its consequences on learning in rats.

To study the learning performance of pentylenetetrazol- and amygdala-kindled Wistar rats we used the following learning tests: short-term memory was tested in the response-to-change model, brightness discrimination was tested in a Y-chamber, and two-way active avoidance learning was tested in a shuttle-box. Short-term memory was not impaired by both kindling procedures. Considering two-way active avoidance learning the performance of pentylenetetrazol (PTZ)-kindled rats was significantly diminished. This effect persists over a period of 4 weeks. However, amygdala (AMY)-kindled rats acquired this task like the controls. In brightness discrimination reaction (BDR) the learning performance of PTZ-kindled animals was not influenced. Although the acquisition of BDR was nearly identical, the 24-h retention was remarkably diminished in AMY-kindled rats. It was hypothesized that the different kindling procedures interfere in different ways and extent with neuronal circuits resulting in different functional impairments.

Amygdala↗

PubMed1989

Paternal and maternal alcohol consumption: effects on offspring in two strains of rats.

Long-Evans and Sprague-Dawley male rats were given liquid alcohol diets containing 35%, 17.5%, or 0% ethanol-derived calories (EDC). The latter two groups were pair fed to the higher alcohol diet group. A fourth group received lab chow and water ad libitum to assess the role of paternal undernutrition associated with alcohol consumption. After three or four weeks of diet consumption, these males were bred to females of the same strain. Pregnant females were divided into similarly treated alcohol groups and were fed these diets beginning on gestation Day 8, thus creating a factorial study with strain, paternal, and maternal alcohol consumption as main factors. Paternal alcohol consumption was associated with decreased litter size, decreased testosterone levels, and a strain-related effect on offspring activity. Offspring activity decreased for those sired by 35% and 17.5% EDC Long-Evans fathers. Activity also decreased for offspring sired by 17.5% EDC Sprague-Dawley fathers but increased for those sired by 35% EDC fathers. Paternal alcohol consumption did not affect postnatal mortality or passive avoidance learning of offspring. Maternal alcohol consumption was associated with lower birth weights, lower offspring weights at weaning, increased postnatal mortality, and poorer passive avoidance learning. However, offspring activity was not affected. In a separate study, levels of alcohol in the testes were found to be somewhat, but not significantly, lower than blood alcohol levels. DNA taken from sperm of Long-Evans males consuming alcohol, migrated farther under pulsed field electrophoresis than DNA from control fathers, suggestive of an alcohol-related effect on sperm DNA.

Alcohol Drinking↗

PubMed1983

Periadolescence: age-dependent behavior and psychopharmacological responsivity in rats.

The behavior and psychopharmacological sensitivity of periadolescent rats are examined in this review. Periadolescent rats are hyperactive and engage in more conspecific play behavior than younger or older rats. When compared with other-aged rats, periadolescents exhibit enhanced performance in simple active-avoidance learning tasks, but perform poorly in more complex appetitive and avoidance learning tasks in which increases in locomotor activity do not improve performance, perhaps as a result of age-specific alterations in selective attention or stimulus processing. Such behavioral "anomalies" of periadolescent animals observed in traditional laboratory situations may be in some way adaptive when considered in the context of the animals' natural habitat. In terms of psychopharmacological responsiveness, periadolescent rats, when compared with younger or older animals, are less sensitive to catecholaminergic agonists but are more responsive to the catecholaminergic antagonist haloperidol. This pattern of psychopharmacological sensitivity suggests that the catecholaminergic systems may be temporarily hyposensitive during the periadolescent period. Evidence is presented that a negative feedback system in the form of dopamine autoreceptors may become functionally mature in mesolimbic brain regions during the periadolescent period. The possibility is presented that maturation of these self-inhibitory autoreceptors might result in a temporary decrease in the efficacy of mesolimbic dopamine projections, perhaps contributing to the psychopharmacological and behavioral characteristics of periadolescent animals. In support of this suggestion, evidence is reviewed indicating that the behavior of adult animals with lesions of the ventral tegmental area, a region containing cell bodies from which these mesolimbic dopaminergic projections originate, resembles that of periadolescent rats.

Age Factors↗

PubMed1995

Behavioral effects of neonatal cocaine exposure using a rodent model.

This study examined the effects of neonatal cocaine exposure on behavior using a rodent model. Rat pups were implanted with intragastric cannulas on postnatal day (PND) 4 and artificially reared (AR) from PND 4-10. The AR groups included two cocaine doses (20 mg/kg per day and 60 mg/kg per day) and an AR control. A sham surgery control group was also included that was reared naturally by its dam. Offspring from these neonatal treatment groups were examined for suckling performance (PND 13), passive avoidance learning (PND 23-24), activity (PND 18-21), or spontaneous alternation (PND 21). Neonatal cocaine exposure had no effect on suckling measures or passive avoidance learning. Activity was increased in the 60 mg/kg per day cocaine group relative to controls. In addition, spontaneous alternation was delayed in the 20 mg/kg per day cocaine-exposed females relative to all other groups. These data suggest that neonatal cocaine exposure may alter performance on some relatively simple tasks. More work is clearly warranted to look at the effects of neonatal cocaine exposure on more complex behaviors.

Animals↗

PubMed1991

Behavioral, endocrine, and neurochemical effects of sulfomucopolysaccharide treatment in the aged Fischer 344 male rat.

1. Daily treatment of male 19- to 22-month-old Fischer 344 male rats with Ateroid (20 mg/kg/day, p.o.), beginning one month before and continuing throughout testing, resulted in a significant partial reversal of age-related deficits in: a) Conditioned one-way (spatial, unsignaled) avoidance acquisition and retention b) Conditioned two-way (nonspatial, signaled) avoidance acquisition. 2. Ateroid reversed the age-related reductions in nucleus accumbens DOPAC and HVA levels, but not the age-related decrease in neostriatal HVA content or concomitant increase in 5-HIAA levels. Reduced dopamine turnover in the nucleus accumbens may underlie, at least in part, age-related deficits in conditioned avoidance learning and retention. Thus, the behavioral effects of Ateroid observed in the present study may be due to its normalizing influence on dopamine neurotransmission in the nucleus accumbens. 3. Stress-induced corticosterone secretion was greater in the old than in the young vehicle-treated rats. Ateroid treatment normalized this exacerbated corticosterone response to stress. 4. Daily Ateroid treatment did not affect any of the parameters measured in the young (5-8 months) F344 male rats. 5. Ateroid treatment did not affect the age-related reductions in exploratory behavior. The aged and young animals did not differ in their swimming ability. Thus, the effect of Ateroid on learning and memory processes does not appear to be due to an effect on locomotor or performance skills. 6. The age-related deficits in conditioned avoidance learning were not associated with abnormal basal (morning trough) plasma corticosterone levels, and Ateroid did not affect basal plasma corticosterone concentrations.

Aging↗

PubMed1979

Long-term consequences of early iron deficiency in the rat.

A period of severe early iron deficiency (birth to 28 days of age) produced a persistent deficit (22%) in brain non-heme iron in adult rehabilitated animals. Long-term effects on behavior and physiological responsiveness were also observed. Although rehabilitated and control animals did not differ either in basal levels of plasma corticosterone or in the time course of the stress response following ether and cardiac puncture, possible differences in pituitary-adrenal responsiveness appeared to emerge following testing in an exploratory task. In addition, significant differences between rehabilitated and control animals were observed in both active and passive avoidance learning. Rehabilitated males made more intertrial responses than control males during active avoidance learning, and rehabilitated animals of both sexes performed better (i.e. showed longer reentry latencies) in a passive avoidance situation. It was suggested that shock may differentially affect motivation or arousal in rehabilitated and control animals.

Animals↗

PubMedDate not supplied

Effects of paternal alcohol consumption on pregnancy outcome in rats.

Male rats were divided into 3 groups and were given ad lib access to a liquid alcohol diet containing 35% ethanol derived calories (EDC) or were pair-fed with an isocaloric control diet, containing 17.5% or 0% EDC, for a minimum of 52 days. A fourth group was fed rat chow ad lib. Males were then mated with non-treated females. Males consuming alcohol did not differ in sexual behavior but were less fertile and sired offspring that were significantly less active than controls and the effects on activity were dose-related. Females sired by males consuming alcohol also performed worse in a two-way shock avoidance learning task although differences in this task were not dose-related. There were no significant effects, however, on body weight of offspring at birth or at 21 days of age or on other behavioral measures such as spontaneous alternation or passive avoidance learning.

Alcoholism↗

PubMedDate not supplied

The effects of telencephalic pallial lesions on spatial, temporal, and emotional learning in goldfish.

In mammals, the pallial amygdala is implicated in emotional learning and memory, whereas the hippocampus is involved in spatial, contextual, or relational memory. This review presents a set of experiments aimed to study the involvement of the dorsomedial and dorsolateral telencephalon of goldfish in spatial and active avoidance learning. Results showed that (1) medial lesions impaired both acquisition and retention of conditioned avoidance response in two-way active avoidance learning experiments with stimuli overlapping (emotional factor) and with an interstimuli gap (temporal and emotional factors), and (2) the medial lesion did not affect spatial learning (spatial, contextual, or relational factors). In contrast, lateral lesions did not impair conditioned avoidance response with stimuli overlapping, but affected conditioned avoidance response with an interstimuli gap and spatial learning. These results support the presence of two differentiated memory systems in teleost fish based on discrete pallial regions: emotional (dorsomedial telencephalon) and spatial/temporal or relational (dorsolateral telencephalon). Furthermore, these functional data support the homology between the medial pallium of the teleost and the pallial amygdala of land vertebrates, and between the teleost lateral pallium and the mammalian hippocampus.

Amygdala↗

PubMed1991

Effects of thyrotropin-releasing hormone on behavioral disturbances in middle cerebral artery-occluded rats.

The effects of thyrotropin releasing hormone (TRH) on behavioral and histological changes were studied in rats subjected to left middle cerebral artery occlusion. The drug was given i.p. once or several times a day from 1 week after occlusion for 2 weeks. A single administration of TRH (1 and 10 mg/kg) did not affect the neurological deficits, but recovery of the deficits was accelerated by multiple administration (7 times a day) of TRH and single administration (once a day) of YM-14673 (N alpha-[[(S)-4-oxo-2-azetidinyl]carbonyl]-L-histidyl-L-prolinamide dihydrate), a new TRH analogue with a longer half-life. Both YM-14673 and single (1 and 10 mg/kg) and multiple administration of TRH ameliorated the disturbance of passive avoidance learning. Neuronal degeneration in the cerebral cortex and striatum was not influenced by the administration of TRH. Thus, we found that neurological deficits and disturbance of passive avoidance learning behavior in middle cerebral artery-occluded rats could be ameliorated by administration of TRH.

Animals↗

PubMed1990

Active avoidance is permanently abolished after lesions of the nucleus interpeduncularis in rat.

Active avoidance learning, retention and relearning were investigated before and after lesions of the interpeduncular nucleus (IP) of rat in a Y-maze and a jump test box. Preoperatively learnt active avoidance was abolished after the lesions and rats were not able to relearn it. Unconditioned escape responses remained unchanged in the Y-maze. Postoperative avoidance learning was impossible. Brightness discrimination in a goal alternation paradigm was learned or relearned, respectively, after IP lesions. The IP rats were hypoactive and showed diminished exploratory activity but had unchanged escape speed. The IP is evidently enclosed in a network controlling avoidance behaviour.

Animals↗

PubMed1985

Passive avoidance in syndromes of disinhibition: psychopathy and extraversion.

According to the physiological animal model proposed by Gorenstein and Newman (1980; see also Newman, Gorenstein, & Kelsey, 1983), psychopaths and extraverts may be characterized by a common psychological diathesis related to behavioral inhibition (see also Fowles, 1980; Gray, 1982). One aspect of this diathesis involves deficient passive avoidance learning, which has been central to explanations of "unsocialized" (e.g., Trasler, 1978) and antisocial behavior (e.g., Hare, 1970). Results from three experiments supported our prediction that psychopaths and extraverts would exhibit deficient passive avoidance relative to nonpsychopaths and introverts, respectively. In addition, the passive avoidance deficit was particularly evident in tasks that required subjects to inhibit a rewarded response in order to avoid punishment. The latter finding may be important for explaining the inconsistent results regarding passive avoidance learning in psychopaths (e.g., Chesno & Kilmann, 1975; Schmauk, 1970). Discussion of the results focuses on the importance of reward in mediating the passive avoidance deficit of "disinhibited" individuals and on the existence of an indirect relationship between psychopathy and extraversion: one that is consistent with the observed experimental parallels as well as with the more ambiguous evidence regarding a direct correlation between measures of the two syndromes.

Adolescent↗

PubMed1992

[Genetic analysis of various behavioral and physiologic characteristics in hybrids between hypertensive and normotensive rats. Analysis of correlational connections].

Hereditary links between different behavioral and physiological traits were studied in rat strains SHR, WKY and their hybrids F1 and F2 by analysis of correlations in segregating and nonsegregating gene-rations. Genetic correlation of arterial pressure with body mass, intake of KC1 solution and the ability to avoidance learning (directed positively) and with characteristics of exploratory activity (directed negatively) was shown. These traits seemed to be possible genetic markers of arterial hypertension. Genetical correlates of the ability to elaborate active avoidance conditional reaction (arterial pressure and pain sensitivity) testify to relief of active avoidance learning in animals with inherited active-defensive type of behaviour, manifested by predisposition to pressor reactions and by suppressed emotional reactions to pain stimulation. Frequency in intertrial crossings during avoidance training displays positive correlation with characteristics of exploratory behaviour. Positive correlation between different characteristics of exploratory activity was established both in segregating and nonsegregating generations.

Animals↗

PubMed1975

Influence of enucleation upon two-way avoidance behavior of rats, hamsters, chinchillas and BALB/cJ mice.

Several rodent species were blinded and their two-way avoidance behavior was compared to unoperated controls. Blindness facilitated avoidance learning in BALB/cJ mice, impaired learning in hamsters and had no significant effect on albino rats, hooded rats and chinchillas. Effects of blindness upon intertrial locomotor activity correlated well with effects of blindness upon avoidance learning. Preventing intertrial activity abolished the effect of blindness in mice, and did not change performance of blind albino rats.

Animals↗