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At least 235 records · Page 13Linked to original sources
PubMed1989

Midazolam induces amnesia in a simple, one-trial, maze-learning task in young chicks.

We report a simple, one-trial, learning paradigm which we have developed for use in young chicks. Chicks were separated from their brood mates and placed in a small isolation chamber. A 'T' corridor, or maze, connected the isolation chamber to the brood space, allowing the chick to escape isolation stress and rejoin the brood. When the chick successfully negotiated the corridor, the latency to perform this task was recorded. On a subsequent trial, any improvement in the speed of performance was reasoned to reflect the chick's memory of the task. Undrugged chicks always showed significant improvement in task latency if they were replaced in the maze 3 hours after a successful escape, suggesting that they had remembered the task. Chicks given midazolam (0.1 or 0.3 mg/kg, IP), a benzodiazepine, before the first escape, showed no improvement on their second escape. Improved performance was seen, however, if a second injection of midazolam was given before the second escape, suggesting a state-dependent effect.

Amnesia↗
PubMed1983

T-maze learning, spontaneous activity and food intake recovery following systemic administration of the noradrenaline neurotoxin, DSP4.

Following systemic administration of the noradrenaline (NA) neurotoxin, DSP4 (50 mg/kg), rats were found to be retarded in the rate at which they acquired the "right-turn" running response in a modified T-maze choice situation, as measured by the total number of errors per session and median latency to reach the goal box. Desipramine (DMI, 20 mg/kg), injected 30 min before DSP4 blocked the acquisition retardation. DSP4 was found to have a short-lasting effect upon spontaneous motor activity, while food and water intake recovery was complete within 7 days of the injection. Both the NA-accumulation data and endogenous NA concentrations indicated profound NA, but not 5-hydroxytryptamine (5-HT) and dopamine (DA), depletions in the cortex, hippocampus and cerebellum. These data seem to confirm the role of the locus coeruleus-noradrenaline (LC-NA) system in an instrumental learning situation.

Amines↗
PubMed1992

Independent effects of age and nucleus basalis magnocellularis lesion: maze learning, cortical neurochemistry, and morphometry.

The effects of age and lesion of the cholinergic nucleus basalis magnocellularis (NBm) were assessed behaviorally, morphologically, and biochemically. Groups consisted of rats lesioned 1 month before testing, rats lesioned 13 months before testing, and their respective age-matched controls. Both age and lesion independently induced behavioral deficits in performance on two water maze tasks. The combined effect of these two factors produced behavioral deficits equal to the sum of the individual impairments. NBm lesion produced a 28% decrease in anterior cortical choline acetyltransferase activity and a 20% decrease in synaptophysin immunoreactivity in the neocortex that was stable over a 12-month period. Neither neuritic plaque nor neurofibrillary-tanglelike structures were found in the brains of 18-month-old control rats, nor were they found in NBm-lesioned rats examined 15 months postlesion. There was an age-related decrease in homovanillic acid levels in both control and NBm groups, which suggests a decrease in dopamine turnover. These results show a lack of biochemical and behavioral recovery after NBm lesion and suggest that the effects of age on behavior are independent of NBm-cortical dysfunction.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1992

Age-related changes in radial-arm maze learning and basal forebrain cholinergic systems in senescence accelerated mice (SAM).

Age-related changes in learning performance and the brain cholinergic system were studied in a senescence accelerated mice-prone series (SAM-P/8) and a senescence accelerated mice-resistant series (SAM-R/1, control) bred under specific pathogen-free conditions. In a radial-arm maze task, SAM-P/8 mice at 4 and 12 months of age showed virtually no significant impairment in working memory or reference memory compared with SAM-R/1 mice at the same age, although they needed more time to complete a trial than SAM-R/1. In contrast, in a passive avoidance task, SAM-P/8 showed a marked age-accelerated deficit in acquisition performance relative to SAM-R/1. Also, SAM-P/8 showed an age-accelerated decrease in locomotion and rearing in an open-field box. At the end of these behavioral tasks, neurochemical analyses showed that there were no differences in the concentrations of acetylcholine (ACh) in the cortex, hippocampus, striatum, midbrain, or cerebellum between SAM-P/8 and SAM-R/1. Although SAM-P/8 mice did not demonstrate any age-accelerated decline in radial-arm maze performance, they showed a normal age-related decline particularly in working memory, equal to that observed in SAM-R/1. Also, ACh levels in the aged groups of SAM-P/8 showed a significant decrease related to normal aging in the hippocampus and striatum, and a slight decrease in the cortex compared to the young group of the same strain. Thus, we found that SAM-P/8 show dissociative effects of aging in spatial learning and passive avoidance performance.

Aging↗
PubMed1994

Effects of amphetamine and medial septal lesions on acquisition and retention of radial maze learning in rats.

Procholinergic drugs have failed to overcome the memory deficit induced by alterations of the cholinergic system because their neurochemical target in the brain is either lacking or disorganised. However, there are many reports on a relative involvement of the dopaminergic system in learning and memory that may compensate for the cholinergic deficit because of the interaction or balance between neurotransmitters and the redundancy of the brain. The aim of our experiments is to examine the activation of the dopaminergic system on the performance of normal and medial septal lesioned rats in the radial maze test involving continuous choices. In the first experiment different groups of normal rats were treated with either 0.5, 1.0 or 2.0 mg/kg of D-amphetamine and tested in the radial maze. In the second experiment, medial septal lesioned rats which had learnt pre-op the radial maze test were retested a month later. Amphetamine had no effect on the memory measures provided by the radial maze test in normal and lesioned rats, but non-memory measures were significantly affected: amphetamine decreased the sequential choice responses and the time taken by the rats to perform the test. The present results show that the activation of the dopaminergic system does not compensate for the alteration of the cholinergic activity inducing amnesia, however, they support the recent data on the improving effect of amphetamine on locomotor activity. The interpretation of drug/lesion interaction effects is discussed in this paper in relation to the literature on the effect of promnesic drugs.

Amphetamine↗
PubMed1991

Radial maze learning deficits and mediodorsal thalamic damage in context of multifocal seizure-induced brain lesions.

Rats were either trained 21 days after seizure induction or trained before seizure induction and tested 21 days later. The seizures, which induce insidious brain damage within a multitude of diencephalic and subcortical telencephalic structures, were induced by a single injection of lithium (3 mEq/kg sc) followed 24 hr later by pilocarpine (30 mg/kg sc). Compared with controls, the treated rats displayed significant deficits in the acquisition and recall of a radial maze task. Although there was multifocal brain damage, only the amount of damage within the mediodorsal thalamic group was significantly and strongly correlated (rho = .79) with numbers of errors.

Analysis of Variance↗
PubMed2001

The effect of L-carnitine on T-maze learning ability in aged rats.

L-carnitine is of considerable interest because of its capacity to counteract several physiological and pathological phenomena typical of brain aging processes. We examined the effects of L-carnitine on the learning ability of old rats. 100 mg/kg per body weight per day L-carnitine was administered orally to old (21 months) male Sprague-Dawley rats (OLD-CAR) for a period of 2 months. Old (21 months, OLD-CO) and young (7 months, YG-CO) control animals received tap water exclusively. Performance of the OLD-CAR and OLD-CO was compared with that of YG-CO in a multiple T-maze. The mean run time values showed a significant (P=0.01) difference of the OLD-CAR rats to the OLD-CO but no significant differences between OLD-CAR and YG-CO. For the T-maze parameter mean correct responses we were able to demonstrate that L-carnitine treated old rats made significantly (P=0.03) less errors and significantly (P=0.01) more animals reached the T-maze goal compared with OLD-CO but no significant differences were observed between OLD-CAR and YG-CO. The results of the present study clearly demonstrate that carnitine treatment improves the learning ability of old rats and seems to be able to reduce the loss of cognitive functions that occur with aging.

Journal Article↗
PubMed1988

Greater efficacy of preweaning than postweaning environmental enrichment on maze learning in adult rats.

In order to assess the behavioural effects of environmental stimulation at different stages of development, two groups of rats were exposed to multisensory enrichment on days 10-24 (preweaning) or 25-39 (postweaning). Both groups had four 25-min sessions per day in a large cage with a variety of stimuli, in addition to 3 min of handling before each session. The mother of the preweaning group remained in the home cage during the stimulation sessions. A third group was maintained in a social condition. Testing in a Hebb-Williams maze started when the rats of the 3 groups were 100 days old. Error, latency and running time scores were lowest in the preweaning group.

Aging↗
PubMed1991

Transplantation of ventral forebrain cholinergic neurons to the hippocampus ameliorates impairment of radial-arm maze learning in rats with AF64A treatment.

Two types of cholinergic neurons were transplanted into the hippoccampus of adult rats chemically damaged by lateral ventricular administration of AF64A, a cholinergic neurotoxin, and the effects were compared with respect to their ability to reinnervate the hippocampus and to repair behavioral deficit. Pieces of brain tissue containing the nucleus basalis magnocellularis (NBM) or the striatum were taken for grafting from 17-day rat fetuses. About 3 months after transplantation, the rats with bilateral NBM grafts showed significant amelioration in radial-arm maze performance and habituation to a novel environment in an open field box, although they had not recovered to the control level. In rats with NBM grafts that showed a good performance, there were surviving grafts and many ingrowths of AChE-positive fibers in the hippocampus. By contrast, rats with striatal grafts showed hardly any significant improvement in these behavioral measures. The AChE staining revealed poor outgrowth of the striatal grafts into the hippocampus. These results indicate that grafting of NBM cholinergic neurons, which are anatomically similar to septal neurons, into the hippocampus produces a partial restorative effect on the cognitive impairment associated with hypofunction of the septohippocampal system.

Analysis of Variance↗
PubMedDate not supplied

Dose-response effects of prenatal phenytoin exposure in rats: effects on early locomotion, maze learning, and memory as a function of phenytoin-induced circling behavior.

Pregnant Sprague-Dawley CD rats were administered 0, 100, or 200 mg/kg of phenytoin on days E7-18. Litters were reduced to 12, balancing for sex. Mean (+/- S.E.) maternal serum concentrations of total phenytoin 1 hr after dosing on E18 were 15.1 +/- 3.1 and 20.9 +/- 4.3 micrograms/ml in the PHT-100 and PHT-200 groups, respectively. Determinations of unbound concentrations revealed the drug to be 89% serum protein bound in both phenytoin groups. Maternal phenytoin concentrations in rats are, therefore, comparable to those seen therapeutically in humans with epilepsy. The PHT-200 group had elevated early postnatal mortality, while the PHT-100 group did not differ from controls. Phenytoin induced the typical dose-dependent increase in preweaning square-field locomotor activity. When this effect was compared to a new circular open field it was found that this device clearly distinguished phenytoin's effects. Phenytoin offspring also showed the typical dose-dependent abnormal circling behavior. Phenytoin offspring exhibited large dose-dependent increases in errors in a complex water maze, an effect which persisted even when rats exhibiting abnormal circling were excluded from the analyses. Offspring were also assessed for ability to locate a hidden vs. visible platform in an open swimming tank. Controls and PHT-100 offspring showed large improvements in performance when the hidden platform was made visible, but the PHT-200 offspring did not. Finally, offspring were assessed for working memory in an appetitive radial-arm maze. Both phenytoin groups exhibited impaired performance as measured by the number of reinforcements obtained in the first 8 arms visited.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗