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At least 505 records · Page 28Linked to original sources
PubMed1992

Early post-natal administration of 5,7-dihydroxytryptamine destroys 5-HT neurons but does not affect spatial memory.

The neurotransmitter serotonin (5-hydroxytryptamine, 5-HT) may play an important role in learning and memory. It has also been suggested that 5-HT abnormalities may mediate some aspects of the cognitive disorders associated with Korsakoff syndrome and Alzheimer's Disease. The effect of intracisternally applied 5-HT neurotoxin, 5,7-dihydroxytryptamine (5,7-DHT) on learning and memory in rodents was evaluated. Three-day-old rat pups were treated with pargyline (40 mg/kg, i.p.) followed by 5,7-DHT (50 micrograms/pup) and returned to the dam for a month. At 75 days of age, rats were tested on a learning set problem in the Morris water maze for 5 days followed by 30 days of testing in a 12-arm radial maze with 8 of the 12 arms baited. In the Morris water maze, the latency to locate the hidden platform did not differ significantly for 5,7-DHT treated and control rats (F less than 1.0). Similarly, 5,7-DHT treated rats performed comparably to controls on the 12-arm radial maze (F less than 1.0). At 106 days of age the assay of tryptophan hydroxylase activity in the dorsal raphe nuclei and hippocampus showed marked reduction (86%, 78%, respectively) in 5,7-DHT treated animals compared to vehicle injected controls. Immunocytochemical analysis was consistent with the biochemical results. In 5,7-DHT treated animals there was severe loss of neurons that bind 5-HT antibody in the dorsal and medial raphe nuclei.(ABSTRACT TRUNCATED AT 250 WORDS)

5,7-Dihydroxytryptamine↗
PubMed1984

Differential effects of frontal-lobe lesions on cognitive estimation and spatial memory.

Patients with unilateral frontal- or temporal-lobe excisions and normal control subjects were tested on the recall of objects and of their location in an array. An incidental-learning situation was used, in which the task was presented as a test of the ability to estimate the prices of the objects. Patients with right frontal-lobe lesions were the only group impaired on price estimation, but a correlation was obtained between error-score in price estimation and lesion-size for the left frontal-lobe group. In contrast to patients with extensive right hippocampal excisions, both frontal-lobe groups were accurate on location-recall when tested immediately and again 24 hr later.

Adolescent↗
PubMed1991

Spatial memory processing during hippocampal long-term potentiation in rats.

It was investigated in rats whether hippocampal long-term potentiation (LTP) influences working and/or reference memory processing in the radial maze. After preliminary training to an intermediate level of performance, experimental subjects received a series of high-frequency trains of electrical pulses applied to the right perforant path. Two control groups were adopted in order to control for possible effects of stimulation plus operation, and operation alone, respectively. Twenty-four hours after the experimental treatment, animals were administered one trial of radial maze training. This sequence of hippocampal stimulation and radial maze training was replicated 15 times. After a retention interval of 2 months, one radial maze trial was presented on each of 3 consecutive days. The analysis of field potential data showed that periodic LTP stimulation produced a state of hippocampal LTP confined to the initial portion of the acquisition phase. Evaluation of radial maze data revealed a marginal improvement of working memory performance in the experimental group during the rising phase of hippocampal LTP.

Animals↗
PubMed1994

A role for acetylcholine in spatial memory in turtles.

The present research was undertaken to determine whether acetylcholine plays a role in memory for a maze in turtles. Cholinergic cells have been observed in the basal forebrain of turtles, and the basal forebrain of turtles projects to the dorsal cortex, a region that has been implicated in associative function. In Experiment 1, turtles were trained on an X-maze for water reward and then given lesions of the dorsal cortex or basal forebrain or sham lesions and retested postoperatively on the maze. Both dorsal cortex and basal forebrain lesions impaired performance on the maze. In Experiment 2, turtles were trained on the maze and then given saline, scopolamine, or methylscopolamine on a 1-day retention test. Scopolamine in the higher doses impaired maze performance on the test day, but methylscopolamine did not. The highest dose of scopolamine had no effect on measures of general activity, showing that the effects of the drug were specific to the learned task.

Acetylcholine↗
PubMed1993

Effects of NBM lesions with two neurotoxins on spatial memory and autoshaping.

Four groups of Wistar rats received either vehicle, quisqualate, or one of two different ibotenic acid infusions into the basal forebrain. Following recovery from surgery, all rats were tested in three distinct behavioral paradigms: the Bättig radial arm maze, the Barnes circular platform, and autoshaping in an operant chamber. The results showed that the size and site of the ibotenic acid lesion had a profound effect on acquisition performance in some, but not all, procedures. Performance in the Bättig maze and acquisition of a food-rewarded lever press were in particular disrupted by ibotenic acid lesions. The severity of the reduction in cortical choline acetyltransferase (ChAT) did not correlate with performance in the tests. Quisqualate produced the largest reduction in ChAT levels but had no significant effect on performance in any of the three procedures used. Anatomic analysis revealed severe nonspecific damage to the striatum following ibotenic acid that was more pronounced in the group receiving a highly concentrated solution of ibotenic acid as compared to rats infused with a greater volume but less concentrated solution of the neurotoxin. Striatal damage was much less severe following quisqualic acid infusions. However, both types of neurotoxins produced equivalent nonspecific degeneration of the reticular thalamic nucleus. These data confirm reports that nonspecific damage appears to define the severity of ibotenic acid lesions on subsequent behavioral performance.

Animals↗
PubMed1996

Contribution of egocentric spatial memory to place navigation of rats in the Morris water maze.

Place navigation in the Morris water maze can be directed by memory of the target coordinates relative to remote landmarks (allocentric) or by the memory of the start-goal route (egocentric). When the start and goal positions remain constant and visual cues are eliminated by darkness, memory of the route may become decisive. This assumption was tested in 10 male hooded rats using an infrared television tracking system allowing navigation training in the dark. In Expt. 1, these animals were trained to swim in the dark from the start at the S rim of the pool to the goal position in the center of the NW quadrant of the pool. Mean escape latencies decreased from 47 s initially to 16 s during the 24 daily sessions. Another group of 10 male hooded rats learned the same task in the light. Mean escape latencies decreased from 20 s initially to 5 s during 4 daily sessions. In Expt. 2, possible allocentric location of the target was tested in the same rats by rotating both the start and goal positions by 90 degrees counterclockwise (i.e., to E-SW and later to N-SE). Mean escape latency during 5 days after the first rotation increased to 24 s, but returned back to the asymptotic level of 18 s after the second rotation. The same change of the start and goal position (from S-NW to E-SW) in the light only increased escape latency in the first session. In Expt. 3, both the goal position and route direction were changed to N-SW. Surprisingly, the animals rapidly acquired a new heading angle at the start and mean escape latencies were not significantly changed. It is concluded that overtrained place navigation in darkness can be easily changed to a new direction.

Animals↗
PubMedDate not supplied

Degeneration of hippocampal fibers and spatial memory deficit in the aged rat.

Old and young Fisher 344 rats were compared for their ability to learn a delayed alternation task. The old animals displayed significant impairment of alternation learning, and were slower than the young animals. The brains of these animals were examined using a silver degeneration stain, and among old rats there was conspicuous degeneration. The greatest density of degenerating fibers was seen in the hippocampus and in anatomically related tracts, but there was substantial fiber staining in the corpus callosum, anterior commissure, and internal capsule. Examination of the young brains revealed only an occasional fiber. There were no signs of cortical atrophy in the old animals. The histopathology of the aged animals' hippocampus and fiber tracts supports the possibility that the delayed alternation impairment shown by these animals was a result of age related degenerative changes.

Aging↗
PubMedDate not supplied

Age-related impairments in spatial memory are independent of those in sensorimotor skills.

Seventy-five aged rats were tested for a variety of motor and cognitive tests which generated 20 separate measures of performance. Considerable variability was observed on many measures in the aged population. Multivariate analyses were performed on the data to determine 1) the extent of intercorrelations between the measures for the aged rats, and 2) whether clusters of related and/or unrelated behavioral measures could be determined. Aged rats that were impaired on measures of cognitive performance are not necessarily impaired in their motor performance and vice versa. These results demonstrate that different age-related variables affect cognitive and motor systems, and suggest that age-related declines in different functional anatomical systems, such as the limbic system and the basal ganglia may progress independently.

Aging↗
PubMedDate not supplied

D-cycloserine, a novel cognitive enhancer, improves spatial memory in aged rats.

D-cycloserine, a partial agonist of the NMDA receptor-associated glycine site, can enhance cognition. The present experiment examines the behavioral effects of D-cycloserine on cognitive deficits in male Fischer-344 rats, 24 months old. Rats 24 months old (n = 42) received either vehicle or one of 3 doses of D-cycloserine prior to testing. Young rats, 4 months old (n = 13), received vehicle prior to testing. Place discrimination and repeated acquisition were tested in the water maze and a variety of sensorimotor tasks were given. Aging impaired performance in all tasks. D-cycloserine improved performance in place discrimination and repeated acquisition. No doses affected sensorimotor function. These results support the hypothesis that D-cycloserine has cognition enhancing properties and that it may be useful in treating disorders involving cognitive impairment.

Aging↗
PubMed1992

Increased expression of brain-derived neurotrophic factor mRNA in rat hippocampus is associated with improved spatial memory and enriched environment.

Enriched environment has been shown to enhance learning and memory and to induce morphological changes in the hippocampus. We report that rats housed in an enriched environment showed improved performance in the Morris water maze and decreased spontaneous motor activity. Exposure to behavioural tests increased expression of the mRNA that encodes brain-derived neurotrophic factor in the hippocampus. This was not seen when rats subjected to impoverished housing were tested suggesting that environmental history of the animal is of importance to induce expression of brain-derived neurotrophic factor in the hippocampus that may promote neuronal changes related to learning and memory.

Analysis of Variance↗
PubMed1993

Differential effects of dentate kindling on working and reference spatial memory in the rat.

An 8-arm radial maze was used to examine the effects of dentate kindling on the performance of a task which requires both working (short-term) and reference (long-term) memory. During the 4-week post-operative training period, control and experimental rats performed both components of the task equally well. Performance of the reference memory component, but not the working memory component of the task was significantly impaired during kindling stimulation. The impairment in reference memory appeared to be primarily due to the elicitation of afterdischarges, since the disruption in maze performance was evident in the pre-convulsive stages of kindling. Following the cessation of kindling stimulation, a gradual recovery in reference memory performance was observed. Dentate kindling may provide a useful model for the study of long-term memory deficits associated with temporal lobe epilepsy.

Animals↗
PubMed1996

Nerve growth factor and nootropic drug Cerebrolysin but not fibroblast growth factor can reduce spatial memory impairment elicited by fimbria-fornix transection: short-term study.

In an attempt to compare effects of different neurotrophic factors on impaired memory function, young adult naive rats were trained to find the hidden platform in the Morris water maze (3 consecutive days, eight trials/day). The fimbria-fornix was unilaterally removed by aspiration and nerve growth factor (NGF) (11 micrograms/ml and 0.5 microgram/ml; groups NGF and ngf, respectively) or basic fibroblast growth factor (bFGF) (0.2 microgram/ml, group FGF) were applied via intra-cerebroventricular infusion by the osmotic minipump (flow rate 0.5 microliter/h, 14 days). Nootropic drug Cerebrolysin (EBEWE Arzneitmittel; 2.5 ml/kg/day, group CER) was applied via intraperitoneal injection (14 days). One group was formed by the rats treated with NGF (11 micrograms/ml) and Cerebrolysin (group NGFCER). Non-lesioned and lesioned only rats served as controls (groups INT and LES). After a 14-day treatment, rats were tested using the retention test (1 day, four trials). On the next day, the rats were tested using transfer test (3 days, eight trials/day). Escape latency and length of trajectory was recorded. Groups NGF, ngf, FGF and LES were similarly impaired in their ability to retrieve the old position of the platform (retention test), as well as in their ability to navigate to the new position of the platform (transfer test). In the latter, NGF group significantly differed from lesioned animals. Groups CER and NGFCER were comparable to group INT in the retention or transfer test. It is concluded that anterograde amnesia elicited by fimbria-fornix lesion can be abbreviated by NGF and/or CER, while retrograde amnesia is absent only in rats treated by CER. No short-term influence of bFGF was found. It is suggested that biochemical systems other than the cholinergic one are involved.

Amino Acids↗
PubMed1996

Central administration of a nitric oxide synthase inhibitor impairs spatial memory in spontaneous hypertensive rats.

Nitric oxide is widely recognized as a putative retrograde messenger in the brain. We infused NG-monomethyl-L-arginine (L-NMMA; 25 mg/kg), an inhibitor of nitric oxide synthase (NOS), continuously for a week into the dorsal third ventricle (D3V) of spontaneous hypertensive rate (SHR) by an osmotic infusion pump. Rats administered with L-NMMA showed impaired performance of a radial arm maze task compared with control rats administered with saline. We observed significant reductions of the NOx level in the cerebrospinal fluid (CSF) of the rats administered with L-NMMA, but not in the control rats. Both groups showed no change in systolic blood pressure or serum NOx level. The results provide evidence of a more specific effect of NOS inhibition to the brain independent of alterations in the systemic hemodynamics.

Animals↗