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PubMed2003

Spatial memory impairment in OLETF rats without cholecystokinin - a receptor.

Cholecystokinin (CCK) is one of the most abundant neurotransmitter peptides in the brain. As Otsuka Long-Evans Tokushima Fatty (OLETF) rats lack CCK-A receptor because of a genetic abnormality, we examined whether learning and memory were impaired in these animals using both Morris water maze (MWM) and step-through type passive avoidance (PA) learning test. In the MWM test, memory impairment was observed in OLETF rats. The number of errors was also significantly higher, and that of the correct choices was significantly lower in OLETF rats compared to the controls [Long-Evans Tokushima Otsuka (LETO)] rats. In PA, OLETF rats did not show facilitating response 24 h after training. From these observations, we concluded that a spatial memory was impaired in the OLETF rats.

Animals↗
PubMed1988

Pre- and postnatal choline supplementation produces long-term facilitation of spatial memory.

Although research has demonstrated that short-term improvement in memory function of adult rats can occur when the availability of precursors for the neurotransmitter acetylcholine is increased, little is known about whether memory function of adult rats can be permanently altered by precursor supplementation during early development. In the present study, male albino rats were exposed to choline chloride supplementation both prenatally (through the diet of pregnant rats) and postnatally (subcutaneous injections). At 60 days of age rats were tested on a 12- and 18-arm radial maze task. Results indicated that compared to control littermates, perinatal choline-treated rats showed more accurate performance on both working and reference memory components of the task. This performance difference was apparent on the first block of sessions and continued throughout training. Further analysis revealed that the difference between choline and control rats is not due to use of differential response or cue-use strategies. Instead, it appears that choline induced performance differences are due to long-term enhancement of spatial memory capacity and precision.

Animals↗
PubMed2004

Allocentric and egocentric updating of spatial memories.

In 4 experiments, the authors investigated spatial updating in a familiar environment. Participants learned locations of objects in a room, walked to the center, and turned to appropriate facing directions before making judgments of relative direction (e.g., "Imagine you are standing at X and facing Y. Point to Z.") or egocentric pointing judgments (e.g., "You are facing Y. Point to Z."). Experiments manipulated the angular difference between the learning heading and the imagined heading and the angular difference between the actual heading and the imagined heading. Pointing performance was best when the imagined heading was parallel to the learning view, even when participants were facing in other directions, and when actual and imagined headings were the same. Room geometry did not affect these results. These findings indicated that spatial reference directions in memory were not updated during locomotion.

Female↗
PubMed2005

Repeated 2 Hz peripheral electrical stimulations suppress morphine-induced CPP and improve spatial memory ability in rats.

Our previous studies have shown that 2 Hz peripheral electrical stimulation (PES) can suppress morphine-induced conditioned place preference (CPP) in the rat, although the mechanisms remain unclear. Since CPP involves the mechanism of learning and memory, it is rational to ask whether the suppressive effect of repeated 2 Hz PES on morphine-induced CPP is due to an impairment of the function of spatial learning and memory. Rats were trained with 4 mg/kg morphine, i.p. for 4 days to establish the CPP. Twenty-four hours after the CPP testing, they were given PES at 2 Hz once a day for 1, 3 or 5 days, followed by another CPP testing. The results showed that (1) the morphine-induced CPP was significantly inhibited by 3 or 5 consecutive sessions, but not by single session of 2 Hz PES. (2) A test of spatial leaning and memory ability using the Morris water maze task revealed that 2 Hz PES per se exhibited a promoting, rather than a deteriorating effect on the ability of spatial memory. (3) 2 Hz PES by itself produced a moderate yet significant CPP. The results imply that (a) a low frequency PES can produce a rewarding effect as revealed by the CPP testing, which may account, at least in part, for its suppressive effect on morphine induced CPP, (b) the suppressive effect of PES on morphine induced CPP is not due to a deteriorating effect on the ability of spatial memory.

Animals↗
PubMed2001

Finding your way in the dark: the retrosplenial cortex contributes to spatial memory and navigation without visual cues.

Path integration is presumed to rely on self-motion cues to identify locations in space and is subject to cumulative error. The authors tested the hypothesis that rats use memory to reduce such errors and that the retrosplenial cortex contributes to this process. Rats were trained for 1 week to hoard food in an arena after beginning a trial from a fixed starting location; probe trials were then conducted in which they began a trial from a novel place in light or darkness. After control injections, rats searched around the training location, showing normal spatial memory. Inactivation of the retrosplenial cortex disrupted this search preference. To assess accuracy during navigation, rats were then trained to perform multiple trials daily, with a fixed or a different starting location in light or darkness. Retrosplenial cortex inactivation impaired accuracy in darkness. The retrosplenial cortex may provide mnemonic information, which decreases errors when navigating in the dark.

Animals↗
PubMed2005

Voluntary exercise rescues deficits in spatial memory and long-term potentiation in prenatal ethanol-exposed male rats.

Prenatal ethanol exposure can lead to long-lasting impairments in the ability to process spatial information in rats, as well as produce long-lasting deficits in the ability of animals to exhibit long-term potentiation, a biological model of learning and memory processing. Conversely, we have recently shown that both spatial memory and long-term potentiation can be enhanced in animals that are given access to a running wheel in their home cage. In the present study, Sprague-Dawley rat dams were given one of three diets throughout gestation: (i) a liquid diet containing ethanol (35.5% ethanol-derived calories); (ii) a liquid diet, isocaloric to the ethanol diet, but with maltose-dextrin substituting for the ethanol derived calories and (iii) an ad libitum diet of standard rat chow. At weaning (28 days) animals were housed individually in either a standard rat cage, or a cage that contained a running wheel. Adult offspring were tested on a two trial version of the Morris water maze beginning at postnatal day 60, for five consecutive days. Following this, the capacity of the perforant path to dentate gyrus pathway to sustain long-term potentiation was examined in these animals using theta-patterned conditioning stimuli. Our results demonstrate that prenatal ethanol exposure can produce pronounced deficits in both spatial memory and long-term potentiation, but that allowing animal's access to voluntary exercise can attenuate these deficits to the point that those exposed to ethanol prenatally can no longer be differentiated from control animals. These findings indicate that voluntary exercise may have therapeutic benefits for individuals that have undergone prenatal ethanol exposure.

Animals↗
PubMed2004

Injection of okadaic acid into the meynert nucleus basalis of rat brain induces decreased acetylcholine level and spatial memory deficit.

Abnormal hyperphosphorylation of tau and cholinergic deficit occur in the early stage of Alzheimer's disease (AD) and relate to the dementia symptom. Hyperphosphorylation of tau, neurofilament (NF) and other proteins in AD brain appears to be caused by a down-regulation of protein phosphatase 2A (PP2A), but the mechanism leading to cholinergic deficit is still unknown. In this study, we selectively inhibited PP2A by injection of okadaic acid (OA) into the Meynert nucleus basalis of rats. We found that injection of OA induced hyperphosphorylation of tau and NF and decreased acetylcholine (ACh) level in the nucleus basalis of Meynert. These alterations were accompanied by spatial memory deficit in OA-injected rats. We also demonstrated that the OA-induced ACh reduction may be due to a failure of intraneuronal transport of choline acetyltransferase (ChAT) from cell body to the neuronal terminals rather than an alteration of activity of ChAT or acetylcholinesterase. This study suggests that a down-regulation of PP2A may underlie both abnormal hyperphosphorylation of cytoskeletal proteins leading to neurofibrillary degeneration and cholinergic deficiency in AD.

Acetylcholine↗
PubMed1992

Amygdala kindling increased fear-response, but did not impair spatial memory in rats.

The behavioral effects of amygdala kindling, a model of experimental epilepsy in rats, are reported. The animals were stimulated twice a day until stage 5 (generalized clonic) seizures were obtained three times. Two weeks later the performance of the amygdala-kindled and sham-operated rats was tested in the open-field test, on the elevated plus maze, elevated bridges, and in the Morris water maze. The results show that amygdala kindling decreased exploratory and other motor activity in the open-field test, had anxiogenic effects on the elevated plus-maze, decreased boldness on the elevated bridges, but had a negligible affect in the spatial memory task. These results suggest that amygdala kindling affects the normal fear reaction of rats, a response that is known to be mediated through the amygdaloid pathways.

Amygdala↗
PubMed2003

Oxytocin improves long-lasting spatial memory during motherhood through MAP kinase cascade.

Oxytocin is an essential hormone for mammalian labor and lactation. Here, we show a new function of oxytocin in causing plastic changes in hippocampal synapses during motherhood. In oxytocin-perfused hippocampal slices, one-train tetanus stimulation induced long-lasting, long-term potentiation (L-LTP) and phosphorylation of cyclic AMP-responsive element binding protein (CREB), and MAP kinase inhibitors blocked these inductions. An increase in CREB phosphorylation and L-LTP induced by one-train tetanus were observed in the multiparous mouse hippocampus without oxytocin application. Furthermore, intracerebroventricular injection of oxytocin in virgin mice improved long-term spatial learning in vivo, whereas an injection of oxytocin antagonist in multiparous mice significantly inhibited the improved spatial memory, L-LTP and CREB phosphorylation. These findings indicate that oxytocin is critically involved in improving hippocampus-dependent learning and memory during motherhood in mice.

Animals↗
PubMed2002

Impairment of hippocampal CA1 heterosynaptic transformation and spatial memory by beta-amyloid(25-35).

In Alzheimer's disease, the cholinergic damage (reduced neurotransmission) and cognitive impairment occur long before beta-amyloid (Abeta) plaque formation. It has not been established whether the link between soluble Abeta and cholinergic functions contributes to synaptic dysfunction that underlies the cognitive impairment. Here, we report that Abeta(25-35), an active form of Abeta, inhibited long-term synaptic modification that depends on the associative activation of cholinergic and GABAergic inputs when bilaterally injected intracerebroventricularly (icv; 200 microg/site). The Abeta microinjections did not affect single-pulse-evoked glutamatergic and GABAergic synaptic transmission onto the hippocampal CA1 pyramidal cells, while cholinergic intracellular theta; was dramatically reduced by the Abeta(25-35) injection. Spatial memory of the water maze task was also impaired by the bilateral icv Abeta(25-35) injections, while bilateral microinjections of the same dose of Abeta(35-25) was ineffective in affecting the long-term synaptic modification evoked by associative activation of cholinergic and GABAergic inputs, the cholinergic intracellular theta;, or producing memory impairments. Thus restoring the synaptic plasticity involved in this associative activation of cholinergic and GABAergic inputs may offer an important therapeutic target in the treatment of early Abeta-induced memory decline.

Amyloid beta-Peptides↗
PubMed2002

Selective immunolesions of CH4 cholinergic neurons do not disrupt spatial memory in rats.

Adult male Long-Evans rats were subjected to bilateral lesions of the cholinergic neurons in the nucleus basalis magnocellularis (NBM) by injection of 0.2 or 0.4 microg 192-IgG-saporin in 0.4 microl phosphate-buffered saline. Control rats received an equivalent amount of phosphate-buffered saline. Starting 2 weeks after surgery, all rats were tested for locomotor activity in their home cage, beam-walking performance, T-maze alternation rates (working memory), reference and working memory performance in a water-maze task, and memory capabilities in the eight-arm radial maze task using uninterrupted and interrupted (delay of 2 min, 2 h and 6 h after four arms had been visited) testing procedures. Histochemical analysis showed a significant decrease of acetylcholinesterase (AChE)-positive reaction products (30-66%) in various cortical regions at the 0.2-microg dose. At the dose of 0.4 microg, there was an additional, although weak, damage to the hippocampus (17-30%) and the cingulate cortex (34%). The behavioral results showed only minor impairments in spatial memory tasks, and only during initial phases of the tests (reference memory in the water maze, working memory in the radial maze). The behavioral effects of the dramatic cholinergic lesions do not support the idea of a substantial implication of cholinergic projections from the NBM to the cortex in the memory processes assessed in this study, but they remain congruent with an involvement of these projections in attentional functions.

Acetylcholinesterase↗
PubMed2000

The effect of steroid sulfatase inhibition on learning and spatial memory.

Steroid sulfatase inhibitors can enhance the concentration of the neurosteroid DHEAS in rat brain. Previous studies have demonstrated that the steroid sulfatase inhibitor (p-O-sulfamoyl)-N-tetradecanoyl tyramine (DU-14) could reverse scopolamine induced amnesia in rats in a passive avoidance memory paradigm. The intent of this study was to determine whether chronic pretreatment with DU-14 could reverse scopolamine amnesia and/or enhance spacial memory in the place, probe and cued versions of the Morris water maze (MWM). Rats were divided into four groups and administered IP for 15 days either DU-14 (30.0 mg/Kg) or corn oil (1.0 ml/Kg) vehicle. On training days animals were administered either scopolamine (1.0 mg/Kg) or saline (1.0 ml/Kg). The groups administered DU-14 displayed a significant enhancement in learning and spacial memory in the place version of the MWM, when compared to respective vehicle-scopolamine and vehicle-saline groups. In the probe version, the DU-14-saline group remained in the target quadrant of the maze significantly longer than any of the other groups indicating enhanced retention. In the cued version of the MWM, treatment with DU-14 did not significantly change escape latency suggesting that the steroid sulfatase inhibitor did not alter motivation or locomotion. These results suggest that the chronic administration of steroid sulfatase inhibitors enhance learning and spatial memory in rats.

Amnesia↗
PubMed1996

Retroactive interference effects of surprising reward omission on serial spatial memory.

Reward omission was used to produce retroactive interference in a serial delayed-alternation task. Rats were given forced choices in 3 T mazes presented in succession followed by free choices in which the alternate arm in each maze was rewarded. Nonreward during the delay between forced- and free-choice runs produced a decrement in performance (i.e., retroactive interference) in comparison to reward during the delay. Interference in retention of the first maze in a list occurred when the second maze contained surprising reward or omission (i.e., an outcome contrary to previous training in that maze) in comparison to expected reward or omission. In addition to producing retroactive interference, omission sometimes increased alternation in the maze in which it occurred. These results support a differential rehearsal hypothesis of spatial memory.

Animals↗
PubMed2005

Testosterone improves spatial memory in men with Alzheimer disease and mild cognitive impairment.

OBJECTIVE: To determine the efficacy of testosterone (T) supplementation on cognition in a sample of men with Alzheimer disease (AD) or mild cognitive impairment (MCI). METHODS: Fifteen patients with AD and 17 patients with MCI aged 63 to 85 years completed a randomized, double-blind, placebo-controlled study. Nineteen participants received weekly intramuscular (IM) injections of 100 mg T enanthate and 13 participants received weekly injections of placebo (saline) for 6 weeks. Cognitive evaluations using a battery of neuropsychological tests were conducted at baseline, week 3, and week 6 of treatment and again after 6 weeks of washout. RESULTS: Peak serum total T levels were raised from baseline an average of 295% in the active treatment group. Improvements in spatial memory (p < 0.05) and constructional abilities (p < 0.05) and verbal memory were evident in the T group. No changes were noted for selective and divided attention or language. Prostate specific antigen did not significantly change during this brief treatment. CONCLUSION: Testosterone supplementation may benefit selective cognitive functions in men with Alzheimer disease and mild cognitive impairment.

Aged↗
PubMed2005

Effect of atorvastatin on spatial memory, neuronal survival, and vascular density in female rats after traumatic brain injury.

OBJECT: Atorvastatin administered after traumatic brain injury (TBI) induced by controlled cortical impact promotes functional improvement in male rats. Note, however, that parallel studies have not been performed in female rats. Therefore, the authors tested the effect of atorvastatin on TBI in female rats. METHODS: Atorvastatin (1 mg/kg/day) was orally administered for 7 consecutive days in female Wistar rats starting I day after TBI; control animals received saline. Modified neurological severity scores, the corner turn test, and the Morris water maze test were used to evaluate functional response to treatment. Rats were killed on Day 15 post-TBI, and brain tissue samples were processed for immunohistochemical staining. Atorvastatin administration after brain injury significantly promoted the restoration of spatial memory but did not reduce sensorimotor functional deficits. Treatment of TBI with atorvastatin increased neuronal survival in the CA3 region and the lesion boundary zone and prevented the loss of neuronal processes of damaged neurons in the hippocampal CA3 region but not in the lesion boundary zone on Day 15 after TBI. The protective effect of atorvastatin on the injured neurons perhaps is mediated by increasing the density of vessels in the lesion boundary zone and the hippocampus after TBI. CONCLUSIONS: . These data indicate that atorvastatin is beneficial in the treatment of TBI in female rats, although the effect may differ between sexes.

Administration, Oral↗
PubMed2003

Integrin requirement for hippocampal synaptic plasticity and spatial memory.

The establishment of memory requires coordinated signaling between presynaptic and postsynaptic terminals in the CNS. The integrins make up a large family of cell adhesion receptors that are known to mediate bidirectional signaling between cells or between cells and their external environment. We show here that many different integrins, including alpha3 and alpha5, are expressed broadly in the adult mouse brain and are associated with synapses. Mice with genetically reduced expression of alpha3 integrin fail to maintain long-term potentiation (LTP) generated in hippocampal CA1 neurons. Mice with reduced expression of the alpha3 and alpha5 integrins exhibit a defect in paired-pulse facilitation. Mice with reduced expression of alpha3, alpha5, and alpha8 are defective in hippocampal LTP and spatial memory in the water maze but have normal fear conditioning. These results demonstrate that several different integrins are involved in physiological plasticity and provide the first evidence of their requirement for behavioral plasticity in vertebrates.

Animals↗
PubMed1984

The effect of hypothermia on the rat's spatial memory in the water tank task.

The effect of hypothermia on the retention of the water tank navigation task has been examined in 21 male hooded rats. After a 3-min swimming test on Day 1 the animals were trained on Days 2 and 3 (2 X 12 trials) to find a small submerged platform 1 cm below the surface of a large pool (120 cm in diameter) of opaque water. On Day 4, the rats were divided into three groups (n = 7) which were cooled to colonic temperatures of 22-24 degrees C (H1), 25-27 degrees C (H2), and 28-31 degrees C (H3), respectively, and given 12 retrieval trials in the water tank. Average escape latencies increased from 6 s in normothermic rats on Day 3 to 33, 19, and 12 s on Day 4 in the H1, H2, and H3 groups, respectively. Under the same testing conditions the performance of groups H1, H2, and H3 improved on Day 5 to 20, 8 and 6 s, respectively. It is concluded that spatial memory retrieval is resistant to mild hypothermia (30 degrees C), but that it is severely impaired at body temperatures below 25 degrees C. Reacquisition of the task is slowed down but not fully prevented in deep hypothermia.

Animals↗
PubMed2004

Executive function is less sensitive to estradiol than spatial memory: performance on an analog of the card sorting test in ovariectomized aged rhesus monkeys.

Functions supported by the frontal lobes are particularly sensitive to the detrimental effects of aging. Recent studies on postmenopausal women find that estrogen replacement therapy benefits performance on tasks dependent on the frontal lobes. To determine whether estrogen has a similar influence in a rhesus monkey model of menopause, we tested five aged, long-term ovariectomized rhesus monkeys in a modified version of the Wisconsin Card Sort test which had been adapted to the nonhuman primate. In this test, monkeys had to select 3-D objects based either on color (blue, red, yellow) or shape (block, tube, cup) and had to be able to switch their response as a function of reinforcement contingencies. The monkeys were treated with placebo and ethinyl estradiol (EE2, 450 ng/kg/day) in alternation with each successive test. Contrary to our hypothesis, estradiol treatment did not affect performance. Because previous studies in the same monkeys [Neurobiol. Aging 23 (2002) 589] had shown that EE2 improves performance on a spatial memory task dependent on the hippocampus, but not on another task dependent upon the frontal lobes (the delayed response), we conclude that executive processes may be less sensitive to the effects of estradiol than hippocampal-dependent tasks.

Age Factors↗