Memory In Adult Male Rats Research Articles

Altered norepinephrine transmission after spatial learning impairs sleep-mediated memory consolidation in rats

The therapeutic use of noradrenergic drugs makes the evaluation of their effects on cognition of high priority. Norepinephrine (NE) is an important neuromodulator for a variety of cognitive processes and may importantly contribute to sleep-mediated memory consolidation. The NE transmission fluctuates with the behavioral and/or brain state and influences associated neural activity. Here, we assessed the effects of altered NE transmission after learning of a hippocampal-dependent task on neural activity and spatial memory in adult male rats. We administered clonidine (0.05 mg/kg, i.p.; n = 12 rats) or propranolol (10 mg/kg, i.p.; n = 11) after each of seven daily learning sessions on an 8-arm radial maze. Compared to the saline group (n = 9), the drug-treated rats showed lower learning rates. To assess the effects of drugs on cortical and hippocampal activity, we recorded prefrontal EEG and local field potentials from the CA1 subfield of the dorsal hippocampus for 2 h after each learning session or drug administration. Both drugs significantly reduced the number of hippocampal ripples for at least 2 h. An EEG-based sleep scoring revealed that clonidine made the sleep onset faster while prolonging quiet wakefulness. Propranolol increased active wakefulness at the expense of non-rapid eye movement (NREM) sleep. Clonidine reduced the occurrence of slow oscillations (SO) and sleep spindles during NREM sleep and altered the temporal coupling between SO and sleep spindles. Thus, pharmacological alteration of NE transmission produced a suboptimal brain state for memory consolidation. Our results suggest that the post-learning NE contributes to the efficiency of hippocampal-cortical communication underlying memory consolidation.

Comparison of Alphapinene and Donpezil Effects on Passive Avoidance Memory in Adult Male Rats

Comparison of Alphapinene and Donpezil Effects on Passive Avoidance Memory in Adult Male Rats

A Single High Dose of Methamphetamine Reduces Monoamines and Impairs Egocentric and Allocentric Learning and Memory in Adult Male Rats.

Methamphetamine (MA) alters dopamine markers and cognitive function in heavy users. In rodents, there are MA dosing regimens that induce concordant effects using repeated administration at spaced intervals. These regimens are effective but complicate experiments designed to disentangle the effects of the drug on different brain regions in relation to their cognitive effects because of treatment spacing. In an effort to simplify the model, we tested whether a single dose of MA could induce the same monoamine and cognitive effects as multiple, spaced dosing without affecting survival. Adult male Sprague-Dawley rats were treated with 40mg/kg MA subcutaneously once and tested starting 2weeks later. MA-treated rats showed deficits in egocentric navigation in Cincinnati water maze, in spatial navigation in the Morris water maze, and in choosing a consistent problem-solving strategy in the Star water maze when given the option to show a preference. MA-treated rats had persistent dopamine and serotonin reductions in the neostriatum and nucleus accumbens, and serotonin reductions in the hippocampus of the same magnitude as in repetitive treatment models. The data demonstrate that a single dose recapitulates the neurocognitive and monoamine effects of multiple-dose regimens, thereby simplifying the model of MA-induced neurotoxicity.

Effects of Euterpe oleracea on learning and memory in adult male rats

Effects of Euterpe oleracea on learning and memory in adult male rats

The Association Between Effective Dose of Magnesium and Mild Compulsive Exercise on Spatial Learning, Memory, and Motor Activity of Adult Male Rats

One of the most important survival mechanisms is learning and memory processes. To emphasize the role of physical exercises and magnesium (Mg) in improvement of cognitive performance, we planned to investigate the effect of Mg and mild compulsive exercise on spatial learning and memory of adult male rats. Accordingly, we divided male Wistar rats into four groups: (I) control, (II) Mg treatment, (III) exercise, and (IV) Mg-exercise in the different dosages of Mg (0.5, 1, 1.5, and 2mmol/kbw) were injected in the form of gavage during 1week. Also, 1-week mild running on treadmill was used for exercise treatment. The Morris water maze (MWM) test and open field tool were used to evaluate spatial learning, memory, and motor activity, respectively. Our results clearly showed that 1mmol/kbw Mg was applied as an effective dosage. Strikingly, 1-week mild exercise on treadmill had no significant effect on spatial motor activity, learning, and memory. Feeding 1mmol/kbw Mg for a week showed a significant difference in learning and exploration stages. Compared to control animals, these results reveal exercise and Mg simultaneously had effect on learning and reminding. As a consequence, although mild exercise had no effect on motor activity and memory, Mg intake improved spatial learning, memory, and locomotor activity. The Mg feeding could be a promising supplemental treatment in the neurodegenerative disease. It is worthwhile to mention consumption of Mg leads to enhancement of memory, so animals find the hidden platform with the highest velocity.

Effects of cafeteria diet and high fat diet intake on anxiety, learning and memory in adult male rats

Objective: The effects of cafeteria and high fat diets were investigated on animal models of behavior.Methods: Male Wistar rats were treated with Control (C), Cafeteria (CD) and High Fat (FD) diets and tested in the Elevated Plus-Maze (EPM) and Morris Water Maze (MWM) procedures. Body weight, length, abdominal circumference, retroperitoneal and epididymal adipose tissues were recorded. Physical parameters, weight of tissues, EPM, and MWM data were subjected to ANOVA followed by Newman–Keuls test (P < 0.05).Results: There were no differences on weight and length parameters between CD and C rats up to 98 days of age. However, abdominal circumferences were higher in CD as compared to C at 35 and 70 days of age, respectively, the 5th and the 7th weeks. FD presented lower measures of weight and abdominal circumference; nevertheless there was an increase on those parameters at the end of the nutritional treatment. Even without an apparent weight gain of CD and FD these animals presented a greater accumulation of retroperitoneal and epididymal adipose tissues. In addition, CD and FD demonstrated behaviors that can suggest lower anxiety. CD showed a better learning performance and FD showed better recall of previous learned information in the memory retention test.Discussion: According to those data it was concluded that hypercaloric diet ingestion was capable of triggering metabolic alterations and possibly lowering anxiety associated to learning or memory improvement on a spatial task.

The effect of intra-nucleus accumbens shell injection of ascorbic acid on spatial learning and memory in adult male rats

The effect of intra-nucleus accumbens shell injection of ascorbic acid on spatial learning and memory in adult male rats

The effect of nigella sativa extract on learning and spatial memory of adult male rats

The effect of nigella sativa extract on learning and spatial memory of adult male rats

3α-diol administration decreases hippocampal PKA (II) mRNA expression and impairs Morris water maze performance in adult male rats

The effect of testosterone and its metabolites on learning and memory has been the subject of many studies. This study used the Morris water maze task to investigate the effect of intra-hippocampal injection of 3α-diol (one of the metabolites of testosterone) on acquisition stage of spatial memory in adult male rats. During the experiment we observed that 3α-diol, significantly impaired Morris water maze performance in treated rat's compared with controls. Because signaling event mediated by protein kinase A (PKA) especially PKA (II) are critical for many neuronal functions such as learning and memory, the hippocampus was analyzed for mRNA expression of PKA (II) using TaqMan real time RT-PCR. The results indicated that the transcription levels of PKA (II) were significantly decreased in animals treated with 3α-diol compared with controls. Thus, the findings suggest that administration of 3α-diol in hippocampus of adult male rats impairs memory function, possibly via down-regulation of PKA.

Central interaction of ascorbic acid and D2 dopamine receptors on spatial learning and memory in adult male rats

Previous studies had reported that extracellular levels of ascorbic acid have modulatory effects on dopamine receptors. Both ascorbic acid and dopamine receptor have an important role in learning and memory processes. However, the central interaction between ascorbic acid and dopamine D2 receptor on spatial learning and memory has not yet been elucidated. All experiments were carried out on male Wistar rats. Animals were subjected to 5 days of training in the Morris water maze (MWM) task; 4 days with an invisible platform to test special learning and the 5th day with a visible platform to test motivation and sensorimotor coordination. The data showed that ascorbic acid (25 µg, i.c.v.) could improve spatial learning and memory indices. Administration of bromocriptine, a D2 agonist, increased the effect of ascorbic acid, while treatment with the selective D2 antagonist sulpiride resulted in prevention of the ascorbate-induced memory consolidation. These results indicate that dopamine D2 receptors may be involved in ascorbic acid-induced learning and memory impairment.

The effect of omega-3 on cognition in hypothyroid adult male rats.

Thyroid hormones and omega-3 are essential for normal brain functions. Recent studies have suggested that omega-3 may protect against the risk of dementia. The aim of this study was to investigate the effect of hypothyroidism on spatial learning and memory in adult male rats, the underlying mechanisms and the possible therapeutic value of omega-3 supplementation. Thirty male rats were divided into three groups; control, hypothyroid and omega-3 treated. Hypothyroidism induced significant deficits in working and reference memories in radial arm maze, retention deficits in passive avoidance test and impaired intermediate and long-term memories in novel object recognition test. Serum total antioxidant capacity (TAC) and hippocampal serotonin and γ-aminobutyric acid (GABA) levels were decreased in the hypothyroid group as compared to the control group. Moreover, the hippocampus of hypothyroid rats showed marked structural changes as diffuse vacuolar degeneration and distortion of the pyramidal cells. Immunohistochemistry showed that the expression of Cav1.2 (the voltage dependent LTCC alpha 1c subunit) protein was increased in the hypothyroid group as compared to the control group. Omega-3 supplementation ameliorated memory deficits, increased TAC, decreased the structural changes and decreased the expression of Cav1.2 protein. In conclusion omega-3 could be useful as a neuroprotective agent against hypothyroidism-induced cognitive impairment.

Early deprivation reduced anxiety and enhanced memory in adult male rats.

The effects of early deprivation (ED, which involves both dam and littermate deprivation) on anxiety and memory are less investigated in comparison with maternal separation (MS), and it is not yet clear how ED affects long-term potentiation (LTP) in the hippocampal Schaffer collateral pathway. By using a series of behavioral tests, enzyme-linked immunosorbent assay and field potential recording, we explored the effect of pre-weaning daily 3-h ED on anxiety, memory and potential mechanisms in adult male rats. Compared with control, ED rats spent longer time in open arms of elevated plus maze and in light compartment of light-dark transition box. Consistently, stress-induced blood plasma corticosterone level was also lower in ED rats. Moreover, ED rats showed better performance in social recognition and Morris water maze test. In accordance with results in memory tests, the threshold of LTP induction in hippocampal CA3-CA1 pathway of ED rats was also reduced. Our results indicate ED reduced anxiety, but enhanced social recognition and spatial reference memory. We suggest the diminished hypothalamic-pituitary-adrenal axis response and facilitated hippocampal LTP may contribute to the anxiety-reducing and memory-enhancing effects of ED, respectively.

Effect of administration of ascorbic acid and dopamine D2 receptors agonist in the hippocampal CA1 area on spatial learning and memory in adult male rats

Summary Previous studies have shown that ascorbic acid (AA) plays a crucial role in mammalian brain as a vitamin and neuronal modulator. There is increasing evidence indicating that dopaminergic system and AA could affect learning and memory processes. In addition, vitamin C acts as a dopamine antagonist in the brain. The aim of the present study was to evaluate the intra-hippocampal co-administration of AA and bromocriptine (Br), a dopamine D2 receptor agonist, on spatial memory and learning. Adult male rats were trained in Morris Water Maze task. Intra-hippocampal injection was performed through an implanted cannula in the CA1 region. Animals were divided into 12 experimental groups (n=7) including: control, AA (6, 12, 24 and 48 µg/rat), Br (0.5, 1, 2 and 2.5 µg/rat), AA plus Br (24 and 2 µg/rat), AA and Br related sham. The results showed that injection of AA caused a significant decrease in both learning and spatial memory. However, administration of Br alone or concomitant with AA caused a significant increase in learning and spatial memory as compared to the control and AA groups. These findings indicate that AA could attenuate the effects of D2 dopamine receptors agonist on spatial memory and learning.

The Effect of Opium Dependency of Parent (s) on Offspring's Spatial Learning & Memory in Adult Male Rats.

As far as we know, there has been no report regarding the effects of opium addiction or dependency of both parents on the learning and memory process in offspring. The aim of this study was to examine the learning and memory changes of adult male offspring whose mothers, fathers and/or both parents had dependency to opium before and during pregnancy. Materials and Methods : All experiments were carried out on Wistar rats. Opium dependency was induced by daily injections of opium (10 mg/kg/SC, bid/10 d) before mating. The presence of a vaginal plug was designated as gestation day. Treatment with opium continued through breeding and gestation until parturition. Spatial memory was tested in male offspring of control, saline and prenatal opium treated groups by a training trial and the probe test in the Morris water maze. Swimming escape latency in the maze and the ability to find the platform in the training trial were recorded. The time spent in the trigger zone and number of times the rats crossed the platform during the probe phase and swimming speed were measured. The data revealed increased escape latency and a greater distance traveled to find the hidden platform in the offspring's whose mother, father and /or both parents were exposed to opium. Crossings to target quadrant at probe trials was significantly reduced in all of the prenatal opium exposed offsprings. The swimming speed showed a significant increase in father and parent's opium exposed offspring. Prenatal opium exposure of either parent may cause deficits in spatial learning, but the precise mechanism(s) remain largely unknown.

Intrahippocampal Injection of 3α Diol (a Testosterone Metabolite ) and Indomethacin (3α-HSD Blocker), Impair Acquisition of Spatial Learning and Memory in Adult Male Rats.

Hippocampus is essentially involved in learning and memory processes, and is known to be a target for androgen actions. The high density of the androgen receptors in hippocampus shows that there must be some relationship between androgens and memory. Androgen effects on spatial memory are complex and contradictory. Some evidence suggests a positive correlation between androgens and spatial memory. While some other reports indicated an impairment effect. The present study was conducted to assess the effect of 3α diol on spatial discrimination of rats. Adult male rats were bilaterally cannulated into CA1 region of hippocampus and then received 3α diol (0.2, 1, 3 and 6 μg/ 0.5 μL/side), indomethacin (1.5, 3 and 6 μg/ 0.5 μL/side), indomethacin (3 μg/ 0.5 μL/side) + 3α diol (1μg/ 0.5 μL/side), 25-35 min before training in Morris Water Maze task. Our results showed that injection of 3α diol (1, 3 and 6 μg/ 0.5 μL/ side) and indomethacin (3 and 6 μg/ 0.5 μL/side) significantly increased the escape latency and traveled distance to find hidden platform. It is concluded that intra CA1 administration of 3α diol and indomethacin could impair spatial learning and memory in acquisition stage. However, intra hippocampal injection of indomethacin plus 3α diol could not change spatial learning and memory impairment effect of indomethacin or 3α diol in Morris Water Maze task.

The role of testicular hormones and luteinizing hormone in spatial memory in adult male rats

Attempts to determine the influence of testicular hormones on learning and memory in males have yielded contradictory results. The present studies examined whether testicular hormones are important for maximal levels of spatial memory in young adult male rats. To minimize any effect of stress, we used the Object Location Task which is a spatial working memory task that does not involve food or water deprivation or aversive stimuli for motivation. In Experiment 1 sham gonadectomized male rats demonstrated robust spatial memory, but gonadectomized males showed diminished spatial memory. In Experiment 2 subcutaneous testosterone (T) capsules restored spatial memory performance in gonadectomized male rats, while rats with blank capsules demonstrated compromised spatial memory. In Experiment 3, gonadectomized male rats implanted with blank capsules again showed compromised spatial memory, while those with T, dihydrotestosterone (DHT), or estradiol (E) capsules demonstrated robust spatial memory, indicating that T's effects may be mediated by its conversion to E or to DHT. Gonadectomized male rats injected with Antide, a gonadotropin-releasing hormone receptor antagonist which lowers luteinizing hormone levels, also demonstrated spatial memory, comparable to that shown by T-, E-, or DHT-treated males. These data indicate that testicular androgens are important for maximal levels of spatial working memory in male rats, that testosterone may be converted to E and/or DHT to exert its effects, and that some of the effects of these steroid hormones may occur via negative feedback effects on LH.

Effect of 3α-anderostanediol and indomethacin on acquisition, consolidation and retrieval stage of spatial memory in adult male rats.

Testosterone and its metabolites have important roles in learning and memory. The current study has conducted to assess the effect of pre-training, post-training and pre-probe trial intrahippocampal CA1 administration of 3α-anderostanediol (one of the metabolites of testosterone) and indomethacin (as 3α-hydroxysteroid dehydrogenase enzyme blocker) on acquisition, consolidation and retrieval in Morris water maze (MWM) task. Adult male rats were bilaterally cannulated into CA1 region of hippocampus and then received 3α-diol (0.2, 1, 3 and 6 mug/0.5 mul/side), indomethacin (1.5, 3 and 6 mug/0.5 mul/side), indomethacin (3 mug/0.5 mul/side) + 3α-diol (1 mug/0.5 mul/side), 25-35 min before training, immediately after training and 25-35 min before probe trial in MWM task. Our results showed that injection of 3α-diol and indomethacin significantly increased the escape latency and traveled distance to find hidden platform in acquisition and consolidation stage, but did not have any effect on retrieval of spatial learning as compared with the control group. It is concluded that intra-CA1 administration of 3α-diol and indomethacin could impair spatial learning and memory in acquisition and consolidation stage. Also, intrahippocampal injection of indomethacin + 3α-diol could not change spatial learning and memory impairment effect of indomethacin or 3α-diol in MWM task.

Effects of testosterone on spatial learning and memory in adult male rats

A male advantage over females for spatial tasks has been well documented in both humans and rodents, but it remains unclear how the activational effects of testosterone influence spatial ability in males. In a series of experiments, we tested how injections of testosterone influenced the spatial working and reference memory of castrated male rats. In the eight-arm radial maze, testosterone injections (0.500 mg/rat) reduced the number of working memory errors during the early blocks of testing but had no effect on the number of reference memory errors relative to the castrated control group. In a reference memory version of the Morris water maze, injections of a wide range of testosterone doses (0.0625–1.000 mg/rat) reduced path lengths to the hidden platform, indicative of improved spatial learning. This improved learning was independent of testosterone dose, with all treatment groups showing better performance than the castrated control males. Furthermore, this effect was only observed when rats were given testosterone injections starting 7 days prior to water maze testing and not when injections were given only on the testing days. We also observed that certain doses of testosterone (0.250 and 1.000 mg/rat) increased perseverative behavior in a reversal-learning task. Finally, testosterone did not have a clear effect on spatial working memory in the Morris water maze, although intermediate doses seemed to optimize performance. Overall, the results indicate that testosterone can have positive activational effects on spatial learning and memory, but the duration of testosterone replacement and the nature of the spatial task modify these effects.

Social Recognition Assay in the Rat

Neuropsychiatric disorders encompass a broad patient population in a variety of disease states across all age groups and are often accompanied by deficits in short-term/working memory. However, most preclinical models that allow for an assessment of cognitive enhancement do not provide robust behavioral readouts with a level of throughput sufficient to support modern drug discovery efforts. The rat social recognition assay presented in this unit is one exception that has been increasingly employed to test new chemical entities for enhancing cognitive activity. The test is simple in design and takes advantage of the spontaneous behavior of rats to investigate conspecifics. The protocol in this unit is designed to evaluate the effects of a test substance on the short-term/working memory of adult male rats employing 30-min or 2-hr pretreatment times.

Novel Object Recognition in the Rat: A Facile Assay for Cognitive Function

The rat novel object recognition (NOR) assay is a relatively high-throughput, robust, and sensitive procedure for evaluating compounds for cognition-enhancing activity. For the test, rats are given the opportunity to explore two identical objects for a predetermined period of time. After a delay, the animals are then presented with two objects to explore, one of which is the same as in the first exploration trial, the other a new object. Depending on the length of the delay between the two trials, the rats will either explore the novel object for a greater time period, indicating memory for the familiar object, or will explore the novel and familiar objects for the same amount of time, indicating a lack of recall or loss of memory for the familiar object presented during the initial trial. The protocol described in this unit can be used to evaluate the effects of a compound on the short-term/working memory of adult male rats following a 24-hr inter-trial interval.