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Introduction: There is strong evidence to indicate that release of glucocorticoids from adrenal glands in emotional states modulates memory storage. The glucocorticoid receptor in the hippocampus may be a target of glucocorticoids in the modulation of memory processing. The aim of this study is to examine the role of the dorsal hippocampus (DH) glucocorticoid receptors on spatial memory in Morris Water Maze task. Material and Methods: Male Long-Evans strain rats, weighing between 280 - 320 grams were surgically implanted bilaterally with cannulae aimed at the DH and were a week later trained in the Morris Water Maze task. The latency time to the fine plexiglass platform and the length of distances were used to measure spatial memory. Dexamethasone (0.1μg/0.6μL per side) as a glucocorticoid agonist and RU38486 (3 ng/0.6μL per side) as a glucocorticoid antagonist were injected bilaterally into DH immediately, and 60 and 120 min after training. Results: Results indicated that infusion of the glucocorticoid agonist and antagonist immediately and 60 min, but not 120 min after training, into the DH significantly enhanced and impaired retention performance, respectively. Conclusion: The above results show that glucocorticoid receptor plays an important role in consolidation of spatial memory in the Morris Water Maze task for at least 60 min after training.

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Introduction: There is much evidence indicating that glucocorticoids receptors are highly involved in emotional learning and memory storage in many areas of the brain. The aim of the present study was to assess the role of glucocorticoid agonists and antagonists on the orbitofrontal cortex (OFC) in spatial memory processes (Acquisition, Consolidation and Retrieval) of the place avoidance learning task. Materials and Methods: Long-Evans strain rats, weighting 280-320 gr, (n=100, in 10 groups) were surgically implanted bilaterally with cannulae aimed at the OFC and were trained to avoid entrance to a 60 degree segment of the arena entering this was punished by mild footshock. The forbidden sector was defined by room cues during rotation in the light and by floor cues in the dark. Place avoidance training occurred in a single 30-min session and avoidance memory was assessed during a 30-min extinction trials, 24 hours later. The time of the first entrance and the number of entrances into the punished sector during extinction were used to measure the place avoidance memory. Bilateral injections of Dexamethasone (0.1μg/0.6 μl/side) as a glucocorticoid agonist and RU38486 (3ng/0.6 μl/side) as a glucocorticoid antagonist were injected to the OFC 5 min before acquisition, immediately, 60 and 120 min after training and 5 min before retrieval test. Control groups simultaneously received just the vehicle of the same volume, that was injected to the other groups. Results: The results indicated that acquisition, consolidation and retrieval of spatial memory were not impaired (P>0.05). Conclusion: The findings above showed that the glucocorticoid receptors in OFC do not have an important role in modulation and storage of spatial memory related to emotional events in place avoidance learning tasks.

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Introduction: Recent evidence indicated that when a stabilized memory is recalled or reactivated, it again becomes labile and initiates a time-dependent process referred to “reconsolidation”. Considering the documented role of stress hormones on emotional memory, the purpose of this study was to compare the effects of glucocorticoids on consolidation and reconsolidation of a fear conditioning memory. Materials and Methods: Adult male Wistar rats were trained in fear conditioning system. In experiment 1, rats were placed into context and after 180 s were given two 2 s, 0.4 mA shocks with an interval of 120 s. Twenty seconds after the final shock, rats removed from the context box and were injected with different doses of corticosterone or vehicle. In reconsolidation experiments, rats received 2 s, 0.4 mA shocks with an interval of 120 s (moderate memory) or given eight 2 s, 1.5 mA shocks with an interval of 62 s (strong memory). Thirty seconds after the final shock, rats removed from the context box. For reactivation, 24 h later rats were returned to the chamber for 90s. Immediately after reactivation, rats were injected with different doses of corticosterone or vehicle. Twenty-four hours after training or memory reactivation, rats were returned to the context box for 5 min. Seconds of freezing (defined as the absence of all visible movement oxcept respiration) during the retrieval testing were scored for each rat. Results: The findings indicated that injections of corticosterone after training enhanced memory consolidation at dose of 3 mg/kg. Injections of the drug after memory reactivation did not change recall of moderate memory, but impaired recall of strong memory at dose of 3 mg/kg. Conclusion: The data indicate that glucocorticoids have opposite effects on consolidation and reconsolidation of contextual fear conditioning memory. Further studies are needed to determine the underlying mechanisms.

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Introduction: While missing breakfast has been known to result in declines in cognitive function, not all studies show positive effects of breakfast consumption on cognitive function. Differences in breakfast composition may account for some of the contradictory results across studies. However, since we could not find any published study from Iran investigating the effect of breakfast composition on cognitive performance, this study designed to assess the effect of 2 common Iranian breakfast foods (high carbohydrate, high protein) on the cognitive performance of elementary school children. Material and Methods: Fifty-one well-nourished children (27 girls) aged 9-11 years took part in the present study. Children consumed one of 2 breakfasts (subjects) or took no breakfast (controls) in a randomized cross-over design with one week in between for a wash-out period. The two breakfasts were high carbohydrate (60%) and high protein (25%), similar in energy and fat, but differing in carbohydrate and protein composition. Cognitive performance was assessed prior to and 30 and 120 minutes after breakfasts, using a selection of tests from the CDR standard computerized assessment system. Statistical analysis was conducted by using SPSS (version 15) and P<0.05 was considered as the level of significance. Results: Results indicated that all 3 treatments (high carbohydrate, high protein, fasted state) were followed by decline in cognitive performance in both sexes, with no significant differences between the 2 groups, in most of the tasks. Conclusion: Our results did not show the effect of breakfast composition on the memories of well-nourished children and further research should address the extent to which different types of breakfast influence different domains of cognitive function. Also quality and quantity of breakfast should be assessed besides cognition, because of their effect on mood.

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Introduction: Evidence indicates that hipppocampus and activation of glucocorticoid receptors in this area are necessary for emotional learning and memory processes also some studies suggest that glucocorticoid’s effects probably involve with processes of protein synthysis in the hippocmapus. The aim of this study was to determine the role of intrahippocampal microinjections of anisomycin [(ANS) as a protein synthysis inhibitor)] on dexamethasone-induced modulation of memory consolidation in the passive avoidance learning (PAL) task in rats. Material and Methods: In this study, 90 male Wistar rats (250–300 gr) were surgically implanted bilaterally with cannulae aimed at the dorsal hippocampus (DH) were trained in PAL task. In experiment 1. Dexamethasone (0.1, 0.5, 1 and 3 mg/kg IP) was injected immediately after training and vehicle injected into DH. In experiment 2. Anisomycin (0.5, 1 µg/µl/side) or vehicle were injected bilaterally into the DH followed immediately by IP injection of Dexamethasone (1 mg/kg) or vehicle. Two days after training, retention tests were done and step-through latency (STL) and total time spent in light chamber (TLC) of apparatus were recorded during 10 min and compared with controls. Results: Data indicated that injection of Dexamethasone immediatly after training enhanced memory consolidation (P<0.01) and this effect was blocked by injection of ANS in to the DH (P<0.01). Conclusion: The findings above showed that glucocorticoids play on important role in consolidation of emotional learning and probably in processes of protein synthesis in the hippocampus may play an important role in mediating these effects.

 

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Introduction: The aim of present study was to evaluate the effects of aerobic training and detraining periods on metabolic risk factors, BDNF and memory function. Materials and Methods: Forty-two middle-aged, sedentary males volunteers were randomly divided into four groups MetS Exercise (ME), MetS Control (MC), Healthy Exercise (HE) and Healthy Controls (HC). Both the ME and HE groups participated in an exercise training (AT) program (6 weeks), followed by 6 weeks of detraining (DT). Midterm and Digit Span memory tests and blood sampling were conducted before and after training and also following detraining. Data were analyzed using Pearson coefficient, multivariate ANOVA and ANCOVA and repeated measure. Results: Most of the metabolic risk factors significantly improved after AT in the ME group waist circumference and FBS however returned to baseline values following DT (P<0.05). Waist circumference and triglycerides in the HE group decreased significantly, but returned to baseline values after DT (P<0.05). Aerobic exercise training could ameliorate overall MetS Z scores in both the ME and HE, groups, effects that disappeared in the ME group, even following DT (P<0.05). Serum BDNF was significantly elevated in HE, but surprisingly decreased in ME, effects that both disappeared after DT (P<0.05). Only in HE, both the short-term and mid-term memory improved significantly after AT (P<0.05). Conclusion: These findings indicate that physical fitness training programs ameliorate metabolic risk factors and improve learning and memory ability.

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