Trim9 Deletion Alters the Morphogenesis of Developing and Adult-Born Hippocampal Neurons and Impairs Spatial Learning and Memory
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Ojbective To study the difference of Aβ 25-35 on neurons between hippocampus and septum. Mdthods employing the method of primary cell culture, neurons survival and SOD were examined ,and amalysed the expression of apoptosis-related gene bcl-xl by Western blot. Result Aβ 25-35 might reduce the survival of hippocampal and septal neurons, increased both activity of CuZn-SOD and expression of Bcl-xl, but decreased the activity of Mn-SOD of hippocampal neurons, and had on obvious effect on septal neurons. Conclusion Aβ 25-35 had the same effect on survival and CuZn-SOD but Mn-SOD between the hippocampus and septum. The cytoxic mechanisms of Aβ 25-35 on hippocampus and septus might be different.
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The hippocampus plays an essential role in spatial learning. To investigate whether the whole structure is equally important, we compared the effects of variously sized and localized hippocampal aspiration lesions on spatial learning in a Morris water maze. The volume of all hippocampal lesions was determined. Dorsal hippocampal lesions consistently impaired spatial learning more than equally large ventral lesions. The dorsal lesions had to be larger than 20% of the total hippocampal volume to prolong final escape latencies. The acquisition rate and precision on a probe test without platform were sensitive to even smaller dorsal lesions. The degree of impairment correlated with the lesion volume. In contrast, the lesions of the ventral half of the hippocampus spared both the rate and the precision of learning unless nearly all of the ventral half was removed. There was no significant effect of the location (dorsal or ventral) of damage to the overlying neocortex only. In conclusion, the dorsal half of the hippocampus appears more important for spatial learning than the ventral half. The spatial learning ability seems related to the amount of damaged dorsal hippocampal tissue, with a threshold at about 20% of the total hippocampal volume, under which normal learning can occur.
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Hippocampal processing is often crucial for normal spatial learning and memory in both birds and mammals, suggesting a general similarity in avian and mammalian hippocampal function. However, few studies using birds have examined the effect of hippocampal lesions on spatial tasks analogous to those typically used with mammals. Therefore, we examined how hippocampal lesions would affect the performance of pigeons in a dry version of the water maze. Experiment 1 showed that hippocampal-lesioned birds were impaired in acquiring the location of hidden food in the maze. Experiment 2 showed that hippocampal-lesioned birds were not impaired when a single cue indicated the location of hidden food. These results support the notion that avian and mammalian hippocampal functions are quite similar, in terms of the tasks for which their processing is crucial and the tasks for which it is not.
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Using quantitative receptor autoradiography, spirodecanone binding was evaluated in the gerbil hippocampus 1 h-1 month after cerebral ischaemia of 10 min. The spirodecanone binding was unaffected in the hippocampus up to 48 h after ischaemia. Thereafter, increased binding was found in the stratum radiatum of hippocampal CA1 sector 7 days and 1 month after ischaemia. Other hippocampal regions showed no significant alterations in the spirodecanone binding. A histological study revealed that the hippocampal CA1 sector was severely damaged 7 days and 1 months after ischaemia. These results demonstrate that spirodecanone binding sites are located on interneurones or glial cells in the hippocampal CA1 sector.
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Objective: To study the effect of chronic stress on spatial learning and memory and nitric oxide (NO) in hippocampus of the rats Method: Chronic stress model was established by electric-foot accompanied with noise Morris watermaze was used to observe spatial learning and memory abilities, contents of NO and activities of NOS in hippocampus were measured during the test Result: The spatial learning and memory of chronic stress rats were significantly decreased in Morris watermaze Contents of NO (3 87±0 47 nmol/mgpro) and NOS activity (102 64±13 33 pmol/mgpro/min) in hippocampus of the stress rats were significantly higher than that of normal rats (2 76±0 43 nmol/mgpro, 78 25±10 67 pmol/mgpro/min respectively) Conclusion: Chronic stress impairs spatial learning and memory abilities of rats, which may be related to the increase of NO in their hippocampus
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This study investigated the effects of neonatal hippocampal ablation on the development of spatial learning and memory abilities in rats. Newborn rats sustained bilateral electrolytic lesions of the hippocampus or were sham-operated on postnatal day 1 (PN1). At PN20–25, PN50–55, or PN90–95, separate groups of rats were tested in a Morris water maze on a visible “cue” condition (visible platform in a fixed location of the maze), a spatial “place” condition (submerged platform in a fixed location), or a no-contingency “random” condition (submerged platform in a random location). Rats were tested for 6 consecutive days, with 12 acquisition trials and 1 retention (probe) trial per day. During acquisition trials, the rat's latency to escape the maze was recorded. During retention trials (last trial for each day, no escape platform available), the total time the rat spent in the probe quadrant was recorded. Data from rats with hippocampal lesions tested as infants (PN20–25) or as adults (PN50–55 and PN90–95) converged across measures to reveal that 1) spatial (place) memory deficits were evident throughout developmental testing, suggesting that the deficits in spatial memory were long-lasting, if not permanent, and 2) behavioral performance measures under the spatial (place) condition were significantly correlated with total volume of hippocampal tissue damage, and with volume of damage to the right and anterior hippocampal regions. These results support the hypothesis that hippocampal integrity is important for the normal development of spatial learning and memory functions, and show that other brain structures do not assume hippocampal-spatial memory functions when the hippocampus is damaged during the neonatal period (even when testing is not begun until adulthood). Thus, neonatal hippocampal damage in rats may serve as a rodent model for assessing treatment strategies (e.g., pharmacological) relevant to human perinatal brain injury and developmental disabilities within the learning and memory realm. Hippocampus 7:403–415, 1997. © 1997 Wiley-Liss, Inc.
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Cognitive map
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In this study, I investigate the role that hippocampal inhibitory cells (intemeurons) have on the synchronization of oscillations between the two hemispheres of the hippocampus. My study focuses in particular on the ripple oscillations, because this network activity is highly synchronous between left and right hippocampus. My hypothesis is that a subset of hippocampal intemeurons might establish axonal connections from the hippocampal area in which the somata reside towards the contralateral side, hence regulating inter-hippocampal ripple discharges. I address this hypothesis injecting in one side of the hippocampus substance P fragment, a peptide that increases the activity of subsets of inhibitory neurons in rat hippocampus, and the antimalarial Quinine whose roles as gap-junction blocker has been well established by numerous publications. Simultaneous recording from both hippocampi are thus compared to investigate whether ipsilateral injected drugs affect hippocampal ripple activity recorded contralaterally. I found that ripple oscillations are indeed affected by injection of the abovementioned drugs: Quinine increases length and decreases Inter Ripple Interval (I.R.I.) in both injected and contralateral hippocampus; on the other hand, SP decreases the average amplitude of the ripple episode, but increases the duration of the ripple event. Most importantly, many of the perturbations observed were preserved between injected and contralateral hippocampus. Since the drugs I employed affect mainly inhibitory neurons, I propose that long-range projecting inhibitory neurons located in the injected hippocampus are responsible for carrying the drugs' effects to the contralateral hippocampus. In conclusion, my results seem to indicate that long-range projecting intemeurons are involved in transmitting ripple synchronization information across the two hippocampi.
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Abstract In previous work, we showed that adult rats that were reared socially for 3 months in a complex (village) environment retained allocentric spatial memory for that environment following hippocampal lesions (Winocur et al., ( 2005 ) Nat Neurosci 8:273–275). In the present series of experiments, we showed that 3 months of postoperative rearing did not confer the same benefits (Experiment 1), although hippocampal groups, with or without rearing experience, exhibited spatial learning after extensive training (Experiments 1 and 2). Experiment 3 showed that as little as 2 weeks of preoperative rearing in the village was sufficient to retain acquired spatial memories after hippocampal lesions. Probe testing revealed that, although rats with hippocampal lesions exhibited remarkably good memory for preoperatively learned locations in the village, they were impaired when changes in task demands required flexible use of existing spatial representations. In a direct test of flexibility (Experiment 4), preoperatively reared rats were administered a blocked‐routes task in the original learning environment, in which on designated trials, a barrier was placed across one of the direct paths to the goal compartment. On encountering the barrier, control rats consistently selected the next most direct route, whereas rats with hippocampal lesions, despite using spatial strategies, made more errors and took longer to find the goal. The present results confirm that allocentric spatial memories can survive hippocampal damage but they are schematic in nature and less cohesive than those associated with cognitive maps in intact brains. As well, there was evidence that, although different processes are involved in their formation, the schematic memories that were acquired preoperatively and survived hippocampal lesions are essentially the same as those laboriously formed postoperatively after extensive training. © 2010 Wiley‐Liss, Inc.
Cognitive flexibility
Environmental Enrichment
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